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Merge branch 'tcp-tcp_tx_timestamp-fix'

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Eric Dumazet says:

====================
tcp: tcp_tx_timestamp() fix

Fix an old bug in tcp_tx_timestamp().

Add one corresponding packetdrill test.
====================

Link: https://patch.msgid.link/20260127123828.4098577-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jakub Kicinski 2026-01-28 19:35:39 -08:00
commit 56763311f6
2 changed files with 73 additions and 0 deletions
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3
net/ipv4/tcp.c
View File

@ -501,6 +501,9 @@ static void tcp_tx_timestamp(struct sock *sk, struct sockcm_cookie *sockc)
struct sk_buff *skb = tcp_write_queue_tail(sk);
u32 tsflags = sockc->tsflags;
if (unlikely(!skb))
skb = skb_rb_last(&sk->tcp_rtx_queue);
if (tsflags && skb) {
struct skb_shared_info *shinfo = skb_shinfo(skb);
struct tcp_skb_cb *tcb = TCP_SKB_CB(skb);

70
tools/testing/selftests/net/packetdrill/tcp_timestamping_tcp_tx_timestamp_bug.pkt Normal file
View File

@ -0,0 +1,70 @@
// SPDX-License-Identifier: GPL-2.0
// Test after "tcp: tcp_tx_timestamp() must look at the rtx queue"
// This test is about receiving the SCM_TSTAMP_ACK,
// we do not care about its SCM_TIMESTAMPING precision.
--tolerance_usecs=1000000
`./defaults.sh
sysctl -q net.ipv4.tcp_min_tso_segs=70
`
// Create a socket and set it to non-blocking.
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 fcntl(3, F_GETFL) = 0x2 (flags O_RDWR)
+0 fcntl(3, F_SETFL, O_RDWR|O_NONBLOCK) = 0
// Establish connection and verify that there was no error.
+0 connect(3, ..., ...) = -1 EINPROGRESS (Operation now in progress)
+0 > S 0:0(0) <mss 1460,sackOK,TS val 100 ecr 0,nop,wscale 8>
+.010 < S. 0:0(0) ack 1 win 65535 <mss 1000,sackOK,TS val 700 ecr 100,nop,wscale 7>
+0 > . 1:1(0) ack 1 <nop,nop,TS val 200 ecr 700>
+0 getsockopt(3, SOL_SOCKET, SO_ERROR, [0], [4]) = 0
+0 setsockopt(3, SOL_SOCKET, SO_SNDBUF, [30000], 4) = 0
+0 write(3, ..., 9880) = 9880
+0 > P. 1:9881(9880) ack 1 <nop,nop,TS val 200 ecr 700>
+.010 < . 1:1(0) ack 9881 win 10000 <nop,nop,TS val 701 ecr 200>
+0 write(3, ..., 19760) = 19760
+0 > P. 9881:29641(19760) ack 1 <nop,nop,TS val 201 ecr 701>
+.010 < . 1:1(0) ack 29641 win 10000 <nop,nop,TS val 702 ecr 201>
+0 write(3, ..., 39520) = 39520
+0 > P. 29641:69161(39520) ack 1 <nop,nop,TS val 202 ecr 702>
+.010 < . 1:1(0) ack 69161 win 10000 <nop,nop,TS val 703 ecr 202>
// One more write to increase cwnd
+0 write(3, ..., 79040) = 79040
+0 > P. 69161:108681(39520) ack 1 <nop,nop,TS val 203 ecr 703>
+0 > P. 108681:148201(39520) ack 1 <nop,nop,TS val 203 ecr 703>
+.010 < . 1:1(0) ack 148201 win 1000 <nop,nop,TS val 704 ecr 203>
+0 setsockopt(3, SOL_SOCKET, SO_TIMESTAMPING,
[SOF_TIMESTAMPING_TX_ACK | SOF_TIMESTAMPING_SOFTWARE |
SOF_TIMESTAMPING_OPT_ID], 4) = 0
// We have one write filling one skb
// last byte can not be stored because of our small SO_SNDBUF
+0 write(3, ..., 65209) = 65208
+0 > P. 148201:213409(65208) ack 1 <nop,nop,TS val 204 ecr 704>
+.010 < . 1:1(0) ack 213409 win 1000 <nop,nop,TS val 705 ecr 204>
// SCM_TSTAMP_ACK should be received after the last ack at
// t=60ms.
+0 recvmsg(3, {msg_name(...)=...,
msg_iov(1)=[{...,0}],
msg_flags=MSG_ERRQUEUE|MSG_TRUNC,
msg_control=[
{cmsg_level=SOL_SOCKET,
cmsg_type=SCM_TIMESTAMPING,
cmsg_data={scm_sec=0,scm_nsec=60000000}},
{cmsg_level=CMSG_LEVEL_IP,
cmsg_type=CMSG_TYPE_RECVERR,
cmsg_data={ee_errno=ENOMSG,
ee_origin=SO_EE_ORIGIN_TIMESTAMPING,
ee_type=0,
ee_code=0,
ee_info=SCM_TSTAMP_ACK,
ee_data=65207}}
]}, MSG_ERRQUEUE) = 0