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/src/lib/libc/net/getaddrinfo.c b/src/lib/libc/net/getaddrinfo.c
index 1326473fb7..0a0b112589 100644
--- a/src/lib/libc/net/getaddrinfo.c
+++ b/src/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/src/lib/libc/net/res_debug.c b/src/lib/libc/net/res_debug.c
index e1894b1508..54be69cef7 100644
--- a/src/lib/libc/net/res_debug.c
+++ b/src/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/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? */
                 }
diff --git a/src/lib/libc/net/res_mkquery.c b/src/lib/libc/net/res_mkquery.c
index 3e7e2ae5d3..61595a6e8c 100644
--- a/src/lib/libc/net/res_mkquery.c
+++ b/src/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/src/lib/libc/net/res_query.c b/src/lib/libc/net/res_query.c
index 01d1f691cb..433e80f648 100644
--- a/src/lib/libc/net/res_query.c
+++ b/src/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)