From: Esko Mobius via B4 Relay <devnull+echoowall.gmail.com@kernel.org>
To: netdev@vger.kernel.org
Cc: Jakub Kicinski <kuba@kernel.org>, Paolo Abeni <pabeni@redhat.com>,
"David S. Miller" <davem@davemloft.net>,
Simon Horman <horms@kernel.org>,
David Ahern <dsahern@kernel.org>,
Ido Schimmel <idosch@nvidia.com>,
Jiayuan Chen <jiayuan.chen@linux.dev>,
Shuah Khan <shuah@kernel.org>,
Thorsten Leemhuis <regressions@leemhuis.info>,
regressions@lists.linux.dev, linux-kselftest@vger.kernel.org,
linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Esko Mobius <echoowall@gmail.com>,
Eric Dumazet <edumazet@kernel.org>
Subject: [PATCH net 1/2] Revert "selftests: net: packetdrill: add tests for advertised MSS with PMTU exceptions"
Date: Mon, 26 Oct 2026 15:23:08 +0800 [thread overview]
Message-ID: <20261026-advmss-revert-v1-1-272fa4b7ecb6@gmail.com> (raw)
In-Reply-To: <20261026-advmss-revert-v1-0-272fa4b7ecb6@gmail.com>
From: Esko Mobius <echoowall@gmail.com>
This reverts commit e5c8e301b497 ("selftests: net: packetdrill: add
tests for advertised MSS with PMTU exceptions").
These tests assert the behaviour introduced by commit 2640e6419594
("net: advertise TCP MSS from the configured MTU, not the learned
PMTU"), which is reverted in the next patch because it causes a
regression. Remove them first so the series stays bisectable.
Signed-off-by: Esko Mobius <echoowall@gmail.com>
---
.../net/packetdrill/tcp_advmss_pmtu_ipv4.pkt | 67 ----------------------
.../net/packetdrill/tcp_advmss_pmtu_ipv6.pkt | 67 ----------------------
2 files changed, 134 deletions(-)
diff --git a/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv4.pkt b/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv4.pkt
deleted file mode 100644
index f2ef931b7..000000000
--- a/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv4.pkt
+++ /dev/null
@@ -1,67 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-//
-// Test that IPv4 advertised MSS in SYN-ACK is derived from the configured
-// interface MTU (1500 -> MSS 1460), not the ICMP-learned Path MTU.
-
---ip_version=ipv4
-
-`./defaults.sh
-ethtool -K tun0 tso off
-`
-
-//
-// Connection 1: Learn PMTU exception (MTU 1200 -> MSS 1160)
-//
- 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
-
- +0 < S 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 8>
- +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
- +.1 < . 1:1(0) ack 1 win 257
- +0 accept(3, ..., ...) = 4
-
-// Send a full 1460-byte segment
- +0 write(4, ..., 1460) = 1460
- +0 > P. 1:1461(1460) ack 1
-
-// ICMP Fragmentation Needed arrives indicating next-hop MTU 1200
- +0 < icmp unreachable frag_needed mtu 1200 [1:1461(1460)]
-
-// Local host retransmits using the learned MTU 1200 (MSS = 1200 - 40 = 1160)
- +0 > . 1:1161(1160) ack 1
- +0 > P. 1161:1461(300) ack 1
- +0 < R 1:1(0) ack 1461 win 0
-
-// Close connection 1 and listener
- +0 close(4) = 0
- +0 close(3) = 0
-
-//
-// Connection 2: New connection from the same peer
-//
- +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
-
- +0 < S 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 8>
-
-// Verify: SYN-ACK MUST advertise configured MSS 1460, NOT the learned PMTU MSS 1160
- +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
- +0 < . 1:1(0) ack 1 win 257
- +0 accept(3, ..., ...) = 4
-
-// Verify: Outgoing transmit MSS is still constrained by the learned PMTU 1200
- +0 write(4, ..., 1460) = 1460
- +0 > . 1:1161(1160) ack 1
- +0 > P. 1161:1461(300) ack 1
- +0 < . 1:1(0) ack 1461 win 257
-
-// Clean up
- +0 close(4) = 0
- +0 > F. 1461:1461(0) ack 1
- +0 < F. 1:1(0) ack 1462 win 257
- +0 > . 1462:1462(0) ack 2
- +0 close(3) = 0
diff --git a/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv6.pkt b/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv6.pkt
deleted file mode 100644
index c7638b11a..000000000
--- a/tools/testing/selftests/net/packetdrill/tcp_advmss_pmtu_ipv6.pkt
+++ /dev/null
@@ -1,67 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-//
-// Test that IPv6 advertised MSS in SYN-ACK is derived from the configured
-// interface MTU (1520 -> MSS 1460), not the ICMPv6-learned Path MTU.
-
---ip_version=ipv6
-
-`./defaults.sh
-ethtool -K tun0 tso off
-`
-
-//
-// Connection 1: Learn PMTU exception (MTU 1280 -> MSS 1220)
-//
- 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
-
- +0 < S 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 8>
- +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
- +.1 < . 1:1(0) ack 1 win 257
- +0 accept(3, ..., ...) = 4
-
-// Send a full 1460-byte segment
- +0 write(4, ..., 1460) = 1460
- +0 > P. 1:1461(1460) ack 1
-
-// ICMPv6 Packet Too Big arrives indicating next-hop MTU 1280
- +0 < icmp packet_too_big mtu 1280 [1:1461(1460)]
-
-// Local host retransmits using the learned MTU 1280 (MSS = 1280 - 40 - 20 = 1220)
- +0 > . 1:1221(1220) ack 1
- +0 > P. 1221:1461(240) ack 1
- +0 < R 1:1(0) ack 1461 win 0
-
-// Close connection 1 and listener
- +0 close(4) = 0
- +0 close(3) = 0
-
-//
-// Connection 2: New connection from the same peer
-//
- +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
-
- +0 < S 0:0(0) win 65535 <mss 1460,sackOK,nop,nop,nop,wscale 8>
-
-// Verify: SYN-ACK MUST advertise configured MSS 1460, NOT the learned PMTU MSS 1220
- +0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
- +0 < . 1:1(0) ack 1 win 257
- +0 accept(3, ..., ...) = 4
-
-// Verify: Outgoing transmit MSS is still constrained by the learned PMTU 1280
- +0 write(4, ..., 1460) = 1460
- +0 > . 1:1221(1220) ack 1
- +0 > P. 1221:1461(240) ack 1
- +0 < . 1:1(0) ack 1461 win 257
-
-// Clean up
- +0 close(4) = 0
- +0 > F. 1461:1461(0) ack 1
- +0 < F. 1:1(0) ack 1462 win 257
- +0 > . 1462:1462(0) ack 2
- +0 close(3) = 0
--
Git-157)
next prev parent reply other threads:[~2026-10-26 7:23 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-10-26 7:23 [PATCH net 0/2] Revert advertising the TCP MSS from the configured MTU Esko Mobius via B4 Relay
2026-10-26 7:23 ` Esko Mobius via B4 Relay [this message]
2026-10-26 7:23 ` [PATCH net 2/2] Revert "net: advertise TCP MSS from the configured MTU, not the learned PMTU" Esko Mobius via B4 Relay
2026-10-26 13:28 ` [PATCH net 0/2] Revert advertising the TCP MSS from the configured MTU Eric Dumazet
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