diff options
| author | Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com> | 2025-09-16 10:24:32 +0200 |
|---|---|---|
| committer | Paolo Abeni <pabeni@redhat.com> | 2025-09-18 08:47:52 +0200 |
| commit | b40671b5ee588c8a61b2d0eacbad32ffc57e9a8f (patch) | |
| tree | 02ce18b911b45d19e014de4c9d9d0fc8f093171e /net/ipv4/tcp_output.c | |
| parent | aa55a7dde7ec506bb23448a5005ae3f4f809d022 (diff) | |
tcp: accecn: AccECN option failure handling
AccECN option may fail in various way, handle these:
- Attempt to negotiate the use of AccECN on the 1st retransmitted SYN
- From the 2nd retransmitted SYN, stop AccECN negotiation
- Remove option from SYN/ACK rexmits to handle blackholes
- If no option arrives in SYN/ACK, assume Option is not usable
- If an option arrives later, re-enabled
- If option is zeroed, disable AccECN option processing
This patch use existing padding bits in tcp_request_sock and
holes in tcp_sock without increasing the size.
Signed-off-by: Ilpo Järvinen <ij@kernel.org>
Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250916082434.100722-9-chia-yu.chang@nokia-bell-labs.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Diffstat (limited to 'net/ipv4/tcp_output.c')
| -rw-r--r-- | net/ipv4/tcp_output.c | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index f897c2594954..65b90f73daa0 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -985,9 +985,14 @@ static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, } } - /* Simultaneous open SYN/ACK needs AccECN option but not SYN */ + /* Simultaneous open SYN/ACK needs AccECN option but not SYN. + * It is attempted to negotiate the use of AccECN also on the first + * retransmitted SYN, as mentioned in "3.1.4.1. Retransmitted SYNs" + * of AccECN draft. + */ if (unlikely((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK) && tcp_ecn_mode_accecn(tp) && + inet_csk(sk)->icsk_retransmits < 2 && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && remaining >= TCPOLEN_ACCECN_BASE)) { opts->use_synack_ecn_bytes = 1; @@ -1076,7 +1081,7 @@ static unsigned int tcp_synack_options(const struct sock *sk, if (treq->accecn_ok && READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option) && - remaining >= TCPOLEN_ACCECN_BASE) { + req->num_timeout < 1 && remaining >= TCPOLEN_ACCECN_BASE) { opts->use_synack_ecn_bytes = 1; remaining -= tcp_options_fit_accecn(opts, 0, remaining); } @@ -1156,7 +1161,7 @@ static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb if (tcp_ecn_mode_accecn(tp)) { int ecn_opt = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_ecn_option); - if (ecn_opt && + if (ecn_opt && tp->saw_accecn_opt && !tcp_accecn_opt_fail_send(tp) && (ecn_opt >= TCP_ACCECN_OPTION_FULL || tp->accecn_opt_demand || tcp_accecn_option_beacon_check(sk))) { opts->use_synack_ecn_bytes = 0; |