From: Eric Dumazet <eric.duma...@gmail.com>
Date: Mon, 27 Jun 2016 17:38:50 +0200
> From: Eric Dumazet <eduma...@google.com>
>
> Arjun reported a bug in TCP stack and bisected it to a recent commit.
>
> In case where we process SACK, we can coalesce multiple skbs
> into fat ones (tcp_shift_skb_data()), to lower write queue
> overhead, because we do not expect to retransmit these packets.
>
> However, SACK reneging can happen, forcing the sender to retransmit
> all these packets. If skb->len is above 64KB, we then send buggy
> IP packets that could hang TSO engine on cxgb4.
>
> Neal suggested to use tcp_tso_autosize() instead of tp->gso_segs
> so that we cook packets of optimal size vs TCP/pacing.
>
> Thanks to Arjun for reporting the bug and running the tests !
>
> Fixes: 10d3be569243 ("tcp-tso: do not split TSO packets at retransmit time")
> Signed-off-by: Eric Dumazet <eduma...@google.com>
> Reported-by: Arjun V <ar...@chelsio.com>
> Tested-by: Arjun V <ar...@chelsio.com>
Applied.
