From 4b01f04f286ab99a26e81be53e43f8bf46f9496d Mon Sep 17 00:00:00 2001
From: pyr <>
Date: Thu, 4 Jun 2009 18:06:35 +0000
Subject: 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.
---
 src/lib/libc/net/getaddrinfo.c | 41 ++++++++++++++++++++++++++++++++++-------
 src/lib/libc/net/res_init.c    | 30 +++++++++++++++++++++++++++++-
 2 files changed, 63 insertions(+), 8 deletions(-)

(limited to 'src/lib')

diff --git a/src/lib/libc/net/getaddrinfo.c b/src/lib/libc/net/getaddrinfo.c
index 0f3b6319f4..87125c89cc 100644
--- a/src/lib/libc/net/getaddrinfo.c
+++ b/src/lib/libc/net/getaddrinfo.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: getaddrinfo.c,v 1.67 2007/05/20 03:54:52 ray Exp $	*/
+/*	$OpenBSD: getaddrinfo.c,v 1.68 2009/06/04 18:06:35 pyr Exp $	*/
 /*	$KAME: getaddrinfo.c,v 1.31 2000/08/31 17:36:43 itojun Exp $	*/
 
 /*
@@ -233,7 +233,8 @@ static struct addrinfo *getanswer(const querybuf *, int, const char *, int,
 static int res_queryN(const char *, struct res_target *);
 static int res_searchN(const char *, struct res_target *);
 static int res_querydomainN(const char *, const char *, struct res_target *);
-static struct addrinfo *_dns_getaddrinfo(const char *, const struct addrinfo *);
+static struct addrinfo *_dns_getaddrinfo(const char *, const struct addrinfo *,
+	const struct __res_state *);
 
 
 /* XXX macros that make external reference is BAD. */
@@ -517,7 +518,7 @@ explore_fqdn(const struct addrinfo *pai, const char *hostname,
 			break;
 #endif
 		case 'b':
-			result = _dns_getaddrinfo(hostname, pai);
+			result = _dns_getaddrinfo(hostname, pai, _resp);
 			break;
 		case 'f':
 			result = _files_getaddrinfo(hostname, pai);
@@ -1142,7 +1143,8 @@ getanswer(const querybuf *answer, int anslen, const char *qname, int qtype,
 
 /*ARGSUSED*/
 static struct addrinfo *
-_dns_getaddrinfo(const char *name, const struct addrinfo *pai)
+_dns_getaddrinfo(const char *name, const struct addrinfo *pai,
+	const struct __res_state *_resp)
 {
 	struct addrinfo *ai;
 	querybuf *buf, *buf2;
@@ -1168,14 +1170,39 @@ _dns_getaddrinfo(const char *name, const struct addrinfo *pai)
 
 	switch (pai->ai_family) {
 	case AF_UNSPEC:
-		/* prefer IPv6 */
+		if (_resp->family[0] == -1) {
+			/* prefer IPv4 by default*/
+			q.qclass = C_IN;
+			q.qtype = T_A;
+			q.answer = buf->buf;
+			q.anslen = sizeof(buf->buf);
+			q.next = &q2;
+			q2.qclass = C_IN;
+			q2.qtype = T_AAAA;
+			q2.answer = buf2->buf;
+			q2.anslen = sizeof(buf2->buf);
+			break;
+		}
+
+		/* respect user supplied order */
 		q.qclass = C_IN;
-		q.qtype = T_AAAA;
+		if (_resp->family[0] == AF_INET6)
+			q.qtype = T_AAAA;
+		else
+			q.qtype = T_A;
 		q.answer = buf->buf;
 		q.anslen = sizeof(buf->buf);
+		if (_resp->family[1] == -1) {
+			q.next = NULL;
+			break;
+		}
 		q.next = &q2;
+
 		q2.qclass = C_IN;
-		q2.qtype = T_A;
+		if (_resp->family[1] == AF_INET6)
+			q2.qtype = T_AAAA;
+		else
+			q2.qtype = T_A;
 		q2.answer = buf2->buf;
 		q2.anslen = sizeof(buf2->buf);
 		break;
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 */
-- 
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