1 # SOME DESCRIPTIVE TITLE
2 # Copyright (C) YEAR Free Software Foundation, Inc.
3 # This file is distributed under the same license as the PACKAGE package.
4 # FIRST AUTHOR <EMAIL@ADDRESS>, YEAR.
9 "Project-Id-Version: PACKAGE VERSION\n"
10 "POT-Creation-Date: 2012-03-22 04:26+0900\n"
11 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
12 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
13 "Language-Team: LANGUAGE <LL@li.org>\n"
16 "Content-Type: text/plain; charset=CHARSET\n"
17 "Content-Transfer-Encoding: 8bit\n"
20 #: build/C/man2/accept.2:39
26 #: build/C/man2/accept.2:39
32 #: build/C/man2/accept.2:39 build/C/man2/bind.2:66 build/C/man2/connect.2:65 build/C/man2/getsockname.2:38 build/C/man2/getsockopt.2:42 build/C/man2/listen.2:43 build/C/man2/recv.2:39 build/C/man2/recvmmsg.2:26 build/C/man2/select.2:38 build/C/man2/select_tut.2:30 build/C/man2/send.2:38 build/C/man2/sendmmsg.2:28 build/C/man3/sockatmark.3:23 build/C/man2/socket.2:41 build/C/man7/socket.7:26 build/C/man2/socketcall.2:26 build/C/man2/socketpair.2:40
38 #: build/C/man2/accept.2:39 build/C/man2/bind.2:66 build/C/man3/bindresvport.3:27 build/C/man2/connect.2:65 build/C/man3/getifaddrs.3:33 build/C/man2/getsockname.2:38 build/C/man2/getsockopt.2:42 build/C/man2/listen.2:43 build/C/man2/recv.2:39 build/C/man2/recvmmsg.2:26 build/C/man2/select.2:38 build/C/man2/select_tut.2:30 build/C/man2/send.2:38 build/C/man2/sendmmsg.2:28 build/C/man3/sockatmark.3:23 build/C/man2/socket.2:41 build/C/man7/socket.7:26 build/C/man2/socketcall.2:26 build/C/man2/socketpair.2:40
40 msgid "Linux Programmer's Manual"
44 #: build/C/man2/accept.2:40 build/C/man2/bind.2:67 build/C/man3/bindresvport.3:28 build/C/man2/connect.2:66 build/C/man3/getifaddrs.3:34 build/C/man2/getsockname.2:39 build/C/man2/getsockopt.2:43 build/C/man2/listen.2:44 build/C/man2/recv.2:40 build/C/man2/recvmmsg.2:27 build/C/man2/select.2:39 build/C/man2/select_tut.2:31 build/C/man2/send.2:39 build/C/man2/sendmmsg.2:29 build/C/man3/sockatmark.3:24 build/C/man2/socket.2:42 build/C/man7/socket.7:27 build/C/man2/socketcall.2:27 build/C/man2/socketpair.2:41
50 #: build/C/man2/accept.2:42
51 msgid "accept - accept a connection on a socket"
55 #: build/C/man2/accept.2:42 build/C/man2/bind.2:69 build/C/man3/bindresvport.3:30 build/C/man2/connect.2:68 build/C/man3/getifaddrs.3:36 build/C/man2/getsockname.2:41 build/C/man2/getsockopt.2:45 build/C/man2/listen.2:46 build/C/man2/recv.2:42 build/C/man2/recvmmsg.2:29 build/C/man2/select.2:42 build/C/man2/select_tut.2:34 build/C/man2/send.2:41 build/C/man2/sendmmsg.2:31 build/C/man3/sockatmark.3:26 build/C/man2/socket.2:44 build/C/man7/socket.7:29 build/C/man2/socketcall.2:29 build/C/man2/socketpair.2:43
61 #: build/C/man2/accept.2:46 build/C/man2/bind.2:73
64 "B<#include E<lt>sys/types.hE<gt>> /* See NOTES */\n"
65 "B<#include E<lt>sys/socket.hE<gt>>\n"
69 #: build/C/man2/accept.2:48
72 "B<int accept(int >I<sockfd>B<, struct sockaddr *>I<addr>B<, socklen_t "
77 #: build/C/man2/accept.2:51
80 "B<#define _GNU_SOURCE> /* See feature_test_macros(7) */\n"
81 "B<#include E<lt>sys/socket.hE<gt>>\n"
85 #: build/C/man2/accept.2:54
88 "B<int accept4(int >I<sockfd>B<, struct sockaddr *>I<addr>B<,>\n"
89 "B< socklen_t *>I<addrlen>B<, int >I<flags>B<);>\n"
93 #: build/C/man2/accept.2:55 build/C/man2/bind.2:77 build/C/man3/bindresvport.3:37 build/C/man2/connect.2:77 build/C/man3/getifaddrs.3:45 build/C/man2/getsockname.2:48 build/C/man2/getsockopt.2:56 build/C/man2/listen.2:54 build/C/man2/recv.2:57 build/C/man2/recvmmsg.2:39 build/C/man2/select.2:81 build/C/man2/select_tut.2:73 build/C/man2/send.2:56 build/C/man2/sendmmsg.2:40 build/C/man3/sockatmark.3:40 build/C/man2/socket.2:50 build/C/man7/socket.7:33 build/C/man2/socketcall.2:31 build/C/man2/socketpair.2:50
99 #: build/C/man2/accept.2:70
101 "The B<accept>() system call is used with connection-based socket types "
102 "(B<SOCK_STREAM>, B<SOCK_SEQPACKET>). It extracts the first connection "
103 "request on the queue of pending connections for the listening socket, "
104 "I<sockfd>, creates a new connected socket, and returns a new file descriptor "
105 "referring to that socket. The newly created socket is not in the listening "
106 "state. The original socket I<sockfd> is unaffected by this call."
110 #: build/C/man2/accept.2:79
112 "The argument I<sockfd> is a socket that has been created with B<socket>(2), "
113 "bound to a local address with B<bind>(2), and is listening for connections "
114 "after a B<listen>(2)."
118 #: build/C/man2/accept.2:97
120 "The argument I<addr> is a pointer to a I<sockaddr> structure. This "
121 "structure is filled in with the address of the peer socket, as known to the "
122 "communications layer. The exact format of the address returned I<addr> is "
123 "determined by the socket's address family (see B<socket>(2) and the "
124 "respective protocol man pages). When I<addr> is NULL, nothing is filled in; "
125 "in this case, I<addrlen> is not used, and should also be NULL."
129 #: build/C/man2/accept.2:105
131 "The I<addrlen> argument is a value-result argument: the caller must "
132 "initialize it to contain the size (in bytes) of the structure pointed to by "
133 "I<addr>; on return it will contain the actual size of the peer address."
137 #: build/C/man2/accept.2:110 build/C/man2/getsockname.2:65
139 "The returned address is truncated if the buffer provided is too small; in "
140 "this case, I<addrlen> will return a value greater than was supplied to the "
145 #: build/C/man2/accept.2:123
147 "If no pending connections are present on the queue, and the socket is not "
148 "marked as nonblocking, B<accept>() blocks the caller until a connection is "
149 "present. If the socket is marked nonblocking and no pending connections are "
150 "present on the queue, B<accept>() fails with the error B<EAGAIN> or "
155 #: build/C/man2/accept.2:137
157 "In order to be notified of incoming connections on a socket, you can use "
158 "B<select>(2) or B<poll>(2). A readable event will be delivered when a new "
159 "connection is attempted and you may then call B<accept>() to get a socket "
160 "for that connection. Alternatively, you can set the socket to deliver "
161 "B<SIGIO> when activity occurs on a socket; see B<socket>(7) for details."
165 #: build/C/man2/accept.2:150
167 "For certain protocols which require an explicit confirmation, such as "
168 "DECNet, B<accept>() can be thought of as merely dequeuing the next "
169 "connection request and not implying confirmation. Confirmation can be "
170 "implied by a normal read or write on the new file descriptor, and rejection "
171 "can be implied by closing the new socket. Currently only DECNet has these "
172 "semantics on Linux."
176 #: build/C/man2/accept.2:160
178 "If I<flags> is 0, then B<accept4>() is the same as B<accept>(). The "
179 "following values can be bitwise ORed in I<flags> to obtain different "
184 #: build/C/man2/accept.2:160 build/C/man2/socket.2:162
186 msgid "B<SOCK_NONBLOCK>"
190 #: build/C/man2/accept.2:168 build/C/man2/socket.2:170
192 "Set the B<O_NONBLOCK> file status flag on the new open file description. "
193 "Using this flag saves extra calls to B<fcntl>(2) to achieve the same "
198 #: build/C/man2/accept.2:168 build/C/man2/socket.2:170
200 msgid "B<SOCK_CLOEXEC>"
204 #: build/C/man2/accept.2:178 build/C/man2/socket.2:180
206 "Set the close-on-exec (B<FD_CLOEXEC>) flag on the new file descriptor. See "
207 "the description of the B<O_CLOEXEC> flag in B<open>(2) for reasons why this "
212 #: build/C/man2/accept.2:178 build/C/man2/bind.2:150 build/C/man3/bindresvport.3:64 build/C/man2/connect.2:125 build/C/man2/getsockname.2:65 build/C/man2/getsockopt.2:129 build/C/man2/listen.2:80 build/C/man2/recv.2:386 build/C/man2/recvmmsg.2:141 build/C/man2/select.2:285 build/C/man2/select_tut.2:483 build/C/man2/send.2:273 build/C/man2/sendmmsg.2:119 build/C/man3/sockatmark.3:49 build/C/man2/socket.2:312 build/C/man2/socketpair.2:67
218 #: build/C/man2/accept.2:185
220 "On success, these system calls return a nonnegative integer that is a "
221 "descriptor for the accepted socket. On error, -1 is returned, and I<errno> "
222 "is set appropriately."
226 #: build/C/man2/accept.2:185
228 msgid "Error Handling"
232 #: build/C/man2/accept.2:212
234 "Linux B<accept>() (and B<accept4>()) passes already-pending network errors "
235 "on the new socket as an error code from B<accept>(). This behavior differs "
236 "from other BSD socket implementations. For reliable operation the "
237 "application should detect the network errors defined for the protocol after "
238 "B<accept>() and treat them like B<EAGAIN> by retrying. In case of TCP/IP "
239 "these are B<ENETDOWN>, B<EPROTO>, B<ENOPROTOOPT>, B<EHOSTDOWN>, B<ENONET>, "
240 "B<EHOSTUNREACH>, B<EOPNOTSUPP>, and B<ENETUNREACH>."
244 #: build/C/man2/accept.2:212 build/C/man2/bind.2:155 build/C/man3/bindresvport.3:69 build/C/man2/connect.2:130 build/C/man3/getifaddrs.3:144 build/C/man2/getsockname.2:70 build/C/man2/getsockopt.2:134 build/C/man2/listen.2:85 build/C/man2/recv.2:391 build/C/man2/recvmmsg.2:149 build/C/man2/select.2:302 build/C/man2/send.2:278 build/C/man2/sendmmsg.2:133 build/C/man3/sockatmark.3:54 build/C/man2/socket.2:317 build/C/man2/socketpair.2:72
250 #: build/C/man2/accept.2:213 build/C/man2/recv.2:396 build/C/man2/send.2:291
252 msgid "B<EAGAIN> or B<EWOULDBLOCK>"
255 #. Actually EAGAIN on Linux
257 #: build/C/man2/accept.2:221
259 "The socket is marked nonblocking and no connections are present to be "
260 "accepted. POSIX.1-2001 allows either error to be returned for this case, "
261 "and does not require these constants to have the same value, so a portable "
262 "application should check for both possibilities."
266 #: build/C/man2/accept.2:221 build/C/man2/bind.2:163 build/C/man2/connect.2:167 build/C/man2/getsockname.2:71 build/C/man2/getsockopt.2:135 build/C/man2/listen.2:89 build/C/man2/recv.2:405 build/C/man2/select.2:303 build/C/man2/send.2:299 build/C/man3/sockatmark.3:55
272 #: build/C/man2/accept.2:224
273 msgid "The descriptor is invalid."
277 #: build/C/man2/accept.2:224
279 msgid "B<ECONNABORTED>"
283 #: build/C/man2/accept.2:227
284 msgid "A connection has been aborted."
288 #: build/C/man2/accept.2:227 build/C/man2/bind.2:189 build/C/man2/connect.2:173 build/C/man2/getsockname.2:76 build/C/man2/getsockopt.2:140 build/C/man2/recv.2:414 build/C/man2/send.2:308 build/C/man2/socketpair.2:76
294 #: build/C/man2/accept.2:232
295 msgid "The I<addr> argument is not in a writable part of the user address space."
299 #: build/C/man2/accept.2:232 build/C/man2/connect.2:201 build/C/man2/recv.2:418 build/C/man2/select.2:308 build/C/man2/send.2:311
305 #: build/C/man2/accept.2:237
307 "The system call was interrupted by a signal that was caught before a valid "
308 "connection arrived; see B<signal>(7)."
312 #: build/C/man2/accept.2:237 build/C/man2/accept.2:242 build/C/man2/bind.2:167 build/C/man2/bind.2:193 build/C/man2/getsockname.2:82 build/C/man2/getsockopt.2:150 build/C/man2/recv.2:423 build/C/man2/recvmmsg.2:153 build/C/man2/select.2:312 build/C/man2/send.2:315 build/C/man3/sockatmark.3:59 build/C/man2/socket.2:325 build/C/man2/socket.2:328
318 #: build/C/man2/accept.2:242
320 "Socket is not listening for connections, or I<addrlen> is invalid (e.g., is "
325 #: build/C/man2/accept.2:247
326 msgid "(B<accept4>()) invalid value in I<flags>."
330 #: build/C/man2/accept.2:247 build/C/man2/socket.2:333 build/C/man2/socketpair.2:81
336 #: build/C/man2/accept.2:250
337 msgid "The per-process limit of open file descriptors has been reached."
341 #: build/C/man2/accept.2:250 build/C/man2/socket.2:336 build/C/man2/socketpair.2:84
347 #: build/C/man2/accept.2:253 build/C/man2/socket.2:339 build/C/man2/socketpair.2:87
348 msgid "The system limit on the total number of open files has been reached."
352 #: build/C/man2/accept.2:253
354 msgid "B<ENOBUFS>, B<ENOMEM>"
358 #: build/C/man2/accept.2:258
360 "Not enough free memory. This often means that the memory allocation is "
361 "limited by the socket buffer limits, not by the system memory."
365 #: build/C/man2/accept.2:258 build/C/man2/bind.2:172 build/C/man2/connect.2:213 build/C/man2/getsockname.2:90 build/C/man2/getsockopt.2:164 build/C/man2/listen.2:94 build/C/man2/recv.2:438 build/C/man2/send.2:344
371 #: build/C/man2/accept.2:261
372 msgid "The descriptor references a file, not a socket."
376 #: build/C/man2/accept.2:261 build/C/man2/listen.2:99 build/C/man2/send.2:349 build/C/man2/socketpair.2:87
378 msgid "B<EOPNOTSUPP>"
382 #: build/C/man2/accept.2:265
383 msgid "The referenced socket is not of type B<SOCK_STREAM>."
387 #: build/C/man2/accept.2:265
393 #: build/C/man2/accept.2:268
394 msgid "Protocol error."
398 #: build/C/man2/accept.2:272
399 msgid "In addition, Linux B<accept>() may fail if:"
403 #: build/C/man2/accept.2:272
409 #: build/C/man2/accept.2:275
410 msgid "Firewall rules forbid connection."
414 #: build/C/man2/accept.2:287
416 "In addition, network errors for the new socket and as defined for the "
417 "protocol may be returned. Various Linux kernels can return other errors "
418 "such as B<ENOSR>, B<ESOCKTNOSUPPORT>, B<EPROTONOSUPPORT>, B<ETIMEDOUT>. The "
419 "value B<ERESTARTSYS> may be seen during a trace."
423 #: build/C/man2/accept.2:287 build/C/man3/getifaddrs.3:157 build/C/man2/recvmmsg.2:157 build/C/man2/select.2:321 build/C/man2/sendmmsg.2:145 build/C/man3/sockatmark.3:66 build/C/man7/socket.7:697
429 #: build/C/man2/accept.2:292
431 "The B<accept4>() system call is available starting with Linux 2.6.28; "
432 "support in glibc is available starting with version 2.10."
436 #: build/C/man2/accept.2:292 build/C/man2/bind.2:220 build/C/man3/bindresvport.3:89 build/C/man2/connect.2:223 build/C/man3/getifaddrs.3:165 build/C/man2/getsockname.2:95 build/C/man2/getsockopt.2:169 build/C/man2/listen.2:104 build/C/man2/recv.2:443 build/C/man2/recvmmsg.2:162 build/C/man2/select.2:327 build/C/man2/send.2:363 build/C/man2/sendmmsg.2:150 build/C/man3/sockatmark.3:69 build/C/man2/socket.2:350 build/C/man2/socketcall.2:43 build/C/man2/socketpair.2:93
438 msgid "CONFORMING TO"
441 #. The BSD man page documents five possible error returns
442 #. (EBADF, ENOTSOCK, EOPNOTSUPP, EWOULDBLOCK, EFAULT).
443 #. POSIX.1-2001 documents errors
444 #. EAGAIN, EBADF, ECONNABORTED, EINTR, EINVAL, EMFILE,
445 #. ENFILE, ENOBUFS, ENOMEM, ENOTSOCK, EOPNOTSUPP, EPROTO, EWOULDBLOCK.
446 #. In addition, SUSv2 documents EFAULT and ENOSR.
448 #: build/C/man2/accept.2:304
450 "B<accept>(): POSIX.1-2001, SVr4, 4.4BSD, (B<accept>() first appeared in "
455 #: build/C/man2/accept.2:307
456 msgid "B<accept4>() is a nonstandard Linux extension."
459 #. Some testing seems to show that Tru64 5.1 and HP-UX 11 also
460 #. do not inherit file status flags -- MTK Jun 05
462 #: build/C/man2/accept.2:322
464 "On Linux, the new socket returned by B<accept>() does I<not> inherit file "
465 "status flags such as B<O_NONBLOCK> and B<O_ASYNC> from the listening "
466 "socket. This behavior differs from the canonical BSD sockets "
467 "implementation. Portable programs should not rely on inheritance or "
468 "noninheritance of file status flags and always explicitly set all required "
469 "flags on the socket returned from B<accept>()."
473 #: build/C/man2/accept.2:322 build/C/man2/bind.2:232 build/C/man3/bindresvport.3:92 build/C/man2/connect.2:239 build/C/man3/getifaddrs.3:185 build/C/man2/getsockname.2:101 build/C/man2/getsockopt.2:176 build/C/man2/listen.2:109 build/C/man2/recv.2:453 build/C/man2/select.2:342 build/C/man2/select_tut.2:501 build/C/man2/send.2:377 build/C/man2/sendmmsg.2:153 build/C/man3/sockatmark.3:71 build/C/man2/socket.2:364 build/C/man7/socket.7:711 build/C/man2/socketcall.2:46 build/C/man2/socketpair.2:101
479 #: build/C/man2/accept.2:328 build/C/man2/bind.2:238 build/C/man2/connect.2:245 build/C/man2/getsockopt.2:182 build/C/man2/listen.2:135 build/C/man2/socket.2:370 build/C/man2/socketpair.2:122
481 "POSIX.1-2001 does not require the inclusion of I<E<lt>sys/types.hE<gt>>, and "
482 "this header file is not required on Linux. However, some historical (BSD) "
483 "implementations required this header file, and portable applications are "
484 "probably wise to include it."
488 #: build/C/man2/accept.2:349
490 "There may not always be a connection waiting after a B<SIGIO> is delivered "
491 "or B<select>(2) or B<poll>(2) return a readability event because the "
492 "connection might have been removed by an asynchronous network error or "
493 "another thread before B<accept>() is called. If this happens then the call "
494 "will block waiting for the next connection to arrive. To ensure that "
495 "B<accept>() never blocks, the passed socket I<sockfd> needs to have the "
496 "B<O_NONBLOCK> flag set (see B<socket>(7))."
500 #: build/C/man2/accept.2:349
502 msgid "The socklen_t type"
506 #: build/C/man2/accept.2:359
508 "The third argument of B<accept>() was originally declared as an I<int *> "
509 "(and is that under libc4 and libc5 and on many other systems like 4.x BSD, "
510 "SunOS 4, SGI); a POSIX.1g draft standard wanted to change it into a I<size_t "
511 "*>, and that is what it is for SunOS 5. Later POSIX drafts have I<socklen_t "
512 "*>, and so do the Single UNIX Specification and glibc2. Quoting Linus "
516 #. .I fails: only italicizes a single line
518 #: build/C/man2/accept.2:376
520 "\"_Any_ sane library _must_ have \"socklen_t\" be the same size as int. "
521 "Anything else breaks any BSD socket layer stuff. POSIX initially I<did> "
522 "make it a size_t, and I (and hopefully others, but obviously not too many) "
523 "complained to them very loudly indeed. Making it a size_t is completely "
524 "broken, exactly because size_t very seldom is the same size as \"int\" on "
525 "64-bit architectures, for example. And it I<has> to be the same size as "
526 "\"int\" because that's what the BSD socket interface is. Anyway, the POSIX "
527 "people eventually got a clue, and created \"socklen_t\". They shouldn't "
528 "have touched it in the first place, but once they did they felt it had to "
529 "have a named type for some unfathomable reason (probably somebody didn't "
530 "like losing face over having done the original stupid thing, so they "
531 "silently just renamed their blunder).\""
535 #: build/C/man2/accept.2:376 build/C/man2/bind.2:252 build/C/man2/connect.2:256 build/C/man3/getifaddrs.3:198 build/C/man2/listen.2:164 build/C/man2/recv.2:488 build/C/man2/select.2:482 build/C/man2/select_tut.2:527 build/C/man2/send.2:414 build/C/man3/sockatmark.3:95 build/C/man2/socket.2:382
541 #: build/C/man2/accept.2:379 build/C/man2/listen.2:167
542 msgid "See B<bind>(2)."
546 #: build/C/man2/accept.2:379 build/C/man2/bind.2:317 build/C/man3/bindresvport.3:98 build/C/man2/connect.2:261 build/C/man3/getifaddrs.3:281 build/C/man2/getsockname.2:110 build/C/man2/getsockopt.2:200 build/C/man2/listen.2:167 build/C/man2/recv.2:493 build/C/man2/recvmmsg.2:165 build/C/man2/select.2:519 build/C/man2/select_tut.2:817 build/C/man2/send.2:419 build/C/man2/sendmmsg.2:168 build/C/man3/sockatmark.3:130 build/C/man2/socket.2:387 build/C/man7/socket.7:742 build/C/man2/socketcall.2:54 build/C/man2/socketpair.2:122
552 #: build/C/man2/accept.2:386
554 "B<bind>(2), B<connect>(2), B<listen>(2), B<select>(2), B<socket>(2), "
559 #: build/C/man2/accept.2:386 build/C/man2/bind.2:330 build/C/man3/bindresvport.3:101 build/C/man2/connect.2:268 build/C/man3/getifaddrs.3:287 build/C/man2/getsockname.2:117 build/C/man2/getsockopt.2:208 build/C/man2/listen.2:173 build/C/man2/recv.2:504 build/C/man2/recvmmsg.2:172 build/C/man2/select.2:534 build/C/man2/select_tut.2:836 build/C/man2/send.2:434 build/C/man2/sendmmsg.2:173 build/C/man3/sockatmark.3:135 build/C/man2/socket.2:418 build/C/man7/socket.7:753 build/C/man2/socketcall.2:72 build/C/man2/socketpair.2:129
565 #: build/C/man2/accept.2:393 build/C/man2/bind.2:337 build/C/man3/bindresvport.3:108 build/C/man2/connect.2:275 build/C/man3/getifaddrs.3:294 build/C/man2/getsockname.2:124 build/C/man2/getsockopt.2:215 build/C/man2/listen.2:180 build/C/man2/recv.2:511 build/C/man2/recvmmsg.2:179 build/C/man2/select.2:541 build/C/man2/select_tut.2:843 build/C/man2/send.2:441 build/C/man2/sendmmsg.2:180 build/C/man3/sockatmark.3:142 build/C/man2/socket.2:425 build/C/man7/socket.7:760 build/C/man2/socketcall.2:79 build/C/man2/socketpair.2:136
567 "This page is part of release 3.37 of the Linux I<man-pages> project. A "
568 "description of the project, and information about reporting bugs, can be "
569 "found at http://www.kernel.org/doc/man-pages/."
