Implement EDNS0 support, as EDNS0 support will be made mandatory for

IPv6 transport-ready resolvers/DNS servers.  Need careful configuration
when enable it. (default config is not affected).
See manpage for details.

XXX visible symbol __res_opt() is added, however, it is not supposed to be
called from outside, libc minor is not bumped.

Obtained from:	KAME/NetBSD

6 files changed, 64 insertions, 2 deletions

diff --git a/lib/libc/net/getaddrinfo.c b/lib/libc/net/getaddrinfo.c
index c54b252..8ff92c2 100644
--- a/lib/libc/net/getaddrinfo.c
+++ b/lib/libc/net/getaddrinfo.c
@@ -79,7 +79,6 @@
  * - other KAME platforms already nuked FAITH ($GAI), but as FreeBSD
  *   4.0-RELEASE supplies it, we still have the code here.
  * - AI_ADDRCONFIG support is supplied
- * - EDNS0 support is not available due to resolver differences
  * - some of FreeBSD style (#define tabify and others)
  * - classful IPv4 numeric (127.1) is allowed.
  */
@@ -101,6 +100,9 @@
 #include <unistd.h>
 #include <stdio.h>
 #include <errno.h>
+#ifdef DEBUG
+#include <syslog.h>
+#endif
 
 #include <syslog.h>
 #include <stdarg.h>
@@ -1718,6 +1720,8 @@ 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 16033f2..b6ed1f5 100644
--- a/lib/libc/net/res_debug.c
+++ b/lib/libc/net/res_debug.c
@@ -519,6 +519,10 @@ p_option(u_long option) {
 	case RES_DNSRCH:	return "dnsrch";
 	case RES_INSECURE1:	return "insecure1";
 	case RES_INSECURE2:	return "insecure2";
+	case RES_NOALIASES:	return "noaliases";
+	case RES_USE_INET6:	return "inet6";
+	case RES_NOTLDQUERY:	return "no-tld-query";
+	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 9203b69..035dd05 100644
--- a/lib/libc/net/res_init.c
+++ b/lib/libc/net/res_init.c
@@ -532,6 +532,8 @@ res_setoptions(options, source)
 			_res.options |= RES_USE_INET6;
 		} else if (!strncmp(cp, "no_tld_query", sizeof("no_tld_query") - 1)) {
 			_res.options |= RES_NOTLDQUERY;
+		} 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 5ac662b..6cbd373 100644
--- a/lib/libc/net/res_mkquery.c
+++ b/lib/libc/net/res_mkquery.c
@@ -204,3 +204,40 @@ res_mkquery(op, dname, class, type, data, datalen, newrr_in, buf, buflen)
  */
 #undef res_mkquery
 __weak_reference(__res_mkquery, res_mkquery);
+
+/* 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 0ee2ad2..8a94a42 100644
--- a/lib/libc/net/res_query.c
+++ b/lib/libc/net/res_query.c
@@ -129,6 +129,8 @@ 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)
diff --git a/lib/libc/net/resolver.3 b/lib/libc/net/resolver.3
index 1fb97f5..e06a5fd 100644
--- a/lib/libc/net/resolver.3
+++ b/lib/libc/net/resolver.3
@@ -119,7 +119,7 @@ are defined in
 and are as follows.
 Options are stored as a simple bit mask containing the bitwise ``or''
 of the options enabled.
-.Bl -tag -width RES_DEFNAMES
+.Bl -tag -width RES_USE_INET6
 .It Dv RES_INIT
 True if the initial name server address and default domain name are
 initialized (i.e.,
@@ -176,6 +176,19 @@ This option is enabled by default.
 This option turns off the user level aliasing feature controlled by the
 .Dq Ev HOSTALIASES
 environment variable.  Network daemons should set this option.
+.It Dv RES_USE_INET6
+Enables support for IPv6-only applications.
+This causes IPv4 addresses to be returned as an IPv4 mapped address.
+For example, 10.1.1.1 will be returned as ::ffff:10.1.1.1.
+The option is meaningful with certain kernel configuration only.
+.It Dv RES_USE_EDNS0
+Enables support for OPT pseudo-RR for EDNS0 extension.
+With the option, resolver code will attach OPT pseudo-RR into DNS queries,
+to inform of our receive buffer size.
+The option will allow DNS servers to take advantage of non-default receive
+buffer size, and to send larger replies.
+DNS query packets with EDNS0 extension is not compatible with
+non-EDNS0 DNS servers.
 .El
 .Pp
 The