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Commit 006f582c authored by Ilpo Järvinen's avatar Ilpo Järvinen Committed by David S. Miller
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tcp: convert retransmit_cnt_hint to seqno 



Main benefit in this is that we can then freely point
the retransmit_skb_hint to anywhere we want to because
there's no longer need to know what would be the count
changes involve, and since this is really used only as a
terminator, unnecessary work is one time walk at most,
and if some retransmissions are necessary after that
point later on, the walk is not full waste of time
anyway.

Since retransmit_high must be kept valid, all lost
markers must ensure that.

Now I also have learned how those "holes" in the
rexmittable skbs can appear, mtu probe does them. So
I removed the misleading comment as well.

Signed-off-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 41ea36e3

include/linux/tcp.h

+1 −1
Original line number Diff line number Diff line
@@ -358,7 +358,7 @@ struct tcp_sock { 
					 */



	int     lost_cnt_hint;

	int     retransmit_cnt_hint;

	u32     retransmit_high;	/* L-bits may be on up to this seqno */



	u32	lost_retrans_low;	/* Sent seq after any rxmit (lowest) */

include/net/tcp.h

+2 −0
Original line number Diff line number Diff line
@@ -472,6 +472,8 @@ extern void tcp_send_delayed_ack(struct sock *sk); 


/* tcp_input.c */

extern void tcp_cwnd_application_limited(struct sock *sk);

extern void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp,

					    struct sk_buff *skb);



/* tcp_timer.c */

extern void tcp_init_xmit_timers(struct sock *);

net/ipv4/tcp_input.c

+20 −14
Original line number Diff line number Diff line
@@ -979,17 +979,17 @@ static void tcp_update_reordering(struct sock *sk, const int metric, 
	}

}



/* RFC: This is from the original, I doubt that this is necessary at all:

 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we

 * retransmitted past LOST markings in the first place? I'm not fully sure

 * about undo and end of connection cases, which can cause R without L?

 */

/* This must be called before lost_out is incremented */

static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb)

{

	if ((tp->retransmit_skb_hint != NULL) &&

	if ((tp->retransmit_skb_hint == NULL) ||

	    before(TCP_SKB_CB(skb)->seq,

		   TCP_SKB_CB(tp->retransmit_skb_hint)->seq))

		tp->retransmit_skb_hint = NULL;

		tp->retransmit_skb_hint = skb;



	if (!tp->lost_out ||

	    after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high))

		tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;

}



static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb)
@@ -1002,6 +1002,16 @@ static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) 
	}

}



void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, struct sk_buff *skb)

{

	tcp_verify_retransmit_hint(tp, skb);



	if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {

		tp->lost_out += tcp_skb_pcount(skb);

		TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;

	}

}



/* This procedure tags the retransmission queue when SACKs arrive.

 *

 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L).
@@ -1178,13 +1188,7 @@ static void tcp_mark_lost_retrans(struct sock *sk) 
			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;

			tp->retrans_out -= tcp_skb_pcount(skb);



			/* clear lost hint */

			tp->retransmit_skb_hint = NULL;



			if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) {

				tp->lost_out += tcp_skb_pcount(skb);

				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;

			}

			tcp_skb_mark_lost_uncond_verify(tp, skb);

			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT);

		} else {

			if (before(ack_seq, new_low_seq))
@@ -1890,6 +1894,7 @@ static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 
		if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) {

			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;

			tp->lost_out += tcp_skb_pcount(skb);

			tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;

		}

	}

	tcp_verify_left_out(tp);
@@ -1974,6 +1979,7 @@ void tcp_enter_loss(struct sock *sk, int how) 
			TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED;

			TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;

			tp->lost_out += tcp_skb_pcount(skb);

			tp->retransmit_high = TCP_SKB_CB(skb)->end_seq;

		}

	}

	tcp_verify_left_out(tp);

net/ipv4/tcp_output.c

+7 −18
Original line number Diff line number Diff line
@@ -1838,7 +1838,7 @@ void tcp_simple_retransmit(struct sock *sk) 
	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *skb;

	unsigned int mss = tcp_current_mss(sk, 0);

	int lost = 0;

	u32 prior_lost = tp->lost_out;



	tcp_for_write_queue(skb, sk) {

		if (skb == tcp_send_head(sk))
@@ -1849,17 +1849,13 @@ void tcp_simple_retransmit(struct sock *sk) 
				TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS;

				tp->retrans_out -= tcp_skb_pcount(skb);

			}

			if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) {

				TCP_SKB_CB(skb)->sacked |= TCPCB_LOST;

				tp->lost_out += tcp_skb_pcount(skb);

				lost = 1;

			}

			tcp_skb_mark_lost_uncond_verify(tp, skb);

		}

	}



	tcp_clear_all_retrans_hints(tp);



	if (!lost)

	if (prior_lost == tp->lost_out)

		return;



	if (tcp_is_reno(tp))
@@ -2009,15 +2005,11 @@ void tcp_xmit_retransmit_queue(struct sock *sk) 
	const struct inet_connection_sock *icsk = inet_csk(sk);

	struct tcp_sock *tp = tcp_sk(sk);

	struct sk_buff *skb;

	int packet_cnt;



	if (tp->retransmit_skb_hint) {

	if (tp->retransmit_skb_hint)

		skb = tp->retransmit_skb_hint;

		packet_cnt = tp->retransmit_cnt_hint;

	} else {

	else

		skb = tcp_write_queue_head(sk);

		packet_cnt = 0;

	}



	/* First pass: retransmit lost packets. */

	if (tp->lost_out) {
@@ -2028,7 +2020,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk) 
				break;

			/* we could do better than to assign each time */

			tp->retransmit_skb_hint = skb;

			tp->retransmit_cnt_hint = packet_cnt;



			/* Assume this retransmit will generate

			 * only one packet for congestion window
@@ -2039,6 +2030,8 @@ void tcp_xmit_retransmit_queue(struct sock *sk) 
			 */

			if (tcp_packets_in_flight(tp) >= tp->snd_cwnd)

				return;

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

				break;



			if (sacked & TCPCB_LOST) {

				if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) {
@@ -2059,10 +2052,6 @@ void tcp_xmit_retransmit_queue(struct sock *sk) 
									  inet_csk(sk)->icsk_rto,

									  TCP_RTO_MAX);

				}



				packet_cnt += tcp_skb_pcount(skb);

				if (packet_cnt >= tp->lost_out)

					break;

			}

		}

	}