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Commit 4389dded authored by Adam Langley's avatar Adam Langley Committed by David S. Miller
Browse files

tcp: Remove redundant checks when setting eff_sacks 



Remove redundant checks when setting eff_sacks and make the number of SACKs a
compile time constant. Now that the options code knows how many SACK blocks can
fit in the header, we don't need to have the SACK code guessing at it.

Signed-off-by: default avatarAdam Langley <agl@imperialviolet.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 33ad798c

include/linux/tcp.h

+6 −0
Original line number Diff line number Diff line
@@ -224,6 +224,12 @@ struct tcp_options_received { 
	u16	mss_clamp;	/* Maximal mss, negotiated at connection setup */

};



/* This is the max number of SACKS that we'll generate and process. It's safe

 * to increse this, although since:

 *   size = TCPOLEN_SACK_BASE_ALIGNED (4) + n * TCPOLEN_SACK_PERBLOCK (8)

 * only four options will fit in a standard TCP header */

#define TCP_NUM_SACKS 4



struct tcp_request_sock {

	struct inet_request_sock 	req;

#ifdef CONFIG_TCP_MD5SIG

net/ipv4/tcp_input.c

+10 −15
Original line number Diff line number Diff line
@@ -1423,10 +1423,10 @@ tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 
	unsigned char *ptr = (skb_transport_header(ack_skb) +

			      TCP_SKB_CB(ack_skb)->sacked);

	struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2);

	struct tcp_sack_block sp[4];

	struct tcp_sack_block sp[TCP_NUM_SACKS];

	struct tcp_sack_block *cache;

	struct sk_buff *skb;

	int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE) >> 3;

	int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3);

	int used_sacks;

	int reord = tp->packets_out;

	int flag = 0;
@@ -3735,8 +3735,7 @@ static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) 
		tp->rx_opt.dsack = 1;

		tp->duplicate_sack[0].start_seq = seq;

		tp->duplicate_sack[0].end_seq = end_seq;

		tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1,

					   4 - tp->rx_opt.tstamp_ok);

		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + 1;

	}

}
@@ -3791,9 +3790,8 @@ static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 
			 * Decrease num_sacks.

			 */

			tp->rx_opt.num_sacks--;

			tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +

						   tp->rx_opt.dsack,

						   4 - tp->rx_opt.tstamp_ok);

			tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +

					       tp->rx_opt.dsack;

			for (i = this_sack; i < tp->rx_opt.num_sacks; i++)

				sp[i] = sp[i + 1];

			continue;
@@ -3843,7 +3841,7 @@ static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 
	 *

	 * If the sack array is full, forget about the last one.

	 */

	if (this_sack >= 4) {

	if (this_sack >= TCP_NUM_SACKS) {

		this_sack--;

		tp->rx_opt.num_sacks--;

		sp--;
@@ -3856,8 +3854,7 @@ static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 
	sp->start_seq = seq;

	sp->end_seq = end_seq;

	tp->rx_opt.num_sacks++;

	tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack,

				   4 - tp->rx_opt.tstamp_ok);

	tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack;

}



/* RCV.NXT advances, some SACKs should be eaten. */
@@ -3894,9 +3891,8 @@ static void tcp_sack_remove(struct tcp_sock *tp) 
	}

	if (num_sacks != tp->rx_opt.num_sacks) {

		tp->rx_opt.num_sacks = num_sacks;

		tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks +

					   tp->rx_opt.dsack,

					   4 - tp->rx_opt.tstamp_ok);

		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks +

				       tp->rx_opt.dsack;

	}

}
@@ -3975,8 +3971,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 


	if (tp->rx_opt.dsack) {

		tp->rx_opt.dsack = 0;

		tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks,

					     4 - tp->rx_opt.tstamp_ok);

		tp->rx_opt.eff_sacks = tp->rx_opt.num_sacks;

	}



	/*  Queue data for delivery to the user.