tcp: Retransmit FINs like data segments

RFC 9293 doesn't distinguish between regular data segments and FIN segments
for the purposes of retransmissions.  Our existing retransmission logic
will also work for FIN segments, except for one detail: we don't currently
set the ACK_FROM_TAP_DUE flag when we send a FIN.  Add the flag, so that
we'll properly retransmit FIN segments like data segments.

Remove the section from the theory of operation comment that describes a
different way of handling FIN timeouts which (a) isn't correct behaviour
and (b) doesn't appear to be implemented.

I've tested this by adding logic to suppress sending the FIN if retries <
some non-zero value.  We correctly resend the FIN and close normally after
the expected timeouts.

Link: https://bugs.passt.top/show_bug.cgi?id=195
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

0 files changed, 0 insertions, 0 deletions