[PATCH v13 net-next 08/15] tcp: add TCP_SYNACK_RETRANS synack_type
From: <hidden>
Date: 2026-01-31 22:25:51
Also in:
bpf, linux-doc, linux-kselftest
Subsystem:
networking [general], networking [tcp], the rest · Maintainers:
"David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Neal Cardwell, Linus Torvalds
From: Chia-Yu Chang <redacted> 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 <redacted> Acked-by: Paolo Abeni <pabeni@redhat.com> Reviewed-by: Eric Dumazet <edumazet@google.com> --- v6: - Add new synack_type instead of moving the increment of num_retran. --- include/net/tcp.h | 1 + net/ipv4/tcp_output.c | 3 ++- 2 files changed, 3 insertions(+), 1 deletion(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index ea9ad0a3e634..ee71cd7df670 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h@@ -541,6 +541,7 @@ enum tcp_synack_type { TCP_SYNACK_NORMAL, TCP_SYNACK_FASTOPEN, TCP_SYNACK_COOKIE, + TCP_SYNACK_RETRANS, }; struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, struct request_sock *req,
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index b28596655d73..a1596fe8dd9f 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c@@ -3929,6 +3929,7 @@ struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, switch (synack_type) { case TCP_SYNACK_NORMAL: + case TCP_SYNACK_RETRANS: skb_set_owner_edemux(skb, req_to_sk(req)); break; case TCP_SYNACK_COOKIE:
@@ -4614,7 +4615,7 @@ int tcp_rtx_synack(const struct sock *sk, struct request_sock *req) /* Paired with WRITE_ONCE() in sock_setsockopt() */ if (READ_ONCE(sk->sk_txrehash) == SOCK_TXREHASH_ENABLED) WRITE_ONCE(tcp_rsk(req)->txhash, net_tx_rndhash()); - res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL, + res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_RETRANS, NULL); if (!res) { TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS);
--
2.34.1