[lwip-devel] [bug #24212] Deadlocked tcp_retransmit due to exceeded pcb->cwnd

[Simon Goldschmidt]

Follow-up Comment #2, bug #24212 (project lwip):

tcp_output not sending because of (tcp_input_pcb == pcb) is clearly a
problem, but could the nagel algorithm (which was introduced in 1.3.0) also be
a problem here? Since it wouldn't cause problems without the (tcp_input_pcb ==
pcb) problem, I think it's not the cause of this bug.

On the other hand, (forgive me for not being too familiar with the tcp code
of lwIP), what would happen if fast-retransmit of 10085 succeeded, would the
unacked queue become unacked->11453->12818->14183->10085 ??

Finally, to detect other problems in this area, it might be a good idea to
include (debug-only-) code to check these lists are sorted. This way, we don't
introduce the overhead of Hans-Joerg's quick fix while (for tests) still being
able to check the queues to find other bugs.

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