573 #: build/C/man2/bind.2:66
579 #: build/C/man2/bind.2:66
585 #: build/C/man2/bind.2:69
586 msgid "bind - bind a name to a socket"
590 #: build/C/man2/bind.2:76
593 "B<int bind(int >I<sockfd>B<, const struct sockaddr *>I<addr>B<,>\n"
594 "B< socklen_t >I<addrlen>B<);>\n"
598 #: build/C/man2/bind.2:90
600 "When a socket is created with B<socket>(2), it exists in a name space "
601 "(address family) but has no address assigned to it. B<bind>() assigns the "
602 "address specified to by I<addr> to the socket referred to by the file "
603 "descriptor I<sockfd>. I<addrlen> specifies the size, in bytes, of the "
604 "address structure pointed to by I<addr>. Traditionally, this operation is "
605 "called \\(lqassigning a name to a socket\\(rq."
609 #: build/C/man2/bind.2:97
611 "It is normally necessary to assign a local address using B<bind>() before a "
612 "B<SOCK_STREAM> socket may receive connections (see B<accept>(2))."
616 #: build/C/man2/bind.2:128
618 "The rules used in name binding vary between address families. Consult the "
619 "manual entries in Section 7 for detailed information. For B<AF_INET> see "
620 "B<ip>(7), for B<AF_INET6> see B<ipv6>(7), for B<AF_UNIX> see B<unix>(7), for "
621 "B<AF_APPLETALK> see B<ddp>(7), for B<AF_PACKET> see B<packet>(7), for "
622 "B<AF_X25> see B<x25>(7) and for B<AF_NETLINK> see B<netlink>(7)."
626 #: build/C/man2/bind.2:135
628 "The actual structure passed for the I<addr> argument will depend on the "
629 "address family. The I<sockaddr> structure is defined as something like:"
633 #: build/C/man2/bind.2:142
636 "struct sockaddr {\n"
637 " sa_family_t sa_family;\n"
638 " char sa_data[14];\n"
643 #: build/C/man2/bind.2:150
645 "The only purpose of this structure is to cast the structure pointer passed "
646 "in I<addr> in order to avoid compiler warnings. See EXAMPLE below."
650 #: build/C/man2/bind.2:155 build/C/man2/getsockname.2:70 build/C/man2/getsockopt.2:134 build/C/man2/listen.2:85 build/C/man2/socketpair.2:72
652 "On success, zero is returned. On error, -1 is returned, and I<errno> is set "
657 #: build/C/man2/bind.2:156 build/C/man2/bind.2:180 build/C/man3/bindresvport.3:74 build/C/man2/connect.2:133 build/C/man2/send.2:283 build/C/man2/socket.2:318
662 #. e.g., privileged port in AF_INET domain
664 #: build/C/man2/bind.2:160
665 msgid "The address is protected, and the user is not the superuser."
669 #: build/C/man2/bind.2:160 build/C/man3/bindresvport.3:79 build/C/man2/connect.2:146 build/C/man2/listen.2:86
671 msgid "B<EADDRINUSE>"
675 #: build/C/man2/bind.2:163
676 msgid "The given address is already in use."
680 #: build/C/man2/bind.2:167
681 msgid "I<sockfd> is not a valid descriptor."
684 #. This may change in the future: see
685 #. .I linux/unix/sock.c for details.
687 #: build/C/man2/bind.2:172
688 msgid "The socket is already bound to an address."
692 #: build/C/man2/bind.2:176
693 msgid "I<sockfd> is a descriptor for a file, not a socket."
697 #: build/C/man2/bind.2:180
698 msgid "The following errors are specific to UNIX domain (B<AF_UNIX>) sockets:"
702 #: build/C/man2/bind.2:185
704 "Search permission is denied on a component of the path prefix. (See also "
705 "B<path_resolution>(7).)"
709 #: build/C/man2/bind.2:185
711 msgid "B<EADDRNOTAVAIL>"
715 #: build/C/man2/bind.2:189
717 "A nonexistent interface was requested or the requested address was not "
722 #: build/C/man2/bind.2:193
723 msgid "I<addr> points outside the user's accessible address space."
727 #: build/C/man2/bind.2:200
728 msgid "The I<addrlen> is wrong, or the socket was not in the B<AF_UNIX> family."
732 #: build/C/man2/bind.2:200
738 #: build/C/man2/bind.2:204
739 msgid "Too many symbolic links were encountered in resolving I<addr>."
743 #: build/C/man2/bind.2:204
745 msgid "B<ENAMETOOLONG>"
749 #: build/C/man2/bind.2:208
750 msgid "I<addr> is too long."
754 #: build/C/man2/bind.2:208
760 #: build/C/man2/bind.2:211
761 msgid "The file does not exist."
765 #: build/C/man2/bind.2:211 build/C/man2/recv.2:427 build/C/man2/select.2:318 build/C/man2/send.2:338
771 #: build/C/man2/bind.2:214
772 msgid "Insufficient kernel memory was available."
776 #: build/C/man2/bind.2:214
782 #: build/C/man2/bind.2:217
783 msgid "A component of the path prefix is not a directory."
787 #: build/C/man2/bind.2:217
793 #: build/C/man2/bind.2:220
794 msgid "The socket inode would reside on a read-only file system."
797 #. SVr4 documents an additional
799 #. general error condition, and
804 #. UNIX-domain error conditions.
806 #: build/C/man2/bind.2:232
807 msgid "SVr4, 4.4BSD, POSIX.1-2001 (B<bind>() first appeared in 4.2BSD)."
811 #: build/C/man2/bind.2:249
813 "The third argument of B<bind>() is in reality an I<int> (and this is what "
814 "4.x BSD and libc4 and libc5 have). Some POSIX confusion resulted in the "
815 "present I<socklen_t>, also used by glibc. See also B<accept>(2)."
819 #: build/C/man2/bind.2:249 build/C/man2/getsockopt.2:197 build/C/man2/select.2:423 build/C/man2/send.2:409 build/C/man3/sockatmark.3:91 build/C/man7/socket.7:729
824 #. FIXME What *are* transparent proxy options?
826 #: build/C/man2/bind.2:252
827 msgid "The transparent proxy options are not described."
831 #: build/C/man2/bind.2:257
833 "An example of the use of B<bind>() with Internet domain sockets can be "
834 "found in B<getaddrinfo>(3)."
837 #. listen.7 refers to this example.
838 #. accept.7 refers to this example.
839 #. unix.7 refers to this example.
841 #: build/C/man2/bind.2:264
843 "The following example shows how to bind a stream socket in the UNIX "
844 "(B<AF_UNIX>) domain, and accept connections:"
848 #: build/C/man2/bind.2:271
851 "#include E<lt>sys/socket.hE<gt>\n"
852 "#include E<lt>sys/un.hE<gt>\n"
853 "#include E<lt>stdlib.hE<gt>\n"
854 "#include E<lt>stdio.hE<gt>\n"
855 "#include E<lt>string.hE<gt>\n"
859 #: build/C/man2/bind.2:274
862 "#define MY_SOCK_PATH \"/somepath\"\n"
863 "#define LISTEN_BACKLOG 50\n"
867 #: build/C/man2/bind.2:277
870 "#define handle_error(msg) \\e\n"
871 " do { perror(msg); exit(EXIT_FAILURE); } while (0)\n"
875 #: build/C/man2/bind.2:284
879 "main(int argc, char *argv[])\n"
882 " struct sockaddr_un my_addr, peer_addr;\n"
883 " socklen_t peer_addr_size;\n"
887 #: build/C/man2/bind.2:288
890 " sfd = socket(AF_UNIX, SOCK_STREAM, 0);\n"
892 " handle_error(\"socket\");\n"
896 #: build/C/man2/bind.2:294
899 " memset(&my_addr, 0, sizeof(struct sockaddr_un));\n"
900 " /* Clear structure */\n"
901 " my_addr.sun_family = AF_UNIX;\n"
902 " strncpy(my_addr.sun_path, MY_SOCK_PATH,\n"
903 " sizeof(my_addr.sun_path) - 1);\n"
907 #: build/C/man2/bind.2:298
910 " if (bind(sfd, (struct sockaddr *) &my_addr,\n"
911 " sizeof(struct sockaddr_un)) == -1)\n"
912 " handle_error(\"bind\");\n"
916 #: build/C/man2/bind.2:301
919 " if (listen(sfd, LISTEN_BACKLOG) == -1)\n"
920 " handle_error(\"listen\");\n"
924 #: build/C/man2/bind.2:304
927 " /* Now we can accept incoming connections one\n"
928 " at a time using accept(2) */\n"
932 #: build/C/man2/bind.2:310
935 " peer_addr_size = sizeof(struct sockaddr_un);\n"
936 " cfd = accept(sfd, (struct sockaddr *) &peer_addr,\n"
937 " &peer_addr_size);\n"
939 " handle_error(\"accept\");\n"
943 #: build/C/man2/bind.2:312
945 msgid " /* Code to deal with incoming connection(s)... */\n"
949 #: build/C/man2/bind.2:316
952 " /* When no longer required, the socket pathname, MY_SOCK_PATH\n"
953 " should be deleted using unlink(2) or remove(3) */\n"
958 #: build/C/man2/bind.2:330
960 "B<accept>(2), B<connect>(2), B<getsockname>(2), B<listen>(2), B<socket>(2), "
961 "B<getaddrinfo>(3), B<getifaddrs>(3), B<ip>(7), B<ipv6>(7), "
962 "B<path_resolution>(7), B<socket>(7), B<unix>(7)"
966 #: build/C/man3/bindresvport.3:27
972 #: build/C/man3/bindresvport.3:27 build/C/man2/connect.2:65 build/C/man2/getsockname.2:38 build/C/man2/getsockopt.2:42 build/C/man3/sockatmark.3:23
978 #: build/C/man3/bindresvport.3:30
979 msgid "bindresvport - bind a socket to a privileged IP port"
983 #: build/C/man3/bindresvport.3:34
986 "B<#include E<lt>sys/types.hE<gt>>\n"
987 "B<#include E<lt>netinet/in.hE<gt>>\n"
991 #: build/C/man3/bindresvport.3:36
993 msgid "B<int bindresvport(int >I<sockfd>B<, struct sockaddr_in *>I<sin>B<);>\n"
996 #. Glibc actually starts searching with a port # in the range 600 to 1023
998 #: build/C/man3/bindresvport.3:43
1000 "B<bindresvport>() is used to bind a socket descriptor to a privileged "
1001 "anonymous IP port, that is, a port number arbitrarily selected from the "
1002 "range 512 to 1023."
1006 #: build/C/man3/bindresvport.3:53
1008 "If the B<bind>(2) performed by B<bindresvport>() is successful, and I<sin> "
1009 "is not NULL, then I<sin-E<gt>sin_port> returns the port number actually "
1014 #: build/C/man3/bindresvport.3:64
1016 "I<sin> can be NULL, in which case I<sin-E<gt>sin_family> is implicitly taken "
1017 "to be B<AF_INET>. However, in this case, B<bindresvport>() has no way to "
1018 "return the port number actually allocated. (This information can later be "
1019 "obtained using B<getsockname>(2).)"
1023 #: build/C/man3/bindresvport.3:69
1025 "B<bindresvport>() returns 0 on success; otherwise -1 is returned and "
1026 "I<errno> set to indicate the cause of the error."
1030 #: build/C/man3/bindresvport.3:74
1032 "B<bindresvport>() can fail for any of the same reasons as B<bind>(2). In "
1033 "addition, the following errors may occur:"
1037 #: build/C/man3/bindresvport.3:79
1039 "The caller did not have superuser privilege (to be precise: the "
1040 "B<CAP_NET_BIND_SERVICE> capability is required)."
1044 #: build/C/man3/bindresvport.3:82
1045 msgid "All privileged ports are in use."
1049 #: build/C/man3/bindresvport.3:82
1051 msgid "B<EAFNOSUPPORT> (B<EPFNOSUPPORT> in glibc 2.7 and earlier)"
1055 #: build/C/man3/bindresvport.3:89
1056 msgid "I<sin> is not NULL and I<sin-E<gt>sin_family> is not B<AF_INET>."
1060 #: build/C/man3/bindresvport.3:92
1061 msgid "Not in POSIX.1-2001. Present on the BSDs, Solaris, and many other systems."
1065 #: build/C/man3/bindresvport.3:98
1067 "Unlike some B<bindresvport>() implementations, the glibc implementation "
1068 "ignores any value that the caller supplies in I<sin-E<gt>sin_port>."
1072 #: build/C/man3/bindresvport.3:101
1073 msgid "B<bind>(2), B<getsockname>(2)"
1077 #: build/C/man2/connect.2:65
1083 #: build/C/man2/connect.2:68
1084 msgid "connect - initiate a connection on a socket"
1088 #: build/C/man2/connect.2:71 build/C/man2/getsockopt.2:48 build/C/man2/listen.2:49
1090 msgid "B<#include E<lt>sys/types.hE<gt>> /* See NOTES */\n"
1094 #: build/C/man2/connect.2:73 build/C/man2/getsockname.2:44 build/C/man2/getsockopt.2:50 build/C/man2/listen.2:51 build/C/man2/recv.2:49
1096 msgid "B<#include E<lt>sys/socket.hE<gt>>\n"
1100 #: build/C/man2/connect.2:76
1103 "B<int connect(int >I<sockfd>B<, const struct sockaddr *>I<addr>B<,>\n"
1104 "B< socklen_t >I<addrlen>B<);>\n"
1108 #: build/C/man2/connect.2:95
1110 "The B<connect>() system call connects the socket referred to by the file "
1111 "descriptor I<sockfd> to the address specified by I<addr>. The I<addrlen> "
1112 "argument specifies the size of I<addr>. The format of the address in "
1113 "I<addr> is determined by the address space of the socket I<sockfd>; see "
1114 "B<socket>(2) for further details."
1118 #: build/C/man2/connect.2:111
1120 "If the socket I<sockfd> is of type B<SOCK_DGRAM> then I<addr> is the address "
1121 "to which datagrams are sent by default, and the only address from which "
1122 "datagrams are received. If the socket is of type B<SOCK_STREAM> or "
1123 "B<SOCK_SEQPACKET>, this call attempts to make a connection to the socket "
1124 "that is bound to the address specified by I<addr>."
1128 #: build/C/man2/connect.2:125
1130 "Generally, connection-based protocol sockets may successfully B<connect>() "
1131 "only once; connectionless protocol sockets may use B<connect>() multiple "
1132 "times to change their association. Connectionless sockets may dissolve the "
1133 "association by connecting to an address with the I<sa_family> member of "
1134 "I<sockaddr> set to B<AF_UNSPEC> (supported on Linux since kernel 2.2)."
1138 #: build/C/man2/connect.2:130
1140 "If the connection or binding succeeds, zero is returned. On error, -1 is "
1141 "returned, and I<errno> is set appropriately."
1145 #: build/C/man2/connect.2:133
1147 "The following are general socket errors only. There may be other "
1148 "domain-specific error codes."
1152 #: build/C/man2/connect.2:141
1154 "For UNIX domain sockets, which are identified by pathname: Write permission "
1155 "is denied on the socket file, or search permission is denied for one of the "
1156 "directories in the path prefix. (See also B<path_resolution>(7).)"
1160 #: build/C/man2/connect.2:141
1162 msgid "B<EACCES>, B<EPERM>"
1166 #: build/C/man2/connect.2:146
1168 "The user tried to connect to a broadcast address without having the socket "
1169 "broadcast flag enabled or the connection request failed because of a local "
1174 #: build/C/man2/connect.2:149
1175 msgid "Local address is already in use."
1179 #: build/C/man2/connect.2:149 build/C/man2/socket.2:322 build/C/man2/socketpair.2:73
1181 msgid "B<EAFNOSUPPORT>"
1185 #: build/C/man2/connect.2:154
1187 "The passed address didn't have the correct address family in its "
1188 "I<sa_family> field."
1192 #: build/C/man2/connect.2:154
1198 #: build/C/man2/connect.2:163
1200 "No more free local ports or insufficient entries in the routing cache. For "
1201 "B<AF_INET> see the description of I</proc/sys/net/ipv4/ip_local_port_range> "
1202 "B<ip>(7) for information on how to increase the number of local ports."
1206 #: build/C/man2/connect.2:163
1212 #: build/C/man2/connect.2:167
1214 "The socket is nonblocking and a previous connection attempt has not yet been "
1219 #: build/C/man2/connect.2:170
1220 msgid "The file descriptor is not a valid index in the descriptor table."
1224 #: build/C/man2/connect.2:170 build/C/man2/recv.2:410
1226 msgid "B<ECONNREFUSED>"
1230 #: build/C/man2/connect.2:173
1231 msgid "No-one listening on the remote address."
1235 #: build/C/man2/connect.2:176
1236 msgid "The socket structure address is outside the user's address space."
1240 #: build/C/man2/connect.2:176
1242 msgid "B<EINPROGRESS>"
1246 #: build/C/man2/connect.2:201
1248 "The socket is nonblocking and the connection cannot be completed "
1249 "immediately. It is possible to B<select>(2) or B<poll>(2) for completion "
1250 "by selecting the socket for writing. After B<select>(2) indicates "
1251 "writability, use B<getsockopt>(2) to read the B<SO_ERROR> option at level "
1252 "B<SOL_SOCKET> to determine whether B<connect>() completed successfully "
1253 "(B<SO_ERROR> is zero) or unsuccessfully (B<SO_ERROR> is one of the usual "
1254 "error codes listed here, explaining the reason for the failure)."
1257 #. For TCP, the connection will complete asynchronously.
1258 #. See http://lkml.org/lkml/2005/7/12/254
1260 #: build/C/man2/connect.2:207
1262 "The system call was interrupted by a signal that was caught; see "
1267 #: build/C/man2/connect.2:207 build/C/man2/send.2:318
1273 #: build/C/man2/connect.2:210
1274 msgid "The socket is already connected."
1278 #: build/C/man2/connect.2:210
1280 msgid "B<ENETUNREACH>"
1284 #: build/C/man2/connect.2:213
1285 msgid "Network is unreachable."
1289 #: build/C/man2/connect.2:216
1290 msgid "The file descriptor is not associated with a socket."
1294 #: build/C/man2/connect.2:216
1296 msgid "B<ETIMEDOUT>"
1300 #: build/C/man2/connect.2:223
1302 "Timeout while attempting connection. The server may be too busy to accept "
1303 "new connections. Note that for IP sockets the timeout may be very long when "
1304 "syncookies are enabled on the server."
1307 #. SVr4 documents the additional
1308 #. general error codes
1309 #. .BR EADDRNOTAVAIL ,
1311 #. .BR EAFNOSUPPORT ,
1318 #. documents many additional error conditions not described here.
1320 #: build/C/man2/connect.2:239
1322 "SVr4, 4.4BSD, (the B<connect>() function first appeared in 4.2BSD), "
1327 #: build/C/man2/connect.2:256
1329 "The third argument of B<connect>() is in reality an I<int> (and this is "
1330 "what 4.x BSD and libc4 and libc5 have). Some POSIX confusion resulted in "
1331 "the present I<socklen_t>, also used by glibc. See also B<accept>(2)."
1335 #: build/C/man2/connect.2:261
1336 msgid "An example of the use of B<connect>() is shown in B<getaddrinfo>(3)."
1340 #: build/C/man2/connect.2:268
1342 "B<accept>(2), B<bind>(2), B<getsockname>(2), B<listen>(2), B<socket>(2), "
1343 "B<path_resolution>(7)"
1347 #: build/C/man3/getifaddrs.3:33
1353 #: build/C/man3/getifaddrs.3:33
1359 #: build/C/man3/getifaddrs.3:33
1365 #: build/C/man3/getifaddrs.3:36
1366 msgid "getifaddrs, freeifaddrs - get interface addresses"
1370 #: build/C/man3/getifaddrs.3:40
1373 "B<#include E<lt>sys/types.hE<gt>>\n"
1374 "B<#include E<lt>ifaddrs.hE<gt>>\n"
1378 #: build/C/man3/getifaddrs.3:42
1380 msgid "B<int getifaddrs(struct ifaddrs **>I<ifap>B<);>\n"
1384 #: build/C/man3/getifaddrs.3:44
1386 msgid "B<void freeifaddrs(struct ifaddrs *>I<ifa>B<);>\n"
1390 #: build/C/man3/getifaddrs.3:55
1392 "The B<getifaddrs>() function creates a linked list of structures describing "
1393 "the network interfaces of the local system, and stores the address of the "
1394 "first item of the list in I<*ifap>. The list consists of I<ifaddrs> "
1395 "structures, defined as follows:"
1399 #: build/C/man3/getifaddrs.3:74
1402 "struct ifaddrs {\n"
1403 " struct ifaddrs *ifa_next; /* Next item in list */\n"
1404 " char *ifa_name; /* Name of interface */\n"
1405 " unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */\n"
1406 " struct sockaddr *ifa_addr; /* Address of interface */\n"
1407 " struct sockaddr *ifa_netmask; /* Netmask of interface */\n"
1409 " struct sockaddr *ifu_broadaddr;\n"
1410 " /* Broadcast address of interface */\n"
1411 " struct sockaddr *ifu_dstaddr;\n"
1412 " /* Point-to-point destination address */\n"
1414 "#define ifa_broadaddr ifa_ifu.ifu_broadaddr\n"
1415 "#define ifa_dstaddr ifa_ifu.ifu_dstaddr\n"
1416 " void *ifa_data; /* Address-specific data */\n"
1421 #: build/C/man3/getifaddrs.3:81
1423 "The I<ifa_next> field contains a pointer to the next structure on the list, "
1424 "or NULL if this is the last item of the list."
1429 #. indicates the maximum length of this field.
1431 #: build/C/man3/getifaddrs.3:88
1432 msgid "The I<ifa_name> points to the null-terminated interface name."
1436 #: build/C/man3/getifaddrs.3:97
1438 "The I<ifa_flags> field contains the interface flags, as returned by the "
1439 "B<SIOCGIFFLAGS> B<ioctl>(2) operation (see B<netdevice>(7) for a list of "
1444 #: build/C/man3/getifaddrs.3:105
1446 "The I<ifa_addr> field points to a structure containing the interface "
1447 "address. (The I<sa_family> subfield should be consulted to determine the "
1448 "format of the address structure.)"
1452 #: build/C/man3/getifaddrs.3:111
1454 "The I<ifa_netmask> field points to a structure containing the netmask "
1455 "associated with I<ifa_addr>, if applicable for the address family."
1459 #: build/C/man3/getifaddrs.3:126
1461 "Depending on whether the bit B<IFF_BROADCAST> or B<IFF_POINTOPOINT> is set "
1462 "in I<ifa_flags> (only one can be set at a time), either I<ifa_broadaddr> "
1463 "will contain the broadcast address associated with I<ifa_addr> (if "
1464 "applicable for the address family) or I<ifa_dstaddr> will contain the "
1465 "destination address of the point-to-point interface."
1469 #: build/C/man3/getifaddrs.3:131
1471 "The I<ifa_data> field points to a buffer containing address-family-specific "
1472 "data; this field may be NULL if there is no such data for this interface."
1476 #: build/C/man3/getifaddrs.3:137
1478 "The data returned by B<getifaddrs>() is dynamically allocated and should be "
1479 "freed using B<freeifaddrs>() when no longer needed."
1483 #: build/C/man3/getifaddrs.3:137
1485 msgid "RETURN VALUES"
1489 #: build/C/man3/getifaddrs.3:144
1491 "On success, B<getifaddrs>() returns zero; on error, -1 is returned, and "
1492 "I<errno> is set appropriately."
1496 #: build/C/man3/getifaddrs.3:157
1498 "B<getifaddrs>() may fail and set I<errno> for any of the errors specified "
1499 "for B<socket>(2), B<bind>(2), B<getsockname>(2), B<recvmsg>(2), "
1500 "B<sendto>(2), B<malloc>(3), or B<realloc>(3)."
1504 #: build/C/man3/getifaddrs.3:165
1506 "The B<getifaddrs>() function first appeared in glibc 2.3, but before glibc "
1507 "2.3.3, the implementation only supported IPv4 addresses; IPv6 support was "
1508 "added in glibc 2.3.3. Support of address families other than IPv4 is only "
1509 "available on kernels that support netlink."
1512 #. , but the BSD-derived documentation generally
1513 #. appears to be confused and obsolete on this point.
1514 #. i.e., commonly it still says one of them will be NULL, even if
1515 #. the ifa_ifu union is already present
1517 #: build/C/man3/getifaddrs.3:185
1519 "Not in POSIX.1-2001. This function first appeared in BSDi and is present on "
1520 "the BSD systems, but with slightly different semantics "
1521 "documented\\(emreturning one entry per interface, not per address. This "
1522 "means I<ifa_addr> and other fields can actually be NULL if the interface has "
1523 "no address, and no link-level address is returned if the interface has an IP "
1524 "address assigned. Also, the way of choosing either I<ifa_broadaddr> or "
1525 "I<ifa_dstaddr> differs on various systems."
