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Commit 1b6d427b authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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[TCP]: Reduce sacked_out with reno when purging write_queue 



Previously TCP had a transitional state during which reno
counted segments that are already below the current window into
sacked_out, which is now prevented. In addition, re-try now
the unconditional S+L skb catching.

This approach conservatively calls just remove_sack and leaves
reset_sack() calls alone. The best solution to the whole problem
would be to first calculate the new sacked_out fully (this patch
does not move reno_sack_reset calls from original sites and thus
does not implement this). However, that would require very
invasive change to fastretrans_alert (perhaps even slicing it to
two halves). Alternatively, all callers of tcp_packets_in_flight
(i.e., users that depend on sacked_out) should be postponed
until the new sacked_out has been calculated but it isn't any
simpler alternative.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d02596e3

include/net/tcp.h

+1 −2
Original line number Diff line number Diff line
@@ -759,8 +759,7 @@ static inline __u32 tcp_current_ssthresh(const struct sock *sk) 
}



/* Use define here intentionally to get BUG_ON location shown at the caller */

#define tcp_verify_left_out(tp) \

	BUG_ON(tp->rx_opt.sack_ok && (tcp_left_out(tp) > tp->packets_out))

#define tcp_verify_left_out(tp)	BUG_ON(tcp_left_out(tp) > tp->packets_out)



extern void tcp_enter_cwr(struct sock *sk, const int set_ssthresh);

extern __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst);

net/ipv4/tcp_input.c

+7 −8
Original line number Diff line number Diff line
@@ -2187,7 +2187,7 @@ static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) 
 * tcp_xmit_retransmit_queue().

 */

static void

tcp_fastretrans_alert(struct sock *sk, int prior_packets, int flag)

tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag)

{

	struct inet_connection_sock *icsk = inet_csk(sk);

	struct tcp_sock *tp = tcp_sk(sk);
@@ -2273,12 +2273,8 @@ tcp_fastretrans_alert(struct sock *sk, int prior_packets, int flag) 
		if (!(flag & FLAG_SND_UNA_ADVANCED)) {

			if (IsReno(tp) && is_dupack)

				tcp_add_reno_sack(sk);

		} else {

			int acked = prior_packets - tp->packets_out;

			if (IsReno(tp))

				tcp_remove_reno_sacks(sk, acked);

			do_lost = tcp_try_undo_partial(sk, acked);

		}

		} else

			do_lost = tcp_try_undo_partial(sk, pkts_acked);

		break;

	case TCP_CA_Loss:

		if (flag&FLAG_DATA_ACKED)
@@ -2577,6 +2573,9 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 
		tcp_ack_update_rtt(sk, acked, seq_rtt);

		tcp_ack_packets_out(sk);



		if (IsReno(tp))

			tcp_remove_reno_sacks(sk, pkts_acked);



		if (ca_ops->pkts_acked) {

			s32 rtt_us = -1;
@@ -2927,7 +2926,7 @@ static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 
		if ((flag & FLAG_DATA_ACKED) && !frto_cwnd &&

		    tcp_may_raise_cwnd(sk, flag))

			tcp_cong_avoid(sk, ack, prior_in_flight, 0);

		tcp_fastretrans_alert(sk, prior_packets, flag);

		tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, flag);

	} else {

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

			tcp_cong_avoid(sk, ack, prior_in_flight, 1);