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.

5 files changed, 56 insertions, 9 deletions

diff --git a/lib/libc/net/getaddrinfo.c b/lib/libc/net/getaddrinfo.c
index 1326473fb74..0a0b112589d 100644
--- a/lib/libc/net/getaddrinfo.c
+++ b/lib/libc/net/getaddrinfo.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: getaddrinfo.c,v 1.27 2000/08/31 17:41:51 itojun Exp $	*/
+/*	$OpenBSD: getaddrinfo.c,v 1.28 2001/06/11 10:05:58 itojun Exp $	*/
 /*	$KAME: getaddrinfo.c,v 1.31 2000/08/31 17:36:43 itojun Exp $	*/
 
 /*
@@ -1511,6 +1511,7 @@ _yp_getaddrinfo(name, pai)
 
 extern const char *__hostalias __P((const char *));
 extern int h_errno;
+extern int res_opt __P((int, u_char *, int, int));
 
 /*
  * Formulate a normal query, send, and await answer.
@@ -1562,6 +1563,8 @@ res_queryN(name, target)
 
 		n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 		    buf, sizeof(buf));
+		if (n > 0 && (_res.options & RES_USE_EDNS0) != 0)
+			n = res_opt(n, buf, sizeof(buf), anslen);
 		if (n <= 0) {
 #ifdef DEBUG
 			if (_res.options & RES_DEBUG)
diff --git a/lib/libc/net/res_debug.c b/lib/libc/net/res_debug.c
index e1894b15086..54be69cef74 100644
--- a/lib/libc/net/res_debug.c
+++ b/lib/libc/net/res_debug.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: res_debug.c,v 1.10 2000/07/07 20:59:47 deraadt Exp $	*/
+/*	$OpenBSD: res_debug.c,v 1.11 2001/06/11 10:05:59 itojun Exp $	*/
 
 /*
  * ++Copyright++ 1985, 1990, 1993
@@ -82,7 +82,7 @@
 static char sccsid[] = "@(#)res_debug.c	8.1 (Berkeley) 6/4/93";
 static char rcsid[] = "$From: res_debug.c,v 8.19 1996/11/26 10:11:23 vixie Exp $";
 #else
-static char rcsid[] = "$OpenBSD: res_debug.c,v 1.10 2000/07/07 20:59:47 deraadt Exp $";
+static char rcsid[] = "$OpenBSD: res_debug.c,v 1.11 2001/06/11 10:05:59 itojun Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -1028,6 +1028,8 @@ __p_option(option)
 	case RES_DNSRCH:	return "dnsrch";
 	case RES_INSECURE1:	return "insecure1";
 	case RES_INSECURE2:	return "insecure2";
+	case RES_USE_INET6:	return "inet6";
+	case RES_USE_EDNS0:	return "edns0";
 	default:		sprintf(nbuf, "?0x%lx?", (u_long)option);
 				return (nbuf);
 	}
diff --git a/lib/libc/net/res_init.c b/lib/libc/net/res_init.c
index bba8cfaad16..c44539604a3 100644
--- a/lib/libc/net/res_init.c
+++ b/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? */
 		}
diff --git a/lib/libc/net/res_mkquery.c b/lib/libc/net/res_mkquery.c
index 3e7e2ae5d31..61595a6e8c5 100644
--- a/lib/libc/net/res_mkquery.c
+++ b/lib/libc/net/res_mkquery.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: res_mkquery.c,v 1.8 1997/04/13 22:37:21 provos Exp $	*/
+/*	$OpenBSD: res_mkquery.c,v 1.9 2001/06/11 10:06:00 itojun Exp $	*/
 
 /*
  * ++Copyright++ 1985, 1993
@@ -60,7 +60,7 @@
 static char sccsid[] = "@(#)res_mkquery.c	8.1 (Berkeley) 6/4/93";
 static char rcsid[] = "$From: res_mkquery.c,v 8.5 1996/08/27 08:33:28 vixie Exp $";
 #else
-static char rcsid[] = "$OpenBSD: res_mkquery.c,v 1.8 1997/04/13 22:37:21 provos Exp $";
+static char rcsid[] = "$OpenBSD: res_mkquery.c,v 1.9 2001/06/11 10:06:00 itojun Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -193,3 +193,40 @@ res_mkquery(op, dname, class, type, data, datalen, newrr_in, buf, buflen)
 	}
 	return (cp - buf);
 }
+
+/* attach OPT pseudo-RR, as documented in RFC2671 (EDNS0). */
+int
+res_opt(n0, buf, buflen, anslen)
+	int n0;
+	u_char *buf;		/* buffer to put query */
+	int buflen;		/* size of buffer */
+	int anslen;		/* answer buffer length */
+{
+	register HEADER *hp;
+	register u_char *cp;
+
+	hp = (HEADER *) buf;
+	cp = buf + n0;
+	buflen -= n0;
+
+	if (buflen < 1 + RRFIXEDSZ)
+		return -1;
+
+	*cp++ = 0;	/* "." */
+	buflen--;
+
+	__putshort(T_OPT, cp);	/* TYPE */
+	cp += INT16SZ;
+	__putshort(anslen & 0xffff, cp);	/* CLASS = UDP payload size */
+	cp += INT16SZ;
+	*cp++ = NOERROR;	/* extended RCODE */
+	*cp++ = 0;		/* EDNS version */
+	__putshort(0, cp);	/* MBZ */
+	cp += INT16SZ;
+	__putshort(0, cp);	/* RDLEN */
+	cp += INT16SZ;
+	hp->arcount = htons(ntohs(hp->arcount) + 1);
+	buflen -= RRFIXEDSZ;
+
+	return cp - buf;
+}
diff --git a/lib/libc/net/res_query.c b/lib/libc/net/res_query.c
index 01d1f691cb7..433e80f6482 100644
--- a/lib/libc/net/res_query.c
+++ b/lib/libc/net/res_query.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: res_query.c,v 1.13 1999/09/27 23:58:26 alex Exp $	*/
+/*	$OpenBSD: res_query.c,v 1.14 2001/06/11 10:06:01 itojun Exp $	*/
 
 /*
  * ++Copyright++ 1988, 1993
@@ -60,7 +60,7 @@
 static char sccsid[] = "@(#)res_query.c	8.1 (Berkeley) 6/4/93";
 static char rcsid[] = "$From: res_query.c,v 8.9 1996/09/22 00:13:28 vixie Exp $";
 #else
-static char rcsid[] = "$OpenBSD: res_query.c,v 1.13 1999/09/27 23:58:26 alex Exp $";
+static char rcsid[] = "$OpenBSD: res_query.c,v 1.14 2001/06/11 10:06:01 itojun Exp $";
 #endif
 #endif /* LIBC_SCCS and not lint */
 
@@ -87,6 +87,7 @@ static char rcsid[] = "$OpenBSD: res_query.c,v 1.13 1999/09/27 23:58:26 alex Exp
 
 const char *hostalias __P((const char *));
 int h_errno;
+extern int res_opt __P((int, u_char *, int, int));
 
 /*
  * Formulate a normal query, send, and await answer.
@@ -122,6 +123,8 @@ res_query(name, class, type, answer, anslen)
 
 	n = res_mkquery(QUERY, name, class, type, NULL, 0, NULL,
 			buf, sizeof(buf));
+	if (n > 0 && (_res.options & RES_USE_EDNS0) != 0)
+		n = res_opt(n, buf, sizeof(buf), anslen);
 	if (n <= 0) {
 #ifdef DEBUG
 		if (_res.options & RES_DEBUG)