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Commit 91fed7a1 authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
Browse files

[TCP]: Make fackets_out accurate 



Substraction for fackets_out is unconditional when snd_una
advances, thus there's no need to do it inside the loop. Just
make sure correct bounds are honored.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 0dde7b54

net/ipv4/tcp_input.c

+3 −7
Original line number Diff line number Diff line
@@ -2299,8 +2299,8 @@ tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) 
	 * 1. Reno does not count dupacks (sacked_out) automatically. */

	if (!tp->packets_out)

		tp->sacked_out = 0;

	/* 2. SACK counts snd_fack in packets inaccurately. */

	if (tp->sacked_out == 0)



	if (WARN_ON(!tp->sacked_out && tp->fackets_out))

		tp->fackets_out = 0;



	/* Now state machine starts.
@@ -2568,10 +2568,6 @@ static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, 
		} else if (*seq_rtt < 0)

			*seq_rtt = now - scb->when;



		if (tp->fackets_out) {

			__u32 dval = min(tp->fackets_out, packets_acked);

			tp->fackets_out -= dval;

		}

		/* hint's skb might be NULL but we don't need to care */

		tp->fastpath_cnt_hint -= min_t(u32, packets_acked,

					       tp->fastpath_cnt_hint);
@@ -2657,7 +2653,6 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 
			seq_rtt = now - scb->when;

			last_ackt = skb->tstamp;

		}

		tcp_dec_pcount_approx(&tp->fackets_out, skb);

		tp->packets_out -= tcp_skb_pcount(skb);

		tcp_unlink_write_queue(skb, sk);

		sk_stream_free_skb(sk, skb);
@@ -2672,6 +2667,7 @@ static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 
		tcp_ack_update_rtt(sk, acked, seq_rtt);

		tcp_rearm_rto(sk);



		tp->fackets_out -= min(pkts_acked, tp->fackets_out);

		if (tcp_is_reno(tp))

			tcp_remove_reno_sacks(sk, pkts_acked);

net/ipv4/tcp_output.c

+26 −18
Original line number Diff line number Diff line
@@ -652,6 +652,26 @@ static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned 
	}

}



/* When a modification to fackets out becomes necessary, we need to check

 * skb is counted to fackets_out or not. Another important thing is to

 * tweak SACK fastpath hint too as it would overwrite all changes unless

 * hint is also changed.

 */

static void tcp_adjust_fackets_out(struct tcp_sock *tp, struct sk_buff *skb,

				   int decr)

{

	if (!tp->sacked_out)

		return;



	if (!before(tp->highest_sack, TCP_SKB_CB(skb)->seq))

		tp->fackets_out -= decr;



	/* cnt_hint is "off-by-one" compared with fackets_out (see sacktag) */

	if (tp->fastpath_skb_hint != NULL &&

	    after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq, TCP_SKB_CB(skb)->seq))

		tp->fastpath_cnt_hint -= decr;

}



/* Function to create two new TCP segments.  Shrinks the given segment

 * to the specified size and appends a new segment with the rest of the

 * packet to the list.  This won't be called frequently, I hope.
@@ -746,21 +766,12 @@ int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss 
		if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST)

			tp->lost_out -= diff;



		if (diff > 0) {

		/* Adjust Reno SACK estimate. */

			if (tcp_is_reno(tp)) {

		if (tcp_is_reno(tp) && diff > 0) {

			tcp_dec_pcount_approx_int(&tp->sacked_out, diff);

			tcp_verify_left_out(tp);

		}



			tcp_dec_pcount_approx_int(&tp->fackets_out, diff);

			/* SACK fastpath might overwrite it unless dealt with */

			if (tp->fastpath_skb_hint != NULL &&

			    after(TCP_SKB_CB(tp->fastpath_skb_hint)->seq,

				  TCP_SKB_CB(skb)->seq)) {

				tcp_dec_pcount_approx_int(&tp->fastpath_cnt_hint, diff);

			}

		}

		tcp_adjust_fackets_out(tp, skb, diff);

	}



	/* Link BUFF into the send queue. */
@@ -1746,10 +1757,7 @@ static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int m 
		if (tcp_is_reno(tp) && tp->sacked_out)

			tcp_dec_pcount_approx(&tp->sacked_out, next_skb);



		/* Not quite right: it can be > snd.fack, but

		 * it is better to underestimate fackets.

		 */

		tcp_dec_pcount_approx(&tp->fackets_out, next_skb);

		tcp_adjust_fackets_out(tp, skb, tcp_skb_pcount(next_skb));

		tp->packets_out -= tcp_skb_pcount(next_skb);

		sk_stream_free_skb(sk, next_skb);

	}