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tcp: round down rcv wnd even if avoiding retraction

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Type: improvement

Signed-off-by: Florin Coras <fcoras@cisco.com>
Change-Id: I7fb3a4a2ffc4c5f42aa043e3a317b52d7767fb81
This commit is contained in:
Florin Coras
2020-07-06 08:06:54 -07:00
committed by Dave Barach
parent 4834a66b7b
commit c78d47b141
1 changed files with 9 additions and 13 deletions
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22
src/vnet/tcp/tcp_output.c
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@@ -121,33 +121,29 @@ tcp_update_rcv_wnd (tcp_connection_t * tc)
*/
available_space = transport_max_rx_enqueue (&tc->connection);
/* Make sure we have a multiple of 1 << rcv_wscale. We round down to
* avoid advertising a window larger than what can be buffered */
available_space = round_down_pow2 (available_space, 1 << tc->rcv_wscale);
if (PREDICT_FALSE (available_space < tc->rcv_opts.mss))
{
tc->rcv_wnd = 0;
return;
}
/*
* Use the above and what we know about what we've previously advertised
* to compute the new window
*/
observed_wnd = (i32) tc->rcv_wnd - (tc->rcv_nxt - tc->rcv_las);
/* Bad. Thou shalt not shrink */
/* Check if we are about to retract the window. Do the comparison before
* rounding to avoid errors. Per RFC7323 sec. 2.4 we could remove this */
if (PREDICT_FALSE ((i32) available_space < observed_wnd))
{
wnd = round_pow2 (clib_max (observed_wnd, 0), 1 << tc->rcv_wscale);
wnd = round_down_pow2 (clib_max (observed_wnd, 0), 1 << tc->rcv_wscale);
TCP_EVT (TCP_EVT_RCV_WND_SHRUNK, tc, observed_wnd, available_space);
}
else
{
wnd = available_space;
/* Make sure we have a multiple of 1 << rcv_wscale. We round down to
* avoid advertising a window larger than what can be buffered */
wnd = round_down_pow2 (available_space, 1 << tc->rcv_wscale);
}
if (PREDICT_FALSE (wnd < tc->rcv_opts.mss))
wnd = 0;
tc->rcv_wnd = clib_min (wnd, TCP_WND_MAX << tc->rcv_wscale);
}