Cluster: FAIL messages from unknown senders are handled better.

Previously the event was not logged but instead the node reported an
unknown packet type received.

src/cluster.c

@@ -1154,20 +1154,26 @@ int clusterProcessPacket(clusterLink *link) {
         /* Update the cluster state if needed */
         if (update_state) clusterUpdateState();
         if (update_config) clusterSaveConfigOrDie();
-    } else if (type == CLUSTERMSG_TYPE_FAIL && sender) {
+    } else if (type == CLUSTERMSG_TYPE_FAIL) {
         clusterNode *failing;
 
-        failing = clusterLookupNode(hdr->data.fail.about.nodename);
-        if (failing && !(failing->flags & (REDIS_NODE_FAIL|REDIS_NODE_MYSELF)))
-        {
+        if (sender) {
+            failing = clusterLookupNode(hdr->data.fail.about.nodename);
+            if (failing && !(failing->flags & (REDIS_NODE_FAIL|REDIS_NODE_MYSELF)))
+            {
+                redisLog(REDIS_NOTICE,
+                    "FAIL message received from %.40s about %.40s",
+                    hdr->sender, hdr->data.fail.about.nodename);
+                failing->flags |= REDIS_NODE_FAIL;
+                failing->fail_time = time(NULL);
+                failing->flags &= ~REDIS_NODE_PFAIL;
+                clusterUpdateState();
+                clusterSaveConfigOrDie();
+            }
+        } else {
             redisLog(REDIS_NOTICE,
-                "FAIL message received from %.40s about %.40s",
+                "Ignoring FAIL message from unknonw node %.40s about %.40s",
                 hdr->sender, hdr->data.fail.about.nodename);
-            failing->flags |= REDIS_NODE_FAIL;
-            failing->fail_time = time(NULL);
-            failing->flags &= ~REDIS_NODE_PFAIL;
-            clusterUpdateState();
-            clusterSaveConfigOrDie();
         }
     } else if (type == CLUSTERMSG_TYPE_PUBLISH) {
         robj *channel, *message;