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 v3: https://lore.kernel.org/netdev/[email protected]/ - Use __sk_dst_reset() instead of sk_dst_reset() since the socket lock is held in all three call sites (Eric Dumazet) - Guard __sk_dst_reset() with sk->sk_family == AF_INET6 since IPv4 ECMP does not use sk_txhash for path selection - Guard __sk_dst_reset() in tcp_plb_check_rehash() with the return value of sk_rethink_txhash() - Move tcp_rsk(req)->txhash initialization before route_req() in tcp_conn_request() to avoid reading uninitialized memory - Add CONFIG_TCP_CONG_DCTCP=m to selftests/net/config for PLB test - Skip PLB test gracefully if DCTCP is not available - Save and restore original congestion control algorithm in PLB test - Default get_netstat_counter() to 0 when counter is not found - Skip all tests if tcp_syn_linear_timeouts is not available - Replace bash/pipe data sources with socat OPEN:/dev/zero for cleaner process cleanup - Fix shellcheck warnings Changes since v2: https://lore.kernel.org/netdev/[email protected]/ - 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/[email protected]/ - 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 | 6 +- net/ipv4/tcp_plb.c | 7 +- net/ipv4/tcp_timer.c | 4 + net/ipv6/af_inet6.c | 3 + net/ipv6/inet6_connection_sock.c | 6 + tools/testing/selftests/net/Makefile | 1 + tools/testing/selftests/net/config | 1 + tools/testing/selftests/net/ecmp_rehash.sh | 582 +++++++++++++++++++++ 8 files changed, 607 insertions(+), 3 deletions(-) create mode 100755 tools/testing/selftests/net/ecmp_rehash.sh -- 2.53.0-Meta
