tcp/lro: If timestamps mismatch or it's a FIN, force flush.

[sepherosa_gmail.com]

Summary

This keeps the segments/ACK/FIN delivery order.

Before this patch, it was observed: if A sent FIN immediately after
an ACK, B would deliver FIN first to the TCP stack, then the ACK.
This out-of-order delivery causes one unnecessary ACK sent from B.

Obtained from:  gallatin, rrs

[• hselasky]

sys/netinet/tcp_lro.c

852–860

Should there be added:

if (force_flush)

return (TCP_LRO_CANNOT);

If no match is found in the list?

[sepherosa_gmail.com]

sys/netinet/tcp_lro.c

852–860

Ah, yeah, it was in the original patch from rrs, got lost by me :P

[sepherosa_gmail.com]

Don't create entry for segments cant be further aggregated/delayed. Noticed-by: hps

[• hselasky]

Looks good to me.

--HPS