[lwip-devel] [bug #50837] LWIP TCP/IP race condition

[preet]

Follow-up Comment #19, bug #50837 (project lwip):

I think the root of the issue is that the mailbox used to post a pbuf pointer
is full, and the RST is dropped.  But even if the client on the other side
goes missing without sending the RST, we should still be able to reset the
connection on the LWIP (server) side.

To recap, what is happening is that the CLIENT(win/python)'s WINDOW is
shrinking, and eventually it is killed.  Meanwhile, our LWIP SERVER (accepted
conn) is stuck in the send() operation.  In this scenario, the mailbox that is
used for "sys_mbox_trypost()" operation is full, and hence it fails to handle
the socket logic gracefully.  The workaround is that I set the socket send
timeout (like 5 seconds), and if that was set, then the send() eventually
times out, rather than being continuously stuck inside.

The mailbox errors that I see continously increment when I do not use the
socket send timeout is this:

      MALLOC_128:   8/  8/8   - 232/0


It doesn't go to the next pool of memory, just that 128byte pool error counter
continues to climb and the send() function never returns.

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