support EDNS0 (RFC2671) buffer size notification on DNS queries.

"options edns0" in /etc/resolv.conf will enable the behavior.  no behavior
change if you don't have the line.  see resolv.conf(5) for more details.

EDNS0 is useful for avoiding TCP DNS queries/replies on larger DNS responses.
also, draft-ietf-dnsext-message-size-* plans to mandate EDNS0 support for DNS
clients that support IPv6 transport.

1 files changed, 4 insertions, 2 deletions

diff --git a/src/lib/libc/net/res_init.c b/src/lib/libc/net/res_init.c
index bba8cfaad1..c44539604a 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 1.20 2000/11/10 15:33:04 provos Exp $    */
+/*      $OpenBSD: res_init.c,v 1.21 2001/06/11 10:06:00 itojun Exp $    */
 
 /*
  * ++Copyright++ 1985, 1989, 1993
@@ -64,7 +64,7 @@
 static char sccsid[] = "@(#)res_init.c  8.1 (Berkeley) 6/7/93";
 static char rcsid[] = "$From: res_init.c,v 8.7 1996/09/28 06:51:07 vixie Exp $";
 #else
-static char rcsid[] = "$OpenBSD: res_init.c,v 1.20 2000/11/10 15:33:04 provos Exp $";
+static char rcsid[] = "$OpenBSD: res_init.c,v 1.21 2001/06/11 10:06:00 itojun Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -608,6 +608,8 @@ res_setoptions(options, source)
 #endif
                 } else if (!strncmp(cp, "inet6", sizeof("inet6") - 1)) {
                         _res.options |= RES_USE_INET6;
+                } else if (!strncmp(cp, "edns0", sizeof("edns0") - 1)) {
+                        _res.options |= RES_USE_EDNS0;
                 } else {
                         /* XXX - print a warning here? */
                 }