lncfg+lnd: add new dev config unsafeconnect

This flag is added so we can use it in the itest to mimic racing inbound
and outbound connections.

lncfg/dev.go

@@ -52,3 +52,9 @@ func (d *DevConfig) GetZombieSweeperInterval() time.Duration {
 func (d *DevConfig) GetMaxWaitNumBlocksFundingConf() uint32 {
 	return DefaultMaxWaitNumBlocksFundingConf
 }
+
+// GetUnsafeConnect returns the config value `UnsafeConnect`, which is always
+// false for production build.
+func (d *DevConfig) GetUnsafeConnect() bool {
+	return false
+}

lncfg/dev_integration.go

@@ -26,6 +26,7 @@ type DevConfig struct {
 	ZombieSweeperInterval       time.Duration `long:"zombiesweeperinterval" description:"The time interval at which channel opening flows are evaluated for zombie status."`
 	UnsafeDisconnect            bool          `long:"unsafedisconnect" description:"Allows the rpcserver to intentionally disconnect from peers with open channels."`
 	MaxWaitNumBlocksFundingConf uint32        `long:"maxwaitnumblocksfundingconf" description:"Maximum blocks to wait for funding confirmation before discarding non-initiated channels."`
+	UnsafeConnect               bool          `long:"unsafeconnect" description:"Allow the rpcserver to connect to a peer even if there's already a connection."`
 }
 
 // ChannelReadyWait returns the config value `ProcessChannelReadyWait`.
@@ -65,3 +66,8 @@ func (d *DevConfig) GetMaxWaitNumBlocksFundingConf() uint32 {
 
 	return d.MaxWaitNumBlocksFundingConf
 }
+
+// GetUnsafeConnect returns the config value `UnsafeConnect`.
+func (d *DevConfig) GetUnsafeConnect() bool {
+	return d.UnsafeConnect
+}

server.go

@@ -4980,7 +4980,11 @@ func (s *server) ConnectToPeer(addr *lnwire.NetAddress,
 
 	// Ensure we're not already connected to this peer.
 	peer, err := s.findPeerByPubStr(targetPub)
-	if err == nil {
+
+	// When there's no error it means we already have a connection with this
+	// peer. If this is a dev environment with the `--unsafeconnect` flag
+	// set, we will ignore the existing connection and continue.
+	if err == nil && !s.cfg.Dev.GetUnsafeConnect() {
 		s.mu.Unlock()
 		return &errPeerAlreadyConnected{peer: peer}
 	}