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."
         }
       }
     },

rpcserver.go

@@ -34,6 +34,7 @@ import (
 	"github.com/lightningnetwork/lnd/chanbackup"
 	"github.com/lightningnetwork/lnd/channeldb"
 	"github.com/lightningnetwork/lnd/channelnotifier"
+	"github.com/lightningnetwork/lnd/discovery"
 	"github.com/lightningnetwork/lnd/htlcswitch"
 	"github.com/lightningnetwork/lnd/input"
 	"github.com/lightningnetwork/lnd/invoices"
@@ -2012,9 +2013,36 @@ func (r *rpcServer) ListPeers(ctx context.Context,
 			satRecv += int64(c.TotalMSatReceived.ToSatoshis())
 		}
 
-		nodePub := serverPeer.addr.IdentityKey.SerializeCompressed()
+		nodePub := serverPeer.PubKey()
+
+		// Retrieve the peer's sync type. If we don't currently have a
+		// syncer for the peer, then we'll default to a passive sync.
+		// This can happen if the RPC is called while a peer is
+		// initializing.
+		syncer, ok := r.server.authGossiper.SyncManager().GossipSyncer(
+			nodePub,
+		)
+
+		var lnrpcSyncType lnrpc.Peer_SyncType
+		if !ok {
+			rpcsLog.Warnf("Gossip syncer for peer=%x not found",
+				nodePub)
+			lnrpcSyncType = lnrpc.Peer_UNKNOWN_SYNC
+		} else {
+			syncType := syncer.SyncType()
+			switch syncType {
+			case discovery.ActiveSync:
+				lnrpcSyncType = lnrpc.Peer_ACTIVE_SYNC
+			case discovery.PassiveSync:
+				lnrpcSyncType = lnrpc.Peer_PASSIVE_SYNC
+			default:
+				return nil, fmt.Errorf("unhandled sync type %v",
+					syncType)
+			}
+		}
+
 		peer := &lnrpc.Peer{
-			PubKey:    hex.EncodeToString(nodePub),
+			PubKey:    hex.EncodeToString(nodePub[:]),
 			Address:   serverPeer.conn.RemoteAddr().String(),
 			Inbound:   serverPeer.inbound,
 			BytesRecv: atomic.LoadUint64(&serverPeer.bytesReceived),
@@ -2022,6 +2050,7 @@ func (r *rpcServer) ListPeers(ctx context.Context,
 			SatSent:   satSent,
 			SatRecv:   satRecv,
 			PingTime:  serverPeer.PingTime(),
+			SyncType:  lnrpcSyncType,
 		}
 
 		resp.Peers = append(resp.Peers, peer)