1529 #: build/C/man3/getifaddrs.3:198
1531 "The addresses returned on Linux will usually be the IPv4 and IPv6 addresses "
1532 "assigned to the interface, but also one B<AF_PACKET> address per interface "
1533 "containing lower-level details about the interface and its physical layer. "
1534 "In this case, the I<ifa_data> field may contain a pointer to a I<struct "
1535 "net_device_stats>, defined in I<E<lt>linux/netdevice.hE<gt>>, which contains "
1536 "various interface attributes and statistics."
1540 #: build/C/man3/getifaddrs.3:205
1542 "The program below demonstrates the use of B<getifaddrs>(), B<freeifaddrs>(), "
1543 "and B<getnameinfo>(3). Here is what we see when running this program on one "
1548 #: build/C/man3/getifaddrs.3:219
1552 "lo address family: 17 (AF_PACKET)\n"
1553 "eth0 address family: 17 (AF_PACKET)\n"
1554 "lo address family: 2 (AF_INET)\n"
1555 " address: E<lt>127.0.0.1E<gt>\n"
1556 "eth0 address family: 2 (AF_INET)\n"
1557 " address: E<lt>10.1.1.4E<gt>\n"
1558 "lo address family: 10 (AF_INET6)\n"
1559 " address: E<lt>::1E<gt>\n"
1560 "eth0 address family: 10 (AF_INET6)\n"
1561 " address: E<lt>fe80::2d0:59ff:feda:eb51%eth0E<gt>\n"
1565 #: build/C/man3/getifaddrs.3:221
1567 msgid "Program source"
1571 #: build/C/man3/getifaddrs.3:231
1574 "#include E<lt>arpa/inet.hE<gt>\n"
1575 "#include E<lt>sys/socket.hE<gt>\n"
1576 "#include E<lt>netdb.hE<gt>\n"
1577 "#include E<lt>ifaddrs.hE<gt>\n"
1578 "#include E<lt>stdio.hE<gt>\n"
1579 "#include E<lt>stdlib.hE<gt>\n"
1580 "#include E<lt>unistd.hE<gt>\n"
1584 #: build/C/man3/getifaddrs.3:238
1588 "main(int argc, char *argv[])\n"
1590 " struct ifaddrs *ifaddr, *ifa;\n"
1592 " char host[NI_MAXHOST];\n"
1596 #: build/C/man3/getifaddrs.3:243
1599 " if (getifaddrs(&ifaddr) == -1) {\n"
1600 " perror(\"getifaddrs\");\n"
1601 " exit(EXIT_FAILURE);\n"
1606 #: build/C/man3/getifaddrs.3:246
1609 " /* Walk through linked list, maintaining head pointer so we\n"
1610 " can free list later */\n"
1614 #: build/C/man3/getifaddrs.3:250
1617 " for (ifa = ifaddr; ifa != NULL; ifa = ifa-E<gt>ifa_next) {\n"
1618 " if (ifa-E<gt>ifa_addr == NULL)\n"
1623 #: build/C/man3/getifaddrs.3:252
1625 msgid " family = ifa-E<gt>ifa_addr-E<gt>sa_family;\n"
1629 #: build/C/man3/getifaddrs.3:255
1632 " /* Display interface name and family (including symbolic\n"
1633 " form of the latter for the common families) */\n"
1637 #: build/C/man3/getifaddrs.3:261
1640 " printf(\"%s\\t address family: %d%s\\en\",\n"
1641 " ifa-E<gt>ifa_name, family,\n"
1642 " (family == AF_PACKET) ? \" (AF_PACKET)\" :\n"
1643 " (family == AF_INET) ? \" (AF_INET)\" :\n"
1644 " (family == AF_INET6) ? \" (AF_INET6)\" : \"\");\n"
1648 #: build/C/man3/getifaddrs.3:263
1650 msgid " /* For an AF_INET* interface address, display the address */\n"
1654 #: build/C/man3/getifaddrs.3:276
1657 " if (family == AF_INET || family == AF_INET6) {\n"
1658 " s = getnameinfo(ifa-E<gt>ifa_addr,\n"
1659 " (family == AF_INET) ? sizeof(struct sockaddr_in) :\n"
1660 " sizeof(struct sockaddr_in6),\n"
1661 " host, NI_MAXHOST, NULL, 0, NI_NUMERICHOST);\n"
1663 " printf(\"getnameinfo() failed: %s\\en\", gai_strerror(s));\n"
1664 " exit(EXIT_FAILURE);\n"
1666 " printf(\"\\etaddress: E<lt>%sE<gt>\\en\", host);\n"
1672 #: build/C/man3/getifaddrs.3:280
1675 " freeifaddrs(ifaddr);\n"
1676 " exit(EXIT_SUCCESS);\n"
1681 #: build/C/man3/getifaddrs.3:287
1682 msgid "B<bind>(2), B<getsockname>(2), B<socket>(2), B<packet>(7), B<ifconfig>(8)"
1686 #: build/C/man2/getsockname.2:38
1692 #: build/C/man2/getsockname.2:41
1693 msgid "getsockname - get socket name"
1697 #: build/C/man2/getsockname.2:47
1700 "B<int getsockname(int >I<sockfd>B<, struct sockaddr *>I<addr>B<, socklen_t "
1701 "*>I<addrlen>B<);>\n"
1705 #: build/C/man2/getsockname.2:60
1707 "B<getsockname>() returns the current address to which the socket I<sockfd> "
1708 "is bound, in the buffer pointed to by I<addr>. The I<addrlen> argument "
1709 "should be initialized to indicate the amount of space (in bytes) pointed to "
1710 "by I<addr>. On return it contains the actual size of the socket address."
1714 #: build/C/man2/getsockname.2:76 build/C/man2/getsockopt.2:140 build/C/man2/listen.2:94
1715 msgid "The argument I<sockfd> is not a valid descriptor."
1719 #: build/C/man2/getsockname.2:82
1721 "The I<addr> argument points to memory not in a valid part of the process "
1726 #: build/C/man2/getsockname.2:86
1727 msgid "I<addrlen> is invalid (e.g., is negative)."
1731 #: build/C/man2/getsockname.2:86 build/C/man2/send.2:330
1737 #: build/C/man2/getsockname.2:90
1739 "Insufficient resources were available in the system to perform the "
1744 #: build/C/man2/getsockname.2:95 build/C/man2/getsockopt.2:169
1745 msgid "The argument I<sockfd> is a file, not a socket."
1748 #. SVr4 documents additional ENOMEM
1749 #. and ENOSR error codes.
1751 #: build/C/man2/getsockname.2:101
1753 "SVr4, 4.4BSD (the B<getsockname>() function call appeared in 4.2BSD), "
1758 #: build/C/man2/getsockname.2:110
1760 "The third argument of B<getsockname>() is in reality an I<int *> (and this "
1761 "is what 4.x BSD and libc4 and libc5 have). Some POSIX confusion resulted in "
1762 "the present I<socklen_t>, also used by glibc. See also B<accept>(2)."
1766 #: build/C/man2/getsockname.2:117
1768 "B<bind>(2), B<socket>(2), B<getifaddrs>(3), B<ip>(7), B<socket>(7), "
1773 #: build/C/man2/getsockopt.2:42
1779 #: build/C/man2/getsockopt.2:45
1780 msgid "getsockopt, setsockopt - get and set options on sockets"
1784 #: build/C/man2/getsockopt.2:55
1787 "B<int getsockopt(int >I<sockfd>B<, int >I<level>B<, int >I<optname>B<,>\n"
1788 "B< void *>I<optval>B<, socklen_t *>I<optlen>B<);>\n"
1789 "B<int setsockopt(int >I<sockfd>B<, int >I<level>B<, int >I<optname>B<,>\n"
1790 "B< const void *>I<optval>B<, socklen_t >I<optlen>B<);>\n"
1794 #: build/C/man2/getsockopt.2:65
1796 "B<getsockopt>() and B<setsockopt>() manipulate options for the socket "
1797 "referred to by the file descriptor I<sockfd>. Options may exist at multiple "
1798 "protocol levels; they are always present at the uppermost socket level."
1802 #: build/C/man2/getsockopt.2:84
1804 "When manipulating socket options, the level at which the option resides and "
1805 "the name of the option must be specified. To manipulate options at the "
1806 "sockets API level, I<level> is specified as B<SOL_SOCKET>. To manipulate "
1807 "options at any other level the protocol number of the appropriate protocol "
1808 "controlling the option is supplied. For example, to indicate that an option "
1809 "is to be interpreted by the B<TCP> protocol, I<level> should be set to the "
1810 "protocol number of B<TCP>; see B<getprotoent>(3)."
1814 #: build/C/man2/getsockopt.2:106
1816 "The arguments I<optval> and I<optlen> are used to access option values for "
1817 "B<setsockopt>(). For B<getsockopt>() they identify a buffer in which the "
1818 "value for the requested option(s) are to be returned. For B<getsockopt>(), "
1819 "I<optlen> is a value-result argument, initially containing the size of the "
1820 "buffer pointed to by I<optval>, and modified on return to indicate the "
1821 "actual size of the value returned. If no option value is to be supplied or "
1822 "returned, I<optval> may be NULL."
1826 #: build/C/man2/getsockopt.2:116
1828 "I<Optname> and any specified options are passed uninterpreted to the "
1829 "appropriate protocol module for interpretation. The include file "
1830 "I<E<lt>sys/socket.hE<gt>> contains definitions for socket level options, "
1831 "described below. Options at other protocol levels vary in format and name; "
1832 "consult the appropriate entries in section 4 of the manual."
1836 #: build/C/man2/getsockopt.2:125
1838 "Most socket-level options utilize an I<int> argument for I<optval>. For "
1839 "B<setsockopt>(), the argument should be nonzero to enable a boolean option, "
1840 "or zero if the option is to be disabled."
1844 #: build/C/man2/getsockopt.2:129
1846 "For a description of the available socket options see B<socket>(7) and the "
1847 "appropriate protocol man pages."
1851 #: build/C/man2/getsockopt.2:150
1853 "The address pointed to by I<optval> is not in a valid part of the process "
1854 "address space. For B<getsockopt>(), this error may also be returned if "
1855 "I<optlen> is not in a valid part of the process address space."
1859 #: build/C/man2/getsockopt.2:161
1861 "I<optlen> invalid in B<setsockopt>(). In some cases this error can also "
1862 "occur for an invalid value in I<optval> (e.g., for the B<IP_ADD_MEMBERSHIP> "
1863 "option described in B<ip>(7))."
1867 #: build/C/man2/getsockopt.2:161
1869 msgid "B<ENOPROTOOPT>"
1873 #: build/C/man2/getsockopt.2:164
1874 msgid "The option is unknown at the level indicated."
1877 #. SVr4 documents additional ENOMEM and ENOSR error codes, but does
1879 #. .BR SO_SNDLOWAT ", " SO_RCVLOWAT ", " SO_SNDTIMEO ", " SO_RCVTIMEO
1882 #: build/C/man2/getsockopt.2:176
1883 msgid "SVr4, 4.4BSD (these system calls first appeared in 4.2BSD), POSIX.1-2001."
1887 #: build/C/man2/getsockopt.2:197
1889 "The I<optlen> argument of B<getsockopt>() and B<setsockopt>() is in "
1890 "reality an I<int [*]> (and this is what 4.x BSD and libc4 and libc5 have). "
1891 "Some POSIX confusion resulted in the present I<socklen_t>, also used by "
1892 "glibc. See also B<accept>(2)."
1896 #: build/C/man2/getsockopt.2:200
1898 "Several of the socket options should be handled at lower levels of the "
1903 #: build/C/man2/getsockopt.2:208
1905 "B<ioctl>(2), B<socket>(2), B<getprotoent>(3), B<protocols>(5), B<socket>(7), "
1906 "B<tcp>(7), B<unix>(7)"
1910 #: build/C/man2/listen.2:43
1916 #: build/C/man2/listen.2:43
1922 #: build/C/man2/listen.2:46
1923 msgid "listen - listen for connections on a socket"
1927 #: build/C/man2/listen.2:53
1929 msgid "B<int listen(int >I<sockfd>B<, int >I<backlog>B<);>\n"
1933 #: build/C/man2/listen.2:61
1935 "B<listen>() marks the socket referred to by I<sockfd> as a passive socket, "
1936 "that is, as a socket that will be used to accept incoming connection "
1937 "requests using B<accept>(2)."
1941 #: build/C/man2/listen.2:68
1943 "The I<sockfd> argument is a file descriptor that refers to a socket of type "
1944 "B<SOCK_STREAM> or B<SOCK_SEQPACKET>."
1948 #: build/C/man2/listen.2:80
1950 "The I<backlog> argument defines the maximum length to which the queue of "
1951 "pending connections for I<sockfd> may grow. If a connection request arrives "
1952 "when the queue is full, the client may receive an error with an indication "
1953 "of B<ECONNREFUSED> or, if the underlying protocol supports retransmission, "
1954 "the request may be ignored so that a later reattempt at connection succeeds."
1958 #: build/C/man2/listen.2:89
1959 msgid "Another socket is already listening on the same port."
1963 #: build/C/man2/listen.2:99 build/C/man2/send.2:349
1964 msgid "The argument I<sockfd> is not a socket."
1968 #: build/C/man2/listen.2:104
1969 msgid "The socket is not of a type that supports the B<listen>() operation."
1973 #: build/C/man2/listen.2:109
1975 "4.4BSD, POSIX.1-2001. The B<listen>() function call first appeared in "
1980 #: build/C/man2/listen.2:111
1981 msgid "To accept connections, the following steps are performed:"
1985 #: build/C/man2/listen.2:112 build/C/man2/select_tut.2:345
1991 #: build/C/man2/listen.2:115
1992 msgid "A socket is created with B<socket>(2)."
1996 #: build/C/man2/listen.2:115 build/C/man2/select_tut.2:354
2002 #: build/C/man2/listen.2:121
2004 "The socket is bound to a local address using B<bind>(2), so that other "
2005 "sockets may be B<connect>(2)ed to it."
2009 #: build/C/man2/listen.2:121 build/C/man2/select_tut.2:358
2015 #: build/C/man2/listen.2:125
2017 "A willingness to accept incoming connections and a queue limit for incoming "
2018 "connections are specified with B<listen>()."
2022 #: build/C/man2/listen.2:125 build/C/man2/select_tut.2:365
2028 #: build/C/man2/listen.2:128
2029 msgid "Connections are accepted with B<accept>(2)."
2033 #: build/C/man2/listen.2:151
2035 "The behavior of the I<backlog> argument on TCP sockets changed with Linux "
2036 "2.2. Now it specifies the queue length for I<completely> established "
2037 "sockets waiting to be accepted, instead of the number of incomplete "
2038 "connection requests. The maximum length of the queue for incomplete sockets "
2039 "can be set using I</proc/sys/net/ipv4/tcp_max_syn_backlog>. When syncookies "
2040 "are enabled there is no logical maximum length and this setting is ignored. "
2041 "See B<tcp>(7) for more information."
2044 #. The following is now rather historic information (MTK, Jun 05)
2045 #. Don't rely on this value in portable applications since BSD
2046 #. (and some BSD-derived systems) limit the backlog to 5.
2048 #: build/C/man2/listen.2:164
2050 "If the I<backlog> argument is greater than the value in "
2051 "I</proc/sys/net/core/somaxconn>, then it is silently truncated to that "
2052 "value; the default value in this file is 128. In kernels before 2.4.25, "
2053 "this limit was a hard coded value, B<SOMAXCONN>, with the value 128."
2057 #: build/C/man2/listen.2:173
2058 msgid "B<accept>(2), B<bind>(2), B<connect>(2), B<socket>(2), B<socket>(7)"
2062 #: build/C/man2/recv.2:39
2068 #: build/C/man2/recv.2:39
2074 #: build/C/man2/recv.2:42
2075 msgid "recv, recvfrom, recvmsg - receive a message from a socket"
2079 #: build/C/man2/recv.2:47 build/C/man2/select.2:53 build/C/man2/select_tut.2:45
2081 msgid "B<#include E<lt>sys/types.hE<gt>>\n"
2085 #: build/C/man2/recv.2:51
2088 "B<ssize_t recv(int >I<sockfd>B<, void *>I<buf>B<, size_t >I<len>B<, int "
2093 #: build/C/man2/recv.2:54
2096 "B<ssize_t recvfrom(int >I<sockfd>B<, void *>I<buf>B<, size_t >I<len>B<, int "
2098 "B< struct sockaddr *>I<src_addr>B<, socklen_t "
2099 "*>I<addrlen>B<);>\n"
2103 #: build/C/man2/recv.2:56
2106 "B<ssize_t recvmsg(int >I<sockfd>B<, struct msghdr *>I<msg>B<, int "
2111 #: build/C/man2/recv.2:64
2113 "The B<recvfrom>() and B<recvmsg>() calls are used to receive messages from "
2114 "a socket, and may be used to receive data on a socket whether or not it is "
2115 "connection-oriented."
2118 #. (Note: for datagram sockets in both the UNIX and Internet domains,
2122 #. is also filled in for stream sockets in the UNIX domain, but is not
2123 #. filled in for stream sockets in the Internet domain.)
2124 #. [The above notes on AF_UNIX and AF_INET sockets apply as at
2125 #. Kernel 2.4.18. (MTK, 22 Jul 02)]
2127 #: build/C/man2/recv.2:93
2129 "If I<src_addr> is not NULL, and the underlying protocol provides the source "
2130 "address, this source address is filled in. When I<src_addr> is NULL, "
2131 "nothing is filled in; in this case, I<addrlen> is not used, and should also "
2132 "be NULL. The argument I<addrlen> is a value-result argument, which the "
2133 "caller should initialize before the call to the size of the buffer "
2134 "associated with I<src_addr>, and modified on return to indicate the actual "
2135 "size of the source address. The returned address is truncated if the buffer "
2136 "provided is too small; in this case, I<addrlen> will return a value greater "
2137 "than was supplied to the call."
2141 #: build/C/man2/recv.2:105
2143 "The B<recv>() call is normally used only on a I<connected> socket (see "
2144 "B<connect>(2)) and is identical to B<recvfrom>() with a NULL I<src_addr> "
2149 #: build/C/man2/recv.2:111
2151 "All three routines return the length of the message on successful "
2152 "completion. If a message is too long to fit in the supplied buffer, excess "
2153 "bytes may be discarded depending on the type of socket the message is "
2158 #: build/C/man2/recv.2:121
2160 "If no messages are available at the socket, the receive calls wait for a "
2161 "message to arrive, unless the socket is nonblocking (see B<fcntl>(2)), in "
2162 "which case the value -1 is returned and the external variable I<errno> is "
2163 "set to B<EAGAIN> or B<EWOULDBLOCK>. The receive calls normally return any "
2164 "data available, up to the requested amount, rather than waiting for receipt "
2165 "of the full amount requested."
2169 #: build/C/man2/recv.2:127
2171 "The B<select>(2) or B<poll>(2) call may be used to determine when more "
2176 #: build/C/man2/recv.2:133
2178 "The I<flags> argument to a B<recv>() call is formed by ORing one or more of "
2179 "the following values:"
2183 #: build/C/man2/recv.2:133
2185 msgid "B<MSG_CMSG_CLOEXEC> (B<recvmsg>() only; since Linux 2.6.23)"
2189 #: build/C/man2/recv.2:144
2191 "Set the close-on-exec flag for the file descriptor received via a UNIX "
2192 "domain file descriptor using the B<SCM_RIGHTS> operation (described in "
2193 "B<unix>(7)). This flag is useful for the same reasons as the B<O_CLOEXEC> "
2194 "flag of B<open>(2)."
2198 #: build/C/man2/recv.2:144 build/C/man2/send.2:186
2200 msgid "B<MSG_DONTWAIT> (since Linux 2.2)"
2204 #: build/C/man2/recv.2:154
2206 "Enables nonblocking operation; if the operation would block, the call fails "
2207 "with the error B<EAGAIN> or B<EWOULDBLOCK> (this can also be enabled using "
2208 "the B<O_NONBLOCK> flag with the B<F_SETFL> B<fcntl>(2))."
2212 #: build/C/man2/recv.2:154
2214 msgid "B<MSG_ERRQUEUE> (since Linux 2.2)"
2218 #: build/C/man2/recv.2:173
2220 "This flag specifies that queued errors should be received from the socket "
2221 "error queue. The error is passed in an ancillary message with a type "
2222 "dependent on the protocol (for IPv4 B<IP_RECVERR>). The user should supply "
2223 "a buffer of sufficient size. See B<cmsg>(3) and B<ip>(7) for more "
2224 "information. The payload of the original packet that caused the error is "
2225 "passed as normal data via I<msg_iovec>. The original destination address of "
2226 "the datagram that caused the error is supplied via I<msg_name>."
2230 #: build/C/man2/recv.2:185 build/C/man2/recv.2:248
2232 "For local errors, no address is passed (this can be checked with the "
2233 "I<cmsg_len> member of the I<cmsghdr>). For error receives, the "
2234 "B<MSG_ERRQUEUE> is set in the I<msghdr>. After an error has been passed, "
2235 "the pending socket error is regenerated based on the next queued error and "
2236 "will be passed on the next socket operation."
2240 #: build/C/man2/recv.2:189
2241 msgid "The error is supplied in a I<sock_extended_err> structure:"
2245 #: build/C/man2/recv.2:196
2248 "#define SO_EE_ORIGIN_NONE 0\n"
2249 "#define SO_EE_ORIGIN_LOCAL 1\n"
2250 "#define SO_EE_ORIGIN_ICMP 2\n"
2251 "#define SO_EE_ORIGIN_ICMP6 3\n"
2255 #: build/C/man2/recv.2:208
2258 "struct sock_extended_err\n"
2260 " uint32_t ee_errno; /* error number */\n"
2261 " uint8_t ee_origin; /* where the error originated */\n"
2262 " uint8_t ee_type; /* type */\n"
2263 " uint8_t ee_code; /* code */\n"
2264 " uint8_t ee_pad; /* padding */\n"
2265 " uint32_t ee_info; /* additional information */\n"
2266 " uint32_t ee_data; /* other data */\n"
2267 " /* More data may follow */\n"
2272 #: build/C/man2/recv.2:210
2274 msgid "struct sockaddr *SO_EE_OFFENDER(struct sock_extended_err *);\n"
2278 #: build/C/man2/recv.2:234
2280 "I<ee_errno> contains the I<errno> number of the queued error. I<ee_origin> "
2281 "is the origin code of where the error originated. The other fields are "
2282 "protocol-specific. The macro B<SOCK_EE_OFFENDER> returns a pointer to the "
2283 "address of the network object where the error originated from given a "
2284 "pointer to the ancillary message. If this address is not known, the "
2285 "I<sa_family> member of the I<sockaddr> contains B<AF_UNSPEC> and the other "
2286 "fields of the I<sockaddr> are undefined. The payload of the packet that "
2287 "caused the error is passed as normal data."
2291 #: build/C/man2/recv.2:248 build/C/man2/recv.2:379 build/C/man2/send.2:228
2297 #: build/C/man2/recv.2:255
2299 "This flag requests receipt of out-of-band data that would not be received in "
2300 "the normal data stream. Some protocols place expedited data at the head of "
2301 "the normal data queue, and thus this flag cannot be used with such "
2306 #: build/C/man2/recv.2:255
2312 #: build/C/man2/recv.2:262
2314 "This flag causes the receive operation to return data from the beginning of "
2315 "the receive queue without removing that data from the queue. Thus, a "
2316 "subsequent receive call will return the same data."
2320 #: build/C/man2/recv.2:262
2322 msgid "B<MSG_TRUNC> (since Linux 2.2)"
2326 #: build/C/man2/recv.2:273
2328 "For raw (B<AF_PACKET>), Internet datagram (since Linux 2.4.27/2.6.8), and "
2329 "netlink (since Linux 2.6.22) sockets: return the real length of the packet "
2330 "or datagram, even when it was longer than the passed buffer. Not "
2331 "implemented for UNIX domain (B<unix>(7)) sockets."
2335 #: build/C/man2/recv.2:276
2336 msgid "For use with Internet stream sockets, see B<tcp>(7)."
2340 #: build/C/man2/recv.2:276
2342 msgid "B<MSG_WAITALL> (since Linux 2.2)"
2346 #: build/C/man2/recv.2:283
2348 "This flag requests that the operation block until the full request is "
2349 "satisfied. However, the call may still return less data than requested if a "
2350 "signal is caught, an error or disconnect occurs, or the next data to be "
2351 "received is of a different type than that returned."
