kernel/linux.git/include/net/tcp.h, branch v6.18.33

tcp: better handle TCP_TX_DELAY on established flows

2026-05-23T11:07:01+00:00

[ Upstream commit 1c51450f1afff1e7419797720df3fbd9ccbf610c ] Some applications uses TCP_TX_DELAY socket option after TCP flow is established. Some metrics need to be updated, otherwise TCP might take time to adapt to the new (emulated) RTT. This patch adjusts tp->srtt_us, tp->rtt_min, icsk_rto and sk->sk_pacing_rate. This is best effort, and for instance icsk_rto is reset without taking backoff into account. Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20251013145926.833198-1-edumazet@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: 290b693ce7c9 ("tcp: annotate data-races around tp->srtt_us") Signed-off-by: Sasha Levin

tcp: add data-races annotations around tp->reordering, tp->snd_cwnd

2026-05-23T11:07:00+00:00

[ Upstream commit 829ba1f329cb7cbd56d599a6d225997fba66dc32 ] tcp_get_timestamping_opt_stats() intentionally runs lockless, we must add READ_ONCE(), WRITE_ONCE() data_race() annotations to keep KCSAN happy. Fixes: bb7c19f96012 ("tcp: add related fields into SCM_TIMESTAMPING_OPT_STATS") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-4-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: annotate data-races in tcp_get_info_chrono_stats()

2026-05-23T11:07:00+00:00

[ Upstream commit 267bf3cf9a6f0ffb98b8afd983c1950e835f07c9 ] tcp_get_timestamping_opt_stats() does not own the socket lock, this is intentional. It calls tcp_get_info_chrono_stats() while other threads could change chrono fields in tcp_chrono_set(). I do not think we need coherent TCP socket state snapshot in tcp_get_timestamping_opt_stats(), I chose to only add annotations to keep KCSAN happy. Fixes: 1c885808e456 ("tcp: SOF_TIMESTAMPING_OPT_STATS option for SO_TIMESTAMPING") Signed-off-by: Eric Dumazet Link: https://patch.msgid.link/20260416200319.3608680-2-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: inline tcp_chrono_start()

2026-05-23T11:07:00+00:00

[ Upstream commit d6d4ff335db2d9242937ca474d292010acd35c38 ] tcp_chrono_start() is small enough, and used in TCP sendmsg() fast path (from tcp_skb_entail()). Note clang is already inlining it from functions in tcp_output.c. Inlining it improves performance and reduces bloat : $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/2 grow/shrink: 1/0 up/down: 1/-84 (-83) Function old new delta tcp_skb_entail 280 281 +1 __pfx_tcp_chrono_start 16 - -16 tcp_chrono_start 68 - -68 Total: Before=25192434, After=25192351, chg -0.00% Note that tcp_chrono_stop() is too big. Signed-off-by: Eric Dumazet Reviewed-by: Neal Cardwell Link: https://patch.msgid.link/20260308123549.2924460-1-edumazet@google.com Signed-off-by: Jakub Kicinski Stable-dep-of: 267bf3cf9a6f ("tcp: annotate data-races in tcp_get_info_chrono_stats()") Signed-off-by: Sasha Levin

tcp: secure_seq: add back ports to TS offset

2026-03-12T11:09:58+00:00

[ Upstream commit 165573e41f2f66ef98940cf65f838b2cb575d9d1 ] This reverts 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets") tcp_tw_recycle went away in 2017. Zhouyan Deng reported off-path TCP source port leakage via SYN cookie side-channel that can be fixed in multiple ways. One of them is to bring back TCP ports in TS offset randomization. As a bonus, we perform a single siphash() computation to provide both an ISN and a TS offset. Fixes: 28ee1b746f49 ("secure_seq: downgrade to per-host timestamp offsets") Reported-by: Zhouyan Deng Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Acked-by: Florian Westphal Link: https://patch.msgid.link/20260302205527.1982836-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: fix potential race in tcp_v6_syn_recv_sock()

