Pengcheng Yang
d9157f6806
tcp: fix F-RTO may not work correctly when receiving DSACK ...
Currently DSACK is regarded as a dupack, which may cause
F-RTO to incorrectly enter "loss was real" when receiving
DSACK.
Packetdrill to demonstrate:
// Enable F-RTO and TLP
0 `sysctl -q net.ipv4.tcp_frto=2`
0 `sysctl -q net.ipv4.tcp_early_retrans=3`
0 `sysctl -q net.ipv4.tcp_congestion_control=cubic`
// Establish a connection
+0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0
// RTT 10ms, RTO 210ms
+.1 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
+0 > S. 0:0(0) ack 1 <...>
+.01 < . 1:1(0) ack 1 win 257
+0 accept(3, ..., ...) = 4
// Send 2 data segments
+0 write(4, ..., 2000) = 2000
+0 > P. 1:2001(2000) ack 1
// TLP
+.022 > P. 1001:2001(1000) ack 1
// Continue to send 8 data segments
+0 write(4, ..., 10000) = 10000
+0 > P. 2001:10001(8000) ack 1
// RTO
+.188 > . 1:1001(1000) ack 1
// The original data is acked and new data is sent(F-RTO step 2.b)
+0 < . 1:1(0) ack 2001 win 257
+0 > P. 10001:12001(2000) ack 1
// D-SACK caused by TLP is regarded as a dupack, this results in
// the incorrect judgment of "loss was real"(F-RTO step 3.a)
+.022 < . 1:1(0) ack 2001 win 257 <sack 1001:2001,nop,nop>
// Never-retransmitted data(3001:4001) are acked and
// expect to switch to open state(F-RTO step 3.b)
+0 < . 1:1(0) ack 4001 win 257
+0 %{ assert tcpi_ca_state == 0, tcpi_ca_state }%
Fixes: e33099f96d99 ("tcp: implement RFC5682 F-RTO")
Signed-off-by: Pengcheng Yang <yangpc@wangsu.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Tested-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://lore.kernel.org/r/1650967419-2150-1-git-send-email-yangpc@wangsu.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-04-28 10:35:38 -07:00
2022-02-04 14:15:11 -08:00
2022-03-15 20:34:40 -05:00
2022-03-17 16:34:49 -07:00
2022-01-22 08:33:37 +02:00
2022-03-29 10:24:34 +02:00
2022-03-07 11:40:41 +00:00
2022-04-26 20:10:51 +02:00
2022-04-11 17:30:15 +02:00
2022-02-25 09:36:06 +01:00
2022-04-22 15:12:18 -07:00
2022-03-04 12:02:19 +00:00
2022-04-17 17:21:22 +02:00
2022-03-01 18:26:36 +01:00
2022-04-27 15:18:40 -07:00
2022-03-03 08:01:55 -08:00
2022-01-27 13:53:27 +00:00
2022-02-28 13:21:32 +00:00
2022-04-25 11:46:24 +01:00
2022-02-23 20:33:05 -08:00
2022-03-11 23:17:24 -08:00
2022-03-03 14:38:48 +00:00
2022-04-28 10:35:38 -07:00
2022-04-25 12:10:11 +01:00
2022-02-22 16:09:13 -08:00
2022-03-10 07:39:47 +01:00
2022-04-15 14:27:24 -07:00
2022-03-25 16:55:41 -07:00
2022-04-11 11:57:27 +02:00
2022-04-26 09:14:47 +02:00
2022-02-10 15:29:39 +00:00
2022-03-23 10:53:49 -07:00
2022-01-15 08:47:31 -08:00
2022-04-28 16:15:23 +02:00
2022-03-21 10:59:11 +00:00
2022-04-19 15:05:03 +02:00
2022-01-07 14:11:05 +00:00
2022-04-13 14:44:44 +01:00
2022-04-15 11:50:02 +01:00
2022-04-15 11:17:30 +01:00
2022-03-07 11:40:41 +00:00
2022-03-18 13:09:17 +02:00
2022-04-15 10:54:49 +01:00
2022-04-15 14:26:11 -07:00
2022-04-23 22:34:17 +01:00
2022-04-25 11:03:48 -07:00
2022-04-12 14:23:19 -10:00
2022-02-24 21:31:43 -08:00
2022-03-23 10:53:49 -07:00
2022-04-27 15:25:20 -07:00
2022-03-23 10:53:49 -07:00
2022-03-24 18:36:36 -07:00
2022-04-11 11:55:36 +02:00
2022-03-26 11:48:16 -07:00
2022-04-26 16:19:54 +02:00
2022-04-04 13:32:56 +02:00
2022-03-03 09:55:28 +00:00
2022-03-22 15:57:03 -07:00
d9157f6806