[lwip-users] lwIP 1.4.1 server's SYN flood hang, no backlog

[Tomek]

Hi,

I have some issues with device based on FreeRTOS (stm32F4 port) and lwIP
1.4.1 stack. There is parallel server and client functionality.

Case similiar to one described here:
http://lwip.100.n7.nabble.com/SYN-flood-attack-lwip-crash-td17632.html, but
with one significant difference: I don't use backlog. All symptoms are the
same: sometimes device runs for few minutes, sometimes few days,but after
some time, server stops accepting new connections. Meantime client
functionality works properly (all tasks but server's one seem to do so).
After SYN flood, communcation looks like:

client          server
SYN       ->
          <-     SYN,ACK
ACK     ->
REQ       ->
          <-     RST,ACK

To reproduce situtation I used SynGUI. I've obtained good reproducibility
and device seems pretty similiar to situation with unforced hangup. I know,
I can check:
tcp_active_pcbs
tcp_bound_pcbs
tcp_listen_pcbs
tcp_tw_pcbs
but what exactly I am looking for?

If requierd I can attach Wireshark's captures / values of variables.

Regards,
Tomek



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