Allow not to limit bandwidth in LAN (fixes #1336)

cmd/syncthing/connections.go

@@ -104,15 +104,18 @@ next:
 					continue next
 				}
 
-				// If rate limiting is set, we wrap the connection in a
-				// limiter.
+				// If rate limiting is set, and based on the address we should
+				// limit the connection, then we wrap it in a limiter.
+
+				limit := shouldLimit(conn.RemoteAddr())
+
 				wr := io.Writer(conn)
-				if writeRateLimit != nil {
+				if limit && writeRateLimit != nil {
 					wr = &limitedWriter{conn, writeRateLimit}
 				}
 
 				rd := io.Reader(conn)
-				if readRateLimit != nil {
+				if limit && readRateLimit != nil {
 					rd = &limitedReader{conn, readRateLimit}
 				}
 
@@ -121,7 +124,7 @@ next:
 
 				l.Infof("Established secure connection to %s at %s", remoteID, name)
 				if debugNet {
-					l.Debugf("cipher suite %04X", conn.ConnectionState().CipherSuite)
+					l.Debugf("cipher suite: %04X in lan: %t", conn.ConnectionState().CipherSuite, !limit)
 				}
 				events.Default.Log(events.DeviceConnected, map[string]string{
 					"id":   remoteID.String(),
@@ -283,3 +286,20 @@ func setTCPOptions(conn *net.TCPConn) {
 		l.Infoln(err)
 	}
 }
+
+func shouldLimit(addr net.Addr) bool {
+	if cfg.Options().LimitBandwidthInLan {
+		return true
+	}
+
+	tcpaddr, ok := addr.(*net.TCPAddr)
+	if !ok {
+		return true
+	}
+	for _, lan := range lans {
+		if lan.Contains(tcpaddr.IP) {
+			return false
+		}
+	}
+	return !tcpaddr.IP.IsLoopback()
+}