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Miller" , Simon Horman , David Ahern , Ido Schimmel , Shuah Khan , Thorsten Leemhuis , regressions@lists.linux.dev, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org, Eric Dumazet References: <20261026-advmss-revert-v1-0-272fa4b7ecb6@gmail.com> <20261026-advmss-revert-v1-1-272fa4b7ecb6@gmail.com> From: Jiayuan Chen In-Reply-To: <20261026-advmss-revert-v1-1-272fa4b7ecb6@gmail.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 10/26/26 3:23 PM, Esko Mobius via B4 Relay wrote: > From: Esko Mobius > > 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 Reviewed-by: Jiayuan Chen > --- > .../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 > - +0 > S. 0:0(0) ack 1 > - +.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 > - > -// Verify: SYN-ACK MUST advertise configured MSS 1460, NOT the learned PMTU MSS 1160 > - +0 > S. 0:0(0) ack 1 > - +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 > - +0 > S. 0:0(0) ack 1 > - +.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 > - > -// Verify: SYN-ACK MUST advertise configured MSS 1460, NOT the learned PMTU MSS 1220 > - +0 > S. 0:0(0) ack 1 > - +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 >