From c083bc8abfefbee48922f6ff7976020abc71253f Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Tue, 7 Aug 2018 21:52:06 -0400 Subject: [PATCH 06/19] net-tcp_bbr: v2: introduce ca_ops->skb_marked_lost() CC module callback API For connections experiencing reordering, RACK can mark packets lost long after we receive the SACKs/ACKs hinting that the packets were actually lost. This means that CC modules cannot easily learn the volume of inflight data at which packet loss happens by looking at the current inflight or even the packets in flight when the most recently SACKed packet was sent. To learn this, CC modules need to know how many packets were in flight at the time lost packets were sent. This new callback, combined with TCP_SKB_CB(skb)->tx.in_flight, allows them to learn this. This also provides a consistent callback that is invoked whether packets are marked lost upon ACK processing, using the RACK reordering timer, or at RTO time. Effort: net-tcp_bbr Origin-9xx-SHA1: afcbebe3374e4632ac6714d39e4dc8a8455956f4 Change-Id: I54826ab53df636be537e5d3c618a46145d12d51a Signed-off-by: Alexandre Frade --- include/net/tcp.h | 3 +++ net/ipv4/tcp_input.c | 5 +++++ 2 files changed, 8 insertions(+) --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1202,6 +1202,9 @@ struct tcp_congestion_ops { /* override sysctl_tcp_min_tso_segs */ u32 (*min_tso_segs)(struct sock *sk); + /* react to a specific lost skb (optional) */ + void (*skb_marked_lost)(struct sock *sk, const struct sk_buff *skb); + /* call when packets are delivered to update cwnd and pacing rate, * after all the ca_state processing. (optional) */ --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -1136,7 +1136,12 @@ static void tcp_verify_retransmit_hint(s */ static void tcp_notify_skb_loss_event(struct tcp_sock *tp, const struct sk_buff *skb) { + struct sock *sk = (struct sock *)tp; + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; + tp->lost += tcp_skb_pcount(skb); + if (ca_ops->skb_marked_lost) + ca_ops->skb_marked_lost(sk, skb); } void tcp_mark_skb_lost(struct sock *sk, struct sk_buff *skb)