+++ /dev/null
-.\" Copyright (c) 2008 Petr Baudis <pasky@suse.cz>
-.\" and copyright (c) 2009, Linux Foundation, written by Michael Kerrisk
-.\" <mtk.manpages@gmail.com>
-.\"
-.\" %%%LICENSE_START(VERBATIM)
-.\" Permission is granted to make and distribute verbatim copies of this
-.\" manual provided the copyright notice and this permission notice are
-.\" preserved on all copies.
-.\"
-.\" Permission is granted to copy and distribute modified versions of this
-.\" manual under the conditions for verbatim copying, provided that the
-.\" entire resulting derived work is distributed under the terms of a
-.\" permission notice identical to this one.
-.\"
-.\" Since the Linux kernel and libraries are constantly changing, this
-.\" manual page may be incorrect or out-of-date. The author(s) assume no
-.\" responsibility for errors or omissions, or for damages resulting from
-.\" the use of the information contained herein. The author(s) may not
-.\" have taken the same level of care in the production of this manual,
-.\" which is licensed free of charge, as they might when working
-.\" professionally.
-.\"
-.\" Formatted or processed versions of this manual, if unaccompanied by
-.\" the source, must acknowledge the copyright and authors of this work.
-.\" %%%LICENSE_END
-.\"
-.\" Redistribution and use in source and binary forms, with or without
-.\" modification, are permitted provided that the following conditions
-.\" are met:
-.\"
-.\" 2008-12-08 Petr Baudis <pasky@suse.cz>
-.\" Rewrite the BSD manpage in the Linux man pages style and account
-.\" for glibc specificities, provide an example.
-.\" 2009-01-14 mtk, many edits and changes, rewrote example program.
-.\"
-.TH GETIFADDRS 3 2014-02-26 "GNU" "Linux Programmer's Manual"
-.SH NAME
-getifaddrs, freeifaddrs \- get interface addresses
-.SH SYNOPSIS
-.nf
-.B #include <sys/types.h>
-.B #include <ifaddrs.h>
-.sp
-.BI "int getifaddrs(struct ifaddrs **" "ifap" );
-.sp
-.BI "void freeifaddrs(struct ifaddrs *" "ifa" );
-.fi
-.SH DESCRIPTION
-The
-.BR getifaddrs ()
-function creates a linked list of structures describing
-the network interfaces of the local system,
-and stores the address of the first item of the list in
-.IR *ifap .
-The list consists of
-.I ifaddrs
-structures, defined as follows:
-.sp
-.in +4n
-.nf
-struct ifaddrs {
- struct ifaddrs *ifa_next; /* Next item in list */
- char *ifa_name; /* Name of interface */
- unsigned int ifa_flags; /* Flags from SIOCGIFFLAGS */
- struct sockaddr *ifa_addr; /* Address of interface */
- struct sockaddr *ifa_netmask; /* Netmask of interface */
- union {
- struct sockaddr *ifu_broadaddr;
- /* Broadcast address of interface */
- struct sockaddr *ifu_dstaddr;
- /* Point-to-point destination address */
- } ifa_ifu;
-#define ifa_broadaddr ifa_ifu.ifu_broadaddr
-#define ifa_dstaddr ifa_ifu.ifu_dstaddr
- void *ifa_data; /* Address-specific data */
-};
-.fi
-.in
-.PP
-The
-.I ifa_next
-field contains a pointer to the next structure on the list,
-or NULL if this is the last item of the list.
-.PP
-The
-.I ifa_name
-points to the null-terminated interface name.
-.\" The constant
-.\" .B IF NAMESIZE
-.\" indicates the maximum length of this field.
-.PP
-The
-.I ifa_flags
-field contains the interface flags, as returned by the
-.B SIOCGIFFLAGS
-.BR ioctl (2)
-operation (see
-.BR netdevice (7)
-for a list of these flags).
-.PP
-The
-.I ifa_addr
-field points to a structure containing the interface address.
-(The
-.I sa_family
-subfield should be consulted to determine the format of the
-address structure.)
-This field may contain a null pointer.
-.PP
-The
-.I ifa_netmask
-field points to a structure containing the netmask associated with
-.IR ifa_addr ,
-if applicable for the address family.
-This field may contain a null pointer.
-.PP
-Depending on whether the bit
-.B IFF_BROADCAST
-or
-.B IFF_POINTOPOINT
-is set in
-.I ifa_flags
-(only one can be set at a time),
-either
-.I ifa_broadaddr
-will contain the broadcast address associated with
-.I ifa_addr
-(if applicable for the address family) or
-.I ifa_dstaddr
-will contain the destination address of the point-to-point interface.
-.PP
-The
-.I ifa_data
-field points to a buffer containing address-family-specific data;
-this field may be NULL if there is no such data for this interface.
-.PP
-The data returned by
-.BR getifaddrs ()
-is dynamically allocated and should be freed using
-.BR freeifaddrs ()
-when no longer needed.
-.SH RETURN VALUE
-On success,
-.BR getifaddrs ()
-returns zero;
-on error, \-1 is returned, and
-.I errno
-is set appropriately.
-.SH ERRORS
-.BR getifaddrs ()
-may fail and set
-.I errno
-for any of the errors specified for
-.BR socket (2),
-.BR bind (2),
-.BR getsockname (2),
-.BR recvmsg (2),
-.BR sendto (2),
-.BR malloc (3),
-or
-.BR realloc (3).
