Add IPv6 support to sentinel.c.

This has been done by exposing the anetSockName() function anet.c
to be used when the sentinel is publishing its existence to the masters.

This implementation is very unintelligent as it will likely break if used
with IPv6 as the nested colons will break any parsing of the PUBLISH string
by the master.

src/anet.h

@@ -57,5 +57,6 @@ int anetDisableTcpNoDelay(char *err, int fd);
 int anetTcpKeepAlive(char *err, int fd);
 int anetPeerToString(int fd, char *ip, size_t ip_len, int *port);
 int anetKeepAlive(char *err, int fd, int interval);
+int anetSockName(int fd, char *ip, size_t ip_len, int *port);
 
 #endif

src/sentinel.c

@@ -1837,14 +1837,13 @@ void sentinelPingInstance(sentinelRedisInstance *ri) {
                (now - ri->last_pub_time) > SENTINEL_PUBLISH_PERIOD)
     {
         /* PUBLISH hello messages only to masters. */
-        struct sockaddr_in sa;
-        socklen_t salen = sizeof(sa);
-
-        if (getsockname(ri->cc->c.fd,(struct sockaddr*)&sa,&salen) != -1) {
+        char ip[INET6_ADDRSTRLEN];
+        if (anetSockName(ri->cc->c.fd,ip,sizeof(ip),NULL) != -1) {
             char myaddr[128];
 
+            // FIXME: IPv6 will break this due to nested : characters -geoffgarside
             snprintf(myaddr,sizeof(myaddr),"%s:%d:%s:%d",
-                inet_ntoa(sa.sin_addr), server.port, server.runid,
+                ip, server.port, server.runid,
                 (ri->flags & SRI_CAN_FAILOVER) != 0);
             retval = redisAsyncCommand(ri->cc,
                 sentinelPublishReplyCallback, NULL, "PUBLISH %s %s",