Adding a timeout to tcp dns lookup connects.

TCP isn't supported on some dns servers, which makes the old code
hang forever.

NOT adding a stopship to remove debugging stuff - it was too painful
(14s timeout on failed tcp dns lookups) so we decided not to bother people.

bug:5766949
Change-Id: I381c20c3e11b8e994438d4f7c58ef643cd36554e

diff --git a/libc/netbsd/resolv/res_send.c b/libc/netbsd/resolv/res_send.c
index b118956..5d25087 100644 (file)
--- a/libc/netbsd/resolv/res_send.c
+++ b/libc/netbsd/resolv/res_send.c
@@ -99,6 +99,7 @@ __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
 #include <arpa/inet.h>
 
 #include <errno.h>
+#include <fcntl.h>
 #include <netdb.h>
 #ifdef ANDROID_CHANGES
 #include "resolv_private.h"
@@ -109,6 +110,7 @@ __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
+#include <time.h>
 #include <unistd.h>
 
 #include <isc/eventlib.h>
@@ -117,6 +119,8 @@ __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
 #  include <resolv_cache.h>
 #endif
 
+#include "logd.h"
+
 #ifndef DE_CONST
 #define DE_CONST(c,v)   v = ((c) ? \
     strchr((const void *)(c), *(const char *)(const void *)(c)) : NULL)
@@ -130,6 +134,7 @@ __RCSID("$NetBSD: res_send.c,v 1.9 2006/01/24 17:41:25 christos Exp $");
 #include "res_private.h"
 
 #define EXT(res) ((res)->_u._ext)
+#define DBG 0
 
 static const int highestFD = FD_SETSIZE - 1;
 
@@ -152,7 +157,10 @@ static int         pselect(int, void *, void *, void *,
                                const sigset_t *);
 #endif
 void res_pquery(const res_state, const u_char *, int, FILE *);
-
+static int connect_with_timeout(int sock, const struct sockaddr *nsap,
+                       socklen_t salen, int sec);
+static int retrying_select(const int sock, fd_set *readset, fd_set *writeset,
+                       const struct timespec *finish);
 
 /* BIONIC-BEGIN: implement source port randomization */
 typedef union {
@@ -521,16 +529,23 @@ res_nsend(res_state statp,
 
                Dprint(((statp->options & RES_DEBUG) &&
                        getnameinfo(nsap, (socklen_t)nsaplen, abuf, sizeof(abuf),
-                                   NULL, 0, niflags) == 0),
-                      (stdout, ";; Querying server (# %d) address = %s\n",
-                       ns + 1, abuf));
+                               NULL, 0, niflags) == 0),
+                               (stdout, ";; Querying server (# %d) address = %s\n",
+                               ns + 1, abuf));
 
 
                if (v_circuit) {
                        /* Use VC; at most one attempt per server. */
                        try = statp->retry;
+
                        n = send_vc(statp, buf, buflen, ans, anssiz, &terrno,
                                    ns);
+
+                       if (DBG) {
+                               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                                       "used send_vc %d\n", n);
+                       }
+
                        if (n < 0)
                                goto fail;
                        if (n == 0)
@@ -538,12 +553,26 @@ res_nsend(res_state statp,
                        resplen = n;
                } else {
                        /* Use datagrams. */
+                       if (DBG) {
+                               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                                       "using send_dg\n");
+                       }
+
                        n = send_dg(statp, buf, buflen, ans, anssiz, &terrno,
                                    ns, &v_circuit, &gotsomewhere);
+                       if (DBG) {
+                               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                                       "used send_dg %d\n",n);
+                       }
+
                        if (n < 0)
                                goto fail;
                        if (n == 0)
                                goto next_ns;
+                       if (DBG) {
+                               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                                       "time=%d, %d\n",time(NULL), time(NULL)%2);
+                       }
                        if (v_circuit)
                                goto same_ns;
                        resplen = n;
@@ -668,6 +697,23 @@ get_nsaddr(statp, n)
        }
 }
 
+static int get_timeout(const res_state statp, const int ns)
+{
+       int timeout = (statp->retrans << ns);
+       if (ns > 0) {
+               timeout /= statp->nscount;
+       }
+       if (timeout <= 0) {
+               timeout = 1;
+       }
+       if (DBG) {
+               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                       "using timeout of %d sec\n", timeout);
+       }
+
+       return timeout;
+}
+
 static int
 send_vc(res_state statp,
        const u_char *buf, int buflen, u_char *ans, int anssiz,
@@ -683,6 +729,10 @@ send_vc(res_state statp,
        u_char *cp;
        void *tmp;
 
+       if (DBG) {
+               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc", "using send_vc\n");
+       }
+
        nsap = get_nsaddr(statp, (size_t)ns);
        nsaplen = get_salen(nsap);
 
@@ -735,7 +785,8 @@ send_vc(res_state statp,
                        res_nclose(statp);
                        return (0);
                }
-               if (connect(statp->_vcsock, nsap, (socklen_t)nsaplen) < 0) {
+               if (connect_with_timeout(statp->_vcsock, nsap, (socklen_t)nsaplen,
+                               get_timeout(statp, ns)) < 0) {
                        *terrno = errno;
                        Aerror(statp, stderr, "connect/vc", errno, nsap,
                            nsaplen);
@@ -859,6 +910,111 @@ send_vc(res_state statp,
        return (resplen);
 }
 
