Fix to 75e2f0aec33e58ef5b8d4d107d821c215a52827c

If identical queries from IPv4 and IPv6 sources are combined by the
new code added in 15b60ddf93 then replies
can end up being sent via the wrong family of socket. The ->fd
should be per query, not per-question.

In bind-interfaces mode, this could also result in replies being sent
via the wrong socket even when IPv4/IPV6 issues are not in play.

src/dnsmasq.h

@@ -664,6 +664,7 @@ struct frec {
     union mysockaddr source;
     union all_addr dest;
     unsigned int iface, log_id;
+    int fd;
     unsigned short orig_id;
     struct frec_src *next;
   } frec_src;
@@ -671,7 +672,7 @@ struct frec {
   struct randfd *rfd4;
   struct randfd *rfd6;
   unsigned short new_id;
-  int fd, forwardall, flags;
+  int forwardall, flags;
   time_t time;
   unsigned char *hash[HASH_SIZE];
 #ifdef HAVE_DNSSEC 

src/forward.c

@@ -378,6 +378,7 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
 	      new->dest = *dst_addr;
 	      new->log_id = daemon->log_id;
 	      new->iface = dst_iface;
+	      forward->frec_src.fd = udpfd;
 	    }
 	  
 	  return 1;
@@ -402,8 +403,8 @@ static int forward_query(int udpfd, union mysockaddr *udpaddr,
 	  forward->frec_src.dest = *dst_addr;
 	  forward->frec_src.iface = dst_iface;
 	  forward->frec_src.next = NULL;
+	  forward->frec_src.fd = udpfd;
 	  forward->new_id = get_id();
-	  forward->fd = udpfd;
 	  memcpy(forward->hash, hash, HASH_SIZE);
 	  forward->forwardall = 0;
 	  forward->flags = fwd_flags;
@@ -1300,7 +1301,7 @@ void reply_query(int fd, int family, time_t now)
 	      dump_packet(DUMP_REPLY, daemon->packet, (size_t)nn, NULL, &src->source);
 #endif
 	      
-	      send_from(forward->fd, option_bool(OPT_NOWILD) || option_bool (OPT_CLEVERBIND), daemon->packet, nn, 
+	      send_from(src->fd, option_bool(OPT_NOWILD) || option_bool (OPT_CLEVERBIND), daemon->packet, nn, 
 			&src->source, &src->dest, src->iface);
 
 	      if (option_bool(OPT_EXTRALOG) && src != &forward->frec_src)