[BZ #4647]

            Tomas Janousek  <tjanouse@redhat.com>
            Ulrich Drepper  <drepper@redhat.com>

	[BZ #4647]
	* resolv/res_send.c (send_dg): Remove socket_pf.  Use ipv6_unavail
	member in __res_state, only convaddr4to6 if nssocks[ns] is a PF_INET6
	socket.
	* resolv/resolv.h (__res_state): Add ipv6_unavail member.  Make
	unused member a bitmap.
	* resolv/res_init.c (__res_vinit): Reset ipv6_unavail if IPv6
	servers are configured.

2007-06-18  Jakub Jelinek  <jakub@redhat.com>

3 files changed, 19 insertions, 11 deletions

diff --git a/resolv/res_init.c b/resolv/res_init.c
index 640e087920..d1a5681a93 100644
--- a/resolv/res_init.c
+++ b/resolv/res_init.c
@@ -241,8 +241,8 @@ __res_vinit(res_state statp, int preinit) {
 	 line[sizeof(name) - 1] == '\t'))
 
 	if ((fp = fopen(_PATH_RESCONF, "rc")) != NULL) {
-		/* No threads use this stream.  */
-		__fsetlocking (fp, FSETLOCKING_BYCALLER);
+	    /* No threads use this stream.  */
+	    __fsetlocking (fp, FSETLOCKING_BYCALLER);
 	    /* read the config file */
 	    while (fgets_unlocked(buf, sizeof(buf), fp) != NULL) {
 		/* skip comments */
@@ -397,8 +397,11 @@ __res_vinit(res_state statp, int preinit) {
 	    if (nserv > 1)
 		statp->nscount = nserv;
 #ifdef _LIBC
-	    if (nservall - nserv > 0)
+	    if (nservall - nserv > 0) {
 		statp->_u._ext.nscount6 = nservall - nserv;
+		/* We try IPv6 servers again.  */
+		statp->ipv6_unavail = false;
+	    }
 #endif
 #ifdef RESOLVSORT
 	    statp->nsort = nsort;
diff --git a/resolv/res_send.c b/resolv/res_send.c
index f38c399ffd..27dd1d4351 100644
--- a/resolv/res_send.c
+++ b/resolv/res_send.c
@@ -813,17 +813,20 @@ send_dg(res_state statp,
 	struct pollfd pfd[1];
         int ptimeout;
 	struct sockaddr_in6 from;
-	static int socket_pf = 0;
 	socklen_t fromlen;
 	int resplen, seconds, n;
 
 	if (EXT(statp).nssocks[ns] == -1) {
 		/* only try IPv6 if IPv6 NS and if not failed before */
-		if ((EXT(statp).nscount6 > 0) && (socket_pf != PF_INET)) {
+		if ((EXT(statp).nscount6 > 0) && !statp->ipv6_unavail) {
 			EXT(statp).nssocks[ns] =
 			    socket(PF_INET6, SOCK_DGRAM, 0);
-			socket_pf = EXT(statp).nssocks[ns] < 0 ? PF_INET
-			                                       : PF_INET6;
+			if (EXT(statp).nssocks[ns] < 0)
+			    statp->ipv6_unavail = errno == EAFNOSUPPORT;
+			/* If IPv6 socket and nsap is IPv4, make it
+			   IPv4-mapped */
+			else if (nsap->sin6_family == AF_INET)
+			    convaddr4to6(nsap);
 		}
 		if (EXT(statp).nssocks[ns] < 0)
 			EXT(statp).nssocks[ns] = socket(PF_INET, SOCK_DGRAM, 0);
@@ -832,9 +835,7 @@ send_dg(res_state statp,
 			Perror(statp, stderr, "socket(dg)", errno);
 			return (-1);
 		}
-		/* If IPv6 socket and nsap is IPv4, make it IPv4-mapped */
-		if ((socket_pf == PF_INET6) && (nsap->sin6_family == AF_INET))
-			convaddr4to6(nsap);
+
 		/*
 		 * On a 4.3BSD+ machine (client and server,
 		 * actually), sending to a nameserver datagram
diff --git a/resolv/resolv.h b/resolv/resolv.h
index 9aa09b8701..105631ee7d 100644
--- a/resolv/resolv.h
+++ b/resolv/resolv.h
@@ -110,21 +110,25 @@ struct __res_state {
 		nsaddr_list[MAXNS];	/* address of name server */
 # define nsaddr	nsaddr_list[0]		/* for backward compatibility */
 	u_short	id;			/* current message id */
+	/* 2 byte hole here.  */
 	char	*dnsrch[MAXDNSRCH+1];	/* components of domain to search */
 	char	defdname[256];		/* default domain (deprecated) */
 	u_long	pfcode;			/* RES_PRF_ flags - see below. */
 	unsigned ndots:4;		/* threshold for initial abs. query */
 	unsigned nsort:4;		/* number of elements in sort_list[] */
-	char	unused[3];
+	unsigned ipv6_unavail:1;	/* connecting to IPv6 server failed */
+	unsigned unused:23;
 	struct {
 		struct in_addr	addr;
 		u_int32_t	mask;
 	} sort_list[MAXRESOLVSORT];
+	/* 4 byte hole here on 64-bit architectures.  */
 	res_send_qhook qhook;		/* query hook */
 	res_send_rhook rhook;		/* response hook */
 	int	res_h_errno;		/* last one set for this context */
 	int	_vcsock;		/* PRIVATE: for res_send VC i/o */
 	u_int	_flags;			/* PRIVATE: see below */
+	/* 4 byte hole here on 64-bit architectures.  */
 	union {
 		char	pad[52];	/* On an i386 this means 512b total. */
 		struct {