2355 #: build/C/man2/recv.2:291
2357 "The B<recvmsg>() call uses a I<msghdr> structure to minimize the number of "
2358 "directly supplied arguments. This structure is defined as follows in "
2359 "I<E<lt>sys/socket.hE<gt>>:"
2363 #: build/C/man2/recv.2:298
2366 "struct iovec { /* Scatter/gather array items */\n"
2367 " void *iov_base; /* Starting address */\n"
2368 " size_t iov_len; /* Number of bytes to transfer */\n"
2373 #: build/C/man2/recv.2:308 build/C/man2/send.2:256
2377 " void *msg_name; /* optional address */\n"
2378 " socklen_t msg_namelen; /* size of address */\n"
2379 " struct iovec *msg_iov; /* scatter/gather array */\n"
2380 " size_t msg_iovlen; /* # elements in msg_iov */\n"
2381 " void *msg_control; /* ancillary data, see below */\n"
2382 " size_t msg_controllen; /* ancillary data buffer len */\n"
2383 " int msg_flags; /* flags on received message */\n"
2388 #: build/C/man2/recv.2:338
2390 "Here I<msg_name> and I<msg_namelen> specify the source address if the socket "
2391 "is unconnected; I<msg_name> may be given as a NULL pointer if no names are "
2392 "desired or required. The fields I<msg_iov> and I<msg_iovlen> describe "
2393 "scatter-gather locations, as discussed in B<readv>(2). The field "
2394 "I<msg_control>, which has length I<msg_controllen>, points to a buffer for "
2395 "other protocol control-related messages or miscellaneous ancillary data. "
2396 "When B<recvmsg>() is called, I<msg_controllen> should contain the length of "
2397 "the available buffer in I<msg_control>; upon return from a successful call "
2398 "it will contain the length of the control message sequence."
2402 #: build/C/man2/recv.2:340
2403 msgid "The messages are of the form:"
2407 #: build/C/man2/recv.2:350
2410 "struct cmsghdr {\n"
2411 " socklen_t cmsg_len; /* data byte count, including hdr */\n"
2412 " int cmsg_level; /* originating protocol */\n"
2413 " int cmsg_type; /* protocol-specific type */\n"
2415 " unsigned char cmsg_data[]; */\n"
2420 #: build/C/man2/recv.2:355
2421 msgid "Ancillary data should only be accessed by the macros defined in B<cmsg>(3)."
2425 #: build/C/man2/recv.2:358
2427 "As an example, Linux uses this ancillary data mechanism to pass extended "
2428 "errors, IP options, or file descriptors over UNIX domain sockets."
2432 #: build/C/man2/recv.2:366
2434 "The I<msg_flags> field in the I<msghdr> is set on return of B<recvmsg>(). "
2435 "It can contain several flags:"
2439 #: build/C/man2/recv.2:366
2445 #: build/C/man2/recv.2:371
2447 "indicates end-of-record; the data returned completed a record (generally "
2448 "used with sockets of type B<SOCK_SEQPACKET>)."
2452 #: build/C/man2/recv.2:371
2454 msgid "B<MSG_TRUNC>"
2458 #: build/C/man2/recv.2:375
2460 "indicates that the trailing portion of a datagram was discarded because the "
2461 "datagram was larger than the buffer supplied."
2465 #: build/C/man2/recv.2:375
2467 msgid "B<MSG_CTRUNC>"
2471 #: build/C/man2/recv.2:379
2473 "indicates that some control data were discarded due to lack of space in the "
2474 "buffer for ancillary data."
2478 #: build/C/man2/recv.2:382
2479 msgid "is returned to indicate that expedited or out-of-band data were received."
2483 #: build/C/man2/recv.2:382
2485 msgid "B<MSG_ERRQUEUE>"
2489 #: build/C/man2/recv.2:386
2491 "indicates that no data was received but an extended error from the socket "
2496 #: build/C/man2/recv.2:391
2498 "These calls return the number of bytes received, or -1 if an error "
2499 "occurred. The return value will be 0 when the peer has performed an orderly "
2504 #: build/C/man2/recv.2:396
2506 "These are some standard errors generated by the socket layer. Additional "
2507 "errors may be generated and returned from the underlying protocol modules; "
2508 "see their manual pages."
2511 #. Actually EAGAIN on Linux
2513 #: build/C/man2/recv.2:405
2515 "The socket is marked nonblocking and the receive operation would block, or a "
2516 "receive timeout had been set and the timeout expired before data was "
2517 "received. POSIX.1-2001 allows either error to be returned for this case, "
2518 "and does not require these constants to have the same value, so a portable "
2519 "application should check for both possibilities."
2523 #: build/C/man2/recv.2:410
2524 msgid "The argument I<sockfd> is an invalid descriptor."
2528 #: build/C/man2/recv.2:414
2530 "A remote host refused to allow the network connection (typically because it "
2531 "is not running the requested service)."
2535 #: build/C/man2/recv.2:418
2536 msgid "The receive buffer pointer(s) point outside the process's address space."
2540 #: build/C/man2/recv.2:423
2542 "The receive was interrupted by delivery of a signal before any data were "
2543 "available; see B<signal>(7)."
2547 #: build/C/man2/recv.2:427 build/C/man2/send.2:318
2548 msgid "Invalid argument passed."
2552 #: build/C/man2/recv.2:431
2553 msgid "Could not allocate memory for B<recvmsg>()."
2557 #: build/C/man2/recv.2:431 build/C/man2/send.2:341
2563 #: build/C/man2/recv.2:438
2565 "The socket is associated with a connection-oriented protocol and has not "
2566 "been connected (see B<connect>(2) and B<accept>(2))."
2570 #: build/C/man2/recv.2:443
2571 msgid "The argument I<sockfd> does not refer to a socket."
2575 #: build/C/man2/recv.2:446
2576 msgid "4.4BSD (these function calls first appeared in 4.2BSD), POSIX.1-2001."
2580 #: build/C/man2/recv.2:453
2582 "POSIX.1-2001 only describes the B<MSG_OOB>, B<MSG_PEEK>, and B<MSG_WAITALL> "
2587 #: build/C/man2/recv.2:469
2589 "The prototypes given above follow glibc2. The Single UNIX Specification "
2590 "agrees, except that it has return values of type I<ssize_t> (while 4.x BSD "
2591 "and libc4 and libc5 all have I<int>). The I<flags> argument is I<int> in "
2592 "4.x BSD, but I<unsigned int> in libc4 and libc5. The I<len> argument is "
2593 "I<int> in 4.x BSD, but I<size_t> in libc4 and libc5. The I<addrlen> "
2594 "argument is I<int\\ *> in 4.x BSD, libc4 and libc5. The present "
2595 "I<socklen_t\\ *> was invented by POSIX. See also B<accept>(2)."
2598 #. glibc bug raised 12 Mar 2006
2599 #. http://sourceware.org/bugzilla/show_bug.cgi?id=2448
2600 #. The problem is an underlying kernel issue: the size of the
2601 #. __kernel_size_t type used to type this field varies
2602 #. across architectures, but socklen_t is always 32 bits.
2604 #: build/C/man2/recv.2:483 build/C/man2/send.2:404
2606 "According to POSIX.1-2001, the I<msg_controllen> field of the I<msghdr> "
2607 "structure should be typed as I<socklen_t>, but glibc currently types it as "
2612 #: build/C/man2/recv.2:488
2614 "See B<recvmmsg(2)> for information about a Linux-specific system call that "
2615 "can be used to receive multiple datagrams in a single call."
2619 #: build/C/man2/recv.2:493
2620 msgid "An example of the use of B<recvfrom>() is shown in B<getaddrinfo>(3)."
2624 #: build/C/man2/recv.2:504
2626 "B<fcntl>(2), B<getsockopt>(2), B<read>(2), B<recvmmsg>(2), B<select>(2), "
2627 "B<shutdown>(2), B<socket>(2), B<cmsg>(3), B<sockatmark>(3), B<socket>(7)"
2631 #: build/C/man2/recvmmsg.2:26
2637 #: build/C/man2/recvmmsg.2:26
2643 #: build/C/man2/recvmmsg.2:29
2644 msgid "recvmmsg - receive multiple messages on a socket"
2648 #: build/C/man2/recvmmsg.2:33 build/C/man2/sendmmsg.2:35
2651 "B<#define _GNU_SOURCE>\n"
2652 "B<#include E<lt>sys/socket.hE<gt>>\n"
2656 #: build/C/man2/recvmmsg.2:36
2659 "B<int recvmmsg(int >I<sockfd>B<, struct mmsghdr *>I<msgvec>B<, unsigned int "
2664 #: build/C/man2/recvmmsg.2:38
2666 msgid "B< unsigned int >I<flags>B<, struct timespec *>I<timeout>B<);>\n"
2670 #: build/C/man2/recvmmsg.2:50
2672 "The B<recvmmsg>() system call is an extension of B<recvmsg>(2) that allows "
2673 "the caller to receive multiple messages from a socket using a single system "
2674 "call. (This has performance benefits for some applications.) A further "
2675 "extension over B<recvmsg>(2) is support for a timeout on the receive "
2680 #: build/C/man2/recvmmsg.2:54
2682 "The I<sockfd> argument is the file descriptor of the socket to receive data "
2687 #: build/C/man2/recvmmsg.2:62 build/C/man2/sendmmsg.2:62
2689 "The I<msgvec> argument is a pointer to an array of I<mmsghdr> structures. "
2690 "The size of this array is specified in I<vlen>."
2694 #: build/C/man2/recvmmsg.2:68 build/C/man2/sendmmsg.2:68
2695 msgid "The I<mmsghdr> structure is defined in I<E<lt>sys/socket.hE<gt>> as:"
2699 #: build/C/man2/recvmmsg.2:75
2702 "struct mmsghdr {\n"
2703 " struct msghdr msg_hdr; /* Message header */\n"
2704 " unsigned int msg_len; /* Number of received bytes for header */\n"
2709 #: build/C/man2/recvmmsg.2:90
2711 "The I<msg_hdr> field is a I<msghdr> structure, as described in "
2712 "B<recvmsg>(2). The I<msg_len> field is the number of bytes returned for the "
2713 "message in the entry. This field has the same value as the return value of "
2714 "a single B<recvmsg>(2) on the header."
2718 #: build/C/man2/recvmmsg.2:97
2720 "The I<flags> argument contains flags ORed together. The flags are the same "
2721 "as documented for B<recvmsg>(2), with the following addition:"
2725 #: build/C/man2/recvmmsg.2:97
2727 msgid "B<MSG_WAITFORONE>"
2731 #: build/C/man2/recvmmsg.2:102
2732 msgid "Turns on B<MSG_DONTWAIT> after the first message has been received."
2736 #: build/C/man2/recvmmsg.2:115
2738 "The I<timeout> argument points to a I<struct timespec> (see "
2739 "B<clock_gettime>(2)) defining a timeout (seconds plus nanoseconds) for the "
2740 "receive operation. If I<timeout> is I<NULL> then the operation blocks "
2745 #: build/C/man2/recvmmsg.2:126
2747 "A blocking B<recvmmsg>() call blocks until I<vlen> messages have been "
2748 "received or until the timeout expires. A nonblocking call reads as many "
2749 "messages as are available (up to the limit specified by I<vlen>) and "
2750 "returns immediately."
2754 #: build/C/man2/recvmmsg.2:141
2756 "On return from B<recvmmsg>(), successive elements of I<msgvec> are updated "
2757 "to contain information about each received message: I<msg_len> contains the "
2758 "size of the received message; the subfields of I<msg_hdr> are updated as "
2759 "described in B<recvmsg>(2). The return value of the call indicates the "
2760 "number of elements of I<msgvec> that have been updated."
2764 #: build/C/man2/recvmmsg.2:149
2766 "On success, B<recvmmsg>() returns the number of messages received in "
2767 "I<msgvec>; on error, -1 is returned, and I<errno> is set to indicate the "
2772 #: build/C/man2/recvmmsg.2:153
2774 "Errors are as for B<recvmsg>(2). In addition, the following error can "
2779 #: build/C/man2/recvmmsg.2:157
2780 msgid "I<timeout> is invalid."
2784 #: build/C/man2/recvmmsg.2:162
2786 "The B<recvmmsg>() system call was added in Linux 2.6.32. Support in glibc "
2787 "was added in version 2.12."
2791 #: build/C/man2/recvmmsg.2:165
2792 msgid "B<recvmmsg>() is Linux-specific."
2796 #: build/C/man2/recvmmsg.2:172
2798 "B<clock_gettime>(2), B<recvmsg>(2), B<sendmmsg>(2), B<sendmsg>(2), "
2799 "B<socket>(2), B<socket>(7)"
2803 #: build/C/man2/select.2:38
2809 #: build/C/man2/select.2:38
2815 #: build/C/man2/select.2:42 build/C/man2/select_tut.2:34
2817 "select, pselect, FD_CLR, FD_ISSET, FD_SET, FD_ZERO - synchronous I/O "
2822 #: build/C/man2/select.2:45 build/C/man2/select_tut.2:37
2824 msgid "/* According to POSIX.1-2001 */\n"
2828 #: build/C/man2/select.2:47 build/C/man2/select.2:68 build/C/man2/select_tut.2:39 build/C/man2/select_tut.2:60
2830 msgid "B<#include E<lt>sys/select.hE<gt>>\n"
2834 #: build/C/man2/select.2:49 build/C/man2/select_tut.2:41
2836 msgid "/* According to earlier standards */\n"
2840 #: build/C/man2/select.2:51 build/C/man2/select_tut.2:43
2842 msgid "B<#include E<lt>sys/time.hE<gt>>\n"
2846 #: build/C/man2/select.2:55 build/C/man2/select_tut.2:47
2848 msgid "B<#include E<lt>unistd.hE<gt>>\n"
2852 #: build/C/man2/select.2:58
2855 "B<int select(int >I<nfds>B<, fd_set *>I<readfds>B<, fd_set "
2856 "*>I<writefds>B<,>\n"
2857 "B< fd_set *>I<exceptfds>B<, struct timeval *>I<timeout>B<);>\n"
2861 #: build/C/man2/select.2:60 build/C/man2/select_tut.2:52
2863 msgid "B<void FD_CLR(int >I<fd>B<, fd_set *>I<set>B<);>\n"
2867 #: build/C/man2/select.2:62 build/C/man2/select_tut.2:54
2869 msgid "B<int FD_ISSET(int >I<fd>B<, fd_set *>I<set>B<);>\n"
2873 #: build/C/man2/select.2:64 build/C/man2/select_tut.2:56
2875 msgid "B<void FD_SET(int >I<fd>B<, fd_set *>I<set>B<);>\n"
2879 #: build/C/man2/select.2:66 build/C/man2/select_tut.2:58
2881 msgid "B<void FD_ZERO(fd_set *>I<set>B<);>\n"
2885 #: build/C/man2/select.2:72
2888 "B<int pselect(int >I<nfds>B<, fd_set *>I<readfds>B<, fd_set "
2889 "*>I<writefds>B<,>\n"
2890 "B< fd_set *>I<exceptfds>B<, const struct timespec "
2891 "*>I<timeout>B<,>\n"
2892 "B< const sigset_t *>I<sigmask>B<);>\n"
2896 #: build/C/man2/select.2:77 build/C/man2/select_tut.2:69 build/C/man3/sockatmark.3:34
2897 msgid "Feature Test Macro Requirements for glibc (see B<feature_test_macros>(7)):"
2901 #: build/C/man2/select.2:81 build/C/man2/select_tut.2:73
2903 "B<pselect>(): _POSIX_C_SOURCE\\ E<gt>=\\ 200112L || _XOPEN_SOURCE\\ E<gt>=\\ "
2908 #: build/C/man2/select.2:92
2910 "B<select>() and B<pselect>() allow a program to monitor multiple file "
2911 "descriptors, waiting until one or more of the file descriptors become "
2912 "\"ready\" for some class of I/O operation (e.g., input possible). A file "
2913 "descriptor is considered ready if it is possible to perform the "
2914 "corresponding I/O operation (e.g., B<read>(2)) without blocking."
2918 #: build/C/man2/select.2:98
2920 "The operation of B<select>() and B<pselect>() is identical, with three "
2925 #: build/C/man2/select.2:98
2931 #: build/C/man2/select.2:108
2933 "B<select>() uses a timeout that is a I<struct timeval> (with seconds and "
2934 "microseconds), while B<pselect>() uses a I<struct timespec> (with seconds "
2939 #: build/C/man2/select.2:108
2945 #: build/C/man2/select.2:116
2947 "B<select>() may update the I<timeout> argument to indicate how much time "
2948 "was left. B<pselect>() does not change this argument."
2952 #: build/C/man2/select.2:116
2958 #: build/C/man2/select.2:125
2960 "B<select>() has no I<sigmask> argument, and behaves as B<pselect>() called "
2961 "with NULL I<sigmask>."
2965 #: build/C/man2/select.2:143
2967 "Three independent sets of file descriptors are watched. Those listed in "
2968 "I<readfds> will be watched to see if characters become available for reading "
2969 "(more precisely, to see if a read will not block; in particular, a file "
2970 "descriptor is also ready on end-of-file), those in I<writefds> will be "
2971 "watched to see if a write will not block, and those in I<exceptfds> will be "
2972 "watched for exceptions. On exit, the sets are modified in place to indicate "
2973 "which file descriptors actually changed status. Each of the three file "
2974 "descriptor sets may be specified as NULL if no file descriptors are to be "
2975 "watched for the corresponding class of events."
2979 #: build/C/man2/select.2:156
2981 "Four macros are provided to manipulate the sets. B<FD_ZERO>() clears a "
2982 "set. B<FD_SET>() and B<FD_CLR>() respectively add and remove a given file "
2983 "descriptor from a set. B<FD_ISSET>() tests to see if a file descriptor is "
2984 "part of the set; this is useful after B<select>() returns."
2988 #: build/C/man2/select.2:159
2990 "I<nfds> is the highest-numbered file descriptor in any of the three sets, "
2995 #: build/C/man2/select.2:175
2997 "I<timeout> is an upper bound on the amount of time elapsed before "
2998 "B<select>() returns. If both fields of the I<timeval> structure are zero, "
2999 "then B<select>() returns immediately. (This is useful for polling.) If "
3000 "I<timeout> is NULL (no timeout), B<select>() can block indefinitely."
3004 #: build/C/man2/select.2:185
3006 "I<sigmask> is a pointer to a signal mask (see B<sigprocmask>(2)); if it is "
3007 "not NULL, then B<pselect>() first replaces the current signal mask by the "
3008 "one pointed to by I<sigmask>, then does the \"select\" function, and then "
3009 "restores the original signal mask."
3013 #: build/C/man2/select.2:191
3015 "Other than the difference in the precision of the I<timeout> argument, the "
3016 "following B<pselect>() call:"
3020 #: build/C/man2/select.2:195
3023 " ready = pselect(nfds, &readfds, &writefds, &exceptfds,\n"
3024 " timeout, &sigmask);\n"
3028 #: build/C/man2/select.2:200
3029 msgid "is equivalent to I<atomically> executing the following calls:"
3033 #: build/C/man2/select.2:203
3035 msgid " sigset_t origmask;\n"
3039 #: build/C/man2/select.2:207
3042 " sigprocmask(SIG_SETMASK, &sigmask, &origmask);\n"
3043 " ready = select(nfds, &readfds, &writefds, &exceptfds, timeout);\n"
3044 " sigprocmask(SIG_SETMASK, &origmask, NULL);\n"
3048 #: build/C/man2/select.2:228
3050 "The reason that B<pselect>() is needed is that if one wants to wait for "
3051 "either a signal or for a file descriptor to become ready, then an atomic "
3052 "test is needed to prevent race conditions. (Suppose the signal handler sets "
3053 "a global flag and returns. Then a test of this global flag followed by a "
3054 "call of B<select>() could hang indefinitely if the signal arrived just "
3055 "after the test but just before the call. By contrast, B<pselect>() allows "
3056 "one to first block signals, handle the signals that have come in, then call "
3057 "B<pselect>() with the desired I<sigmask>, avoiding the race.)"
3061 #: build/C/man2/select.2:228
3067 #: build/C/man2/select.2:232
3069 "The time structures involved are defined in I<E<lt>sys/time.hE<gt>> and look "
3074 #: build/C/man2/select.2:239
3077 "struct timeval {\n"
3078 " long tv_sec; /* seconds */\n"
3079 " long tv_usec; /* microseconds */\n"
3084 #: build/C/man2/select.2:243
3089 #: build/C/man2/select.2:250
3092 "struct timespec {\n"
3093 " long tv_sec; /* seconds */\n"
3094 " long tv_nsec; /* nanoseconds */\n"
3099 #: build/C/man2/select.2:254
3100 msgid "(However, see below on the POSIX.1-2001 versions.)"
3104 #: build/C/man2/select.2:262
3106 "Some code calls B<select>() with all three sets empty, I<nfds> zero, and a "
3107 "non-NULL I<timeout> as a fairly portable way to sleep with subsecond "
3111 #. .PP - it is rumored that:
3112 #. On BSD, when a timeout occurs, the file descriptor bits are not changed.
3113 #. - it is certainly true that:
3114 #. Linux follows SUSv2 and sets the bit masks to zero upon a timeout.
3116 #: build/C/man2/select.2:285
3118 "On Linux, B<select>() modifies I<timeout> to reflect the amount of time not "
3119 "slept; most other implementations do not do this. (POSIX.1-2001 permits "
3120 "either behavior.) This causes problems both when Linux code which reads "
3121 "I<timeout> is ported to other operating systems, and when code is ported to "
3122 "Linux that reuses a I<struct timeval> for multiple B<select>()s in a loop "
3123 "without reinitializing it. Consider I<timeout> to be undefined after "
3124 "B<select>() returns."
3128 #: build/C/man2/select.2:302
3130 "On success, B<select>() and B<pselect>() return the number of file "
3131 "descriptors contained in the three returned descriptor sets (that is, the "
3132 "total number of bits that are set in I<readfds>, I<writefds>, I<exceptfds>) "
3133 "which may be zero if the timeout expires before anything interesting "
3134 "happens. On error, -1 is returned, and I<errno> is set appropriately; the "
3135 "sets and I<timeout> become undefined, so do not rely on their contents after "
3140 #: build/C/man2/select.2:308
3142 "An invalid file descriptor was given in one of the sets. (Perhaps a file "
3143 "descriptor that was already closed, or one on which an error has occurred.)"
3147 #: build/C/man2/select.2:312
3148 msgid "A signal was caught; see B<signal>(7)."
3152 #: build/C/man2/select.2:318
3153 msgid "I<nfds> is negative or the value contained within I<timeout> is invalid."
3157 #: build/C/man2/select.2:321
3158 msgid "unable to allocate memory for internal tables."
3162 #: build/C/man2/select.2:327
3164 "B<pselect>() was added to Linux in kernel 2.6.16. Prior to this, "
3165 "B<pselect>() was emulated in glibc (but see BUGS)."
3169 #: build/C/man2/select.2:338
3171 "B<select>() conforms to POSIX.1-2001 and 4.4BSD (B<select>() first "
3172 "appeared in 4.2BSD). Generally portable to/from non-BSD systems supporting "
3173 "clones of the BSD socket layer (including System V variants). However, note "
3174 "that the System V variant typically sets the timeout variable before exit, "
3175 "but the BSD variant does not."
3179 #: build/C/man2/select.2:342
3180 msgid "B<pselect>() is defined in POSIX.1g, and in POSIX.1-2001."
3184 #: build/C/man2/select.2:359
3186 "An I<fd_set> is a fixed size buffer. Executing B<FD_CLR>() or B<FD_SET>() "
3187 "with a value of I<fd> that is negative or is equal to or larger than "
3188 "B<FD_SETSIZE> will result in undefined behavior. Moreover, POSIX requires "
3189 "I<fd> to be a valid file descriptor."
3193 #: build/C/man2/select.2:368
3195 "Concerning the types involved, the classical situation is that the two "
3196 "fields of a I<timeval> structure are typed as I<long> (as shown above), and "
3197 "the structure is defined in I<E<lt>sys/time.hE<gt>>. The POSIX.1-2001 "
3202 #: build/C/man2/select.2:375
3205 "struct timeval {\n"
3206 " time_t tv_sec; /* seconds */\n"
3207 " suseconds_t tv_usec; /* microseconds */\n"
3212 #: build/C/man2/select.2:386
3214 "where the structure is defined in I<E<lt>sys/select.hE<gt>> and the data "
3215 "types I<time_t> and I<suseconds_t> are defined in I<E<lt>sys/types.hE<gt>>."
