Patchwork [2.6.27] tcp_htcp: last_cong bug fix

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Submitter Douglas Leith
Date Nov. 12, 2008, 8:58 a.m.
Message ID <63599554-7243-4E44-BFEF-5B4B36743606@nuim.ie>
Download mbox | patch
Permalink /patch/8341/
State Accepted
Delegated to: David Miller
Headers show

Comments

Douglas Leith - Nov. 12, 2008, 8:58 a.m.
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@nuim.ie>

---

Resending with patch as attachment.   Hope this does the trick.
David Miller - Nov. 12, 2008, 9:44 a.m.
From: Douglas Leith <Doug.Leith@nuim.ie>
Date: Wed, 12 Nov 2008 08:58:18 +0000

> 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@nuim.ie>

Applied, but I still had to fix up a bunch of details :-(

+		ca->undo_last_cong = 0;  

That line had trailing whitespace.

+	case TCP_CA_Open: 

That one too.

+        		if (ca->undo_last_cong) { 

That line had an initial set of space characters, instead
of pure leading tab characters.

+				ca->last_cong = jiffies;   

More trailing whitespace.

+		break;	

And some more trailing whitespace.
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Patch

--- 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: