From ffc56c90819e86d3a8c4eff6f831317d1c1476b6 Mon Sep 17 00:00:00 2001 From: Kuniyuki Iwashima Date: Thu, 6 Nov 2025 00:32:45 +0000 Subject: [PATCH] selftest: packetdrill: Add max RTO test for SYN+ACK. This script sets net.ipv4.tcp_rto_max_ms to 1000 and checks if SYN+ACK RTO is capped at 1s for TFO and non-TFO. Without the previous patch, the max RTO is applied to TFO SYN+ACK only, and non-TFO SYN+ACK RTO increases exponentially. # selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt # TAP version 13 # 1..2 # tcp_rto_synack_rto_max.pkt:46: error handling packet: timing error: expected outbound packet at 5.091936 sec but happened at 6.107826 sec; tolerance 0.127974 sec # script packet: 5.091936 S. 0:0(0) ack 1 # actual packet: 6.107826 S. 0:0(0) ack 1 win 65535 # not ok 1 ipv4 # tcp_rto_synack_rto_max.pkt:46: error handling packet: timing error: expected outbound packet at 5.075901 sec but happened at 6.091841 sec; tolerance 0.127976 sec # script packet: 5.075901 S. 0:0(0) ack 1 # actual packet: 6.091841 S. 0:0(0) ack 1 win 65535 # not ok 2 ipv6 # # Totals: pass:0 fail:2 xfail:0 xpass:0 skip:0 error:0 not ok 49 selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt # exit=1 With the previous patch, all SYN+ACKs are retransmitted after 1s. # selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt # TAP version 13 # 1..2 # ok 1 ipv4 # ok 2 ipv6 # # Totals: pass:2 fail:0 xfail:0 xpass:0 skip:0 error:0 ok 49 selftests: net/packetdrill: tcp_rto_synack_rto_max.pkt Signed-off-by: Kuniyuki Iwashima Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20251106003357.273403-7-kuniyu@google.com Signed-off-by: Jakub Kicinski --- .../packetdrill/tcp_rto_synack_rto_max.pkt | 54 +++++++++++++++++++ 1 file changed, 54 insertions(+) create mode 100644 tools/testing/selftests/net/packetdrill/tcp_rto_synack_rto_max.pkt diff --git a/tools/testing/selftests/net/packetdrill/tcp_rto_synack_rto_max.pkt b/tools/testing/selftests/net/packetdrill/tcp_rto_synack_rto_max.pkt new file mode 100644 index 0000000000000..47550df124cec --- /dev/null +++ b/tools/testing/selftests/net/packetdrill/tcp_rto_synack_rto_max.pkt @@ -0,0 +1,54 @@ +// SPDX-License-Identifier: GPL-2.0 +// +// Test SYN+ACK RTX with 1s RTO. +// +`./defaults.sh + ./set_sysctls.py /proc/sys/net/ipv4/tcp_rto_max_ms=1000` + +// +// Test 1: TFO SYN+ACK +// + 0 socket(..., SOCK_STREAM|SOCK_NONBLOCK, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + +0 setsockopt(3, SOL_TCP, TCP_FASTOPEN, [1], 4) = 0 + + +0 < S 0:10(10) win 1000 + +0 > S. 0:0(0) ack 11 + +// RTO must be capped to 1s + +1 > S. 0:0(0) ack 11 + +1 > S. 0:0(0) ack 11 + +1 > S. 0:0(0) ack 11 + + +0 < . 11:11(0) ack 1 win 1000 + +0 accept(3, ..., ...) = 4 + +0 %{ assert (tcpi_options & TCPI_OPT_SYN_DATA) != 0, tcpi_options }% + + +0 close(4) = 0 + +0 close(3) = 0 + + +// +// Test 2: non-TFO SYN+ACK +// + +0 socket(..., SOCK_STREAM|SOCK_NONBLOCK, IPPROTO_TCP) = 3 + +0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0 + +0 bind(3, ..., ...) = 0 + +0 listen(3, 1) = 0 + + +0 < S 0:0(0) win 1000 + +0 > S. 0:0(0) ack 1 + +// RTO must be capped to 1s + +1 > S. 0:0(0) ack 1 + +1 > S. 0:0(0) ack 1 + +1 > S. 0:0(0) ack 1 + + +0 < . 1:1(0) ack 1 win 1000 + +0 accept(3, ..., ...) = 4 + +0 %{ assert (tcpi_options & TCPI_OPT_SYN_DATA) == 0, tcpi_options }% + + +0 close(4) = 0 + +0 close(3) = 0 -- 2.47.3