Add resolv.conf(5) option to force lookups by TCP: "options tcp"

Also Extend "nameserver" declaration syntax to support port
numbers.  To avoid ambiguity these are only parsed when the address
is enclosed in square brackets, e.g. "nameserver [127.0.0.1]:5353"

Together these changes make forwarding DNS over a SSH tunnel very
easy, but unfortunately some programs in ports/ implement their
own resolvers (e.g. firefox). These will need to be modified to
support these options separately.

fixes jsing@ reyk@
ok deraadt@ millert@ krw@ + "I like it" from lots

1 files changed, 20 insertions, 18 deletions

diff --git a/src/lib/libc/net/res_init.c b/src/lib/libc/net/res_init.c
index ebfc5f3db2..42d3b3ca1e 100644
--- a/src/lib/libc/net/res_init.c
+++ b/src/lib/libc/net/res_init.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: res_init.c,v 1.36 2007/08/05 16:11:09 ray Exp $       */
+/*      $OpenBSD: res_init.c,v 1.37 2008/08/15 14:57:20 djm Exp $       */
 
 /*
  * ++Copyright++ 1985, 1989, 1993
@@ -376,18 +376,13 @@ _res_init(int usercall)
                 }
                 /* read nameservers to query */
                 if (MATCH(buf, "nameserver") && nserv < MAXNS) {
-#ifdef INET6
                     char *q;
                     struct addrinfo hints, *res;
                     char pbuf[NI_MAXSERV];
-#else
-                    struct in_addr a;
-#endif /* INET6 */
 
                     cp = buf + sizeof("nameserver") - 1;
                     while (*cp == ' ' || *cp == '\t')
                         cp++;
-#ifdef INET6
                     if ((*cp == '\0') || (*cp == '\n'))
                         continue;
                     for (q = cp; *q; q++) {
@@ -396,10 +391,26 @@ _res_init(int usercall)
                             break;
                         }
                     }
+
+                    /* Handle addresses enclosed in [] */
+                    *pbuf = '\0';
+                    if (*cp == '[') {
+                        cp++;
+                        if ((q = strchr(cp, ']')) == NULL)
+                                continue;
+                        *q++ = '\0';
+                        /* Extract port, if specified */
+                        if (*q++ == ':') {
+                            if (strlcpy(pbuf, q, sizeof(pbuf)) >= sizeof(pbuf))
+                                continue;
+                        }
+                    }
+                    if (*pbuf == '\0')
+                        snprintf(pbuf, sizeof(pbuf), "%u", NAMESERVER_PORT);
+
                     memset(&hints, 0, sizeof(hints));
                     hints.ai_flags = AI_NUMERICHOST;
                     hints.ai_socktype = SOCK_DGRAM;
-                    snprintf(pbuf, sizeof(pbuf), "%u", NAMESERVER_PORT);
                     res = NULL;
                     if (getaddrinfo(cp, pbuf, &hints, &res) == 0 &&
                             res->ai_next == NULL) {
@@ -421,17 +432,6 @@ _res_init(int usercall)
                     }
                     if (res)
                         freeaddrinfo(res);
-#else /* INET6 */
-                    if ((*cp != '\0') && (*cp != '\n') && inet_aton(cp, &a)) {
-                        _resp->nsaddr_list[nserv].sin_addr = a;
-                        _resp->nsaddr_list[nserv].sin_family = AF_INET;
-                        _resp->nsaddr_list[nserv].sin_port =
-                                htons(NAMESERVER_PORT);
-                        _resp->nsaddr_list[nserv].sin_len =
-                                sizeof(struct sockaddr_in);
-                        nserv++;
-                    }
-#endif /* INET6 */
                     continue;
                 }
 #ifdef RESOLVSORT
@@ -641,6 +641,8 @@ res_setoptions(char *options, char *source)
                         _resp->options |= RES_INSECURE2;
                 } else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
                         _resp->options |= RES_USE_EDNS0;
+                } else if (!strncmp(cp, "tcp", sizeof("tcp") - 1)) {
+                        _resp->options |= RES_USEVC;
                 } else {
                         /* XXX - print a warning here? */
                 }