Commit 79861919 authored Oct 18, 2018 by Eric Dumazet Committed by David S. Miller Oct 18, 2018

tcp: fix TCP_REPAIR xmit queue setup



Andrey reported the following warning triggered while running CRIU tests:

tcp_clean_rtx_queue()
...
	last_ackt = tcp_skb_timestamp_us(skb);
	WARN_ON_ONCE(last_ackt == 0);

This is caused by 5f6188a8 ("tcp: do not change tcp_wstamp_ns
in tcp_mstamp_refresh"), as we end up having skbs in retransmit queue
with a zero skb->skb_mstamp_ns field.

We could fix this bug in different ways, like making sure
tp->tcp_wstamp_ns is not zero at socket creation, but as Neal pointed
out, we also do not want that pacing status of a repaired socket
could push tp->tcp_wstamp_ns far ahead in the future.

So we prefer changing tcp_write_xmit() to not call tcp_update_skb_after_send()
and instead do what is requested by TCP_REPAIR logic.

Fixes: 5f6188a8 ("tcp: do not change tcp_wstamp_ns in tcp_mstamp_refresh")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reported-by: Andrey Vagin <avagin@openvz.org>
Acked-by: Soheil Hassas Yeganeh <soheil@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

parent cc18a754

net/ipv4/tcp_output.c

+7 −6

Original line number	Diff line number	Diff line
		@@ -2321,18 +2321,19 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
		while ((skb = tcp_send_head(sk))) {
		unsigned int limit;

		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
		/* "skb_mstamp_ns" is used as a start point for the retransmit timer */
		skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache;
		list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue);
		goto repair; /* Skip network transmission */
		}

		if (tcp_pacing_check(sk))
		break;

		tso_segs = tcp_init_tso_segs(skb, mss_now);
		BUG_ON(!tso_segs);

		if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) {
		/* "skb_mstamp" is used as a start point for the retransmit timer */
		tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns);
		goto repair; /* Skip network transmission */
		}

		cwnd_quota = tcp_cwnd_test(tp, skb);
		if (!cwnd_quota) {
		if (push_one == 2)

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