From: Pengcheng Yang yangpc@wangsu.com
[ Upstream commit b253a0680ceadc5d7b4acca7aa2d870326cad8ad ]
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 yangpc@wangsu.com Cc: Paolo Abeni pabeni@redhat.com Acked-by: Neal Cardwell ncardwell@google.com Tested-by: Neal Cardwell ncardwell@google.com Reviewed-by: Eric Dumazet edumazet@google.com Link: https://lore.kernel.org/r/1650422081-22153-1-git-send-email-yangpc@wangsu.co... Signed-off-by: Jakub Kicinski kuba@kernel.org Signed-off-by: Sasha Levin sashal@kernel.org --- 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 334b8d1b5442..c74befd89ee9 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1041,6 +1041,7 @@ 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? */ @@ -1151,6 +1152,11 @@ 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 0de693565963..6ab197928abb 100644 --- a/net/ipv4/tcp_rate.c +++ b/net/ipv4/tcp_rate.c @@ -73,26 +73,31 @@ 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 = 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);