+/* return -1 on error (errno set), 0 on success */
+static int
+connect_with_timeout(int sock, const struct sockaddr *nsap, socklen_t salen, int sec)
+{
+       int res, origflags;
+       fd_set rset, wset;
+       struct timespec now, timeout, finish;
+
+       origflags = fcntl(sock, F_GETFL, 0);
+       fcntl(sock, F_SETFL, origflags | O_NONBLOCK);
+
+       res = connect(sock, nsap, salen);
+       if (res < 0 && errno != EINPROGRESS) {
+                res = -1;
+                goto done;
+       }
+       if (res != 0) {
+               now = evNowTime();
+               timeout = evConsTime((long)sec, 0L);
+               finish = evAddTime(now, timeout);
+               if (DBG) {
+                       __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                               "  %d send_vc\n", sock);
+               }
+
+               res = retrying_select(sock, &rset, &wset, &finish);
+               if (res <= 0) {
+                        res = -1;
+               }
+       }
+done:
+       fcntl(sock, F_SETFL, origflags);
+       if (DBG) {
+               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                       "  %d connect_with_timeout returning %s\n", sock, res);
+       }
+       return res;
+}
+
+static int
+retrying_select(const int sock, fd_set *readset, fd_set *writeset, const struct timespec *finish)
+{
+       struct timespec now, timeout;
+       int n, error;
+       socklen_t len;
+
+
+retry:
+       if (DBG) {
+               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc", "  %d retying_select\n", sock);
+       }
+
+       now = evNowTime();
+       if (readset) {
+               FD_ZERO(readset);
+               FD_SET(sock, readset);
+       }
+       if (writeset) {
+               FD_ZERO(writeset);
+               FD_SET(sock, writeset);
+       }
+       if (evCmpTime(*finish, now) > 0)
+               timeout = evSubTime(*finish, now);
+       else
+               timeout = evConsTime(0L, 0L);
+
+       n = pselect(sock + 1, readset, writeset, NULL, &timeout, NULL);
+       if (n == 0) {
+               if (DBG) {
+                       __libc_android_log_print(ANDROID_LOG_DEBUG, " libc",
+                               "  %d retrying_select timeout\n", sock);
+               }
+               errno = ETIMEDOUT;
+               return 0;
+       }
+       if (n < 0) {
+               if (errno == EINTR)
+                       goto retry;
+               if (DBG) {
+                       __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                               "  %d retrying_select got error %d\n",sock, n);
+               }
+               return n;
+       }
+       if ((readset && FD_ISSET(sock, readset)) || (writeset && FD_ISSET(sock, writeset))) {
+               len = sizeof(error);
+               if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &error, &len) < 0 || error) {
+                       errno = error;
+                       if (DBG) {
+                               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                                       "  %d retrying_select dot error2 %d\n", sock, errno);
+                       }
+
+                       return -1;
+               }
+       }
+       if (DBG) {
+               __libc_android_log_print(ANDROID_LOG_DEBUG, "libc",
+                       "  %d retrying_select returning %d for %d\n",sock, n);
+       }
+
+       return n;
+}
+
+
 static int
 send_dg(res_state statp,
        const u_char *buf, int buflen, u_char *ans, int anssiz,
@@ -944,33 +1100,19 @@ send_dg(res_state statp,
        /*
         * Wait for reply.
         */
-       seconds = (statp->retrans << ns);
-       if (ns > 0)
-               seconds /= statp->nscount;
-       if (seconds <= 0)
-               seconds = 1;
+       seconds = get_timeout(statp, ns);
        now = evNowTime();
        timeout = evConsTime((long)seconds, 0L);
        finish = evAddTime(now, timeout);
-       goto nonow;
- wait:
-       now = evNowTime();
- nonow:
-       FD_ZERO(&dsmask);
-       FD_SET(s, &dsmask);
-       if (evCmpTime(finish, now) > 0)
-               timeout = evSubTime(finish, now);
-       else
-               timeout = evConsTime(0L, 0L);
-       n = pselect(s + 1, &dsmask, NULL, NULL, &timeout, NULL);
+retry:
+       n = retrying_select(s, &dsmask, NULL, &finish);
+
        if (n == 0) {
                Dprint(statp->options & RES_DEBUG, (stdout, ";; timeout\n"));
                *gotsomewhere = 1;
                return (0);
        }
        if (n < 0) {
-               if (errno == EINTR)
-                       goto wait;
                Perror(statp, stderr, "select", errno);
                res_nclose(statp);
                return (0);
@@ -1006,7 +1148,7 @@ send_dg(res_state statp,
                        (statp->pfcode & RES_PRF_REPLY),
                        (stdout, ";; old answer:\n"),
                        ans, (resplen > anssiz) ? anssiz : resplen);
-               goto wait;
+               goto retry;
        }
        if (!(statp->options & RES_INSECURE1) &&
            !res_ourserver_p(statp, (struct sockaddr *)(void *)&from)) {
@@ -1019,7 +1161,7 @@ send_dg(res_state statp,
                        (statp->pfcode & RES_PRF_REPLY),
                        (stdout, ";; not our server:\n"),
                        ans, (resplen > anssiz) ? anssiz : resplen);
-               goto wait;
+               goto retry;
        }
 #ifdef RES_USE_EDNS0
        if (anhp->rcode == FORMERR && (statp->options & RES_USE_EDNS0) != 0U) {
@@ -1049,7 +1191,7 @@ send_dg(res_state statp,
                        (statp->pfcode & RES_PRF_REPLY),
                        (stdout, ";; wrong query name:\n"),
                        ans, (resplen > anssiz) ? anssiz : resplen);
-               goto wait;
+               goto retry;;
        }
        if (anhp->rcode == SERVFAIL ||
            anhp->rcode == NOTIMP ||