netdev - [RFC PATCHv5 1/5] [TCP]: Add highest_sack seqno, points to globally highest SACK

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Date:	Fri, 16 Mar 2007 20:41:02 +0200
From:	"Ilpo JÃ¤rvinen" <ilpo.jarvinen@...sinki.fi>
To:	netdev@...r.kernel.org
Cc:	David Miller <davem@...emloft.net>,
	"Ilpo JÃ¤rvinen" <ilpo.jarvinen@...sinki.fi>
Subject: [RFC PATCHv5 1/5] [TCP]: Add highest_sack seqno, points to globally highest SACK

It is guaranteed to be valid only when !tp->sacked_out. In most
cases this seqno is available in the last ACK but there is no
guarantee for that. The new fast recovery loss marking algorithm
needs this as entry point.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@...sinki.fi>
---
 include/linux/tcp.h  |    2 ++
 net/ipv4/tcp_input.c |    8 +++++++-
 2 files changed, 9 insertions(+), 1 deletions(-)

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 09f2d66..9e542d5 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -335,6 +335,8 @@ #endif
 
 	struct tcp_sack_block_wire recv_sack_cache[4];
 
+	u32	highest_sack;	/* Start seq of globally highest revd SACK (valid only in slowpath) */
+
 	/* from STCP, retrans queue hinting */
 	struct sk_buff* lost_skb_hint;
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 9c3b4c7..dbc98ce 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -954,8 +954,10 @@ tcp_sacktag_write_queue(struct sock *sk,
 	int i;
 	int first_sack_index;
 
-	if (!tp->sacked_out)
+	if (!tp->sacked_out) {
 		tp->fackets_out = 0;
+		tp->highest_sack = tp->snd_una;
+	}
 	prior_fackets = tp->fackets_out;
 
 	/* Check for D-SACK. */
@@ -1189,6 +1191,10 @@ tcp_sacktag_write_queue(struct sock *sk,
 
 				if (fack_count > tp->fackets_out)
 					tp->fackets_out = fack_count;
+
+				if (after(TCP_SKB_CB(skb)->seq,
+				    tp->highest_sack))
+					tp->highest_sack = TCP_SKB_CB(skb)->seq;
 			} else {
 				if (dup_sack && (sacked&TCPCB_RETRANS))
 					reord = min(fack_count, reord);
-- 
1.4.2

-
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