Commit 6f74651a authored by Baruch Even's avatar Baruch Even Committed by David S. Miller
Browse files

[TCP]: Seperate DSACK from SACK fast path 



Move DSACK code outside the SACK fast-path checking code. If the DSACK
determined that the information was too old we stayed with a partial cache
copied. Most likely this matters very little since the next packet will not be
DSACK and we will find it in the cache. but it's still not good form and there
is little reason to couple the two checks.

Since the SACK receive cache doesn't need the data to be in host order we also
remove the ntohl in the checking loop.

Signed-off-by: default avatarBaruch Even <baruch@ev-en.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent fda03fbb

include/linux/tcp.h

+1 −1
Original line number Diff line number Diff line
@@ -316,7 +316,7 @@ struct tcp_sock { 
	struct tcp_sack_block duplicate_sack[1]; /* D-SACK block */

	struct tcp_sack_block selective_acks[4]; /* The SACKS themselves*/



	struct tcp_sack_block recv_sack_cache[4];

	struct tcp_sack_block_wire recv_sack_cache[4];



	/* from STCP, retrans queue hinting */

	struct sk_buff* lost_skb_hint;

net/ipv4/tcp_input.c

+31 −35
Original line number Diff line number Diff line
@@ -951,37 +951,14 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_ 
		tp->fackets_out = 0;

	prior_fackets = tp->fackets_out;



	/* SACK fastpath:

	 * if the only SACK change is the increase of the end_seq of

	 * the first block then only apply that SACK block

	 * and use retrans queue hinting otherwise slowpath */

	flag = 1;

	for (i = 0; i< num_sacks; i++) {

		__u32 start_seq = ntohl(sp[i].start_seq);

		__u32 end_seq =	 ntohl(sp[i].end_seq);



		if (i == 0){

			if (tp->recv_sack_cache[i].start_seq != start_seq)

				flag = 0;

		} else {

			if ((tp->recv_sack_cache[i].start_seq != start_seq) ||

			    (tp->recv_sack_cache[i].end_seq != end_seq))

				flag = 0;

		}

		tp->recv_sack_cache[i].start_seq = start_seq;

		tp->recv_sack_cache[i].end_seq = end_seq;



	/* Check for D-SACK. */

		if (i == 0) {

			u32 ack = TCP_SKB_CB(ack_skb)->ack_seq;



			if (before(start_seq, ack)) {

	if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) {

		dup_sack = 1;

		tp->rx_opt.sack_ok |= 4;

		NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV);

	} else if (num_sacks > 1 &&

				   !after(end_seq, ntohl(sp[1].end_seq)) &&

				   !before(start_seq, ntohl(sp[1].start_seq))) {

			!after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) &&

			!before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) {

		dup_sack = 1;

		tp->rx_opt.sack_ok |= 4;

		NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV);
@@ -990,17 +967,36 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_ 
	/* D-SACK for already forgotten data...

	 * Do dumb counting. */

	if (dup_sack &&

			    !after(end_seq, prior_snd_una) &&

			    after(end_seq, tp->undo_marker))

			!after(ntohl(sp[0].end_seq), prior_snd_una) &&

			after(ntohl(sp[0].end_seq), tp->undo_marker))

		tp->undo_retrans--;



	/* Eliminate too old ACKs, but take into

	 * account more or less fresh ones, they can

	 * contain valid SACK info.

	 */

			if (before(ack, prior_snd_una - tp->max_window))

	if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window))

		return 0;



	/* SACK fastpath:

	 * if the only SACK change is the increase of the end_seq of

	 * the first block then only apply that SACK block

	 * and use retrans queue hinting otherwise slowpath */

	flag = 1;

	for (i = 0; i < num_sacks; i++) {

		__be32 start_seq = sp[i].start_seq;

		__be32 end_seq = sp[i].end_seq;



		if (i == 0) {

			if (tp->recv_sack_cache[i].start_seq != start_seq)

				flag = 0;

		} else {

			if ((tp->recv_sack_cache[i].start_seq != start_seq) ||

			    (tp->recv_sack_cache[i].end_seq != end_seq))

				flag = 0;

		}

		tp->recv_sack_cache[i].start_seq = start_seq;

		tp->recv_sack_cache[i].end_seq = end_seq;

	}



	first_sack_index = 0;

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