[lwip-devel] [bug #20075] A problem with keep-alive timer and TCP flags

[Frédéric Bernon]

Follow-up Comment #4, bug #20075 (project lwip):

I have set in tcp_keepalive a TCPH_FLAGS_SET(tcphdr, 0);

I have test with a pseudo telnet server with lwip with these parameters:

int flag=1;
setsockopt( sock, SOL_SOCKET, SO_KEEPALIVE, (char*)&flag, sizeof(flag));
flag=10;
setsockopt( sock, IPPROTO_TCP, TCP_KEEPIDLE, (char*)&flag, sizeof(flag));
flag=2;
setsockopt( sock, IPPROTO_TCP, TCP_KEEPINTVL, (char*)&flag, sizeof(flag));
flag=10;
setsockopt( sock, IPPROTO_TCP, TCP_KEEPCNT, (char*)&flag, sizeof(flag));

Like this, when my client (the Windows 2000 Telnet client) connect, and wait
forever, I see the keepalive exchange. All seems ok, the TCP connection is
maintained. But, if I cut the network between lwip and my pc, after 10sec,
keepalive exchange become faster, and after 10 retry, the TCP connection is
abort:

tcp_slowtmr: KEEPALIVE timeout. Aborting connection to 192.168.1.85.

I attach the network capture file for the first part of the test. Ethereal
seems correctly "detect" keepalives packets. In this capture, 192.168.1.246
is my lwIP device (and 192.168.1.85 the PC).

So, if no objects about that, I will check in with 0 in TCP flags for
tcp_keepalive...




(file #13012)
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Additional Item Attachment:

File name: KeepAlive.cap                  Size:1 KB


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