netdev - [PATCH 2.6.27] tcp_htcp: last

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Date:	Tue, 11 Nov 2008 15:33:33 +0000
From:	Douglas Leith <Doug.Leith@...m.ie>
To:	David Miller <davem@...emloft.net>
Cc:	Netdev <netdev@...r.kernel.org>,
	Stephen Hemminger <shemminger@...tta.com>
Subject: [PATCH 2.6.27] tcp_htcp: last_cong bug fix


This patch fixes a minor bug in tcp_htcp.c which has been
highlighted by Lachlan Andrew and Lawrence Stewart.  Currently, the
time since the last congestion event, which is stored in variable
last_cong, is reset whenever there is a state change into
TCP_CA_Open.  This includes transitions of the type
TCP_CA_Open->TCP_CA_Disorder->TCP_CA_Open which are not associated
with backoff of cwnd.  The patch changes last_cong to be updated
only on transitions into TCP_CA_Open that occur after experiencing
the congestion-related states TCP_CA_Loss, TCP_CA_Recovery,
TCP_CA_CWR.

Signed-off-by:  Doug Leith <doug.leith@...m.ie>

---

Revised patch with requested style changes.

--- net/ipv4/tcp_htcp.c 2008-11-05 15:50:18.000000000 +0000
+++ net/ipv4/tcp_htcp.c.new     2008-11-11 15:20:31.000000000 +0000
@@ -71,5 +71,8 @@ static u32 htcp_cwnd_undo(struct sock *s

-       ca->last_cong = ca->undo_last_cong;
-       ca->maxRTT = ca->undo_maxRTT;
-       ca->old_maxB = ca->undo_old_maxB;
+       if (ca->undo_last_cong) {
+               ca->last_cong = ca->undo_last_cong;
+               ca->maxRTT = ca->undo_maxRTT;
+               ca->old_maxB = ca->undo_old_maxB;
+               ca->undo_last_cong = 0;
+       }

@@ -267,8 +270,11 @@ static void htcp_state(struct sock *sk,
         switch (new_state) {
-       case TCP_CA_Open:
+       case TCP_CA_Open:
                 {
                         struct htcp *ca = inet_csk_ca(sk);
-                       ca->last_cong = jiffies;
+                       if (ca->undo_last_cong) {
+                               ca->last_cong = jiffies;
+                               ca->undo_last_cong = 0;
+                       }
                 }
-               break;
+               break;
         case TCP_CA_CWR:



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