From: Ilpo Järvinen ij@kernel.org
Armed with ceb delta from option, delivered bytes, and delivered packets it is possible to estimate how many times ACE field wrapped.
This calculation is necessary only if more than one wrap is possible. Without SACK, delivered bytes and packets are not always trustworthy in which case TCP falls back to the simpler no-or-all wraps ceb algorithm.
Signed-off-by: Ilpo Järvinen ij@kernel.org Signed-off-by: Chia-Yu Chang chia-yu.chang@nokia-bell-labs.com --- net/ipv4/tcp_input.c | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+)
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index f206c1a93a56..deced87f31f8 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -748,6 +748,24 @@ static u32 __tcp_accecn_process(struct sock *sk, const struct sk_buff *skb, d_ceb = tp->delivered_ecn_bytes[INET_ECN_CE - 1] - old_ceb; if (!d_ceb) return delta; + + if ((delivered_pkts >= (TCP_ACCECN_CEP_ACE_MASK + 1) * 2) && + (tcp_is_sack(tp) || + ((1 << inet_csk(sk)->icsk_ca_state) & + (TCPF_CA_Open | TCPF_CA_CWR)))) { + u32 est_d_cep; + + if (delivered_bytes <= d_ceb) + return safe_delta; + + est_d_cep = DIV_ROUND_UP_ULL((u64)d_ceb * + delivered_pkts, + delivered_bytes); + return min(safe_delta, + delta + + (est_d_cep & ~TCP_ACCECN_CEP_ACE_MASK)); + } + if (d_ceb > delta * tp->mss_cache) return safe_delta; if (d_ceb <