interceptor - Android VpnService: Reading from Tun device hangs -

my app using vpnservice traffic interception.

what does:
1.reads tun device in loop:

while (started && tundevice.valid()) {     final byte[] bytes = tundevice.read();     ippacket packet = packetfactory.createpacket(bytes);     if (packet == null) {         thread.yield();     } else {         proxyservice.handlepacket(packet);     } } 

tundevice.read:

@override public byte[] read() throws ioexception {     if (!valid()) {         log.warn("tun: file descriptor not valid more");         return null;     }      int length = tuninputstream.read(readbuffer);     log.debug("tun: received packet length={}", length);     if (length < 0) {         throw new ioexception("tun device closed");     }     if (length == 0) {         return null;     }     return arrays.copyofrange(readbuffer, 0, length); } 

2.proxifies data protected socket.

the problem after time stops reading tun device. read method hangs , waits time (like 3-5 minutes).

using netstat see new connections in syn_sent state , can understand why - cannot receive ack code because cannot receive these syn packets.

the question is: be? when tun device behave this?

in our case problem in our tcp implementation. have written more data tcp receive (advertised window).