kernel/linux.git/include/net/tcp.h, branch linux-7.0.y

tcp: fix stale per-CPU tcp_tw_isn leak enabling ISN prediction

2026-06-01T15:54:52+00:00

[ Upstream commit 1bbf0ced1d9db73ac7893c2187f3459288603e0d ] Blamed commit moved the TIME_WAIT-derived ISN from the skb control block to a per-CPU variable, assuming the value would always be consumed by tcp_conn_request() for the same packet that wrote it. That assumption is violated by multiple drop paths between the producer (__this_cpu_write(tcp_tw_isn, isn) in tcp_v{4,6}_rcv()) and the consumer (tcp_conn_request()): - min_ttl / min_hopcount check - xfrm policy check - tcp_inbound_hash() MD5/AO mismatch - tcp_filter() eBPF/SO_ATTACH_FILTER drop - th->syn && th->fin discard in tcp_rcv_state_process() TCP_LISTEN - psp_sk_rx_policy_check() in tcp_v{4,6}_do_rcv() - tcp_checksum_complete() in tcp_v{4,6}_do_rcv() - tcp_v{4,6}_cookie_check() returning NULL When a packet is dropped on any of these paths, tcp_tw_isn is left set. The next SYN processed on the same CPU then consumes the non zero value in tcp_conn_request(), receiving a potentially predictable ISN. This patch moves back tcp_tw_isn to skb->cb[], getting rid of the per-cpu variable. Note that tcp_v{4,6}_fill_cb() do not set it. Very litle impact on overall code size/complexity: $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/0 grow/shrink: 2/1 up/down: 8/-15 (-7) Function old new delta tcp_v6_rcv 3038 3042 +4 tcp_v4_rcv 3035 3039 +4 tcp_conn_request 2938 2923 -15 Total: Before=24436060, After=24436053, chg -0.00% Fixes: 41eecbd712b7 ("tcp: replace TCP_SKB_CB(skb)->tcp_tw_isn with a per-cpu field") Reported-by: Chris Mason Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260519084611.2485277-1-edumazet@google.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

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

2026-05-23T11:09:18+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()

2026-05-23T11:09:18+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()

2026-05-23T11:09:18+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

2026-03-05T01:44:35+00:00

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

tcp: fix potential race in tcp_v6_syn_recv_sock()

2026-02-19T22:02:19+00:00

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

tcp: inline tcp_filter()

2026-02-07T04:12:11+00:00

This helper is already (auto)inlined from IPv4 TCP stack. Make it an inline function to benefit IPv6 as well. $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 0/2 grow/shrink: 1/0 up/down: 30/-49 (-19) Function old new delta tcp_v6_rcv 3448 3478 +30 __pfx_tcp_filter 16 - -16 tcp_filter 33 - -33 Total: Before=24891904, After=24891885, chg -0.00% Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260205164329.3401481-1-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: split tcp_check_space() in two parts

2026-02-05T04:37:06+00:00

tcp_check_space() is fat and not inlined. Move its slow path in (out of line) __tcp_check_space() and make tcp_check_space() an inline function for better TCP performance. $ scripts/bloat-o-meter -t vmlinux.old vmlinux.new add/remove: 2/2 grow/shrink: 4/0 up/down: 708/-582 (126) Function old new delta __tcp_check_space - 521 +521 tcp_rcv_established 1860 1916 +56 tcp_rcv_state_process 3342 3384 +42 tcp_event_new_data_sent 248 286 +38 tcp_data_snd_check 71 106 +35 __pfx___tcp_check_space - 16 +16 __pfx_tcp_check_space 16 - -16 tcp_check_space 566 - -566 Total: Before=24896373, After=24896499, chg +0.00% Signed-off-by: Eric Dumazet Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260203050932.3522221-1-edumazet@google.com Signed-off-by: Jakub Kicinski

tcp: add TCP_SYNACK_RETRANS synack_type

2026-02-03T14:13:24+00:00

Before this patch, retransmitted SYN/ACK did not have a specific synack_type; however, the upcoming patch needs to distinguish between retransmitted and non-retransmitted SYN/ACK for AccECN negotiation to transmit the fallback SYN/ACK during AccECN negotiation. Therefore, this patch introduces a new synack_type (TCP_SYNACK_RETRANS). Signed-off-by: Chia-Yu Chang Acked-by: Paolo Abeni Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260131222515.8485-9-chia-yu.chang@nokia-bell-labs.com Signed-off-by: Paolo Abeni

tcp: disable RFC3168 fallback identifier for CC modules

2026-02-03T14:13:24+00:00

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