diff options
| author | Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com> | 2026-02-01 01:25:05 +0300 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2026-02-27 02:01:10 +0300 |
| commit | 96d23737532feaa6bd00932cc5e8a7c6d6fb409f (patch) | |
| tree | 90cc4f146c599a8d20a19d2f5c6a3443bb128b48 /include | |
| parent | df64ca7b3849c95e9d0fcac33c3d9cb7a9b95191 (diff) | |
| download | linux-96d23737532feaa6bd00932cc5e8a7c6d6fb409f.tar.xz | |
tcp: disable RFC3168 fallback identifier for CC modules
[ 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 <chia-yu.chang@nokia-bell-labs.com>
Acked-by: Paolo Abeni <pabeni@redhat.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260131222515.8485-6-chia-yu.chang@nokia-bell-labs.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Stable-dep-of: c5ff6b837159 ("tcp: accecn: handle unexpected AccECN negotiation feedback")
Signed-off-by: Sasha Levin <sashal@kernel.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/net/tcp.h | 12 | ||||
| -rw-r--r-- | include/net/tcp_ecn.h | 11 |
2 files changed, 19 insertions, 4 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index c4c25f2e0c0d..e0a5cf2f7818 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1207,8 +1207,11 @@ enum tcp_ca_ack_event_flags { #define TCP_CONG_NEEDS_ACCECN BIT(2) /* Use ECT(1) instead of ECT(0) while the CA is uninitialized */ #define TCP_CONG_ECT_1_NEGOTIATION BIT(3) +/* Cannot fallback to RFC3168 during AccECN negotiation */ +#define TCP_CONG_NO_FALLBACK_RFC3168 BIT(4) #define TCP_CONG_MASK (TCP_CONG_NON_RESTRICTED | TCP_CONG_NEEDS_ECN | \ - TCP_CONG_NEEDS_ACCECN | TCP_CONG_ECT_1_NEGOTIATION) + TCP_CONG_NEEDS_ACCECN | TCP_CONG_ECT_1_NEGOTIATION | \ + TCP_CONG_NO_FALLBACK_RFC3168) union tcp_cc_info; @@ -1354,6 +1357,13 @@ static inline bool tcp_ca_ect_1_negotiation(const struct sock *sk) return icsk->icsk_ca_ops->flags & TCP_CONG_ECT_1_NEGOTIATION; } +static inline bool tcp_ca_no_fallback_rfc3168(const struct sock *sk) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + return icsk->icsk_ca_ops->flags & TCP_CONG_NO_FALLBACK_RFC3168; +} + static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event) { const struct inet_connection_sock *icsk = inet_csk(sk); diff --git a/include/net/tcp_ecn.h b/include/net/tcp_ecn.h index fdde1c342b35..2e1637edf1d3 100644 --- a/include/net/tcp_ecn.h +++ b/include/net/tcp_ecn.h @@ -507,7 +507,9 @@ static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct sk_buff *skb * | ECN | AccECN | 0 0 1 | Classic ECN | * +========+========+============+=============+ */ - if (tcp_ecn_mode_pending(tp)) + if (tcp_ca_no_fallback_rfc3168(sk)) + tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); + else if (tcp_ecn_mode_pending(tp)) /* Downgrade from AccECN, or requested initially */ tcp_ecn_mode_set(tp, TCP_ECN_MODE_RFC3168); break; @@ -531,9 +533,11 @@ static inline void tcp_ecn_rcv_synack(struct sock *sk, const struct sk_buff *skb } } -static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th, +static inline void tcp_ecn_rcv_syn(struct sock *sk, const struct tcphdr *th, const struct sk_buff *skb) { + struct tcp_sock *tp = tcp_sk(sk); + if (tcp_ecn_mode_pending(tp)) { if (!tcp_accecn_syn_requested(th)) { /* Downgrade to classic ECN feedback */ @@ -545,7 +549,8 @@ static inline void tcp_ecn_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th, tcp_ecn_mode_set(tp, TCP_ECN_MODE_ACCECN); } } - if (tcp_ecn_mode_rfc3168(tp) && (!th->ece || !th->cwr)) + if (tcp_ecn_mode_rfc3168(tp) && + (!th->ece || !th->cwr || tcp_ca_no_fallback_rfc3168(sk))) tcp_ecn_mode_set(tp, TCP_ECN_DISABLED); } |