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tcp: update sacked after tracepoint in __tcp_retransmit_skb

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Marking TCP_SKB_CB(skb)->sacked with TCPCB_EVER_RETRANS after the
traceopint (trace_tcp_retransmit_skb), then we can get the
retransmission efficiency by counting skbs w/ and w/o TCPCB_EVER_RETRANS
mark in this tracepoint.

We have discussed to achieve this with BPF_SOCK_OPS in [0], and using
tracepoint is thought to be a better solution.

[0]
https://lore.kernel.org/all/20240417124622.35333-1-lulie@linux.alibaba.com/

Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Philo Lu 2024-04-21 12:20:09 +08:00 committed by David S. Miller
parent 14b5fb2145
commit 2bf90a57f0
1 changed files with 6 additions and 5 deletions
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11
net/ipv4/tcp_output.c
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@ -3418,11 +3418,6 @@ start:
err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC);
}
/* To avoid taking spuriously low RTT samples based on a timestamp
* for a transmit that never happened, always mark EVER_RETRANS
*/
TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG))
tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB,
TCP_SKB_CB(skb)->seq, segs, err);
@ -3432,6 +3427,12 @@ start:
} else if (err != -EBUSY) {
NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs);
}
/* To avoid taking spuriously low RTT samples based on a timestamp
* for a transmit that never happened, always mark EVER_RETRANS
*/
TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS;
return err;
}