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Tue, 05 May 2026 12:38:25 -0700 (PDT) X-Received: by 2002:a05:6808:1917:b0:479:e96e:65b6 with SMTP id 5614622812f47-480428e14fdmr223858b6e.13.1778009905227; Tue, 05 May 2026 12:38:25 -0700 (PDT) Received: from localhost ([2a03:2880:12ff::]) by smtp.gmail.com with ESMTPSA id 5614622812f47-47c763b2ef3sm9262623b6e.2.2026.05.05.12.38.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 May 2026 12:38:24 -0700 (PDT) From: Neil Spring To: netdev@vger.kernel.org Cc: davem@davemloft.net, edumazet@google.com, kuba@kernel.org, pabeni@redhat.com, ncardwell@google.com, dsahern@kernel.org, ntspring@meta.com Subject: [PATCH net-next v3 0/2] tcp: rehash onto different local ECMP path on retransmit timeout Date: Tue, 5 May 2026 12:38:22 -0700 Message-ID: <20260505193824.2791642-1-ntspring@meta.com> X-Mailer: git-send-email 2.52.0 Precedence: bulk X-Mailing-List: netdev@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Proofpoint-ORIG-GUID: P2nlxDGLKYXi6Z1ZvkmqfVpYq_uhan7m X-Proofpoint-GUID: P2nlxDGLKYXi6Z1ZvkmqfVpYq_uhan7m X-Authority-Analysis: v=2.4 cv=DtFmPm/+ c=1 sm=1 tr=0 ts=69fa4733 cx=c_pps a=AKZTfHrQPB8q3CcvmcIuDA==:117 a=xqWC_Br6kY4A:10 a=NGcC8JguVDcA:10 a=f7IdgyKtn90A:10 a=VkNPw1HP01LnGYTKEx00:22 a=7x6HtfJdh03M6CCDgxCd:22 a=jCddH8ec0KUNCymVuxII:22 a=VwQbUJbxAAAA:8 a=VabnemYjAAAA:8 a=g8Q-s5m5DLHQX5cPw7MA:9 a=pF_qn-MSjDawc0seGVz6:22 a=gKebqoRLp9LExxC7YDUY:22 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjYwNTA1MDE5MSBTYWx0ZWRfXw7InYdTxZP7K 2KRJ/uaDAMhBrfKQ+7YFIi7jSKLVJRVr6PQP72D8eD3guoJwm/oH6G4n3Je/+vrmopfA2Inz8jT isNCDiOkoy4jX2rxBslEpZperZG0WfcCipsDUJ9ZL4u9zCu8Z16Qpd7dGiLuFO7iOSBe2rMQO95 b/3p26wDunoMWVlTi1f+pEsAuO6XdkYfOb/TL/4CuDXCVZMz2eYBpU7vmIvuBBSQposYPRbVklY vdm/DwVYOHpAqDC6JFXbaWhtL+JCyXduTTjEI8fKOZ+IVYknNQRpkoBMdy4Rx7fJ2uBSxCzE3M6 MdWlrmu+t+W2RfPCvfbe871xGzZblBBb5XwgXt6HNaLl1j1soEaxqyOyyQw94vcZkeC8K1YmamL rzq9elD0lwxsv8YIDbL0dUGzvEW/YwnVKGlxCIxVSHko3A8grf/ywK6iQ4NEVNH/xYtXvszLHkR cSZqvh3m01Qj3rWu/9w== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1143,Hydra:6.1.51,FMLib:17.12.100.49 definitions=2026-05-05_02,2026-04-30_02,2025-10-01_01 Make TCP retransmission timeouts select a different ECMP path for IPv6. Currently sk_rethink_txhash() changes the socket's txhash on RTO, but the cached route is reused and the new hash is not propagated into the ECMP path selection logic. This series adds sk_dst_reset() alongside sk_rethink_txhash() to force a fresh route lookup, and sets fl6->mp_hash from sk_txhash so fib6_select_path() picks a path based on the new hash. Five selftest scenarios verify the behavior across connection setup and established flows, forward and reverse path failures, and PLB: - SYN retransmission (forward path blocked during setup) - SYN/ACK retransmission (reverse path blocked during setup) - Midstream RTO (forward path blocked on established connection) - Midstream ACK rehash (reverse path blocked on established connection) - PLB rehash (ECN-driven congestion on established connection) Changes since v2: https://lore.kernel.org/netdev/20260408070514.1840227-1-ntspring@meta.com/ - Retitle "ECMP" to "local ECMP" to distinguish from remote ECMP (Neal Cardwell) - Add fl6->mp_hash propagation in inet6_sk_rebuild_header() (af_inet6.c), covering the dst rebuild path used on established sockets - Remove incorrect ir_iif update from tcp_check_req() in tcp_minisocks.c; the SYN/ACK rehash is already handled by tcp_rtx_synack() re-rolling txhash which feeds into inet6_csk_route_req()'s mp_hash (Eric Dumazet) - Add ACK rehash and PLB rehash selftests - Improve selftest reliability Changes since v1: https://lore.kernel.org/netdev/20260408002802.2448424-1-ntspring@meta.com/ - Use tcp_rsk(req)->txhash instead of jhash_1word(req->num_retrans, ...) for ECMP path selection in inet6_csk_route_req(), making the request socket path consistent with the established socket path (Eric Dumazet) - Add comments explaining the >> 1 shift for 31-bit mp_hash range - Use socat -u (unidirectional) in selftest to avoid SIGPIPE race - Increase tcp_syn_retries and tcp_syn_linear_timeouts to 25 for better rehash coverage Neil Spring (2): tcp: rehash onto different local ECMP path on retransmit timeout selftests: net: add local ECMP rehash test net/ipv4/tcp_input.c | 4 +- net/ipv4/tcp_plb.c | 1 + net/ipv4/tcp_timer.c | 1 + net/ipv6/af_inet6.c | 3 + net/ipv6/inet6_connection_sock.c | 6 + tools/testing/selftests/net/Makefile | 1 + tools/testing/selftests/net/ecmp_rehash.sh | 569 +++++++++++++++++++++ 7 files changed, 584 insertions(+), 1 deletion(-) create mode 100755 tools/testing/selftests/net/ecmp_rehash.sh -- 2.52.0