Add a resolv.conf option to specify the order in which getaddrinfo

PF_UNSPEC queries are made. While there change the default from inet6
first then inet4 to inet4 first then inet6, this prevents the many
people with IPv4 only connectivity from constantly trying to contact
IPv6 addresses, and also unbreaks many ports who don't use getaddrinfo
right.

ok deraadt@, plenty of cheering in the room wrt the idea, not loud
enough complaining from the v6 crowd.

1 files changed, 29 insertions, 1 deletions

diff --git a/src/lib/libc/net/res_init.c b/src/lib/libc/net/res_init.c
index 42d3b3ca1e..5cb597dad8 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 1.37 2008/08/15 14:57:20 djm Exp $       */
+/*      $OpenBSD: res_init.c,v 1.38 2009/06/04 18:06:35 pyr Exp $       */
 
 /*
  * ++Copyright++ 1985, 1989, 1993
@@ -165,6 +165,7 @@ _res_init(int usercall)
         FILE *fp;
         char *cp, **pp;
         int n;
+        int findex;
         char buf[BUFSIZ];
         int nserv = 0;    /* number of nameserver records read from file */
         int haveenv = 0;
@@ -296,6 +297,33 @@ _res_init(int usercall)
                         *cp = '\0';
                 if (buf[0] == '\0')
                         continue;
+                /* set family lookup order */
+                if (MATCH(buf, "family")) {
+                        cp = buf + sizeof("family") - 1;
+                        cp += strspn(cp, " \t");
+                        cp[strcspn(cp, "\n")] = '\0';
+                        findex = 0;
+                        _resp->family[0] = _resp->family[1] = -1;
+                        while (*cp != '\0' && findex < 2) {
+                                if (!strncmp(cp, "inet6", strlen("inet6"))) {
+                                        _resp->family[findex] = AF_INET6;
+                                        cp += strlen("inet6");
+                                } else if (!strncmp(cp, "inet4",
+                                     strlen("inet4"))) {
+                                        _resp->family[findex] = AF_INET;
+                                        cp += strlen("inet4");
+                                }
+                                if (*cp != ' ' && *cp != '\t' && *cp != '\0') {
+                                        _resp->family[findex] = -1;
+                                        break;
+                                }
+                                findex++;
+                                cp += strspn(cp, " \t");
+                        }
+
+                        if (_resp->family[0] == _resp->family[1])
+                                _resp->family[1] = -1;
+                }
                 /* read default domain name */
                 if (MATCH(buf, "domain")) {
                     if (haveenv)        /* skip if have from environ */