Add a filter option to drop all cluster packets (valkey-io#1252)

A minor debugging change that helped in the investigation of
valkey-io#1251. Basically there are
some edge cases where we want to fully isolate a note from receiving
packets, but can't suspend the process because we need it to continue
sending outbound traffic. So, added a filter for that.

Signed-off-by: Madelyn Olson <[email protected]>

Author: madolson

src/cluster_legacy.c

@@ -3016,7 +3016,7 @@ int clusterIsValidPacket(clusterLink *link) {
         return 0;
     }
 
-    if (type == server.cluster_drop_packet_filter) {
+    if (type == server.cluster_drop_packet_filter || server.cluster_drop_packet_filter == -2) {
         serverLog(LL_WARNING, "Dropping packet that matches debug drop filter");
         return 0;
     }
@@ -3105,7 +3105,8 @@ int clusterProcessPacket(clusterLink *link) {
     if (!clusterIsValidPacket(link)) {
         clusterMsg *hdr = (clusterMsg *)link->rcvbuf;
         uint16_t type = ntohs(hdr->type);
-        if (server.debug_cluster_close_link_on_packet_drop && type == server.cluster_drop_packet_filter) {
+        if (server.debug_cluster_close_link_on_packet_drop &&
+            (type == server.cluster_drop_packet_filter || server.cluster_drop_packet_filter == -2)) {
             freeClusterLink(link);
             serverLog(LL_WARNING, "Closing link for matching packet type %hu", type);
             return 0;

src/debug.c

@@ -431,7 +431,7 @@ void debugCommand(client *c) {
             "    Some fields of the default behavior may be time consuming to fetch,",
             "    and `fast` can be passed to avoid fetching them.",
             "DROP-CLUSTER-PACKET-FILTER <packet-type>",
-            "    Drop all packets that match the filtered type. Set to -1 allow all packets.",
+            "    Drop all packets that match the filtered type. Set to -1 allow all packets or -2 to drop all packets.",
             "CLOSE-CLUSTER-LINK-ON-PACKET-DROP <0|1>",
             "    This is valid only when DROP-CLUSTER-PACKET-FILTER is set to a valid packet type.",
             "    When set to 1, the cluster link is closed after dropping a packet based on the filter.",