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Commit bef06223 authored by Yuchung Cheng's avatar Yuchung Cheng Committed by David S. Miller
Browse files

tcp: a small refactor of RACK loss detection 



Refactor the RACK loop to improve readability and speed up the checks.

Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
Signed-off-by: default avatarNeal Cardwell <ncardwell@google.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 043b87d7

net/ipv4/tcp_recovery.c

+18 −22
Original line number Diff line number Diff line
@@ -61,32 +61,28 @@ static void tcp_rack_detect_loss(struct sock *sk, u32 *reo_timeout) 
	list_for_each_entry_safe(skb, n, &tp->tsorted_sent_queue,

				 tcp_tsorted_anchor) {

		struct tcp_skb_cb *scb = TCP_SKB_CB(skb);



		if (tcp_rack_sent_after(tp->rack.mstamp, skb->skb_mstamp,

					tp->rack.end_seq, scb->end_seq)) {

			/* Step 3 in draft-cheng-tcpm-rack-00.txt:

			 * A packet is lost if its elapsed time is beyond

			 * the recent RTT plus the reordering window.

			 */

			u32 elapsed = tcp_stamp_us_delta(tp->tcp_mstamp,

							 skb->skb_mstamp);

			s32 remaining = tp->rack.rtt_us + reo_wnd - elapsed;



			if (remaining < 0) {

				tcp_rack_mark_skb_lost(sk, skb);

				list_del_init(&skb->tcp_tsorted_anchor);

				continue;

			}

		s32 remaining;



		/* Skip ones marked lost but not yet retransmitted */

		if ((scb->sacked & TCPCB_LOST) &&

		    !(scb->sacked & TCPCB_SACKED_RETRANS))

			continue;



		if (!tcp_rack_sent_after(tp->rack.mstamp, skb->skb_mstamp,

					 tp->rack.end_seq, scb->end_seq))

			break;



		/* A packet is lost if it has not been s/acked beyond

		 * the recent RTT plus the reordering window.

		 */

		remaining = tp->rack.rtt_us + reo_wnd -

			    tcp_stamp_us_delta(tp->tcp_mstamp, skb->skb_mstamp);

		if (remaining < 0) {

			tcp_rack_mark_skb_lost(sk, skb);

			list_del_init(&skb->tcp_tsorted_anchor);

		} else {

			/* Record maximum wait time (+1 to avoid 0) */

			*reo_timeout = max_t(u32, *reo_timeout, 1 + remaining);

		} else {

			break;

		}

	}

}