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charset="utf-8" Content-Transfer-Encoding: 7bit X-B4-Tracking: v=1; b=H4sIALSI6WoC/yWMwQqDMBAFf0XeuQtGwbb+ivRgzMZuoaskUQTx3 03rcRhmdkQOwhFtsSPwKlEmzWBuBYZ3ryOTuMyoyqoxpqzpmxaaw2RFR7pa6h93Wz+9s+w8cjg H9rL9px2UEylvCa/LxMV+eEi/J47jBKx0Vy6AAAAA X-Change-ID: 20261103-mtu-probing-series-a87b39fdbedf To: ncardwell@google.com, horms@kernel.org, edumazet@kernel.org, kuba@kernel.org, kuniyu@google.com, shuah@kernel.org, davem@davemloft.net, pabeni@redhat.com Cc: netdev@vger.kernel.org, panweiping3@gmail.com, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org, Yongjian Wang X-Mailer: b4 0.16.0 X-Developer-Signature: v=1; a=ed25519-sha256; t=1793689782; l=1412; i=echoowall@gmail.com; s=20261026; h=from:subject:message-id; bh=jaAiv7oc3XrWZgOFj0uLPEs+taPtXcOPn4WA+vqNjCA=; b=R0ssqhNpJtIIHhSW9RvoiT8+/dGCb3h6d3O0KPiv9vOh9NXFRP2xho9/v7joOVVI+7gvT8doP zAUmTlJqhtiC9As3pxD/3ZsBYNPq1EaKoZDsZA+kHGPg4t5nPkXsIIX X-Developer-Key: i=echoowall@gmail.com; a=ed25519; pk=9XP6JhqjjPsHCF6UZZZTeqTRnXIa4+ufggnxXtTJ+no= X-Endpoint-Received: by B4 Relay for echoowall@gmail.com/20261026 with auth_id=1323 X-Original-From: Yongjian Wang Reply-To: echoowall@gmail.com While adding selftests for MTU probing, I noticed that passive connections do not start at tcp_base_mss with tcp_mtu_probing=2. Patch 1 fixes that and patch 2 adds a regression test. This has been wrong since 2014 and only matters with a non-default sysctl, so I am sending it to net-next. Patch 1 changes behaviour for users of tcp_mtu_probing=2. Please let me know if you would prefer it to go through net or to be backported to stable. Patches 3 and 4 add the missing coverage for black hole detection (tcp_mtu_probing=1) and for the MTU search on active connections (tcp_mtu_probing=2). --- Yongjian Wang (4): tcp: sync MSS after enabling MTU probing on passive connections selftests/net: packetdrill: test tcp_base_mss on passive connections selftests/net: packetdrill: add TCP black hole detection test selftests/net: packetdrill: add TCP MTU probing test net/ipv4/tcp_input.c | 1 + .../net/packetdrill/tcp_mtu_probing_blackhole.pkt | 37 +++++++++++++++++++ .../net/packetdrill/tcp_mtu_probing_passive.pkt | 27 ++++++++++++++ .../net/packetdrill/tcp_mtu_probing_search.pkt | 43 ++++++++++++++++++++++ 4 files changed, 108 insertions(+) --- base-commit: 4dd16e31135ea8437a720222df34e8745f385d6d change-id: 20261103-mtu-probing-series-a87b39fdbedf Best regards, -- Yongjian Wang