Bug 614526: Pass AI_ADDRCONFIG to getaddrinfo if PR_AI_ADDRCONFIG is …

…set.

Filter the various localhost names to work around a AI_ADDRCONFIG problem
with loopback addresses in some implementations.  The patch is contributed
by Honza Bambas <honzab.moz@firemni.cz>.  r=wtc.  a=blocking+approval2.0.

nsprpub/pr/src/misc/prnetdb.c

@@ -2039,7 +2039,32 @@ PR_IMPLEMENT(PRAddrInfo *) PR_GetAddrInfoByName(const char  *hostname,
          */
 
         memset(&hints, 0, sizeof(hints));
-        hints.ai_flags = (flags & PR_AI_NOCANONNAME) ? 0: AI_CANONNAME;
+        if (flags & PR_AI_NOCANONNAME)
+            hints.ai_flags |= AI_CANONNAME;
+#ifdef AI_ADDRCONFIG
+        /* 
+         * Propagate AI_ADDRCONFIG to the GETADDRINFO call if PR_AI_ADDRCONFIG
+         * is set.
+         * 
+         * Need a workaround for loopback host addresses:         
+         * The problem is that in glibc and Windows, AI_ADDRCONFIG applies the
+         * existence of an outgoing network interface to IP addresses of the
+         * loopback interface, due to a strict interpretation of the
+         * specification.  For example, if a computer does not have any
+         * outgoing IPv6 network interface, but its loopback network interface
+         * supports IPv6, a getaddrinfo call on "localhost" with AI_ADDRCONFIG
+         * won't return the IPv6 loopback address "::1", because getaddrinfo
+         * thinks the computer cannot connect to any IPv6 destination,
+         * ignoring the remote vs. local/loopback distinction.
+         */
+        if ((flags & PR_AI_ADDRCONFIG) &&
+            strcmp(hostname, "localhost") != 0 &&
+            strcmp(hostname, "localhost.localdomain") != 0 &&
+            strcmp(hostname, "localhost6") != 0 &&
+            strcmp(hostname, "localhost6.localdomain6") != 0) {
+            hints.ai_flags |= AI_ADDRCONFIG;
+        }
+#endif
         hints.ai_family = (af == PR_AF_INET) ? AF_INET : AF_UNSPEC;
 
         /*