lnd: add config option for specifying particular peers to connect to

config.go

@@ -293,6 +293,7 @@ type Config struct {
 	WSPingInterval    time.Duration `long:"ws-ping-interval" description:"The ping interval for REST based WebSocket connections, set to 0 to disable sending ping messages from the server side"`
 	WSPongWait        time.Duration `long:"ws-pong-wait" description:"The time we wait for a pong response message on REST based WebSocket connections before the connection is closed as inactive"`
 	NAT               bool          `long:"nat" description:"Toggle NAT traversal support (using either UPnP or NAT-PMP) to automatically advertise your external IP address to the network -- NOTE this does not support devices behind multiple NATs"`
+	AddPeers          []string      `long:"addpeer" description:"Specify peers to connect to first"`
 	MinBackoff        time.Duration `long:"minbackoff" description:"Shortest backoff when reconnecting to persistent peers. Valid time units are {s, m, h}."`
 	MaxBackoff        time.Duration `long:"maxbackoff" description:"Longest backoff when reconnecting to persistent peers. Valid time units are {s, m, h}."`
 	ConnectionTimeout time.Duration `long:"connectiontimeout" description:"The timeout value for network connections. Valid time units are {ms, s, m, h}."`

lncfg/address.go

@@ -278,36 +278,9 @@ func ParseAddressString(strAddress string, defaultPort string,
 func ParseLNAddressString(strAddress string, defaultPort string,
 	tcpResolver TCPResolver) (*lnwire.NetAddress, error) {
 
-	// Split the address string around the @ sign.
-	parts := strings.Split(strAddress, "@")
-
-	// The string is malformed if there are not exactly two parts.
-	if len(parts) != 2 {
-		return nil, fmt.Errorf("invalid lightning address %s: "+
-			"must be of the form <pubkey-hex>@<addr>", strAddress)
-	}
-
-	// Now, take the first portion as the hex pubkey, and the latter as the
-	// address string.
-	parsedPubKey, parsedAddr := parts[0], parts[1]
-
-	// Decode the hex pubkey to get the raw compressed pubkey bytes.
-	pubKeyBytes, err := hex.DecodeString(parsedPubKey)
+	pubKey, parsedAddr, err := ParseLNAddressPubkey(strAddress)
 	if err != nil {
-		return nil, fmt.Errorf("invalid lightning address pubkey: %v", err)
-	}
-
-	// The compressed pubkey should have a length of exactly 33 bytes.
-	if len(pubKeyBytes) != 33 {
-		return nil, fmt.Errorf("invalid lightning address pubkey: "+
-			"length must be 33 bytes, found %d", len(pubKeyBytes))
-	}
-
-	// Parse the pubkey bytes to verify that it corresponds to valid public
-	// key on the secp256k1 curve.
-	pubKey, err := btcec.ParsePubKey(pubKeyBytes)
-	if err != nil {
-		return nil, fmt.Errorf("invalid lightning address pubkey: %v", err)
+		return nil, err
 	}
 
 	// Finally, parse the address string using our generic address parser.
@@ -322,6 +295,45 @@ func ParseLNAddressString(strAddress string, defaultPort string,
 	}, nil
 }
 
+// ParseLNAddressPubkey converts a string of the form <pubkey>@<addr> into two
+// pieces: the pubkey bytes and an addr string. It validates that the pubkey
+// is of a valid form.
+func ParseLNAddressPubkey(strAddress string) (*btcec.PublicKey, string, error) {
+	// Split the address string around the @ sign.
+	parts := strings.Split(strAddress, "@")
+
+	// The string is malformed if there are not exactly two parts.
+	if len(parts) != 2 {
+		return nil, "", fmt.Errorf("invalid lightning address %s: "+
+			"must be of the form <pubkey-hex>@<addr>", strAddress)
+	}
+
+	// Now, take the first portion as the hex pubkey, and the latter as the
+	// address string.
+	parsedPubKey, parsedAddr := parts[0], parts[1]
+
+	// Decode the hex pubkey to get the raw compressed pubkey bytes.
+	pubKeyBytes, err := hex.DecodeString(parsedPubKey)
+	if err != nil {
+		return nil, "", fmt.Errorf("invalid lightning address pubkey: %v", err)
+	}
+
+	// The compressed pubkey should have a length of exactly 33 bytes.
+	if len(pubKeyBytes) != 33 {
+		return nil, "", fmt.Errorf("invalid lightning address pubkey: "+
+			"length must be 33 bytes, found %d", len(pubKeyBytes))
+	}
+
+	// Parse the pubkey bytes to verify that it corresponds to valid public
+	// key on the secp256k1 curve.
+	pubKey, err := btcec.ParsePubKey(pubKeyBytes)
+	if err != nil {
+		return nil, "", fmt.Errorf("invalid lightning address pubkey: %v", err)
+	}
+
+	return pubKey, parsedAddr, nil
+}
+
 // verifyPort makes sure that an address string has both a host and a port. If
 // there is no port found, the default port is appended. If the address is just
 // a port, then we'll assume that the user is using the short cut to specify a

sample-lnd.conf

@@ -183,6 +183,9 @@
 ; Disable TLS for the REST API.
 ; no-rest-tls=true
 
+; Specify peer(s) to connect to first.
+; addpeer=
+
 ; The ping interval for REST based WebSocket connections, set to 0 to disable
 ; sending ping messages from the server side. Valid time units are {s, m, h}.
 ; ws-ping-interval=30s

server.go

@@ -1905,6 +1905,43 @@ func (s *server) Start() error {
 			return nil
 		})
 
+		// If peers are specified as a config option, we'll add those
+		// peers first.
+		for _, peerAddrCfg := range s.cfg.AddPeers {
+			parsedPubkey, parsedHost, err := lncfg.ParseLNAddressPubkey(
+				peerAddrCfg,
+			)
+			if err != nil {
+				startErr = fmt.Errorf("unable to parse peer "+
+					"pubkey from config: %v", err)
+				return
+			}
+			addr, err := parseAddr(parsedHost, s.cfg.net)
+			if err != nil {
+				startErr = fmt.Errorf("unable to parse peer "+
+					"address provided as a config option: "+
+					"%v", err)
+				return
+			}
+
+			peerAddr := &lnwire.NetAddress{
+				IdentityKey: parsedPubkey,
+				Address:     addr,
+				ChainNet:    s.cfg.ActiveNetParams.Net,
+			}
+
+			err = s.ConnectToPeer(
+				peerAddr, true,
+				s.cfg.ConnectionTimeout,
+			)
+			if err != nil {
+				startErr = fmt.Errorf("unable to connect to "+
+					"peer address provided as a config "+
+					"option: %v", err)
+				return
+			}
+		}
+
 		// Subscribe to NodeAnnouncements that advertise new addresses
 		// our persistent peers.
 		if err := s.updatePersistentPeerAddrs(); err != nil {