Re: [PATCH nf-next] netfilter: tcp: Use TCP_MAX_WSCALE instead of literal 14

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Wed, Apr 19, 2017 at 09:22:08AM -0700, Eric Dumazet wrote:
> On Wed, 2017-04-19 at 17:58 +0200, Pablo Neira Ayuso wrote:
> > On Wed, Apr 19, 2017 at 09:23:42AM +0800, gfree.wind@foxmail.com wrote:
> > > From: Gao Feng <fgao@ikuai8.com>
> > > 
> > > The window scale may be enlarged from 14 to 15 according to the itef
> > > draft https://tools.ietf.org/html/draft-nishida-tcpm-maxwin-03.
> > > 
> > > Use the macro TCP_MAX_WSCALE to support it easily with TCP stack in
> > > the future.
> > 
> > Applied, thanks.
> 
> Note that linux kernel is not ready yet for a TCP_MAX_WSCALE being
> changed to 15.
> 
> Signed 32bit sk counters can already be abused with 1GB TCP windows, for
> malicious peers sending SACK forcing linux to increase its memory usage
> above 2GB and overflows are pretty bad.

We have tend to use our own definitions for the TCP connection
tracking so far. This one I checked it refers RFC1323 too.

If this semantics may change from one way to another in a way that may
break conntracking, please let me know, I can toss it here.

Thanks Eric!