12.08.2015 18:16, Josef Bacik пишет:
> While adding tcp window scaling support I was finding that I'd get some packet
> loss or reordering when transferring from large distances and grub would just
> timeout. This is because we weren't ack'ing when we got our OOO packet, so
> the
> sender didn't know it needed to retransmit anything, so eventually it would
> fill
> the window and stop transmitting, and we'd time out. Fix this by ACK'ing when
> we don't find our next sequence numbered packet. With this fix I no longer
> time
> out. Thanks,
>
Applied. Sorry, it somehow slipped through.
More ideas in the same direction.
1. GRUB timeout for receiving currently is ~33 seconds. It is too small
comparing with anything else. I am pretty sure in situation from tcpdump
you sent me we could recover if timeout was in order of several minutes :)
2. We may consider sending ACK in grub_net_tcp_retransmit()
additionally, although it probably needs proper rate-limiting based on RTT.
3. Using timestamp option may improve RTT detection for partner and is
pretty cheap to implement.
> Signed-off-by: Josef Bacik <jba...@fb.com>
> ---
> grub-core/net/tcp.c | 5 ++++-
> 1 file changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/grub-core/net/tcp.c b/grub-core/net/tcp.c
> index 25720b1..6b411dd 100644
> --- a/grub-core/net/tcp.c
> +++ b/grub-core/net/tcp.c
> @@ -902,7 +902,10 @@ grub_net_recv_tcp_packet (struct grub_net_buff *nb,
> grub_priority_queue_pop (sock->pq);
> }
> if (grub_be_to_cpu32 (tcph->seqnr) != sock->their_cur_seq)
> - return GRUB_ERR_NONE;
> + {
> + ack (sock);
> + return GRUB_ERR_NONE;
> + }
> while (1)
> {
> nb_top_p = grub_priority_queue_top (sock->pq);
>
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