[lwip-devel] [bug #20640] Request getting lost/unanswered in lwip stack

[Kieran Mansley]

Follow-up Comment #3, bug #20640 (project lwip):

Not sure how to reduce the RSTs - we'd need to get to the bottom of what's
causing them to work out how to reduce them.  They're going in both
directions, which doesn't help narrow it down.

I suppose you could using some of the DEBUG print statements in lwIP to trace
why it is sending RST packets, but that's only the lwIP half of the story.

>From looking at the trace, lwIP seems to send a RST when it serves no purpose
- for example the connection beginning at packet 120 is RST by packet 185 just
1.5 seconds both ends have sent a FIN.  I suppose if packet 135 got lost or
dropped in the network it might not know the other end has responded to its
FIN, but to RST so quickly is odd - usually it would wait considerably longer.
 I wonder if you're calling the TCP timers correctly?  Also, for the PC to not
retransmit packet 135 in the intervening time is odd.

The RSTs from the PC may just be Windows being overly-aggressive in the way
it closes connections, but again it's giving up so quickly that it's a bit
odd: e.g the connection beginning in packet 240 is reset in packet 244 just
200ms later.


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