3219 #: build/C/man2/select.2:398
3221 "Concerning prototypes, the classical situation is that one should include "
3222 "I<E<lt>time.hE<gt>> for B<select>(). The POSIX.1-2001 situation is that one "
3223 "should include I<E<lt>sys/select.hE<gt>> for B<select>() and B<pselect>()."
3227 #: build/C/man2/select.2:410
3229 "Libc4 and libc5 do not have a I<E<lt>sys/select.hE<gt>> header; under glibc "
3230 "2.0 and later this header exists. Under glibc 2.0 it unconditionally gives "
3231 "the wrong prototype for B<pselect>(). Under glibc 2.1 to 2.2.1 it gives "
3232 "B<pselect>() when B<_GNU_SOURCE> is defined. Since glibc 2.2.2 the "
3233 "requirements are as shown in the SYNOPSIS."
3237 #: build/C/man2/select.2:410
3243 #: build/C/man2/select.2:423
3245 "The Linux B<pselect>() system call modifies its I<timeout> argument. "
3246 "However, the glibc wrapper function hides this behavior by using a local "
3247 "variable for the timeout argument that is passed to the system call. Thus, "
3248 "the glibc B<pselect>() function does not modify its timeout argument; this "
3249 "is the behavior required by POSIX.1-2001."
3253 #: build/C/man2/select.2:429
3255 "Glibc 2.0 provided a version of B<pselect>() that did not take a I<sigmask> "
3260 #: build/C/man2/select.2:442
3262 "Starting with version 2.1, glibc provided an emulation of B<pselect>() that "
3263 "was implemented using B<sigprocmask>(2) and B<select>(). This "
3264 "implementation remained vulnerable to the very race condition that "
3265 "B<pselect>() was designed to prevent. Modern versions of glibc use the "
3266 "(race-free) B<pselect>() system call on kernels where it is provided."
3270 #: build/C/man2/select.2:451
3272 "On systems that lack B<pselect>(), reliable (and more portable) signal "
3273 "trapping can be achieved using the self-pipe trick (where a signal handler "
3274 "writes a byte to a pipe whose other end is monitored by B<select>() in the "
3278 #. Stevens discusses a case where accept can block after select
3279 #. returns successfully because of an intervening RST from the client.
3280 #. Maybe the kernel should have returned EIO in such a situation?
3282 #: build/C/man2/select.2:467
3284 "Under Linux, B<select>() may report a socket file descriptor as \"ready for "
3285 "reading\", while nevertheless a subsequent read blocks. This could for "
3286 "example happen when data has arrived but upon examination has wrong checksum "
3287 "and is discarded. There may be other circumstances in which a file "
3288 "descriptor is spuriously reported as ready. Thus it may be safer to use "
3289 "B<O_NONBLOCK> on sockets that should not block."
3293 #: build/C/man2/select.2:482
3295 "On Linux, B<select>() also modifies I<timeout> if the call is interrupted "
3296 "by a signal handler (i.e., the B<EINTR> error return). This is not "
3297 "permitted by POSIX.1-2001. The Linux B<pselect>() system call has the same "
3298 "behavior, but the glibc wrapper hides this behavior by internally copying "
3299 "the I<timeout> to a local variable and passing that variable to the system "
3304 #: build/C/man2/select.2:489
3307 "#include E<lt>stdio.hE<gt>\n"
3308 "#include E<lt>stdlib.hE<gt>\n"
3309 "#include E<lt>sys/time.hE<gt>\n"
3310 "#include E<lt>sys/types.hE<gt>\n"
3311 "#include E<lt>unistd.hE<gt>\n"
3315 #: build/C/man2/select.2:496
3322 " struct timeval tv;\n"
3327 #: build/C/man2/select.2:500
3330 " /* Watch stdin (fd 0) to see when it has input. */\n"
3331 " FD_ZERO(&rfds);\n"
3332 " FD_SET(0, &rfds);\n"
3336 #: build/C/man2/select.2:504
3339 " /* Wait up to five seconds. */\n"
3341 " tv.tv_usec = 0;\n"
3345 #: build/C/man2/select.2:507
3348 " retval = select(1, &rfds, NULL, NULL, &tv);\n"
3349 " /* Don't rely on the value of tv now! */\n"
3353 #: build/C/man2/select.2:515
3356 " if (retval == -1)\n"
3357 " perror(\"select()\");\n"
3358 " else if (retval)\n"
3359 " printf(\"Data is available now.\\en\");\n"
3360 " /* FD_ISSET(0, &rfds) will be true. */\n"
3362 " printf(\"No data within five seconds.\\en\");\n"
3366 #: build/C/man2/select.2:518
3369 " exit(EXIT_SUCCESS);\n"
3374 #: build/C/man2/select.2:522
3375 msgid "For a tutorial with discussion and examples, see B<select_tut>(2)."
3379 #: build/C/man2/select.2:534
3381 "For vaguely related stuff, see B<accept>(2), B<connect>(2), B<poll>(2), "
3382 "B<read>(2), B<recv>(2), B<send>(2), B<sigprocmask>(2), B<write>(2), "
3383 "B<epoll>(7), B<time>(7)"
3387 #: build/C/man2/select_tut.2:30
3393 #: build/C/man2/select_tut.2:30
3399 #: build/C/man2/select_tut.2:50
3402 "B<int select(int >I<nfds>B<, fd_set *>I<readfds>B<, fd_set "
3403 "*>I<writefds>B<,>\n"
3404 "B< fd_set *>I<exceptfds>B<, struct timeval *>I<utimeout>B<);>\n"
3408 #: build/C/man2/select_tut.2:64
3411 "B<int pselect(int >I<nfds>B<, fd_set *>I<readfds>B<, fd_set "
3412 "*>I<writefds>B<,>\n"
3413 "B< fd_set *>I<exceptfds>B<, const struct timespec "
3414 "*>I<ntimeout>B<,>\n"
3415 "B< const sigset_t *>I<sigmask>B<);>\n"
3419 #: build/C/man2/select_tut.2:81
3421 "B<select>() (or B<pselect>()) is used to efficiently monitor multiple file "
3422 "descriptors, to see if any of them is, or becomes, \"ready\"; that is, to "
3423 "see whether I/O becomes possible, or an \"exceptional condition\" has "
3424 "occurred on any of the descriptors."
3428 #: build/C/man2/select_tut.2:106
3430 "Its principal arguments are three \"sets\" of file descriptors: I<readfds>, "
3431 "I<writefds>, and I<exceptfds>. Each set is declared as type I<fd_set>, and "
3432 "its contents can be manipulated with the macros B<FD_CLR>(), B<FD_ISSET>(), "
3433 "B<FD_SET>(), and B<FD_ZERO>(). A newly declared set should first be cleared "
3434 "using B<FD_ZERO>(). B<select>() modifies the contents of the sets "
3435 "according to the rules described below; after calling B<select>() you can "
3436 "test if a file descriptor is still present in a set with the B<FD_ISSET>() "
3437 "macro. B<FD_ISSET>() returns nonzero if a specified file descriptor is "
3438 "present in a set and zero if it is not. B<FD_CLR>() removes a file "
3439 "descriptor from a set."
3443 #: build/C/man2/select_tut.2:106
3449 #: build/C/man2/select_tut.2:107
3455 #: build/C/man2/select_tut.2:116
3457 "This set is watched to see if data is available for reading from any of its "
3458 "file descriptors. After B<select>() has returned, I<readfds> will be "
3459 "cleared of all file descriptors except for those that are immediately "
3460 "available for reading."
3464 #: build/C/man2/select_tut.2:116
3470 #: build/C/man2/select_tut.2:125
3472 "This set is watched to see if there is space to write data to any of its "
3473 "file descriptors. After B<select>() has returned, I<writefds> will be "
3474 "cleared of all file descriptors except for those that are immediately "
3475 "available for writing."
3479 #: build/C/man2/select_tut.2:125
3481 msgid "I<exceptfds>"
3485 #: build/C/man2/select_tut.2:147
3487 "This set is watched for \"exceptional conditions\". In practice, only one "
3488 "such exceptional condition is common: the availability of I<out-of-band> "
3489 "(OOB) data for reading from a TCP socket. See B<recv>(2), B<send>(2), and "
3490 "B<tcp>(7) for more details about OOB data. (One other less common case "
3491 "where B<select>(2) indicates an exceptional condition occurs with "
3492 "pseudoterminals in packet mode; see B<tty_ioctl>(4).) After B<select>() "
3493 "has returned, I<exceptfds> will be cleared of all file descriptors except "
3494 "for those for which an exceptional condition has occurred."
3498 #: build/C/man2/select_tut.2:147
3504 #: build/C/man2/select_tut.2:154
3506 "This is an integer one more than the maximum of any file descriptor in any "
3507 "of the sets. In other words, while adding file descriptors to each of the "
3508 "sets, you must calculate the maximum integer value of all of them, then "
3509 "increment this value by one, and then pass this as I<nfds>."
3513 #: build/C/man2/select_tut.2:154
3519 #: build/C/man2/select_tut.2:167
3521 "This is the longest time B<select>() may wait before returning, even if "
3522 "nothing interesting happened. If this value is passed as NULL, then "
3523 "B<select>() blocks indefinitely waiting for a file descriptor to become "
3524 "ready. I<utimeout> can be set to zero seconds, which causes B<select>() to "
3525 "return immediately, with information about the readiness of file descriptors "
3526 "at the time of the call. The structure I<struct timeval> is defined as:"
3530 #: build/C/man2/select_tut.2:174
3533 "struct timeval {\n"
3534 " time_t tv_sec; /* seconds */\n"
3535 " long tv_usec; /* microseconds */\n"
3540 #: build/C/man2/select_tut.2:176
3546 #: build/C/man2/select_tut.2:185
3548 "This argument for B<pselect>() has the same meaning as I<utimeout>, but "
3549 "I<struct timespec> has nanosecond precision as follows:"
3553 #: build/C/man2/select_tut.2:192
3556 "struct timespec {\n"
3557 " long tv_sec; /* seconds */\n"
3558 " long tv_nsec; /* nanoseconds */\n"
3563 #: build/C/man2/select_tut.2:194
3569 #: build/C/man2/select_tut.2:211
3571 "This argument holds a set of signals that the kernel should unblock (i.e., "
3572 "remove from the signal mask of the calling thread), while the caller is "
3573 "blocked inside the B<pselect>() call (see B<sigaddset>(3) and "
3574 "B<sigprocmask>(2)). It may be NULL, in which case the call does not modify "
3575 "the signal mask on entry and exit to the function. In this case, "
3576 "B<pselect>() will then behave just like B<select>()."
3580 #: build/C/man2/select_tut.2:211
3582 msgid "Combining Signal and Data Events"
3586 #: build/C/man2/select_tut.2:255
3588 "B<pselect>() is useful if you are waiting for a signal as well as for file "
3589 "descriptor(s) to become ready for I/O. Programs that receive signals "
3590 "normally use the signal handler only to raise a global flag. The global "
3591 "flag will indicate that the event must be processed in the main loop of the "
3592 "program. A signal will cause the B<select>() (or B<pselect>()) call to "
3593 "return with I<errno> set to B<EINTR>. This behavior is essential so that "
3594 "signals can be processed in the main loop of the program, otherwise "
3595 "B<select>() would block indefinitely. Now, somewhere in the main loop will "
3596 "be a conditional to check the global flag. So we must ask: what if a signal "
3597 "arrives after the conditional, but before the B<select>() call? The answer "
3598 "is that B<select>() would block indefinitely, even though an event is "
3599 "actually pending. This race condition is solved by the B<pselect>() call. "
3600 "This call can be used to set the signal mask to a set of signals that are "
3601 "only to be received within the B<pselect>() call. For instance, let us say "
3602 "that the event in question was the exit of a child process. Before the "
3603 "start of the main loop, we would block B<SIGCHLD> using B<sigprocmask>(2). "
3604 "Our B<pselect>() call would enable B<SIGCHLD> by using an empty signal "
3605 "mask. Our program would look like:"
3609 #: build/C/man2/select_tut.2:258
3611 msgid "static volatile sig_atomic_t got_SIGCHLD = 0;\n"
3615 #: build/C/man2/select_tut.2:264
3619 "child_sig_handler(int sig)\n"
3621 " got_SIGCHLD = 1;\n"
3626 #: build/C/man2/select_tut.2:272
3630 "main(int argc, char *argv[])\n"
3632 " sigset_t sigmask, empty_mask;\n"
3633 " struct sigaction sa;\n"
3634 " fd_set readfds, writefds, exceptfds;\n"
3639 #: build/C/man2/select_tut.2:279
3642 " sigemptyset(&sigmask);\n"
3643 " sigaddset(&sigmask, SIGCHLD);\n"
3644 " if (sigprocmask(SIG_BLOCK, &sigmask, NULL) == -1) {\n"
3645 " perror(\"sigprocmask\");\n"
3646 " exit(EXIT_FAILURE);\n"
3651 #: build/C/man2/select_tut.2:287
3654 " sa.sa_flags = 0;\n"
3655 " sa.sa_handler = child_sig_handler;\n"
3656 " sigemptyset(&sa.sa_mask);\n"
3657 " if (sigaction(SIGCHLD, &sa, NULL) == -1) {\n"
3658 " perror(\"sigaction\");\n"
3659 " exit(EXIT_FAILURE);\n"
3664 #: build/C/man2/select_tut.2:289
3666 msgid " sigemptyset(&empty_mask);\n"
3670 #: build/C/man2/select_tut.2:293
3673 " for (;;) { /* main loop */\n"
3674 " /* Initialize readfds, writefds, and exceptfds\n"
3675 " before the pselect() call. (Code omitted.) */\n"
3679 #: build/C/man2/select_tut.2:299
3682 " r = pselect(nfds, &readfds, &writefds, &exceptfds,\n"
3683 " NULL, &empty_mask);\n"
3684 " if (r == -1 && errno != EINTR) {\n"
3685 " /* Handle error */\n"
3690 #: build/C/man2/select_tut.2:302
3693 " if (got_SIGCHLD) {\n"
3694 " got_SIGCHLD = 0;\n"
3698 #: build/C/man2/select_tut.2:306
3701 " /* Handle signalled event here; e.g., wait() for all\n"
3702 " terminated children. (Code omitted.) */\n"
3707 #: build/C/man2/select_tut.2:310
3710 " /* main body of program */\n"
3716 #: build/C/man2/select_tut.2:311
3722 #: build/C/man2/select_tut.2:332
3724 "So what is the point of B<select>()? Can't I just read and write to my "
3725 "descriptors whenever I want? The point of B<select>() is that it watches "
3726 "multiple descriptors at the same time and properly puts the process to sleep "
3727 "if there is no activity. UNIX programmers often find themselves in a "
3728 "position where they have to handle I/O from more than one file descriptor "
3729 "where the data flow may be intermittent. If you were to merely create a "
3730 "sequence of B<read>(2) and B<write>(2) calls, you would find that one of "
3731 "your calls may block waiting for data from/to a file descriptor, while "
3732 "another file descriptor is unused though ready for I/O. B<select>() "
3733 "efficiently copes with this situation."
3737 #: build/C/man2/select_tut.2:332
3743 #: build/C/man2/select_tut.2:345
3745 "Many people who try to use B<select>() come across behavior that is "
3746 "difficult to understand and produces nonportable or borderline results. For "
3747 "instance, the above program is carefully written not to block at any point, "
3748 "even though it does not set its file descriptors to nonblocking mode. It is "
3749 "easy to introduce subtle errors that will remove the advantage of using "
3750 "B<select>(), so here is a list of essentials to watch for when using "
3755 #: build/C/man2/select_tut.2:354
3757 "You should always try to use B<select>() without a timeout. Your program "
3758 "should have nothing to do if there is no data available. Code that depends "
3759 "on timeouts is not usually portable and is difficult to debug."
3763 #: build/C/man2/select_tut.2:358
3765 "The value I<nfds> must be properly calculated for efficiency as explained "
3770 #: build/C/man2/select_tut.2:365
3772 "No file descriptor must be added to any set if you do not intend to check "
3773 "its result after the B<select>() call, and respond appropriately. See next "
3778 #: build/C/man2/select_tut.2:371
3780 "After B<select>() returns, all file descriptors in all sets should be "
3781 "checked to see if they are ready."
3785 #: build/C/man2/select_tut.2:371
3791 #: build/C/man2/select_tut.2:386
3793 "The functions B<read>(2), B<recv>(2), B<write>(2), and B<send>(2) do I<not> "
3794 "necessarily read/write the full amount of data that you have requested. If "
3795 "they do read/write the full amount, it's because you have a low traffic load "
3796 "and a fast stream. This is not always going to be the case. You should "
3797 "cope with the case of your functions only managing to send or receive a "
3802 #: build/C/man2/select_tut.2:386
3808 #: build/C/man2/select_tut.2:394
3810 "Never read/write only in single bytes at a time unless you are really sure "
3811 "that you have a small amount of data to process. It is extremely "
3812 "inefficient not to read/write as much data as you can buffer each time. The "
3813 "buffers in the example below are 1024 bytes although they could easily be "
3818 #: build/C/man2/select_tut.2:394
3823 #. Nonetheless, you should still cope with these errors for completeness.
3825 #: build/C/man2/select_tut.2:416
3827 "The functions B<read>(2), B<recv>(2), B<write>(2), and B<send>(2) as well "
3828 "as the B<select>() call can return -1 with I<errno> set to B<EINTR>, or "
3829 "with I<errno> set to B<EAGAIN> (B<EWOULDBLOCK>). These results must be "
3830 "properly managed (not done properly above). If your program is not going to "
3831 "receive any signals, then it is unlikely you will get B<EINTR>. If your "
3832 "program does not set nonblocking I/O, you will not get B<EAGAIN>."
3836 #: build/C/man2/select_tut.2:416
3842 #: build/C/man2/select_tut.2:425
3844 "Never call B<read>(2), B<recv>(2), B<write>(2), or B<send>(2) with a buffer "
3849 #: build/C/man2/select_tut.2:425
3855 #: build/C/man2/select_tut.2:441
3857 "If the functions B<read>(2), B<recv>(2), B<write>(2), and B<send>(2) fail "
3858 "with errors other than those listed in B<7.>, or one of the input functions "
3859 "returns 0, indicating end of file, then you should I<not> pass that "
3860 "descriptor to B<select>() again. In the example below, I close the "
3861 "descriptor immediately, and then set it to -1 to prevent it being included "
3866 #: build/C/man2/select_tut.2:441
3872 #: build/C/man2/select_tut.2:448
3874 "The timeout value must be initialized with each new call to B<select>(), "
3875 "since some operating systems modify the structure. B<pselect>() however "
3876 "does not modify its timeout structure."
3880 #: build/C/man2/select_tut.2:448
3885 #. "I have heard" does not fill me with confidence, and doesn't
3886 #. belong in a man page, so I've commented this point out.
3889 #. I have heard that the Windows socket layer does not cope with OOB data
3891 #. It also does not cope with
3893 #. calls when no file descriptors are set at all.
3894 #. Having no file descriptors set is a useful
3895 #. way to sleep the process with subsecond precision by using the timeout.
3896 #. (See further on.)
3898 #: build/C/man2/select_tut.2:467
3900 "Since B<select>() modifies its file descriptor sets, if the call is being "
3901 "used in a loop, then the sets must be reinitialized before each call."
3905 #: build/C/man2/select_tut.2:467
3907 msgid "Usleep Emulation"
3911 #: build/C/man2/select_tut.2:474
3913 "On systems that do not have a B<usleep>(3) function, you can call "
3914 "B<select>() with a finite timeout and no file descriptors as follows:"
3918 #: build/C/man2/select_tut.2:480
3921 " struct timeval tv;\n"
3923 " tv.tv_usec = 200000; /* 0.2 seconds */\n"
3924 " select(0, NULL, NULL, NULL, &tv);\n"
3928 #: build/C/man2/select_tut.2:483
3929 msgid "This is only guaranteed to work on UNIX systems, however."
3933 #: build/C/man2/select_tut.2:488
3935 "On success, B<select>() returns the total number of file descriptors still "
3936 "present in the file descriptor sets."
3940 #: build/C/man2/select_tut.2:494
3942 "If B<select>() timed out, then the return value will be zero. The file "
3943 "descriptors set should be all empty (but may not be on some systems)."
3947 #: build/C/man2/select_tut.2:501
3949 "A return value of -1 indicates an error, with I<errno> being set "
3950 "appropriately. In the case of an error, the contents of the returned sets "
3951 "and the I<struct timeout> contents are undefined and should not be used. "
3952 "B<pselect>() however never modifies I<ntimeout>."
3956 #: build/C/man2/select_tut.2:510
3958 "Generally speaking, all operating systems that support sockets also support "
3959 "B<select>(). B<select>() can be used to solve many problems in a portable "
3960 "and efficient way that naive programmers try to solve in a more complicated "
3961 "manner using threads, forking, IPCs, signals, memory sharing, and so on."
3965 #: build/C/man2/select_tut.2:519
3967 "The B<poll>(2) system call has the same functionality as B<select>(), and "
3968 "is somewhat more efficient when monitoring sparse file descriptor sets. It "
3969 "is nowadays widely available, but historically was less portable than "
3974 #: build/C/man2/select_tut.2:527
3976 "The Linux-specific B<epoll>(7) API provides an interface that is more "
3977 "efficient than B<select>(2) and B<poll>(2) when monitoring large numbers "
3978 "of file descriptors."
3982 #: build/C/man2/select_tut.2:532
3984 "Here is an example that better demonstrates the true utility of "
3985 "B<select>(). The listing below is a TCP forwarding program that forwards "
3986 "from one TCP port to another."
