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Commit f1c6ea38 authored by Eric Dumazet's avatar Eric Dumazet Committed by David S. Miller
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tcp: refine tcp_tso_should_defer() after EDT adoption 



tcp_tso_should_defer() last step tries to check if the probable
next ACK packet is coming in less than half rtt.

Problem is that the head->tstamp might be in the future,
so we need to use signed arithmetics to avoid overflows.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Acked-by: default avatarSoheil Hassas Yeganeh <soheil@google.com>
Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 1c09f7d0

net/ipv4/tcp_output.c

+4 −3
Original line number Diff line number Diff line
@@ -1907,10 +1907,11 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, 
				 bool *is_cwnd_limited, u32 max_segs)

{

	const struct inet_connection_sock *icsk = inet_csk(sk);

	u32 age, send_win, cong_win, limit, in_flight;

	u32 send_win, cong_win, limit, in_flight;

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *head;

	int win_divisor;

	s64 delta;



	if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)

		goto send_now;
@@ -1972,9 +1973,9 @@ static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, 
	head = tcp_rtx_queue_head(sk);

	if (!head)

		goto send_now;

	age = tcp_stamp_us_delta(tp->tcp_mstamp, tcp_skb_timestamp_us(head));

	delta = tp->tcp_clock_cache - head->tstamp;

	/* If next ACK is likely to come too late (half srtt), do not defer */

	if (age < (tp->srtt_us >> 4))

	if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0)

		goto send_now;



	/* Ok, it looks like it is advisable to defer. */