[PATCH] netfilter: don't scale the size of the window up twice

[PATCH] netfilter: don't scale the size of the window up twice

[Changli Gao]

For a picked up connection, the window win is scaled twice: one is by the
initialization code, and the other is by the sender updating code.

I use the temporary variable swin instead of modifying the variable win.

Signed-off-by: Changli Gao <xiaosuo@gmail.com>
---
 net/netfilter/nf_conntrack_proto_tcp.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
index 361eade..0d07a1d 100644
--- a/net/netfilter/nf_conntrack_proto_tcp.c
+++ b/net/netfilter/nf_conntrack_proto_tcp.c
@@ -584,8 +584,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
 			 * Let's try to use the data from the packet.
 			 */
 			sender->td_end = end;
-			win <<= sender->td_scale;
-			sender->td_maxwin = (win == 0 ? 1 : win);
+			swin = win << sender->td_scale;
+			sender->td_maxwin = (swin == 0 ? 1 : swin);
 			sender->td_maxend = end + sender->td_maxwin;
 			/*
 			 * We haven't seen traffic in the other direction yet

Re: [PATCH] netfilter: don't scale the size of the window up twice

[Pablo Neira Ayuso]

On Mon, Apr 02, 2012 at 11:25:06AM +0800, Changli Gao wrote:
> For a picked up connection, the window win is scaled twice: one is by the
> initialization code, and the other is by the sender updating code.
> 
> I use the temporary variable swin instead of modifying the variable win.
> 
> Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> ---
>  net/netfilter/nf_conntrack_proto_tcp.c |    4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
> index 361eade..0d07a1d 100644
> --- a/net/netfilter/nf_conntrack_proto_tcp.c
> +++ b/net/netfilter/nf_conntrack_proto_tcp.c
> @@ -584,8 +584,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
>  			 * Let's try to use the data from the packet.
>  			 */
>  			sender->td_end = end;
> -			win <<= sender->td_scale;
> -			sender->td_maxwin = (win == 0 ? 1 : win);
> +			swin = win << sender->td_scale;
> +			sender->td_maxwin = (swin == 0 ? 1 : swin);
>  			sender->td_maxend = end + sender->td_maxwin;
>  			/*
>  			 * We haven't seen traffic in the other direction yet

Jozsef, do you remember if this is intentional?

I'm going to test this patch in my testbed to make sure this does not
break conntrackd.

Re: [PATCH] netfilter: don't scale the size of the window up twice

[Jozsef Kadlecsik]

On Wed, 4 Apr 2012, Pablo Neira Ayuso wrote:

> On Mon, Apr 02, 2012 at 11:25:06AM +0800, Changli Gao wrote:
> > For a picked up connection, the window win is scaled twice: one is by the
> > initialization code, and the other is by the sender updating code.
> > 
> > I use the temporary variable swin instead of modifying the variable win.
> > 
> > Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> > ---
> >  net/netfilter/nf_conntrack_proto_tcp.c |    4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
> > index 361eade..0d07a1d 100644
> > --- a/net/netfilter/nf_conntrack_proto_tcp.c
> > +++ b/net/netfilter/nf_conntrack_proto_tcp.c
> > @@ -584,8 +584,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
> >  			 * Let's try to use the data from the packet.
> >  			 */
> >  			sender->td_end = end;
> > -			win <<= sender->td_scale;
> > -			sender->td_maxwin = (win == 0 ? 1 : win);
> > +			swin = win << sender->td_scale;
> > +			sender->td_maxwin = (swin == 0 ? 1 : swin);
> >  			sender->td_maxend = end + sender->td_maxwin;
> >  			/*
> >  			 * We haven't seen traffic in the other direction yet
> 
> Jozsef, do you remember if this is intentional?

No, it's a good spotting.

Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

> I'm going to test this patch in my testbed to make sure this does not
> break conntrackd.

A checking in a testbed doesn't hurt :-).

Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary

Re: [PATCH] netfilter: don't scale the size of the window up twice

[Pablo Neira Ayuso]

On Wed, Apr 04, 2012 at 09:05:26PM +0200, Jozsef Kadlecsik wrote:
> On Wed, 4 Apr 2012, Pablo Neira Ayuso wrote:
> 
> > On Mon, Apr 02, 2012 at 11:25:06AM +0800, Changli Gao wrote:
> > > For a picked up connection, the window win is scaled twice: one is by the
> > > initialization code, and the other is by the sender updating code.
> > > 
> > > I use the temporary variable swin instead of modifying the variable win.
> > > 
> > > Signed-off-by: Changli Gao <xiaosuo@gmail.com>
> > > ---
> > >  net/netfilter/nf_conntrack_proto_tcp.c |    4 ++--
> > >  1 file changed, 2 insertions(+), 2 deletions(-)
> > > diff --git a/net/netfilter/nf_conntrack_proto_tcp.c b/net/netfilter/nf_conntrack_proto_tcp.c
> > > index 361eade..0d07a1d 100644
> > > --- a/net/netfilter/nf_conntrack_proto_tcp.c
> > > +++ b/net/netfilter/nf_conntrack_proto_tcp.c
> > > @@ -584,8 +584,8 @@ static bool tcp_in_window(const struct nf_conn *ct,
> > >  			 * Let's try to use the data from the packet.
> > >  			 */
> > >  			sender->td_end = end;
> > > -			win <<= sender->td_scale;
> > > -			sender->td_maxwin = (win == 0 ? 1 : win);
> > > +			swin = win << sender->td_scale;
> > > +			sender->td_maxwin = (swin == 0 ? 1 : swin);
> > >  			sender->td_maxend = end + sender->td_maxwin;
> > >  			/*
> > >  			 * We haven't seen traffic in the other direction yet
> > 
> > Jozsef, do you remember if this is intentional?
> 
> No, it's a good spotting.
> 
> Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

Applied, thanks.