3990 #: build/C/man2/select_tut.2:545
3993 "#include E<lt>stdlib.hE<gt>\n"
3994 "#include E<lt>stdio.hE<gt>\n"
3995 "#include E<lt>unistd.hE<gt>\n"
3996 "#include E<lt>sys/time.hE<gt>\n"
3997 "#include E<lt>sys/types.hE<gt>\n"
3998 "#include E<lt>string.hE<gt>\n"
3999 "#include E<lt>signal.hE<gt>\n"
4000 "#include E<lt>sys/socket.hE<gt>\n"
4001 "#include E<lt>netinet/in.hE<gt>\n"
4002 "#include E<lt>arpa/inet.hE<gt>\n"
4003 "#include E<lt>errno.hE<gt>\n"
4007 #: build/C/man2/select_tut.2:547
4009 msgid "static int forward_port;\n"
4013 #: build/C/man2/select_tut.2:550
4017 "#define max(x,y) ((x) E<gt> (y) ? (x) : (y))\n"
4021 #: build/C/man2/select_tut.2:557
4025 "listen_socket(int listen_port)\n"
4027 " struct sockaddr_in a;\n"
4033 #: build/C/man2/select_tut.2:581
4036 " if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {\n"
4037 " perror(\"socket\");\n"
4041 " if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,\n"
4042 " (char *) &yes, sizeof(yes)) == -1) {\n"
4043 " perror(\"setsockopt\");\n"
4047 " memset(&a, 0, sizeof(a));\n"
4048 " a.sin_port = htons(listen_port);\n"
4049 " a.sin_family = AF_INET;\n"
4050 " if (bind(s, (struct sockaddr *) &a, sizeof(a)) == -1) {\n"
4051 " perror(\"bind\");\n"
4055 " printf(\"accepting connections on port %d\\en\", listen_port);\n"
4062 #: build/C/man2/select_tut.2:587
4066 "connect_socket(int connect_port, char *address)\n"
4068 " struct sockaddr_in a;\n"
4073 #: build/C/man2/select_tut.2:593
4076 " if ((s = socket(AF_INET, SOCK_STREAM, 0)) == -1) {\n"
4077 " perror(\"socket\");\n"
4084 #: build/C/man2/select_tut.2:597
4087 " memset(&a, 0, sizeof(a));\n"
4088 " a.sin_port = htons(connect_port);\n"
4089 " a.sin_family = AF_INET;\n"
4093 #: build/C/man2/select_tut.2:603
4096 " if (!inet_aton(address, (struct in_addr *) &a.sin_addr.s_addr)) {\n"
4097 " perror(\"bad IP address format\");\n"
4104 #: build/C/man2/select_tut.2:612
4107 " if (connect(s, (struct sockaddr *) &a, sizeof(a)) == -1) {\n"
4108 " perror(\"connect()\");\n"
4109 " shutdown(s, SHUT_RDWR);\n"
4118 #: build/C/man2/select_tut.2:620
4121 "#define SHUT_FD1 do { \\e\n"
4122 " if (fd1 E<gt>= 0) { \\e\n"
4123 " shutdown(fd1, SHUT_RDWR); \\e\n"
4124 " close(fd1); \\e\n"
4131 #: build/C/man2/select_tut.2:628
4134 "#define SHUT_FD2 do { \\e\n"
4135 " if (fd2 E<gt>= 0) { \\e\n"
4136 " shutdown(fd2, SHUT_RDWR); \\e\n"
4137 " close(fd2); \\e\n"
4144 #: build/C/man2/select_tut.2:630
4146 msgid "#define BUF_SIZE 1024\n"
4150 #: build/C/man2/select_tut.2:639
4154 "main(int argc, char *argv[])\n"
4157 " int fd1 = -1, fd2 = -1;\n"
4158 " char buf1[BUF_SIZE], buf2[BUF_SIZE];\n"
4159 " int buf1_avail, buf1_written;\n"
4160 " int buf2_avail, buf2_written;\n"
4164 #: build/C/man2/select_tut.2:645
4167 " if (argc != 4) {\n"
4168 " fprintf(stderr, \"Usage\\en\\etfwd E<lt>listen-portE<gt> \"\n"
4169 " \"E<lt>forward-to-portE<gt> "
4170 "E<lt>forward-to-ip-addressE<gt>\\en\");\n"
4171 " exit(EXIT_FAILURE);\n"
4176 #: build/C/man2/select_tut.2:647
4178 msgid " signal(SIGPIPE, SIG_IGN);\n"
4182 #: build/C/man2/select_tut.2:649
4184 msgid " forward_port = atoi(argv[2]);\n"
4188 #: build/C/man2/select_tut.2:653
4191 " h = listen_socket(atoi(argv[1]));\n"
4193 " exit(EXIT_FAILURE);\n"
4197 #: build/C/man2/select_tut.2:657
4201 " int r, nfds = 0;\n"
4202 " fd_set rd, wr, er;\n"
4206 #: build/C/man2/select_tut.2:687
4212 " FD_SET(h, &rd);\n"
4213 " nfds = max(nfds, h);\n"
4214 " if (fd1 E<gt> 0 && buf1_avail E<lt> BUF_SIZE) {\n"
4215 " FD_SET(fd1, &rd);\n"
4216 " nfds = max(nfds, fd1);\n"
4218 " if (fd2 E<gt> 0 && buf2_avail E<lt> BUF_SIZE) {\n"
4219 " FD_SET(fd2, &rd);\n"
4220 " nfds = max(nfds, fd2);\n"
4222 " if (fd1 E<gt> 0 && buf2_avail - buf2_written E<gt> 0) {\n"
4223 " FD_SET(fd1, &wr);\n"
4224 " nfds = max(nfds, fd1);\n"
4226 " if (fd2 E<gt> 0 && buf1_avail - buf1_written E<gt> 0) {\n"
4227 " FD_SET(fd2, &wr);\n"
4228 " nfds = max(nfds, fd2);\n"
4230 " if (fd1 E<gt> 0) {\n"
4231 " FD_SET(fd1, &er);\n"
4232 " nfds = max(nfds, fd1);\n"
4234 " if (fd2 E<gt> 0) {\n"
4235 " FD_SET(fd2, &er);\n"
4236 " nfds = max(nfds, fd2);\n"
4241 #: build/C/man2/select_tut.2:689
4243 msgid " r = select(nfds + 1, &rd, &wr, &er, NULL);\n"
4247 #: build/C/man2/select_tut.2:692
4250 " if (r == -1 && errno == EINTR)\n"
4255 #: build/C/man2/select_tut.2:697
4259 " perror(\"select()\");\n"
4260 " exit(EXIT_FAILURE);\n"
4265 #: build/C/man2/select_tut.2:701
4268 " if (FD_ISSET(h, &rd)) {\n"
4269 " unsigned int l;\n"
4270 " struct sockaddr_in client_address;\n"
4274 #: build/C/man2/select_tut.2:720
4277 " memset(&client_address, 0, l = sizeof(client_address));\n"
4278 " r = accept(h, (struct sockaddr *) &client_address, &l);\n"
4280 " perror(\"accept()\");\n"
4284 " buf1_avail = buf1_written = 0;\n"
4285 " buf2_avail = buf2_written = 0;\n"
4287 " fd2 = connect_socket(forward_port, argv[3]);\n"
4291 " printf(\"connect from %s\\en\",\n"
4292 " inet_ntoa(client_address.sin_addr));\n"
4298 #: build/C/man2/select_tut.2:722
4300 msgid " /* NB: read oob data before normal reads */\n"
4304 #: build/C/man2/select_tut.2:726
4307 " if (fd1 E<gt> 0)\n"
4308 " if (FD_ISSET(fd1, &er)) {\n"
4313 #: build/C/man2/select_tut.2:736
4316 " r = recv(fd1, &c, 1, MSG_OOB);\n"
4320 " send(fd2, &c, 1, MSG_OOB);\n"
4322 " if (fd2 E<gt> 0)\n"
4323 " if (FD_ISSET(fd2, &er)) {\n"
4328 #: build/C/man2/select_tut.2:779
4331 " r = recv(fd2, &c, 1, MSG_OOB);\n"
4335 " send(fd1, &c, 1, MSG_OOB);\n"
4337 " if (fd1 E<gt> 0)\n"
4338 " if (FD_ISSET(fd1, &rd)) {\n"
4339 " r = read(fd1, buf1 + buf1_avail,\n"
4340 " BUF_SIZE - buf1_avail);\n"
4344 " buf1_avail += r;\n"
4346 " if (fd2 E<gt> 0)\n"
4347 " if (FD_ISSET(fd2, &rd)) {\n"
4348 " r = read(fd2, buf2 + buf2_avail,\n"
4349 " BUF_SIZE - buf2_avail);\n"
4353 " buf2_avail += r;\n"
4355 " if (fd1 E<gt> 0)\n"
4356 " if (FD_ISSET(fd1, &wr)) {\n"
4357 " r = write(fd1, buf2 + buf2_written,\n"
4358 " buf2_avail - buf2_written);\n"
4362 " buf2_written += r;\n"
4364 " if (fd2 E<gt> 0)\n"
4365 " if (FD_ISSET(fd2, &wr)) {\n"
4366 " r = write(fd2, buf1 + buf1_written,\n"
4367 " buf1_avail - buf1_written);\n"
4371 " buf1_written += r;\n"
4376 #: build/C/man2/select_tut.2:781
4378 msgid " /* check if write data has caught read data */\n"
4382 #: build/C/man2/select_tut.2:786
4385 " if (buf1_written == buf1_avail)\n"
4386 " buf1_written = buf1_avail = 0;\n"
4387 " if (buf2_written == buf2_avail)\n"
4388 " buf2_written = buf2_avail = 0;\n"
4392 #: build/C/man2/select_tut.2:789
4395 " /* one side has closed the connection, keep\n"
4396 " writing to the other side until empty */\n"
4400 #: build/C/man2/select_tut.2:797
4403 " if (fd1 E<lt> 0 && buf1_avail - buf1_written == 0)\n"
4405 " if (fd2 E<lt> 0 && buf2_avail - buf2_written == 0)\n"
4408 " exit(EXIT_SUCCESS);\n"
4413 #: build/C/man2/select_tut.2:811
4415 "The above program properly forwards most kinds of TCP connections including "
4416 "OOB signal data transmitted by B<telnet> servers. It handles the tricky "
4417 "problem of having data flow in both directions simultaneously. You might "
4418 "think it more efficient to use a B<fork>(2) call and devote a thread to "
4419 "each stream. This becomes more tricky than you might suspect. Another idea "
4420 "is to set nonblocking I/O using B<fcntl>(2). This also has its problems "
4421 "because you end up using inefficient timeouts."
4425 #: build/C/man2/select_tut.2:817
4427 "The program does not handle more than one simultaneous connection at a time, "
4428 "although it could easily be extended to do this with a linked list of "
4429 "buffers\\(emone for each connection. At the moment, new connections cause "
4430 "the current connection to be dropped."
4434 #. This man page was written by Paul Sheer.
4436 #: build/C/man2/select_tut.2:836
4438 "B<accept>(2), B<connect>(2), B<ioctl>(2), B<poll>(2), B<read>(2), "
4439 "B<recv>(2), B<select>(2), B<send>(2), B<sigprocmask>(2), B<write>(2), "
4440 "B<sigaddset>(3), B<sigdelset>(3), B<sigemptyset>(3), B<sigfillset>(3), "
4441 "B<sigismember>(3), B<epoll>(7)"
4445 #: build/C/man2/send.2:38
4451 #: build/C/man2/send.2:38 build/C/man2/sendmmsg.2:28
4457 #: build/C/man2/send.2:41
4458 msgid "send, sendto, sendmsg - send a message on a socket"
4462 #: build/C/man2/send.2:45
4465 "B<#include E<lt>sys/types.hE<gt>>\n"
4466 "B<#include E<lt>sys/socket.hE<gt>>\n"
4470 #: build/C/man2/send.2:48
4473 "B<ssize_t send(int >I<sockfd>B<, const void *>I<buf>B<, size_t >I<len>B<, "
4474 "int >I<flags>B<);>\n"
4478 #: build/C/man2/send.2:52
4481 "B<ssize_t sendto(int >I<sockfd>B<, const void *>I<buf>B<, size_t >I<len>B<, "
4482 "int >I<flags>B<,>\n"
4483 "B< const struct sockaddr *>I<dest_addr>B<, socklen_t "
4484 ">I<addrlen>B<);>\n"
4488 #: build/C/man2/send.2:55
4491 "B<ssize_t sendmsg(int >I<sockfd>B<, const struct msghdr *>I<msg>B<, int "
4496 #: build/C/man2/send.2:63
4498 "The system calls B<send>(), B<sendto>(), and B<sendmsg>() are used to "
4499 "transmit a message to another socket."
4503 #: build/C/man2/send.2:82
4505 "The B<send>() call may be used only when the socket is in a I<connected> "
4506 "state (so that the intended recipient is known). The only difference "
4507 "between B<send>() and B<write>(2) is the presence of I<flags>. With a "
4508 "zero I<flags> argument, B<send>() is equivalent to B<write>(2). Also, the "
4513 #: build/C/man2/send.2:84
4515 msgid " send(sockfd, buf, len, flags);\n"
4519 #: build/C/man2/send.2:86
4520 msgid "is equivalent to"
4524 #: build/C/man2/send.2:88
4526 msgid " sendto(sockfd, buf, len, flags, NULL, 0);\n"
4530 #: build/C/man2/send.2:92
4531 msgid "The argument I<sockfd> is the file descriptor of the sending socket."
4535 #: build/C/man2/send.2:120
4537 "If B<sendto>() is used on a connection-mode (B<SOCK_STREAM>, "
4538 "B<SOCK_SEQPACKET>) socket, the arguments I<dest_addr> and I<addrlen> are "
4539 "ignored (and the error B<EISCONN> may be returned when they are not NULL and "
4540 "0), and the error B<ENOTCONN> is returned when the socket was not actually "
4541 "connected. Otherwise, the address of the target is given by I<dest_addr> "
4542 "with I<addrlen> specifying its size. For B<sendmsg>(), the address of the "
4543 "target is given by I<msg.msg_name>, with I<msg.msg_namelen> specifying its "
4548 #: build/C/man2/send.2:136
4550 "For B<send>() and B<sendto>(), the message is found in I<buf> and has "
4551 "length I<len>. For B<sendmsg>(), the message is pointed to by the elements "
4552 "of the array I<msg.msg_iov>. The B<sendmsg>() call also allows sending "
4553 "ancillary data (also known as control information)."
4557 #: build/C/man2/send.2:141
4559 "If the message is too long to pass atomically through the underlying "
4560 "protocol, the error B<EMSGSIZE> is returned, and the message is not "
4565 #: build/C/man2/send.2:145
4567 "No indication of failure to deliver is implicit in a B<send>(). Locally "
4568 "detected errors are indicated by a return value of -1."
4572 #: build/C/man2/send.2:158
4574 "When the message does not fit into the send buffer of the socket, B<send>() "
4575 "normally blocks, unless the socket has been placed in nonblocking I/O mode. "
4576 "In nonblocking mode it would fail with the error B<EAGAIN> or B<EWOULDBLOCK> "
4577 "in this case. The B<select>(2) call may be used to determine when it is "
4578 "possible to send more data."
4581 #. FIXME ? document MSG_PROXY (which went away in 2.3.15)
4583 #: build/C/man2/send.2:164
4585 "The I<flags> argument is the bitwise OR of zero or more of the following "
4590 #: build/C/man2/send.2:164
4592 msgid "B<MSG_CONFIRM> (Since Linux 2.3.15)"
4596 #: build/C/man2/send.2:178
4598 "Tell the link layer that forward progress happened: you got a successful "
4599 "reply from the other side. If the link layer doesn't get this it will "
4600 "regularly reprobe the neighbor (e.g., via a unicast ARP). Only valid on "
4601 "B<SOCK_DGRAM> and B<SOCK_RAW> sockets and currently only implemented for "
4602 "IPv4 and IPv6. See B<arp>(7) for details."
4606 #: build/C/man2/send.2:178
4608 msgid "B<MSG_DONTROUTE>"
4612 #: build/C/man2/send.2:186
4614 "Don't use a gateway to send out the packet, only send to hosts on directly "
4615 "connected networks. This is usually used only by diagnostic or routing "
4616 "programs. This is only defined for protocol families that route; packet "
4621 #: build/C/man2/send.2:197
4623 "Enables nonblocking operation; if the operation would block, B<EAGAIN> or "
4624 "B<EWOULDBLOCK> is returned (this can also be enabled using the B<O_NONBLOCK> "
4625 "flag with the B<F_SETFL> B<fcntl>(2))."
4629 #: build/C/man2/send.2:197
4631 msgid "B<MSG_EOR> (since Linux 2.2)"
4635 #: build/C/man2/send.2:201
4637 "Terminates a record (when this notion is supported, as for sockets of type "
4638 "B<SOCK_SEQPACKET>)."
4642 #: build/C/man2/send.2:201
4644 msgid "B<MSG_MORE> (Since Linux 2.4.4)"
4648 #: build/C/man2/send.2:210
4650 "The caller has more data to send. This flag is used with TCP sockets to "
4651 "obtain the same effect as the B<TCP_CORK> socket option (see B<tcp>(7)), "
4652 "with the difference that this flag can be set on a per-call basis."
4656 #: build/C/man2/send.2:219
4658 "Since Linux 2.6, this flag is also supported for UDP sockets, and informs "
4659 "the kernel to package all of the data sent in calls with this flag set into "
4660 "a single datagram which is only transmitted when a call is performed that "
4661 "does not specify this flag. (See also the B<UDP_CORK> socket option "
4662 "described in B<udp>(7).)"
4666 #: build/C/man2/send.2:219
4668 msgid "B<MSG_NOSIGNAL> (since Linux 2.2)"
4672 #: build/C/man2/send.2:228
4674 "Requests not to send B<SIGPIPE> on errors on stream oriented sockets when "
4675 "the other end breaks the connection. The B<EPIPE> error is still returned."
4679 #: build/C/man2/send.2:237
4681 "Sends I<out-of-band> data on sockets that support this notion (e.g., of type "
4682 "B<SOCK_STREAM>); the underlying protocol must also support I<out-of-band> "
4687 #: build/C/man2/send.2:244
4689 "The definition of the I<msghdr> structure follows. See B<recv>(2) and "
4690 "below for an exact description of its fields."
4693 #. Still to be documented:
4694 #. Send file descriptors and user credentials using the
4695 #. msg_control* fields.
4696 #. The flags returned in msg_flags.
4698 #: build/C/man2/send.2:273
4700 "You may send control information using the I<msg_control> and "
4701 "I<msg_controllen> members. The maximum control buffer length the kernel can "
4702 "process is limited per socket by the value in "
4703 "I</proc/sys/net/core/optmem_max>; see B<socket>(7)."
4707 #: build/C/man2/send.2:278
4709 "On success, these calls return the number of characters sent. On error, -1 "
4710 "is returned, and I<errno> is set appropriately."
4714 #: build/C/man2/send.2:283
4716 "These are some standard errors generated by the socket layer. Additional "
4717 "errors may be generated and returned from the underlying protocol modules; "
4718 "see their respective manual pages."
4722 #: build/C/man2/send.2:291
4724 "(For UNIX domain sockets, which are identified by pathname) Write "
4725 "permission is denied on the destination socket file, or search permission is "
4726 "denied for one of the directories the path prefix. (See "
4727 "B<path_resolution>(7).)"
4730 #. Actually EAGAIN on Linux
4732 #: build/C/man2/send.2:299
4734 "The socket is marked nonblocking and the requested operation would block. "
4735 "POSIX.1-2001 allows either error to be returned for this case, and does not "
4736 "require these constants to have the same value, so a portable application "
4737 "should check for both possibilities."
4741 #: build/C/man2/send.2:302
4742 msgid "An invalid descriptor was specified."
4746 #: build/C/man2/send.2:302
4748 msgid "B<ECONNRESET>"
4752 #: build/C/man2/send.2:305
4753 msgid "Connection reset by peer."
4757 #: build/C/man2/send.2:305
4759 msgid "B<EDESTADDRREQ>"
4763 #: build/C/man2/send.2:308
4764 msgid "The socket is not connection-mode, and no peer address is set."
4768 #: build/C/man2/send.2:311
4769 msgid "An invalid user space address was specified for an argument."
4773 #: build/C/man2/send.2:315
4774 msgid "A signal occurred before any data was transmitted; see B<signal>(7)."
4778 #: build/C/man2/send.2:324
4780 "The connection-mode socket was connected already but a recipient was "
4781 "specified. (Now either this error is returned, or the recipient "
4782 "specification is ignored.)"
4786 #: build/C/man2/send.2:324
4791 #. (e.g., SOCK_DGRAM )
4793 #: build/C/man2/send.2:330
4795 "The socket type requires that message be sent atomically, and the size of "
4796 "the message to be sent made this impossible."
4800 #: build/C/man2/send.2:338
4802 "The output queue for a network interface was full. This generally indicates "
4803 "that the interface has stopped sending, but may be caused by transient "
4804 "congestion. (Normally, this does not occur in Linux. Packets are just "
4805 "silently dropped when a device queue overflows.)"
4809 #: build/C/man2/send.2:341
4810 msgid "No memory available."
4814 #: build/C/man2/send.2:344
4815 msgid "The socket is not connected, and no target has been given."
4819 #: build/C/man2/send.2:354
4820 msgid "Some bit in the I<flags> argument is inappropriate for the socket type."
4824 #: build/C/man2/send.2:354
4830 #: build/C/man2/send.2:363
4832 "The local end has been shut down on a connection oriented socket. In this "
4833 "case the process will also receive a B<SIGPIPE> unless B<MSG_NOSIGNAL> is "
4838 #: build/C/man2/send.2:366
4839 msgid "4.4BSD, SVr4, POSIX.1-2001. These function calls appeared in 4.2BSD."
4843 #: build/C/man2/send.2:377
4845 "POSIX.1-2001 only describes the B<MSG_OOB> and B<MSG_EOR> flags. "
4846 "POSIX.1-2008 adds a specification of B<MSG_NOSIGNAL>. The B<MSG_CONFIRM> "
4847 "flag is a Linux extension."
4851 #: build/C/man2/send.2:390
4853 "The prototypes given above follow the Single UNIX Specification, as glibc2 "
4854 "also does; the I<flags> argument was I<int> in 4.x BSD, but I<unsigned int> "
4855 "in libc4 and libc5; the I<len> argument was I<int> in 4.x BSD and libc4, but "
4856 "I<size_t> in libc5; the I<addrlen> argument was I<int> in 4.x BSD and libc4 "
4857 "and libc5. See also B<accept>(2)."
4861 #: build/C/man2/send.2:409
4863 "See B<sendmmsg(2)> for information about a Linux-specific system call that "
4864 "can be used to transmit multiple datagrams in a single call."
4868 #: build/C/man2/send.2:414
4869 msgid "Linux may return B<EPIPE> instead of B<ENOTCONN>."
4873 #: build/C/man2/send.2:419
4874 msgid "An example of the use of B<sendto>() is shown in B<getaddrinfo>(3)."
4878 #: build/C/man2/send.2:434
4880 "B<fcntl>(2), B<getsockopt>(2), B<recv>(2), B<select>(2), B<sendfile>(2), "
4881 "B<sendmmsg>(2), B<shutdown>(2), B<socket>(2), B<write>(2), B<cmsg>(3), "
4882 "B<ip>(7), B<socket>(7), B<tcp>(7), B<udp>(7)"
4886 #: build/C/man2/sendmmsg.2:28
4892 #: build/C/man2/sendmmsg.2:31
4893 msgid "sendmmsg - send multiple messages on a socket"
4897 #: build/C/man2/sendmmsg.2:39
4900 "B<int sendmmsg(int >I<sockfd>B<, struct mmsghdr *>I<msgvec>B<, unsigned int "
4902 "B< unsigned int >I<flags>B<);>\n"
4905 #. See commit 228e548e602061b08ee8e8966f567c12aa079682
4907 #: build/C/man2/sendmmsg.2:49
4909 "The B<sendmmsg>() system call is an extension of B<sendmsg>(2) that allows "
4910 "the caller to transmit multiple messages on a socket using a single system "
4911 "call. (This has performance benefits for some applications.)"
4915 #: build/C/man2/sendmmsg.2:54
4917 "The I<sockfd> argument is the file descriptor of the socket on which data is "
4918 "to be transmitted."
4922 #: build/C/man2/sendmmsg.2:75
4925 "struct mmsghdr {\n"
4926 " struct msghdr msg_hdr; /* Message header */\n"
4927 " unsigned int msg_len; /* Number of bytes transmitted */\n"
4932 #: build/C/man2/sendmmsg.2:91
4934 "The I<msg_hdr> field is a I<msghdr> structure, as described in "
4935 "B<sendmsg>(2). The I<msg_len> field is used to return the number of bytes "
4936 "sent from the message in I<msg_hdr> (i.e., the same as the return value from "
4937 "a single B<sendmsg>(2) call)."
4941 #: build/C/man2/sendmmsg.2:97
4943 "The I<flags> argument contains flags ORed together. The flags are the same "
4944 "as for B<sendmsg>(2)."
4948 #: build/C/man2/sendmmsg.2:107
4950 "A blocking B<sendmmsg>() call blocks until I<vlen> messages have been "
4951 "sent. A nonblocking call sends as many messages as possible (up to the "
4952 "limit specified by I<vlen>) and returns immediately."
4956 #: build/C/man2/sendmmsg.2:119
4958 "On return from B<sendmmsg>(), the I<msg_len> fields of successive elements "
4959 "of I<msgvec> are updated to contain the number of bytes transmitted from the "
4960 "corresponding I<msg_hdr>. The return value of the call indicates the number "
4961 "of elements of I<msgvec> that have been updated."
4965 #: build/C/man2/sendmmsg.2:129
4967 "On success, B<sendmmsg>() returns the number of messages sent from "
4968 "I<msgvec>; if this is less than I<vlen>, the caller can retry with a further "
4969 "B<sendmmsg>() call to send the remaining messages."
4973 #: build/C/man2/sendmmsg.2:133
4974 msgid "On error, -1 is returned, and I<errno> is set to indicate the error."
4977 #. commit 728ffb86f10873aaf4abd26dde691ee40ae731fe
4978 #. ... only return an error if no datagrams could be sent.
4979 #. If less than the requested number of messages were sent, the application
4980 #. must retry starting at the first failed one and if the problem is
4981 #. persistent the error will be returned.
4983 #. This matches the behaviour of other syscalls like read/write - it
4984 #. is not an error if less than the requested number of elements are sent.
4986 #: build/C/man2/sendmmsg.2:145
4988 "Errors are as for B<sendmsg>(2). An error is returned only if no datagrams "
4993 #: build/C/man2/sendmmsg.2:150
4995 "The B<sendmmsg>() system call was added in Linux 3.0. Support in glibc was "
4996 "added in version 2.14."
5000 #: build/C/man2/sendmmsg.2:153
5001 msgid "B<sendmmsg>() is Linux-specific."
5004 #. commit 98382f419f32d2c12d021943b87dea555677144b
5005 #. net: Cap number of elements for sendmmsg
5007 #. To limit the amount of time we can spend in sendmmsg, cap the
5008 #. number of elements to UIO_MAXIOV (currently 1024).
5010 #. For error handling an application using sendmmsg needs to retry at
5011 #. the first unsent message, so capping is simpler and requires less
5012 #. application logic than returning EINVAL.
