[lwip-users] LwIP 1.4.1: Outgoing TCP connection does not work - LwIP sends RST, ACK

[Marco Jakobs]

Hi,

 

while updating my projects to LwIP 1.4.1, i've noticed that outgoing TCP connections from LwIP to TCP server applications do not work properly :-(

 

Setting up the connection as I did in LwIP 1.4.0 with the netconn interface like this:

 

ssrv_netconn[nconn-1].conn = netconn_new_with_callback (NETCONN_TCP, ssrv_tcpcln_callback);

…

netconn_set_nonblocking(ssrv_netconn[nconn-1].conn, 1);

…

err = netconn_bind (ssrv_netconn[nconn-1].conn,NULL,ssrv_conn[f].absport);

…

err = netconn_connect (ssrv_netconn[ssrv_conn[f].netconn[0]-1].conn, &ssrv_addr, port);

 

I receive a proper callback that the connection was set up and acknowledged, but sending packets to the server does not work!

 

Wireshark gives this output:

 

55        13:40:56.348413        192.168.4.11   192.168.0.221 TCP      60        49153 > 14713 [SYN] Seq=6509 Win=2048 Len=0 MSS=1024

56        13:40:56.348517        192.168.0.221 192.168.4.11   TCP      60        14713 > 49153 [ACK] Seq=1144619934 Ack=6510 Win=65535 Len=0

57        13:40:56.348986        192.168.4.11   192.168.0.221 TCP      60        49153 > 14713 [RST, ACK] Seq=6510 Ack=1144619934 Win=2048 Len=0

 

So right after the acknowledgement from the server, LwIP now sends a RST,ACK instead a single ACK (what it did in 1.4.0 and what I'd expect).

 

Any idea how to fix this?

 

Marco