2026-03-04T12:20:44+00:00

[ Upstream commit 858d2a4f67ff69e645a43487ef7ea7f28f06deae ] Code in tcp_v6_syn_recv_sock() after the call to tcp_v4_syn_recv_sock() is done too late. After tcp_v4_syn_recv_sock(), the child socket is already visible from TCP ehash table and other cpus might use it. Since newinet->pinet6 is still pointing to the listener ipv6_pinfo bad things can happen as syzbot found. Move the problematic code in tcp_v6_mapped_child_init() and call this new helper from tcp_v4_syn_recv_sock() before the ehash insertion. This allows the removal of one tcp_sync_mss(), since tcp_v4_syn_recv_sock() will call it with the correct context. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Reported-by: syzbot+937b5bbb6a815b3e5d0b@syzkaller.appspotmail.com Closes: https://lore.kernel.org/netdev/69949275.050a0220.2eeac1.0145.GAE@google.com/ Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260217161205.2079883-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

tcp: disable RFC3168 fallback identifier for CC modules

2026-02-26T22:59:20+00:00

[ Upstream commit e68c28f22f46ecfdec3656ae785dd8ccbb4d557d ] When AccECN is not successfully negociated for a TCP flow, it defaults fallback to classic ECN (RFC3168). However, L4S service will fallback to non-ECN. This patch enables congestion control module to control whether it should not fallback to classic ECN after unsuccessful AccECN negotiation. A new CA module flag (TCP_CONG_NO_FALLBACK_RFC3168) identifies this behavior expected by the CA. Signed-off-by: Chia-Yu Chang Acked-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260131222515.8485-6-chia-yu.chang@nokia-bell-labs.com Signed-off-by: Paolo Abeni Stable-dep-of: c5ff6b837159 ("tcp: accecn: handle unexpected AccECN negotiation feedback") Signed-off-by: Sasha Levin

tcp: ECT_1_NEGOTIATION and NEEDS_ACCECN identifiers

2026-02-26T22:59:20+00:00

[ Upstream commit 100f946b8d44b64bc0b8a8c30d283105031c0a77 ] Two flags for congestion control (CC) module are added in this patch related to AccECN negotiation. First, a new flag (TCP_CONG_NEEDS_ACCECN) defines that the CC expects to negotiate AccECN functionality using the ECE, CWR and AE flags in the TCP header. Second, during ECN negotiation, ECT(0) in the IP header is used. This patch enables CC to control whether ECT(0) or ECT(1) should be used on a per-segment basis. A new flag (TCP_CONG_ECT_1_NEGOTIATION) defines the expected ECT value in the IP header by the CA when not-yet initialized for the connection. The detailed AccECN negotiaotn can be found in IETF RFC9768. Co-developed-by: Olivier Tilmans Signed-off-by: Olivier Tilmans Signed-off-by: Ilpo Järvinen Signed-off-by: Chia-Yu Chang Acked-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260131222515.8485-5-chia-yu.chang@nokia-bell-labs.com Signed-off-by: Paolo Abeni Stable-dep-of: c5ff6b837159 ("tcp: accecn: handle unexpected AccECN negotiation feedback") Signed-off-by: Sasha Levin

tcp: add newval parameter to tcp_rcvbuf_grow()

2025-10-30T00:30:19+00:00

This patch has no functional change, and prepares the following one. tcp_rcvbuf_grow() will need to have access to tp->rcvq_space.space old and new values. Change mptcp_rcvbuf_grow() in a similar way. Signed-off-by: Eric Dumazet [ Moved 'oldval' declaration to the next patch to avoid warnings at build time. ] Signed-off-by: Matthieu Baerts (NGI0) Reviewed-by: Neal Cardwell Link: https://patch.msgid.link/20251028-net-tcp-recv-autotune-v3-3-74b43ba4c84c@kernel.org Signed-off-by: Jakub Kicinski

tcp: make tcp_rcvbuf_grow() accessible to mptcp code

2025-09-30T01:23:35+00:00

To leverage the auto-tuning improvements brought by commit 2da35e4b4df9 ("Merge branch 'tcp-receive-side-improvements'"), the MPTCP stack need to access the mentioned helper. Acked-by: Geliang Tang Acked-by: Matthieu Baerts (NGI0) Signed-off-by: Paolo Abeni Signed-off-by: Matthieu Baerts (NGI0) Link: https://patch.msgid.link/20250927-net-next-mptcp-rcv-path-imp-v1-2-5da266aa9c1a@kernel.org Signed-off-by: Jakub Kicinski