tcp: fix no cwnd growth after timeout (16edfe7e) · Commits · 戴 / test

In commit "tcp: increase throughput when reordering is high", it only allows cwnd to increase in Open state. This mistakenly disables slow start after timeout (CA_Loss). Moreover cwnd won't grow if the state moves from Disorder to Open later in tcp_fastretrans_alert(). Therefore the correct logic should be to allow cwnd to grow as long as the data is received in order in Open, Loss, or even Disorder state. Signed-off-by:

Yuchung Cheng <ycheng@google.com> Acked-by:

Neal Cardwell <ncardwell@google.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

net/ipv4/tcp_input.c

+2 −4

Original line number	Diff line number	Diff line
		@@ -3162,16 +3162,14 @@ static inline bool tcp_may_raise_cwnd(const struct sock *sk, const int flag)

		/* If reordering is high then always grow cwnd whenever data is
		* delivered regardless of its ordering. Otherwise stay conservative
		* and only grow cwnd on in-order delivery in Open state, and retain
		* cwnd in Disordered state (RFC5681). A stretched ACK with
		* and only grow cwnd on in-order delivery (RFC5681). A stretched ACK w/
		* new SACK or ECE mark may first advance cwnd here and later reduce
		* cwnd in tcp_fastretrans_alert() based on more states.
		*/
		if (tcp_sk(sk)->reordering > sysctl_tcp_reordering)
		return flag & FLAG_FORWARD_PROGRESS;

		return inet_csk(sk)->icsk_ca_state == TCP_CA_Open &&
		flag & FLAG_DATA_ACKED;
		return flag & FLAG_DATA_ACKED;
		}

		/* Check that window update is acceptable.

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