-.SH VERSIONS
-The
-.BR getifaddrs ()
-function first appeared in glibc 2.3, but before glibc 2.3.3,
-the implementation supported only IPv4 addresses;
-IPv6 support was added in glibc 2.3.3.
-Support of address families other than IPv4 is available only
-on kernels that support netlink.
-.SH CONFORMING TO
-Not in POSIX.1-2001.
-This function first appeared in BSDi and is
-present on the BSD systems, but with slightly different
-semantics documented\(emreturning one entry per interface,
-not per address.
-This means
-.I ifa_addr
-and other fields can actually be NULL if the interface has no address,
-and no link-level address is returned if the interface has an IP address
-assigned.
-Also, the way of choosing either
-.I ifa_broadaddr
-or
-.I ifa_dstaddr
-differs on various systems.
-.\" , but the BSD-derived documentation generally
-.\" appears to be confused and obsolete on this point.
-.\" i.e., commonly it still says one of them will be NULL, even if
-.\" the ifa_ifu union is already present
-.SH NOTES
-The addresses returned on Linux will usually be the IPv4 and IPv6 addresses
-assigned to the interface, but also one
-.B AF_PACKET
-address per interface containing lower-level details about the interface
-and its physical layer.
-In this case, the
-.I ifa_data
-field may contain a pointer to a
-.IR "struct rtnl_link_stats" ,
-defined in
-.IR <linux/if_link.h>
-(in Linux 2.4 and earlier,
-.IR "struct net_device_stats" ,
-defined in
-.IR <linux/netdevice.h> ),
-which contains various interface attributes and statistics.
-.SH EXAMPLE
-The program below demonstrates the use of
-.BR getifaddrs (),
-.BR freeifaddrs (),
-and
-.BR getnameinfo (3).
-Here is what we see when running this program on one system:
-.in +4n
-.nf
-
-$ \fB./a.out\fP
-lo AF_PACKET (17)
- tx_packets = 524; rx_packets = 524
- tx_bytes = 38788; rx_bytes = 38788
-wlp3s0 AF_PACKET (17)
- tx_packets = 108391; rx_packets = 130245
- tx_bytes = 30420659; rx_bytes = 94230014
-em1 AF_PACKET (17)
- tx_packets = 0; rx_packets = 0
- tx_bytes = 0; rx_bytes = 0
-lo AF_INET (2)
- address: <127.0.0.1>
-wlp3s0 AF_INET (2)
- address: <192.168.235.137>
-lo AF_INET6 (10)
- address: <::1>
-wlp3s0 AF_INET6 (10)
- address: <fe80::7ee9:d3ff:fef5:1a91%wlp3s0>
-.fi
-.in
-.SS Program source
-\&
-.nf
-#define _GNU_SOURCE /* To get defns of NI_MAXSERV and NI_MAXHOST */
-#include <arpa/inet.h>
-#include <sys/socket.h>
-#include <netdb.h>
-#include <ifaddrs.h>
-#include <stdio.h>
-#include <stdlib.h>
-#include <unistd.h>
-#include <linux/if_link.h>
-
-int main(int argc, char *argv[])
-{
- struct ifaddrs *ifaddr, *ifa;
- int family, s, n;
- char host[NI_MAXHOST];
-
- if (getifaddrs(&ifaddr) == \-1) {
- perror("getifaddrs");
- exit(EXIT_FAILURE);
- }
-
- /* Walk through linked list, maintaining head pointer so we
- can free list later */
-
- for (ifa = ifaddr, n = 0; ifa != NULL; ifa = ifa\->ifa_next, n++) {
- if (ifa\->ifa_addr == NULL)
- continue;
-
- family = ifa\->ifa_addr\->sa_family;
-
- /* Display interface name and family (including symbolic
- form of the latter for the common families) */
-
- printf("%\-8s %s (%d)\\n",
- ifa\->ifa_name,
- (family == AF_PACKET) ? "AF_PACKET" :
- (family == AF_INET) ? "AF_INET" :
- (family == AF_INET6) ? "AF_INET6" : "???",
- family);
-
- /* For an AF_INET* interface address, display the address */
-
- if (family == AF_INET || family == AF_INET6) {
- s = getnameinfo(ifa\->ifa_addr,
- (family == AF_INET) ? sizeof(struct sockaddr_in) :
- sizeof(struct sockaddr_in6),
- host, NI_MAXHOST,
- NULL, 0, NI_NUMERICHOST);
- if (s != 0) {
- printf("getnameinfo() failed: %s\\n", gai_strerror(s));
- exit(EXIT_FAILURE);
- }
-
- printf("\\t\\taddress: <%s>\\n", host);
-
- } else if (family == AF_PACKET && ifa\->ifa_data != NULL) {
- struct rtnl_link_stats *stats = ifa\->ifa_data;
-
- printf("\\t\\ttx_packets = %10u; rx_packets = %10u\\n"
- "\\t\\ttx_bytes = %10u; rx_bytes = %10u\\n",
- stats\->tx_packets, stats\->rx_packets,
- stats\->tx_bytes, stats\->rx_bytes);
- }
- }
-
- freeifaddrs(ifaddr);
- exit(EXIT_SUCCESS);
-}
-.fi
-.SH SEE ALSO
-.BR bind (2),
-.BR getsockname (2),
-.BR socket (2),
-.BR packet (7),
-.BR ifconfig (8)
-.SH COLOPHON
-This page is part of release 3.79 of the Linux
-.I man-pages
-project.
-A description of the project,
-information about reporting bugs,
-and the latest version of this page,
-can be found at
-\%http://www.kernel.org/doc/man\-pages/.
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