Cluster: free HANDSHAKE nodes after node_timeout.

Handshake nodes should turn into normal nodes or be freed in a
reasonable amount of time, otherwise they'll keep accumulating if the
address they are associated with is not reachable for some reason.

src/cluster.c

@@ -359,6 +359,7 @@ clusterNode *createClusterNode(char *nodename, int flags) {
         memcpy(node->name, nodename, REDIS_CLUSTER_NAMELEN);
     else
         getRandomHexChars(node->name, REDIS_CLUSTER_NAMELEN);
+    node->ctime = time(NULL);
     node->flags = flags;
     memset(node->slots,0,sizeof(node->slots));
     node->numslots = 0;
@@ -1588,6 +1589,16 @@ void clusterCron(void) {
         clusterNode *node = dictGetVal(de);
 
         if (node->flags & (REDIS_NODE_MYSELF|REDIS_NODE_NOADDR)) continue;
+
+        /* A Node in HANDSHAKE state has a limited lifespan equal to the
+         * configured node timeout. */
+        if (node->flags & REDIS_NODE_HANDSHAKE &&
+            server.unixtime - node->ctime > server.cluster_node_timeout)
+        {
+            freeClusterNode(node);
+            continue;
+        }
+
         if (node->link == NULL) {
             int fd;
             time_t old_ping_sent;

src/redis.h

@@ -614,6 +614,7 @@ struct clusterNodeFailReport {
 } typedef clusterNodeFailReport;
 
 struct clusterNode {
+    time_t ctime;   /* Node object creation time. */
     char name[REDIS_CLUSTER_NAMELEN]; /* Node name, hex string, sha1-size */
     int flags;      /* REDIS_NODE_... */
     unsigned char slots[REDIS_CLUSTER_SLOTS/8]; /* slots handled by this node */