5014 #: build/C/man2/sendmmsg.2:168
5015 msgid "The value specified in I<vlen> is capped to B<UIO_MAXIOV> (1024)."
5019 #: build/C/man2/sendmmsg.2:173
5020 msgid "B<recvmmsg>(2), B<sendmsg>(2), B<socket>(2), B<socket>(7)"
5024 #: build/C/man3/sockatmark.3:23
5030 #: build/C/man3/sockatmark.3:26
5031 msgid "sockatmark - determine whether socket is at out-of-band mark"
5035 #: build/C/man3/sockatmark.3:28 build/C/man2/socket.2:48 build/C/man7/socket.7:31 build/C/man2/socketpair.2:47
5036 msgid "B<#include E<lt>sys/socket.hE<gt>>"
5040 #: build/C/man3/sockatmark.3:30
5041 msgid "B<int sockatmark(int >I<sockfd>B<);>"
5045 #: build/C/man3/sockatmark.3:39
5047 "B<sockatmark>(): _POSIX_C_SOURCE\\ E<gt>=\\ 200112L || _XOPEN_SOURCE\\ "
5052 #: build/C/man3/sockatmark.3:49
5054 "B<sockatmark>() returns a value indicating whether or not the socket "
5055 "referred to by the file descriptor I<sockfd> is at the out-of-band mark. If "
5056 "the socket is at the mark, then 1 is returned; if the socket is not at the "
5057 "mark, 0 is returned. This function does not remove the out-of-band mark."
5061 #: build/C/man3/sockatmark.3:54
5063 "A successful call to B<sockatmark>() returns 1 if the socket is at the "
5064 "out-of-band mark, or 0 if it is not. On error, -1 is returned and I<errno> "
5065 "is set to indicate the error."
5069 #: build/C/man3/sockatmark.3:59
5070 msgid "I<sockfd> is not a valid file descriptor."
5073 #. POSIX.1 says ENOTTY for this case
5075 #: build/C/man3/sockatmark.3:66
5076 msgid "I<sockfd> is not a file descriptor to which B<sockatmark>() can be applied."
5080 #: build/C/man3/sockatmark.3:69
5081 msgid "B<sockatmark>() was added to glibc in version 2.2.4."
5085 #: build/C/man3/sockatmark.3:71
5086 msgid "POSIX.1-2001."
5090 #: build/C/man3/sockatmark.3:78
5092 "If B<sockatmark>() returns 1, then the out-of-band data can be read using "
5093 "the B<MSG_OOB> flag of B<recv>(2)."
5097 #: build/C/man3/sockatmark.3:80
5098 msgid "Out-of-band data is only supported on some stream socket protocols."
5102 #: build/C/man3/sockatmark.3:85
5104 "B<sockatmark>() can safely be called from a handler for the B<SIGURG> "
5109 #: build/C/man3/sockatmark.3:91
5111 "B<sockatmark>() is implemented using the B<SIOCATMARK> B<ioctl>(2) "
5116 #: build/C/man3/sockatmark.3:95
5117 msgid "Prior to glibc 2.4, B<sockatmark>() did not work."
5121 #: build/C/man3/sockatmark.3:100
5123 "The following code can be used after receipt of a B<SIGURG> signal to read "
5124 "(and discard) all data up to the mark, and then read the byte of data at the "
5129 #: build/C/man3/sockatmark.3:105
5132 " char buf[BUF_LEN];\n"
5138 #: build/C/man3/sockatmark.3:112
5142 " atmark = sockatmark(sockfd);\n"
5143 " if (atmark == -1) {\n"
5144 " perror(\"sockatmark\");\n"
5150 #: build/C/man3/sockatmark.3:115
5158 #: build/C/man3/sockatmark.3:122
5161 " s = read(sockfd, buf, BUF_LEN) E<lt>= 0);\n"
5163 " perror(\"read\");\n"
5164 " if (s E<lt>= 0)\n"
5170 #: build/C/man3/sockatmark.3:129
5173 " if (atmark == 1) {\n"
5174 " if (recv(sockfd, &oobdata, 1, MSG_OOB) == -1) {\n"
5175 " perror(\"recv\");\n"
5182 #: build/C/man3/sockatmark.3:135
5183 msgid "B<fcntl>(2), B<recv>(2), B<send>(2), B<tcp>(7)"
5187 #: build/C/man2/socket.2:41 build/C/man7/socket.7:26
5193 #: build/C/man2/socket.2:41
5199 #: build/C/man2/socket.2:44
5200 msgid "socket - create an endpoint for communication"
5204 #: build/C/man2/socket.2:46 build/C/man2/socketpair.2:45
5205 msgid "B<#include E<lt>sys/types.hE<gt>> /* See NOTES */"
5209 #: build/C/man2/socket.2:50
5210 msgid "B<int socket(int >I<domain>B<, int >I<type>B<, int >I<protocol>B<);>"
5214 #: build/C/man2/socket.2:53
5215 msgid "B<socket>() creates an endpoint for communication and returns a descriptor."
5219 #: build/C/man2/socket.2:61
5221 "The I<domain> argument specifies a communication domain; this selects the "
5222 "protocol family which will be used for communication. These families are "
5223 "defined in I<E<lt>sys/socket.hE<gt>>. The currently understood formats "
5228 #: build/C/man2/socket.2:64
5230 msgid "Name:Purpose:Man page\n"
5234 #: build/C/man2/socket.2:65 build/C/man2/socket.2:72 build/C/man2/socket.2:77 build/C/man2/socket.2:82 build/C/man2/socket.2:85 build/C/man2/socket.2:92 build/C/man2/socket.2:97 build/C/man2/socket.2:102 build/C/man2/socket.2:105 build/C/man2/socket.2:110
5240 #: build/C/man2/socket.2:66
5242 msgid "B<AF_UNIX>, B<AF_LOCAL>\n"
5246 #: build/C/man2/socket.2:67 build/C/man2/socket.2:69 build/C/man2/socket.2:87 build/C/man2/socket.2:89 build/C/man2/socket.2:99 build/C/man2/socket.2:112 build/C/man2/socket.2:114 build/C/man7/socket.7:162
5252 #: build/C/man2/socket.2:68
5254 msgid "Local communication\n"
5258 #: build/C/man2/socket.2:70
5260 msgid "B<unix>(7)\n"
5264 #: build/C/man2/socket.2:71 build/C/man2/socket.2:76 build/C/man2/socket.2:81 build/C/man2/socket.2:91 build/C/man2/socket.2:96 build/C/man2/socket.2:109 build/C/man2/socket.2:116 build/C/man7/socket.7:141 build/C/man7/socket.7:145 build/C/man7/socket.7:148 build/C/man7/socket.7:154 build/C/man7/socket.7:157 build/C/man7/socket.7:166 build/C/man7/socket.7:173
5270 #: build/C/man2/socket.2:73
5272 msgid "B<AF_INET>\n"
5276 #: build/C/man2/socket.2:74
5278 msgid "T}:IPv4 Internet protocols:T{\n"
5282 #: build/C/man2/socket.2:75
5288 #: build/C/man2/socket.2:78
5290 msgid "B<AF_INET6>\n"
5294 #: build/C/man2/socket.2:79
5296 msgid "T}:IPv6 Internet protocols:T{\n"
5300 #: build/C/man2/socket.2:80
5302 msgid "B<ipv6>(7)\n"
5306 #: build/C/man2/socket.2:83
5312 #: build/C/man2/socket.2:84
5314 msgid "T}:IPX - Novell protocols:\n"
5318 #: build/C/man2/socket.2:86
5320 msgid "B<AF_NETLINK>\n"
5324 #: build/C/man2/socket.2:88
5326 msgid "Kernel user interface device\n"
5330 #: build/C/man2/socket.2:90
5332 msgid "B<netlink>(7)\n"
5336 #: build/C/man2/socket.2:93
5342 #: build/C/man2/socket.2:94
5344 msgid "T}:ITU-T X.25 / ISO-8208 protocol:T{\n"
5348 #: build/C/man2/socket.2:95
5354 #: build/C/man2/socket.2:98
5356 msgid "B<AF_AX25>\n"
5360 #: build/C/man2/socket.2:100
5362 msgid "Amateur radio AX.25 protocol\n"
5366 #: build/C/man2/socket.2:101
5372 #: build/C/man2/socket.2:103
5374 msgid "B<AF_ATMPVC>\n"
5378 #: build/C/man2/socket.2:104
5380 msgid "T}:Access to raw ATM PVCs:\n"
5384 #: build/C/man2/socket.2:106
5386 msgid "B<AF_APPLETALK>\n"
5390 #: build/C/man2/socket.2:107
5392 msgid "T}:Appletalk:T{\n"
5396 #: build/C/man2/socket.2:108
5402 #: build/C/man2/socket.2:111
5404 msgid "B<AF_PACKET>\n"
5408 #: build/C/man2/socket.2:113
5410 msgid "Low level packet interface\n"
5414 #: build/C/man2/socket.2:115
5416 msgid "B<packet>(7)\n"
5420 #: build/C/man2/socket.2:124
5422 "The socket has the indicated I<type>, which specifies the communication "
5423 "semantics. Currently defined types are:"
5427 #: build/C/man2/socket.2:124
5429 msgid "B<SOCK_STREAM>"
5433 #: build/C/man2/socket.2:128
5435 "Provides sequenced, reliable, two-way, connection-based byte streams. An "
5436 "out-of-band data transmission mechanism may be supported."
5440 #: build/C/man2/socket.2:128
5442 msgid "B<SOCK_DGRAM>"
5446 #: build/C/man2/socket.2:132
5448 "Supports datagrams (connectionless, unreliable messages of a fixed maximum "
5453 #: build/C/man2/socket.2:132
5455 msgid "B<SOCK_SEQPACKET>"
5459 #: build/C/man2/socket.2:137
5461 "Provides a sequenced, reliable, two-way connection-based data transmission "
5462 "path for datagrams of fixed maximum length; a consumer is required to read "
5463 "an entire packet with each input system call."
5467 #: build/C/man2/socket.2:137
5473 #: build/C/man2/socket.2:140
5474 msgid "Provides raw network protocol access."
5478 #: build/C/man2/socket.2:140
5484 #: build/C/man2/socket.2:143
5485 msgid "Provides a reliable datagram layer that does not guarantee ordering."
5489 #: build/C/man2/socket.2:143
5491 msgid "B<SOCK_PACKET>"
5495 #: build/C/man2/socket.2:148
5496 msgid "Obsolete and should not be used in new programs; see B<packet>(7)."
5500 #: build/C/man2/socket.2:154
5502 "Some socket types may not be implemented by all protocol families; for "
5503 "example, B<SOCK_SEQPACKET> is not implemented for B<AF_INET>."
5507 #: build/C/man2/socket.2:162
5509 "Since Linux 2.6.27, the I<type> argument serves a second purpose: in "
5510 "addition to specifying a socket type, it may include the bitwise OR of any "
5511 "of the following values, to modify the behavior of B<socket>():"
5515 #: build/C/man2/socket.2:196
5517 "The I<protocol> specifies a particular protocol to be used with the socket. "
5518 "Normally only a single protocol exists to support a particular socket type "
5519 "within a given protocol family, in which case I<protocol> can be specified "
5520 "as 0. However, it is possible that many protocols may exist, in which case "
5521 "a particular protocol must be specified in this manner. The protocol number "
5522 "to use is specific to the ``communication domain'' in which communication is "
5523 "to take place; see B<protocols>(5). See B<getprotoent>(3) on how to map "
5524 "protocol name strings to protocol numbers."
5528 #: build/C/man2/socket.2:226
5530 "Sockets of type B<SOCK_STREAM> are full-duplex byte streams, similar to "
5531 "pipes. They do not preserve record boundaries. A stream socket must be in "
5532 "a I<connected> state before any data may be sent or received on it. A "
5533 "connection to another socket is created with a B<connect>(2) call. Once "
5534 "connected, data may be transferred using B<read>(2) and B<write>(2) calls "
5535 "or some variant of the B<send>(2) and B<recv>(2) calls. When a session "
5536 "has been completed a B<close>(2) may be performed. Out-of-band data may "
5537 "also be transmitted as described in B<send>(2) and received as described in "
5542 #: build/C/man2/socket.2:252
5544 "The communications protocols which implement a B<SOCK_STREAM> ensure that "
5545 "data is not lost or duplicated. If a piece of data for which the peer "
5546 "protocol has buffer space cannot be successfully transmitted within a "
5547 "reasonable length of time, then the connection is considered to be dead. "
5548 "When B<SO_KEEPALIVE> is enabled on the socket the protocol checks in a "
5549 "protocol-specific manner if the other end is still alive. A B<SIGPIPE> "
5550 "signal is raised if a process sends or receives on a broken stream; this "
5551 "causes naive processes, which do not handle the signal, to exit. "
5552 "B<SOCK_SEQPACKET> sockets employ the same system calls as B<SOCK_STREAM> "
5553 "sockets. The only difference is that B<read>(2) calls will return only the "
5554 "amount of data requested, and any data remaining in the arriving packet will "
5555 "be discarded. Also all message boundaries in incoming datagrams are "
5560 #: build/C/man2/socket.2:262
5562 "B<SOCK_DGRAM> and B<SOCK_RAW> sockets allow sending of datagrams to "
5563 "correspondents named in B<sendto>(2) calls. Datagrams are generally "
5564 "received with B<recvfrom>(2), which returns the next datagram along with the "
5565 "address of its sender."
5569 #: build/C/man2/socket.2:269
5571 "B<SOCK_PACKET> is an obsolete socket type to receive raw packets directly "
5572 "from the device driver. Use B<packet>(7) instead."
5576 #: build/C/man2/socket.2:292
5578 "An B<fcntl>(2) B<F_SETOWN> operation can be used to specify a process or "
5579 "process group to receive a B<SIGURG> signal when the out-of-band data "
5580 "arrives or B<SIGPIPE> signal when a B<SOCK_STREAM> connection breaks "
5581 "unexpectedly. This operation may also be used to set the process or process "
5582 "group that receives the I/O and asynchronous notification of I/O events via "
5583 "B<SIGIO>. Using B<F_SETOWN> is equivalent to an B<ioctl>(2) call with the "
5584 "B<FIOSETOWN> or B<SIOCSPGRP> argument."
5588 #: build/C/man2/socket.2:302
5590 "When the network signals an error condition to the protocol module (e.g., "
5591 "using a ICMP message for IP) the pending error flag is set for the socket. "
5592 "The next operation on this socket will return the error code of the pending "
5593 "error. For some protocols it is possible to enable a per-socket error queue "
5594 "to retrieve detailed information about the error; see B<IP_RECVERR> in "
5599 #: build/C/man2/socket.2:312
5601 "The operation of sockets is controlled by socket level I<options>. These "
5602 "options are defined in I<E<lt>sys/socket.hE<gt>>. The functions "
5603 "B<setsockopt>(2) and B<getsockopt>(2) are used to set and get options, "
5608 #: build/C/man2/socket.2:317
5610 "On success, a file descriptor for the new socket is returned. On error, -1 "
5611 "is returned, and I<errno> is set appropriately."
5615 #: build/C/man2/socket.2:322
5617 "Permission to create a socket of the specified type and/or protocol is "
5622 #: build/C/man2/socket.2:325
5623 msgid "The implementation does not support the specified address family."
5627 #: build/C/man2/socket.2:328
5628 msgid "Unknown protocol, or protocol family not available."
5631 #. Since Linux 2.6.27
5633 #: build/C/man2/socket.2:333
5634 msgid "Invalid flags in I<type>."
5638 #: build/C/man2/socket.2:336
5639 msgid "Process file table overflow."
5643 #: build/C/man2/socket.2:339
5645 msgid "B<ENOBUFS> or B<ENOMEM>"
5649 #: build/C/man2/socket.2:344
5651 "Insufficient memory is available. The socket cannot be created until "
5652 "sufficient resources are freed."
5656 #: build/C/man2/socket.2:344 build/C/man2/socketpair.2:90
5658 msgid "B<EPROTONOSUPPORT>"
5662 #: build/C/man2/socket.2:348
5664 "The protocol type or the specified protocol is not supported within this "
5669 #: build/C/man2/socket.2:350
5670 msgid "Other errors may be generated by the underlying protocol modules."
5674 #: build/C/man2/socket.2:352
5675 msgid "4.4BSD, POSIX.1-2001."
5679 #: build/C/man2/socket.2:358
5680 msgid "The B<SOCK_NONBLOCK> and B<SOCK_CLOEXEC> flags are Linux-specific."
5684 #: build/C/man2/socket.2:364
5686 "B<socket>() appeared in 4.2BSD. It is generally portable to/from non-BSD "
5687 "systems supporting clones of the BSD socket layer (including System V "
5692 #: build/C/man2/socket.2:382
5694 "The manifest constants used under 4.x BSD for protocol families are "
5695 "B<PF_UNIX>, B<PF_INET>, etc., while B<AF_UNIX> etc. are used for address "
5696 "families. However, already the BSD man page promises: \"The protocol family "
5697 "generally is the same as the address family\", and subsequent standards use "
5702 #: build/C/man2/socket.2:387
5703 msgid "An example of the use of B<socket>() is shown in B<getaddrinfo>(3)."
5707 #: build/C/man2/socket.2:410
5709 "B<accept>(2), B<bind>(2), B<connect>(2), B<fcntl>(2), B<getpeername>(2), "
5710 "B<getsockname>(2), B<getsockopt>(2), B<ioctl>(2), B<listen>(2), B<read>(2), "
5711 "B<recv>(2), B<select>(2), B<send>(2), B<shutdown>(2), B<socketpair>(2), "
5712 "B<write>(2), B<getprotoent>(3), B<ip>(7), B<socket>(7), B<tcp>(7), "
5713 "B<udp>(7), B<unix>(7)"
5717 #: build/C/man2/socket.2:414
5719 "\\(lqAn Introductory 4.3BSD Interprocess Communication Tutorial\\(rq is "
5720 "reprinted in I<UNIX Programmer's Supplementary Documents Volume 1.>"
5724 #: build/C/man2/socket.2:418
5726 "\\(lqBSD Interprocess Communication Tutorial\\(rq is reprinted in I<UNIX "
5727 "Programmer's Supplementary Documents Volume 1.>"
5731 #: build/C/man7/socket.7:26
5737 #: build/C/man7/socket.7:29
5738 msgid "socket - Linux socket interface"
5742 #: build/C/man7/socket.7:33
5744 "I<sockfd>B< = socket(int >I<socket_family>B<, int >I<socket_type>B<, int "
5749 #: build/C/man7/socket.7:52
5751 "This manual page describes the Linux networking socket layer user "
5752 "interface. The BSD compatible sockets are the uniform interface between the "
5753 "user process and the network protocol stacks in the kernel. The protocol "
5754 "modules are grouped into I<protocol families> like B<AF_INET>, B<AF_IPX>, "
5755 "B<AF_PACKET> and I<socket types> like B<SOCK_STREAM> or B<SOCK_DGRAM>. See "
5756 "B<socket>(2) for more information on families and types."
5760 #: build/C/man7/socket.7:52
5762 msgid "Socket Layer Functions"
5766 #: build/C/man7/socket.7:56
5768 "These functions are used by the user process to send or receive packets and "
5769 "to do other socket operations. For more information see their respective "
5774 #: build/C/man7/socket.7:72
5776 "B<socket>(2) creates a socket, B<connect>(2) connects a socket to a remote "
5777 "socket address, the B<bind>(2) function binds a socket to a local socket "
5778 "address, B<listen>(2) tells the socket that new connections shall be "
5779 "accepted, and B<accept>(2) is used to get a new socket with a new incoming "
5780 "connection. B<socketpair>(2) returns two connected anonymous sockets (only "
5781 "implemented for a few local families like B<AF_UNIX>)"
5785 #: build/C/man7/socket.7:94
5787 "B<send>(2), B<sendto>(2), and B<sendmsg>(2) send data over a socket, and "
5788 "B<recv>(2), B<recvfrom>(2), B<recvmsg>(2) receive data from a socket. "
5789 "B<poll>(2) and B<select>(2) wait for arriving data or a readiness to send "
5790 "data. In addition, the standard I/O operations like B<write>(2), "
5791 "B<writev>(2), B<sendfile>(2), B<read>(2), and B<readv>(2) can be used to "
5792 "read and write data."
5796 #: build/C/man7/socket.7:105
5798 "B<getsockname>(2) returns the local socket address and B<getpeername>(2) "
5799 "returns the remote socket address. B<getsockopt>(2) and B<setsockopt>(2) "
5800 "are used to set or get socket layer or protocol options. B<ioctl>(2) can "
5801 "be used to set or read some other options."
5805 #: build/C/man7/socket.7:110
5807 "B<close>(2) is used to close a socket. B<shutdown>(2) closes parts of a "
5808 "full-duplex socket connection."
5812 #: build/C/man7/socket.7:116
5814 "Seeking, or calling B<pread>(2) or B<pwrite>(2) with a nonzero position is "
5815 "not supported on sockets."
5819 #: build/C/man7/socket.7:133
5821 "It is possible to do nonblocking I/O on sockets by setting the B<O_NONBLOCK> "
5822 "flag on a socket file descriptor using B<fcntl>(2). Then all operations "
5823 "that would block will (usually) return with B<EAGAIN> (operation should be "
5824 "retried later); B<connect>(2) will return B<EINPROGRESS> error. The user "
5825 "can then wait for various events via B<poll>(2) or B<select>(2)."
5829 #: build/C/man7/socket.7:137
5831 msgid "I/O events\n"
5835 #: build/C/man7/socket.7:138
5837 msgid "Event:Poll flag:Occurrence\n"
5841 #: build/C/man7/socket.7:139 build/C/man7/socket.7:142
5843 msgid "Read:POLLIN:T{\n"
5847 #: build/C/man7/socket.7:140
5849 msgid "New data arrived.\n"
5853 #: build/C/man7/socket.7:143
5855 msgid "A connection setup has been completed\n"
5859 #: build/C/man7/socket.7:144
5861 msgid "(for connection-oriented sockets)\n"
5865 #: build/C/man7/socket.7:146 build/C/man7/socket.7:149
5867 msgid "Read:POLLHUP:T{\n"
5871 #: build/C/man7/socket.7:147
5873 msgid "A disconnection request has been initiated by the other end.\n"
5877 #: build/C/man7/socket.7:150
5879 msgid "A connection is broken (only for connection-oriented protocols).\n"
5883 #: build/C/man7/socket.7:151
5885 msgid "When the socket is written\n"
5889 #: build/C/man7/socket.7:152
5891 msgid "B<SIGPIPE>\n"
5895 #: build/C/man7/socket.7:153
5897 msgid "is also sent.\n"
5901 #: build/C/man7/socket.7:155
5903 msgid "Write:POLLOUT:T{\n"
5907 #: build/C/man7/socket.7:156
5909 msgid "Socket has enough send buffer space for writing new data.\n"
5913 #: build/C/man7/socket.7:158
5915 msgid "Read/Write:T{\n"
5919 #: build/C/man7/socket.7:159
5925 #: build/C/man7/socket.7:160
5931 #: build/C/man7/socket.7:161
5937 #: build/C/man7/socket.7:163
5939 msgid "An outgoing\n"
5943 #: build/C/man7/socket.7:164
5945 msgid "B<connect>(2)\n"
5949 #: build/C/man7/socket.7:165
5955 #: build/C/man7/socket.7:167
5957 msgid "Read/Write:POLLERR:An asynchronous error occurred.\n"
5961 #: build/C/man7/socket.7:168
5963 msgid "Read/Write:POLLHUP:The other end has shut down one direction.\n"
5967 #: build/C/man7/socket.7:169
5969 msgid "Exception:POLLPRI:T{\n"
5973 #: build/C/man7/socket.7:170
5975 msgid "Urgent data arrived.\n"
5979 #: build/C/man7/socket.7:171
5985 #: build/C/man7/socket.7:172
5987 msgid "is sent then.\n"
5991 #: build/C/man7/socket.7:202
5993 "An alternative to B<poll>(2) and B<select>(2) is to let the kernel inform "
5994 "the application about events via a B<SIGIO> signal. For that the B<O_ASYNC> "
5995 "flag must be set on a socket file descriptor via B<fcntl>(2) and a valid "
5996 "signal handler for B<SIGIO> must be installed via B<sigaction>(2). See the "
5997 "I<Signals> discussion below."
