[lwip-devel] [bug #20779] Keep-Alive and SYNs

[Oleg Tyshev]

Follow-up Comment #8, bug #20779 (project lwip):

Stats is OK.

We should not drop SYN silently,
lwip should reply and _replies_ with old SEQ_NO and old ACK.
It is correct.
(RFC 793, 3.4, Figure 10 Half-Open Connection Discovery)

The question is now only about (in)activity timer.
Should it be updated on discarded packets or not.

RFC 1122 - 4.2.3.6 TCP Keep-Alives
Keep-alive packets MUST only be sent when no data or acknowledgement packets
have been received for the connection within an interval.

Does SYN packet data or not?

And second,
variable tcplen for SYN packet is 1,
if SEQ_NO of SYN is inside receive window of old pcb,
it would be processed in
tcp_receive and added to out of sequence queue.

Small fix to tcp_in ver 1.74.
Lines 1214, 1216 is possible to delete without any loss in logic.


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