Always resolve v4 and v6 addresses

Otherwise the code will never work on v6-only hosts, when the domain
resolves to v4 addresses.

The latency is negligible. The order of resolved addresses is already a
good hint on which connectivity is available.
If IPv6 is returned, but no such connectivity is there, it's a system
configuration mistake.

Additionally, repetitive re-connections to Redis should be avoided
anyway.

net.c

@@ -319,20 +319,18 @@ static int _redisContextConnectTcp(redisContext *c, const char *addr, int port,
 
     snprintf(_port, 6, "%d", port);
     memset(&hints,0,sizeof(hints));
-    hints.ai_family = AF_INET;
+    hints.ai_family = AF_UNSPEC;
     hints.ai_socktype = SOCK_STREAM;
 
-    /* Try with IPv6 if no IPv4 address was found. We do it in this order since
-     * in a Redis client you can't afford to test if you have IPv6 connectivity
-     * as this would add latency to every connect. Otherwise a more sensible
-     * route could be: Use IPv6 if both addresses are available and there is IPv6
-     * connectivity. */
+    /* We always check for both IPv4 and IPv6 addresses.
+     * This is the only way it will work on v6-only hosts
+     * (and will work on v4-only hosts as well).
+     * In general we can rely on the order of addresses returned
+     * to avoid additional connect latency.
+     */
     if ((rv = getaddrinfo(c->tcp.host,_port,&hints,&servinfo)) != 0) {
-         hints.ai_family = AF_INET6;
-         if ((rv = getaddrinfo(addr,_port,&hints,&servinfo)) != 0) {
-            __redisSetError(c,REDIS_ERR_OTHER,gai_strerror(rv));
-            return REDIS_ERR;
-        }
+        __redisSetError(c,REDIS_ERR_OTHER,gai_strerror(rv));
+        return REDIS_ERR;
     }
     for (p = servinfo; p != NULL; p = p->ai_next) {
 addrretry: