htlcswitch/link: fail channel on lnwire.Error

htlcswitch/link.go

@@ -1319,7 +1319,21 @@ func (l *channelLink) handleUpstreamMsg(msg lnwire.Message) {
 			l.fail("error receiving fee update: %v", err)
 			return
 		}
+	case *lnwire.Error:
+		// Error received from remote, MUST fail channel, but should
+		// only print the contents of the error message if all
+		// characters are printable ASCII.
+		errMsg := "non-ascii data"
+		if isASCII(msg.Data) {
+			errMsg = string(msg.Data)
+		}
+		l.fail("ChannelPoint(%v): recieved error from peer: %v",
+			l.channel.ChannelPoint(), errMsg)
+	default:
+		log.Warnf("ChannelPoint(%v): received unknown message of type %T",
+			l.channel.ChannelPoint(), msg)
 	}
+
 }
 
 // ackDownStreamPackets is responsible for removing htlcs from a link's
@@ -2407,3 +2421,16 @@ func (l *channelLink) tracef(format string, a ...interface{}) {
 	msg := fmt.Sprintf(format, a...)
 	log.Tracef("ChannelLink(%s) %s", l.ShortChanID(), msg)
 }
+
+// isASCII is a helper method that checks whether all bytes in `data` would be
+// printable ASCII characters if interpreted as a string.
+func isASCII(data []byte) bool {
+	isASCII := true
+	for _, c := range data {
+		if c < 32 || c > 126 {
+			isASCII = false
+			break
+		}
+	}
+	return isASCII
+}