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Pengcheng Yang aa138efd2b tcp: fix F-RTO may not work correctly when receiving DSACK
[ Upstream commit d9157f6806d1499e173770df1f1b234763de5c79 ]

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: e33099f96d ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-05-09 09:05:06 +02:00
arch arm64: dts: imx8mn-ddr4-evk: Describe the 32.768 kHz PMIC clock 2022-05-09 09:05:03 +02:00
block iocost: don't reset the inuse weight of under-weighted debtors 2022-05-09 09:05:00 +02:00
certs certs: Trigger creation of RSA module signing key if it's not an RSA key 2021-09-15 09:50:29 +02:00
crypto crypto: authenc - Fix sleep in atomic context in decrypt_tail 2022-04-08 14:39:59 +02:00
Documentation ext4, doc: fix incorrect h_reserved size 2022-04-27 13:53:57 +02:00
drivers Revert "ibmvnic: Add ethtool private flag for driver-defined queue limits" 2022-05-09 09:05:06 +02:00
fs jbd2: fix a potential race while discarding reserved buffers after an abort 2022-04-27 13:53:57 +02:00
include tcp: make sure treq->af_specific is initialized 2022-05-09 09:05:04 +02:00
init init/main.c: return 1 from handled __setup() functions 2022-04-13 21:01:01 +02:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-12-01 09:19:10 +01:00
kernel perf/core: Fix perf_mmap fail when CONFIG_PERF_USE_VMALLOC enabled 2022-04-27 13:53:56 +02:00
lib hex2bin: fix access beyond string end 2022-05-09 09:04:59 +02:00
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mm mm/mmu_notifier.c: fix race in mmu_interval_notifier_remove() 2022-04-27 13:53:54 +02:00
net tcp: fix F-RTO may not work correctly when receiving DSACK 2022-05-09 09:05:06 +02:00
samples samples/bpf, xdpsock: Fix race when running for fix duration of time 2022-04-08 14:40:21 +02:00
scripts gcc-plugins: latent_entropy: use /dev/urandom 2022-04-20 09:23:26 +02:00
security Fix incorrect type in assignment of ipv6 port for audit 2022-04-08 14:40:31 +02:00
sound ASoC: soc-dapm: fix two incorrect uses of list iterator 2022-04-27 13:53:55 +02:00
tools perf report: Set PERF_SAMPLE_DATA_SRC bit for Arm SPE event 2022-04-27 13:53:56 +02:00
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Linux kernel
============

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Documentation/admin-guide/README.rst first.

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several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
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