From b253a0680ceadc5d7b4acca7aa2d870326cad8ad Mon Sep 17 00:00:00 2001 From: Pengcheng Yang Date: Wed, 20 Apr 2022 10:34:41 +0800 Subject: [PATCH] tcp: ensure to use the most recently sent skb when filling the rate sample If an ACK (s)acks multiple skbs, we favor the information from the most recently sent skb by choosing the skb with the highest prior_delivered count. But in the interval between receiving ACKs, we send multiple skbs with the same prior_delivered, because the tp->delivered only changes when we receive an ACK. We used RACK's solution, copying tcp_rack_sent_after() as tcp_skb_sent_after() helper to determine "which packet was sent last?". Later, we will use tcp_skb_sent_after() instead in RACK. Fixes: b9f64820fb22 ("tcp: track data delivery rate for a TCP connection") Signed-off-by: Pengcheng Yang Cc: Paolo Abeni Acked-by: Neal Cardwell Tested-by: Neal Cardwell Reviewed-by: Eric Dumazet Link: https://lore.kernel.org/r/1650422081-22153-1-git-send-email-yangpc@wangsu.com Signed-off-by: Jakub Kicinski --- include/net/tcp.h | 6 ++++++ net/ipv4/tcp_rate.c | 11 ++++++++--- 2 files changed, 14 insertions(+), 3 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 70ca4a5e330a..be712fb9ddd7 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1042,6 +1042,7 @@ struct rate_sample { int losses; /* number of packets marked lost upon ACK */ u32 acked_sacked; /* number of packets newly (S)ACKed upon ACK */ u32 prior_in_flight; /* in flight before this ACK */ + u32 last_end_seq; /* end_seq of most recently ACKed packet */ bool is_app_limited; /* is sample from packet with bubble in pipe? */ bool is_retrans; /* is sample from retransmission? */ bool is_ack_delayed; /* is this (likely) a delayed ACK? */ @@ -1164,6 +1165,11 @@ void tcp_rate_gen(struct sock *sk, u32 delivered, u32 lost, bool is_sack_reneg, struct rate_sample *rs); void tcp_rate_check_app_limited(struct sock *sk); +static inline bool tcp_skb_sent_after(u64 t1, u64 t2, u32 seq1, u32 seq2) +{ + return t1 > t2 || (t1 == t2 && after(seq1, seq2)); +} + /* These functions determine how the current flow behaves in respect of SACK * handling. SACK is negotiated with the peer, and therefore it can vary * between different flows. diff --git a/net/ipv4/tcp_rate.c b/net/ipv4/tcp_rate.c index fbab921670cc..9a8e014d9b5b 100644 --- a/net/ipv4/tcp_rate.c +++ b/net/ipv4/tcp_rate.c @@ -74,27 +74,32 @@ void tcp_rate_skb_sent(struct sock *sk, struct sk_buff *skb) * * If an ACK (s)acks multiple skbs (e.g., stretched-acks), this function is * called multiple times. We favor the information from the most recently - * sent skb, i.e., the skb with the highest prior_delivered count. + * sent skb, i.e., the skb with the most recently sent time and the highest + * sequence. */ void tcp_rate_skb_delivered(struct sock *sk, struct sk_buff *skb, struct rate_sample *rs) { struct tcp_sock *tp = tcp_sk(sk); struct tcp_skb_cb *scb = TCP_SKB_CB(skb); + u64 tx_tstamp; if (!scb->tx.delivered_mstamp) return; + tx_tstamp = tcp_skb_timestamp_us(skb); if (!rs->prior_delivered || - after(scb->tx.delivered, rs->prior_delivered)) { + tcp_skb_sent_after(tx_tstamp, tp->first_tx_mstamp, + scb->end_seq, rs->last_end_seq)) { rs->prior_delivered_ce = scb->tx.delivered_ce; rs->prior_delivered = scb->tx.delivered; rs->prior_mstamp = scb->tx.delivered_mstamp; rs->is_app_limited = scb->tx.is_app_limited; rs->is_retrans = scb->sacked & TCPCB_RETRANS; + rs->last_end_seq = scb->end_seq; /* Record send time of most recently ACKed packet: */ - tp->first_tx_mstamp = tcp_skb_timestamp_us(skb); + tp->first_tx_mstamp = tx_tstamp; /* Find the duration of the "send phase" of this window: */ rs->interval_us = tcp_stamp_us_delta(tp->first_tx_mstamp, scb->tx.first_tx_mstamp);