6001 #: build/C/man7/socket.7:202
6003 msgid "Socket Options"
6007 #. In the list below, the text used to describe argument types
6008 #. for each socket option should be more consistent
6010 #. SO_ACCEPTCONN is in POSIX.1-2001, and its origin is explained in
6011 #. W R Stevens, UNPv1
6013 #: build/C/man7/socket.7:216
6015 "These socket options can be set by using B<setsockopt>(2) and read with "
6016 "B<getsockopt>(2) with the socket level set to B<SOL_SOCKET> for all "
6021 #: build/C/man7/socket.7:216
6023 msgid "B<SO_ACCEPTCONN>"
6027 #: build/C/man7/socket.7:224
6029 "Returns a value indicating whether or not this socket has been marked to "
6030 "accept connections with B<listen>(2). The value 0 indicates that this is "
6031 "not a listening socket, the value 1 indicates that this is a listening "
6032 "socket. This socket option is read-only."
6036 #: build/C/man7/socket.7:224
6038 msgid "B<SO_BINDTODEVICE>"
6042 #: build/C/man7/socket.7:243
6044 "Bind this socket to a particular device like \\(lqeth0\\(rq, as specified in "
6045 "the passed interface name. If the name is an empty string or the option "
6046 "length is zero, the socket device binding is removed. The passed option is "
6047 "a variable-length null-terminated interface name string with the maximum "
6048 "size of B<IFNAMSIZ>. If a socket is bound to an interface, only packets "
6049 "received from that particular interface are processed by the socket. Note "
6050 "that this only works for some socket types, particularly B<AF_INET> "
6051 "sockets. It is not supported for packet sockets (use normal B<bind>(2) "
6056 #: build/C/man7/socket.7:243
6058 msgid "B<SO_BROADCAST>"
6062 #: build/C/man7/socket.7:250
6064 "Set or get the broadcast flag. When enabled, datagram sockets receive "
6065 "packets sent to a broadcast address and they are allowed to send packets to "
6066 "a broadcast address. This option has no effect on stream-oriented sockets."
6070 #: build/C/man7/socket.7:250
6072 msgid "B<SO_BSDCOMPAT>"
6076 #: build/C/man7/socket.7:262
6078 "Enable BSD bug-to-bug compatibility. This is used by the UDP protocol "
6079 "module in Linux 2.0 and 2.2. If enabled ICMP errors received for a UDP "
6080 "socket will not be passed to the user program. In later kernel versions, "
6081 "support for this option has been phased out: Linux 2.4 silently ignores it, "
6082 "and Linux 2.6 generates a kernel warning (printk()) if a program uses this "
6083 "option. Linux 2.0 also enabled BSD bug-to-bug compatibility options (random "
6084 "header changing, skipping of the broadcast flag) for raw sockets with this "
6085 "option, but that was removed in Linux 2.2."
6089 #: build/C/man7/socket.7:262
6095 #: build/C/man7/socket.7:268
6097 "Enable socket debugging. Only allowed for processes with the "
6098 "B<CAP_NET_ADMIN> capability or an effective user ID of 0."
6102 #: build/C/man7/socket.7:268
6104 msgid "B<SO_DOMAIN> (since Linux 2.6.32)"
6108 #: build/C/man7/socket.7:276
6110 "Retrieves the socket domain as an integer, returning a value such as "
6111 "B<AF_INET6>. See B<socket>(2) for details. This socket option is "
6116 #: build/C/man7/socket.7:276
6122 #: build/C/man7/socket.7:281
6124 "Get and clear the pending socket error. This socket option is read-only. "
6125 "Expects an integer."
6129 #: build/C/man7/socket.7:281
6131 msgid "B<SO_DONTROUTE>"
6135 #: build/C/man7/socket.7:290
6137 "Don't send via a gateway, only send to directly connected hosts. The same "
6138 "effect can be achieved by setting the B<MSG_DONTROUTE> flag on a socket "
6139 "B<send>(2) operation. Expects an integer boolean flag."
6143 #: build/C/man7/socket.7:290
6145 msgid "B<SO_KEEPALIVE>"
6149 #: build/C/man7/socket.7:294
6151 "Enable sending of keep-alive messages on connection-oriented sockets. "
6152 "Expects an integer boolean flag."
6156 #: build/C/man7/socket.7:294
6158 msgid "B<SO_LINGER>"
6162 #: build/C/man7/socket.7:302
6164 "Sets or gets the B<SO_LINGER> option. The argument is a I<linger> "
6169 #: build/C/man7/socket.7:309
6173 " int l_onoff; /* linger active */\n"
6174 " int l_linger; /* how many seconds to linger for */\n"
6179 #: build/C/man7/socket.7:323
6181 "When enabled, a B<close>(2) or B<shutdown>(2) will not return until all "
6182 "queued messages for the socket have been successfully sent or the linger "
6183 "timeout has been reached. Otherwise, the call returns immediately and the "
6184 "closing is done in the background. When the socket is closed as part of "
6185 "B<exit>(2), it always lingers in the background."
6189 #: build/C/man7/socket.7:323
6191 msgid "B<SO_OOBINLINE>"
6194 #. don't document it because it can do too much harm.
6197 #: build/C/man7/socket.7:332
6199 "If this option is enabled, out-of-band data is directly placed into the "
6200 "receive data stream. Otherwise out-of-band data is only passed when the "
6201 "B<MSG_OOB> flag is set during receiving."
6205 #: build/C/man7/socket.7:332
6207 msgid "B<SO_PASSCRED>"
6210 #. FIXME Document SO_PASSSEC, added in 2.6.18; there is some info
6211 #. in the 2.6.18 ChangeLog
6213 #: build/C/man7/socket.7:341
6215 "Enable or disable the receiving of the B<SCM_CREDENTIALS> control message. "
6216 "For more information see B<unix>(7)."
6220 #: build/C/man7/socket.7:341
6222 msgid "B<SO_PEERCRED>"
6226 #: build/C/man7/socket.7:361
6228 "Return the credentials of the foreign process connected to this socket. "
6229 "This is only possible for connected B<AF_UNIX> stream sockets and B<AF_UNIX> "
6230 "stream and datagram socket pairs created using B<socketpair>(2); see "
6231 "B<unix>(7). The returned credentials are those that were in effect at the "
6232 "time of the call to B<connect>(2) or B<socketpair>(2). Argument is a "
6233 "I<ucred> structure. This socket option is read-only."
6237 #: build/C/man7/socket.7:361
6239 msgid "B<SO_PRIORITY>"
6243 #: build/C/man7/socket.7:374
6245 "Set the protocol-defined priority for all packets to be sent on this "
6246 "socket. Linux uses this value to order the networking queues: packets with "
6247 "a higher priority may be processed first depending on the selected device "
6248 "queueing discipline. For B<ip>(7), this also sets the IP type-of-service "
6249 "(TOS) field for outgoing packets. Setting a priority outside the range 0 to "
6250 "6 requires the B<CAP_NET_ADMIN> capability."
6254 #: build/C/man7/socket.7:374
6256 msgid "B<SO_PROTOCOL> (since Linux 2.6.32)"
6260 #: build/C/man7/socket.7:382
6262 "Retrieves the socket protocol as an integer, returning a value such as "
6263 "B<IPPROTO_SCTP>. See B<socket>(2) for details. This socket option is "
6268 #: build/C/man7/socket.7:382
6270 msgid "B<SO_RCVBUF>"
6273 #. Most (all?) other implementations do not do this -- MTK, Dec 05
6275 #: build/C/man7/socket.7:397
6277 "Sets or gets the maximum socket receive buffer in bytes. The kernel doubles "
6278 "this value (to allow space for bookkeeping overhead) when it is set using "
6279 "B<setsockopt>(2), and this doubled value is returned by B<getsockopt>(2). "
6280 "The default value is set by the I</proc/sys/net/core/rmem_default> file, and "
6281 "the maximum allowed value is set by the I</proc/sys/net/core/rmem_max> "
6282 "file. The minimum (doubled) value for this option is 256."
6286 #: build/C/man7/socket.7:397
6288 msgid "B<SO_RCVBUFFORCE> (since Linux 2.6.14)"
6292 #: build/C/man7/socket.7:406
6294 "Using this socket option, a privileged (B<CAP_NET_ADMIN>) process can "
6295 "perform the same task as B<SO_RCVBUF>, but the I<rmem_max> limit can be "
6300 #: build/C/man7/socket.7:406
6302 msgid "B<SO_RCVLOWAT> and B<SO_SNDLOWAT>"
6305 #. See http://marc.theaimsgroup.com/?l=linux-kernel&m=111049368106984&w=2
6306 #. Tested on kernel 2.6.14 -- mtk, 30 Nov 05
6308 #: build/C/man7/socket.7:435
6310 "Specify the minimum number of bytes in the buffer until the socket layer "
6311 "will pass the data to the protocol (B<SO_SNDLOWAT>) or the user on "
6312 "receiving (B<SO_RCVLOWAT>). These two values are initialized to 1. "
6313 "B<SO_SNDLOWAT> is not changeable on Linux (B<setsockopt>(2) fails with the "
6314 "error B<ENOPROTOOPT>). B<SO_RCVLOWAT> is changeable only since Linux 2.4. "
6315 "The B<select>(2) and B<poll>(2) system calls currently do not respect the "
6316 "B<SO_RCVLOWAT> setting on Linux, and mark a socket readable when even a "
6317 "single byte of data is available. A subsequent read from the socket will "
6318 "block until B<SO_RCVLOWAT> bytes are available."
6322 #: build/C/man7/socket.7:435
6324 msgid "B<SO_RCVTIMEO> and B<SO_SNDTIMEO>"
6327 #. Not implemented in 2.0.
6328 #. Implemented in 2.1.11 for getsockopt: always return a zero struct.
6329 #. Implemented in 2.3.41 for setsockopt, and actually used.
6330 #. in fact to EAGAIN
6332 #: build/C/man7/socket.7:466
6334 "Specify the receiving or sending timeouts until reporting an error. The "
6335 "argument is a I<struct timeval>. If an input or output function blocks for "
6336 "this period of time, and data has been sent or received, the return value of "
6337 "that function will be the amount of data transferred; if no data has been "
6338 "transferred and the timeout has been reached then -1 is returned with "
6339 "I<errno> set to B<EAGAIN> or B<EWOULDBLOCK> just as if the socket was "
6340 "specified to be nonblocking. If the timeout is set to zero (the default) "
6341 "then the operation will never timeout. Timeouts only have effect for system "
6342 "calls that perform socket I/O (e.g., B<read>(2), B<recvmsg>(2), B<send>(2), "
6343 "B<sendmsg>(2)); timeouts have no effect for B<select>(2), B<poll>(2), "
6344 "B<epoll_wait>(2), etc."
6348 #: build/C/man7/socket.7:466
6350 msgid "B<SO_REUSEADDR>"
6354 #: build/C/man7/socket.7:481
6356 "Indicates that the rules used in validating addresses supplied in a "
6357 "B<bind>(2) call should allow reuse of local addresses. For B<AF_INET> "
6358 "sockets this means that a socket may bind, except when there is an active "
6359 "listening socket bound to the address. When the listening socket is bound "
6360 "to B<INADDR_ANY> with a specific port then it is not possible to bind to "
6361 "this port for any local address. Argument is an integer boolean flag."
6365 #: build/C/man7/socket.7:481
6367 msgid "B<SO_SNDBUF>"
6370 #. Most (all?) other implementations do not do this -- MTK, Dec 05
6372 #: build/C/man7/socket.7:496
6374 "Sets or gets the maximum socket send buffer in bytes. The kernel doubles "
6375 "this value (to allow space for bookkeeping overhead) when it is set using "
6376 "B<setsockopt>(2), and this doubled value is returned by B<getsockopt>(2). "
6377 "The default value is set by the I</proc/sys/net/core/wmem_default> file and "
6378 "the maximum allowed value is set by the I</proc/sys/net/core/wmem_max> "
6379 "file. The minimum (doubled) value for this option is 2048."
6383 #: build/C/man7/socket.7:496
6385 msgid "B<SO_SNDBUFFORCE> (since Linux 2.6.14)"
6389 #: build/C/man7/socket.7:505
6391 "Using this socket option, a privileged (B<CAP_NET_ADMIN>) process can "
6392 "perform the same task as B<SO_SNDBUF>, but the I<wmem_max> limit can be "
6397 #: build/C/man7/socket.7:505
6399 msgid "B<SO_TIMESTAMP>"
6403 #: build/C/man7/socket.7:521
6405 "Enable or disable the receiving of the B<SO_TIMESTAMP> control message. The "
6406 "timestamp control message is sent with level B<SOL_SOCKET> and the "
6407 "I<cmsg_data> field is a I<struct timeval> indicating the reception time of "
6408 "the last packet passed to the user in this call. See B<cmsg>(3) for "
6409 "details on control messages."
6413 #: build/C/man7/socket.7:521
6419 #: build/C/man7/socket.7:526
6421 "Gets the socket type as an integer (e.g., B<SOCK_STREAM>). This socket "
6422 "option is read-only."
6426 #: build/C/man7/socket.7:526
6432 #: build/C/man7/socket.7:537
6434 "When writing onto a connection-oriented socket that has been shut down (by "
6435 "the local or the remote end) B<SIGPIPE> is sent to the writing process and "
6436 "B<EPIPE> is returned. The signal is not sent when the write call specified "
6437 "the B<MSG_NOSIGNAL> flag."
6441 #: build/C/man7/socket.7:562
6443 "When requested with the B<FIOSETOWN> B<fcntl>(2) or B<SIOCSPGRP> "
6444 "B<ioctl>(2), B<SIGIO> is sent when an I/O event occurs. It is possible to "
6445 "use B<poll>(2) or B<select>(2) in the signal handler to find out which "
6446 "socket the event occurred on. An alternative (in Linux 2.2) is to set a "
6447 "real-time signal using the B<F_SETSIG> B<fcntl>(2); the handler of the real "
6448 "time signal will be called with the file descriptor in the I<si_fd> field of "
6449 "its I<siginfo_t>. See B<fcntl>(2) for more information."
6452 #. .SS Ancillary Messages
6454 #: build/C/man7/socket.7:570
6456 "Under some circumstances (e.g., multiple processes accessing a single "
6457 "socket), the condition that caused the B<SIGIO> may have already disappeared "
6458 "when the process reacts to the signal. If this happens, the process should "
6459 "wait again because Linux will resend the signal later."
6463 #: build/C/man7/socket.7:570
6465 msgid "/proc interfaces"
6469 #: build/C/man7/socket.7:574
6471 "The core socket networking parameters can be accessed via files in the "
6472 "directory I</proc/sys/net/core/>."
6476 #: build/C/man7/socket.7:574
6478 msgid "I<rmem_default>"
6482 #: build/C/man7/socket.7:577
6483 msgid "contains the default setting in bytes of the socket receive buffer."
6487 #: build/C/man7/socket.7:577
6493 #: build/C/man7/socket.7:583
6495 "contains the maximum socket receive buffer size in bytes which a user may "
6496 "set by using the B<SO_RCVBUF> socket option."
6500 #: build/C/man7/socket.7:583
6502 msgid "I<wmem_default>"
6506 #: build/C/man7/socket.7:586
6507 msgid "contains the default setting in bytes of the socket send buffer."
6511 #: build/C/man7/socket.7:586
6517 #: build/C/man7/socket.7:592
6519 "contains the maximum socket send buffer size in bytes which a user may set "
6520 "by using the B<SO_SNDBUF> socket option."
6524 #: build/C/man7/socket.7:592
6526 msgid "I<message_cost> and I<message_burst>"
6530 #: build/C/man7/socket.7:596
6532 "configure the token bucket filter used to load limit warning messages caused "
6533 "by external network events."
6537 #: build/C/man7/socket.7:596
6539 msgid "I<netdev_max_backlog>"
6543 #: build/C/man7/socket.7:599
6544 msgid "Maximum number of packets in the global input queue."
6548 #: build/C/man7/socket.7:599
6550 msgid "I<optmem_max>"
6553 #. netdev_fastroute is not documented because it is experimental
6555 #: build/C/man7/socket.7:604
6557 "Maximum length of ancillary data and user control data like the iovecs per "
6562 #: build/C/man7/socket.7:604
6568 #: build/C/man7/socket.7:607
6569 msgid "These operations can be accessed using B<ioctl>(2):"
6573 #: build/C/man7/socket.7:611
6576 "I<error>B< = ioctl(>I<ip_socket>B<, >I<ioctl_type>B<, "
6577 ">I<&value_result>B<);>\n"
6581 #: build/C/man7/socket.7:613
6583 msgid "B<SIOCGSTAMP>"
6587 #: build/C/man7/socket.7:637
6589 "Return a I<struct timeval> with the receive timestamp of the last packet "
6590 "passed to the user. This is useful for accurate round trip time "
6591 "measurements. See B<setitimer>(2) for a description of I<struct timeval>. "
6592 "This ioctl should only be used if the socket option B<SO_TIMESTAMP> is not "
6593 "set on the socket. Otherwise, it returns the timestamp of the last packet "
6594 "that was received while B<SO_TIMESTAMP> was not set, or it fails if no such "
6595 "packet has been received, (i.e., B<ioctl>(2) returns -1 with I<errno> set "
6600 #: build/C/man7/socket.7:637
6602 msgid "B<SIOCSPGRP>"
6606 #: build/C/man7/socket.7:656
6608 "Set the process or process group to send B<SIGIO> or B<SIGURG> signals to "
6609 "when an asynchronous I/O operation has finished or urgent data is "
6610 "available. The argument is a pointer to a I<pid_t>. If the argument is "
6611 "positive, send the signals to that process. If the argument is negative, "
6612 "send the signals to the process group with the ID of the absolute value of "
6613 "the argument. The process may only choose itself or its own process group "
6614 "to receive signals unless it has the B<CAP_KILL> capability or an effective "
6619 #: build/C/man7/socket.7:656
6625 #: build/C/man7/socket.7:666
6627 "Change the B<O_ASYNC> flag to enable or disable asynchronous I/O mode of the "
6628 "socket. Asynchronous I/O mode means that the B<SIGIO> signal or the signal "
6629 "set with B<F_SETSIG> is raised when a new I/O event occurs."
6633 #: build/C/man7/socket.7:674
6635 "Argument is an integer boolean flag. (This operation is synonymous with the "
6636 "use of B<fcntl>(2) to set the B<O_ASYNC> flag.)"
6640 #: build/C/man7/socket.7:674
6642 msgid "B<SIOCGPGRP>"
6646 #: build/C/man7/socket.7:683
6648 "Get the current process or process group that receives B<SIGIO> or B<SIGURG> "
6649 "signals, or 0 when none is set."
6653 #: build/C/man7/socket.7:687
6654 msgid "Valid B<fcntl>(2) operations:"
6658 #: build/C/man7/socket.7:687
6660 msgid "B<FIOGETOWN>"
6664 #: build/C/man7/socket.7:692
6665 msgid "The same as the B<SIOCGPGRP> B<ioctl>(2)."
6669 #: build/C/man7/socket.7:692
6671 msgid "B<FIOSETOWN>"
6675 #: build/C/man7/socket.7:697
6676 msgid "The same as the B<SIOCSPGRP> B<ioctl>(2)."
6680 #: build/C/man7/socket.7:711
6682 "B<SO_BINDTODEVICE> was introduced in Linux 2.0.30. B<SO_PASSCRED> is new in "
6683 "Linux 2.2. The I</proc> interfaces was introduced in Linux 2.2. "
6684 "B<SO_RCVTIMEO> and B<SO_SNDTIMEO> are supported since Linux 2.3.41. "
6685 "Earlier, timeouts were fixed to a protocol-specific setting, and could not "
6686 "be read or written."
6690 #: build/C/man7/socket.7:716
6692 "Linux assumes that half of the send/receive buffer is used for internal "
6693 "kernel structures; thus the values in the corresponding I</proc> files are "
6694 "twice what can be observed on the wire."
6698 #: build/C/man7/socket.7:729
6700 "Linux will only allow port reuse with the B<SO_REUSEADDR> option when this "
6701 "option was set both in the previous program that performed a B<bind>(2) to "
6702 "the port and in the program that wants to reuse the port. This differs from "
6703 "some implementations (e.g., FreeBSD) where only the later program needs to "
6704 "set the B<SO_REUSEADDR> option. Typically this difference is invisible, "
6705 "since, for example, a server program is designed to always set this option."
6708 #. FIXME Document SO_ATTACH_FILTER and SO_DETACH_FILTER
6710 #. This man page was written by Andi Kleen.
6712 #: build/C/man7/socket.7:742
6714 "The B<CONFIG_FILTER> socket options B<SO_ATTACH_FILTER> and "
6715 "B<SO_DETACH_FILTER> are not documented. The suggested interface to use them "
6716 "is via the libpcap library."
6720 #: build/C/man7/socket.7:753
6722 "B<getsockopt>(2), B<setsockopt>(2), B<socket>(2), B<capabilities>(7), "
6723 "B<ddp>(7), B<ip>(7), B<packet>(7), B<tcp>(7), B<udp>(7), B<unix>(7)"
6727 #: build/C/man2/socketcall.2:26
6733 #: build/C/man2/socketcall.2:26
6739 #: build/C/man2/socketcall.2:29
6740 msgid "socketcall - socket system calls"
6744 #: build/C/man2/socketcall.2:31
6745 msgid "B<int socketcall(int >I<call>B<, unsigned long *>I<args>B<);>"
6749 #: build/C/man2/socketcall.2:39
6751 "B<socketcall>() is a common kernel entry point for the socket system "
6752 "calls. I<call> determines which socket function to invoke. I<args> points "
6753 "to a block containing the actual arguments, which are passed through to the "
6758 #: build/C/man2/socketcall.2:43
6760 "User programs should call the appropriate functions by their usual names. "
6761 "Only standard library implementors and kernel hackers need to know about "
6766 #: build/C/man2/socketcall.2:46
6768 "This call is specific to Linux, and should not be used in programs intended "
6773 #: build/C/man2/socketcall.2:54
6775 "On a few architectures, for example ia64, there is no B<socketcall>() "
6776 "system call; instead B<socket>(2), B<accept>(2), B<bind>(2), and so on "
6777 "really are implemented as separate system calls."
6781 #: build/C/man2/socketcall.2:72
6783 "B<accept>(2), B<bind>(2), B<connect>(2), B<getpeername>(2), "
6784 "B<getsockname>(2), B<getsockopt>(2), B<listen>(2), B<recv>(2), "
6785 "B<recvfrom>(2), B<recvmsg>(2), B<send>(2), B<sendmsg>(2), B<sendto>(2), "
6786 "B<setsockopt>(2), B<shutdown>(2), B<socket>(2), B<socketpair>(2)"
6790 #: build/C/man2/socketpair.2:40
6796 #: build/C/man2/socketpair.2:40
6802 #: build/C/man2/socketpair.2:43
6803 msgid "socketpair - create a pair of connected sockets"
6807 #: build/C/man2/socketpair.2:50
6809 "B<int socketpair(int >I<domain>B<, int >I<type>B<, int >I<protocol>B<, int "
6814 #: build/C/man2/socketpair.2:61
6816 "The B<socketpair>() call creates an unnamed pair of connected sockets in "
6817 "the specified I<domain>, of the specified I<type>, and using the optionally "
6818 "specified I<protocol>. For further details of these arguments, see "
6823 #: build/C/man2/socketpair.2:67
6825 "The descriptors used in referencing the new sockets are returned in I<sv>[0] "
6826 "and I<sv>[1]. The two sockets are indistinguishable."
6830 #: build/C/man2/socketpair.2:76
6831 msgid "The specified address family is not supported on this machine."
6835 #: build/C/man2/socketpair.2:81
6837 "The address I<sv> does not specify a valid part of the process address "
6842 #: build/C/man2/socketpair.2:84
6843 msgid "Too many descriptors are in use by this process."
6847 #: build/C/man2/socketpair.2:90
6848 msgid "The specified protocol does not support creation of socket pairs."
6852 #: build/C/man2/socketpair.2:93
6853 msgid "The specified protocol is not supported on this machine."
6857 #: build/C/man2/socketpair.2:101
6859 "4.4BSD, POSIX.1-2001. The B<socketpair>() function call appeared in "
6860 "4.2BSD. It is generally portable to/from non-BSD systems supporting clones "
6861 "of the BSD socket layer (including System V variants)."
6865 #: build/C/man2/socketpair.2:107
6867 "On Linux, the only supported domain for this call is B<AF_UNIX> (or "
6868 "synonymously, B<AF_LOCAL>). (Most implementations have the same "
6873 #: build/C/man2/socketpair.2:116
6875 "Since Linux 2.6.27, B<socketpair>() supports the B<SOCK_NONBLOCK> and "
6876 "B<SOCK_CLOEXEC> flags described in B<socket>(2)."
6880 #: build/C/man2/socketpair.2:129
6881 msgid "B<pipe>(2), B<read>(2), B<socket>(2), B<write>(2), B<socket>(7), B<unix>(7)"