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Commit e636f8b0 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

tcp: new helper for RACK to detect loss 



Create a new helper tcp_rack_detect_loss to prepare the upcoming
RACK reordering timer patch.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Acked-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent db8da6bb

include/net/tcp.h

+1 −2
Original line number Diff line number Diff line
@@ -1863,8 +1863,7 @@ extern int sysctl_tcp_recovery; 
/* Use TCP RACK to detect (some) tail and retransmit losses */

#define TCP_RACK_LOST_RETRANS  0x1



extern int tcp_rack_mark_lost(struct sock *sk);



extern void tcp_rack_mark_lost(struct sock *sk);

extern void tcp_rack_advance(struct tcp_sock *tp,

			     const struct skb_mstamp *xmit_time, u8 sacked);

net/ipv4/tcp_input.c

+8 −4
Original line number Diff line number Diff line
@@ -2865,11 +2865,15 @@ static void tcp_fastretrans_alert(struct sock *sk, const int acked, 
	}



	/* Use RACK to detect loss */

	if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS &&

	    tcp_rack_mark_lost(sk)) {

	if (sysctl_tcp_recovery & TCP_RACK_LOST_RETRANS) {

		u32 prior_retrans = tp->retrans_out;



		tcp_rack_mark_lost(sk);

		if (prior_retrans > tp->retrans_out) {

			flag |= FLAG_LOST_RETRANS;

			*ack_flag |= FLAG_LOST_RETRANS;

		}

	}



	/* E. Process state. */

	switch (icsk->icsk_ca_state) {

net/ipv4/tcp_recovery.c

+13 −9
Original line number Diff line number Diff line
@@ -32,17 +32,11 @@ static void tcp_rack_mark_skb_lost(struct sock *sk, struct sk_buff *skb) 
 * The current version is only used after recovery starts but can be

 * easily extended to detect the first loss.

 */

int tcp_rack_mark_lost(struct sock *sk)

static void tcp_rack_detect_loss(struct sock *sk)

{

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *skb;

	u32 reo_wnd, prior_retrans = tp->retrans_out;



	if (inet_csk(sk)->icsk_ca_state < TCP_CA_Recovery || !tp->rack.advanced)

		return 0;



	/* Reset the advanced flag to avoid unnecessary queue scanning */

	tp->rack.advanced = 0;

	u32 reo_wnd;



	/* To be more reordering resilient, allow min_rtt/4 settling delay

	 * (lower-bounded to 1000uS). We use min_rtt instead of the smoothed
@@ -82,7 +76,17 @@ int tcp_rack_mark_lost(struct sock *sk) 
			break;

		}

	}

	return prior_retrans - tp->retrans_out;

}



void tcp_rack_mark_lost(struct sock *sk)

{

	struct tcp_sock *tp = tcp_sk(sk);



	if (inet_csk(sk)->icsk_ca_state < TCP_CA_Recovery || !tp->rack.advanced)

		return;

	/* Reset the advanced flag to avoid unnecessary queue scanning */

	tp->rack.advanced = 0;

	tcp_rack_detect_loss(sk);

}



/* Record the most recently (re)sent time among the (s)acked packets */