From c503b82e91f932c2b1014a89132bbfc00552648f Mon Sep 17 00:00:00 2001
From: Wilmer Paulino <wilmer.paulino@gmail.com>
Date: Tue, 14 Apr 2020 16:16:26 -0700
Subject: [PATCH] server: ignore reconnection for unadvertised inbound peers
 over Tor

A peer's remote address isn't known to us if we accepted the connection
over Tor, instead we know the address the onion service used to dial to
lnd. If said peer also doesn't have any advertised addresses, then we
don't have enough information to attempt a reconnect, so we avoid doing
so. Allowing the reconnection to happen isn't necessarily an issue, but
not allowing it prevents the configured SOCKS proxy from dialing to
private addresses.
---
 server.go | 44 +++++++++++++++++++++++++++++++++++---------
 1 file changed, 35 insertions(+), 9 deletions(-)

diff --git a/server.go b/server.go
index f8c36b30..84779da2 100644
--- a/server.go
+++ b/server.go
@@ -3002,15 +3002,37 @@ func (s *server) peerTerminationWatcher(p *peer, ready chan struct{}) {
 		//
 		// TODO(roasbeef): use them all?
 		if p.inbound {
-			advertisedAddr, err := s.fetchNodeAdvertisedAddr(
-				pubKey,
-			)
-			if err != nil {
-				srvrLog.Errorf("Unable to retrieve advertised "+
-					"address for node %x: %v",
-					pubKey.SerializeCompressed(), err)
-			} else {
+			advertisedAddr, err := s.fetchNodeAdvertisedAddr(pubKey)
+			switch {
+			// We found an advertised address, so use it.
+			case err == nil:
 				p.addr.Address = advertisedAddr
+
+			// The peer doesn't have an advertised address.
+			case err == errNoAdvertisedAddr:
+				// Fall back to the existing peer address if
+				// we're not accepting connections over Tor.
+				if s.torController == nil {
+					break
+				}
+
+				// If we are, the peer's address won't be known
+				// to us (we'll see a private address, which is
+				// the address used by our onion service to dial
+				// to lnd), so we don't have enough information
+				// to attempt a reconnect.
+				srvrLog.Debugf("Ignoring reconnection attempt "+
+					"to inbound peer %v without "+
+					"advertised address", p)
+				return
+
+			// We came across an error retrieving an advertised
+			// address, log it, and fall back to the existing peer
+			// address.
+			default:
+				srvrLog.Errorf("Unable to retrieve advertised "+
+					"address for node %x: %v", p.PubKey(),
+					err)
 			}
 		}
 
@@ -3408,6 +3430,10 @@ func computeNextBackoff(currBackoff time.Duration) time.Duration {
 	return nextBackoff + (time.Duration(wiggle.Uint64()) - margin/2)
 }
 
+// errNoAdvertisedAddr is an error returned when we attempt to retrieve the
+// advertised address of a node, but they don't have one.
+var errNoAdvertisedAddr = errors.New("no advertised address found")
+
 // fetchNodeAdvertisedAddr attempts to fetch an advertised address of a node.
 func (s *server) fetchNodeAdvertisedAddr(pub *btcec.PublicKey) (net.Addr, error) {
 	vertex, err := route.NewVertexFromBytes(pub.SerializeCompressed())
@@ -3421,7 +3447,7 @@ func (s *server) fetchNodeAdvertisedAddr(pub *btcec.PublicKey) (net.Addr, error)
 	}
 
 	if len(node.Addresses) == 0 {
-		return nil, errors.New("no advertised addresses found")
+		return nil, errNoAdvertisedAddr
 	}
 
 	return node.Addresses[0], nil