rpc: expose peer's GossipSyncer sync type

lnrpc/rpc.proto

@@ -1257,6 +1257,26 @@ message Peer {
 
     /// Ping time to this peer
     int64 ping_time = 9 [json_name = "ping_time"];
+
+    enum SyncType {
+        /**
+        Denotes that we cannot determine the peer's current sync type.
+        */
+        UNKNOWN_SYNC = 0;
+
+        /**
+        Denotes that we are actively receiving new graph updates from the peer.
+        */
+        ACTIVE_SYNC = 1;
+
+        /**
+        Denotes that we are not receiving new graph updates from the peer.
+        */
+        PASSIVE_SYNC = 2;
+    }
+
+    // The type of sync we are currently performing with this peer.
+    SyncType sync_type = 10 [json_name = "sync_type"];
 }
 
 message ListPeersRequest {

lnrpc/rpc.swagger.json

@@ -1305,6 +1305,16 @@
       ],
       "default": "OPEN"
     },
+    "PeerSyncType": {
+      "type": "string",
+      "enum": [
+        "UNKNOWN_SYNC",
+        "ACTIVE_SYNC",
+        "PASSIVE_SYNC"
+      ],
+      "default": "UNKNOWN_SYNC",
+      "description": " - UNKNOWN_SYNC: *\nDenotes that we cannot determine the peer's current sync type.\n - ACTIVE_SYNC: *\nDenotes that we are actively receiving new graph updates from the peer.\n - PASSIVE_SYNC: *\nDenotes that we are not receiving new graph updates from the peer."
+    },
     "PendingChannelsResponseClosedChannel": {
       "type": "object",
       "properties": {
@@ -2856,6 +2866,10 @@
           "type": "string",
           "format": "int64",
           "title": "/ Ping time to this peer"
+        },
+        "sync_type": {
+          "$ref": "#/definitions/PeerSyncType",
+          "description": "The type of sync we are currently performing with this peer."
         }
       }
     },