Re: (OT kinda) Newly-discovered TCP flaw

[Joe <joe@jretrading.com>]

On Thu, 11 Aug 2016 22:35:06 +0200
deloptes <deloptes@gmail.com> wrote:

> Joe wrote:
> 
> > On Thu, 11 Aug 2016 20:31:37 +0100
> > Lisi Reisz <lisi.reisz@gmail.com> wrote:
> > 
> >   
> >> 
> >> I copied and pasted the commands exactly, and ran them as root, and
> >> got an echo of net.ipv4.tcp_challenge_ack_limit = 999999999 in
> >> response to the first and a blank return in response to the second.
> >> I don't know the significance.
> >>   
> > 
> > Go and read /proc/net/ipv4... and it should show the changed value.
> > 
> > I believe the echo means it worked. I also believe it needs to be
> > added to /etc/sysctl.conf (without the 'sysctl -p') to be redone on
> > boot. It seems to affect every current Debian up to sid.  
> 
> I don't see it in the /proc tree (kernel 4.6.4 on jessie)
>  
> # ls -1 /proc/net/ip*
> /proc/net/ip6_flowlabel
> /proc/net/ip_tables_matches
> /proc/net/ip_tables_names
> /proc/net/ip_tables_targets
> /proc/net/ipv6_route
> 
> and on the firewall (2.6.26.2 wheezy)
> 
>  sysctl -w net.ipv4.tcp_challenge_ack_limit=999999999
> sysctl: cannot stat /proc/sys/net/ipv4/tcp_challenge_ack_limit: No
> such file or directory
> 
> I don't understand if it is bad.
> 
> on the file server (kernel 3.2.0 jessie)
> 
> cat /proc/sys/net/ipv4/tcp_challenge_ack_limit
> 999999999
> 
> interesting ...
> 
> Do you have recommendations?
> 

I forgot the /sys/. Sorry. It is present on my wheezy and sid (4.6.4-1).

-- 
Joe