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Commit 7c9a4a5b authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
Browse files

[TCP]: Prevent unrelated cwnd adjustment while using FRTO 



FRTO controls cwnd when it still processes the ACK input or it
has just reverted back to conventional RTO recovery; the normal
rules apply when FRTO has reverted to standard congestion
control.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 94d0ea77

net/ipv4/tcp_input.c

+11 −7
Original line number Diff line number Diff line
@@ -2522,7 +2522,7 @@ static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 
 *     to prove that the RTO is indeed spurious. It transfers the control

 *     from F-RTO to the conventional RTO recovery

 */

static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)

static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag)

{

	struct tcp_sock *tp = tcp_sk(sk);
@@ -2534,7 +2534,7 @@ static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) 


	if (!before(tp->snd_una, tp->frto_highmark)) {

		tcp_enter_frto_loss(sk, tp->frto_counter + 1);

		return;

		return 1;

	}



	/* RFC4138 shortcoming in step 2; should also have case c): ACK isn't
@@ -2542,20 +2542,22 @@ static void tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) 
	 */

	if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) &&

	    !(flag&FLAG_FORWARD_PROGRESS))

		return;

		return 1;



	if (!(flag&FLAG_DATA_ACKED)) {

		tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3));

		return;

		return 1;

	}



	if (tp->frto_counter == 1) {

		tp->snd_cwnd = tcp_packets_in_flight(tp) + 2;

		tp->frto_counter = 2;

		return 1;

	} else /* frto_counter == 2 */ {

		tcp_conservative_spur_to_response(tp);

		tp->frto_counter = 0;

	}

	return 0;

}



/* This routine deals with incoming acks, but not outgoing ones. */
@@ -2569,6 +2571,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 
	u32 prior_in_flight;

	s32 seq_rtt;

	int prior_packets;

	int frto_cwnd = 0;



	/* If the ack is newer than sent or older than previous acks

	 * then we can probably ignore it.
@@ -2631,15 +2634,16 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 
	flag |= tcp_clean_rtx_queue(sk, &seq_rtt);



	if (tp->frto_counter)

		tcp_process_frto(sk, prior_snd_una, flag);

		frto_cwnd = tcp_process_frto(sk, prior_snd_una, flag);



	if (tcp_ack_is_dubious(sk, flag)) {

		/* Advance CWND, if state allows this. */

		if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag))

		if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&

		    tcp_may_raise_cwnd(sk, flag))

			tcp_cong_avoid(sk, ack,  seq_rtt, prior_in_flight, 0);

		tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag);

	} else {

		if ((flag & FLAG_DATA_ACKED))

		if ((flag & FLAG_DATA_ACKED) && !frto_cwnd)

			tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1);

	}