Subject: Re: Possible DoS with 6RD border relay

From: Brent Cook <[email-masked]>
Date: Wed, 4 Jan 2012 11:35:54 -0600

On Wednesday, January 04, 2012 11:25:31 AM Eric Dumazet wrote:
> Le mercredi 04 janvier 2012 à 11:02 -0600, Brent Cook a écrit :
> > I forgot to mention, I'm testing 3.2 rc7:
> > 
> > Linux target1 3.2.0-7-generic #13-Ubuntu SMP Sat Dec 24 18:06:57 UTC 2011
> > x86_64 x86_64 x86_64 GNU/Linux
> > 
> > but the same behavior occurs with 2.6.35
> 
> Please check :
> 
> grep . /proc/sys/net/ipv6/route/*

/proc/sys/net/ipv6/route/gc_elasticity:9
/proc/sys/net/ipv6/route/gc_interval:30
/proc/sys/net/ipv6/route/gc_min_interval:0
/proc/sys/net/ipv6/route/gc_min_interval_ms:500
/proc/sys/net/ipv6/route/gc_thresh:1024
/proc/sys/net/ipv6/route/gc_timeout:60
/proc/sys/net/ipv6/route/max_size:4096
/proc/sys/net/ipv6/route/min_adv_mss:1220
/proc/sys/net/ipv6/route/mtu_expires:600

This is a system with 8GB of ram.

If I modify gc_thresh to be >= the number of bits the client varies, the 
system works OK:

/proc/sys/net/ipv6/neigh/default/gc_thresh1:128
/proc/sys/net/ipv6/neigh/default/gc_thresh2:512
/proc/sys/net/ipv6/neigh/default/gc_thresh3:1024

root@target1:~# echo 200000 > /proc/sys/net/ipv6/neigh/default/gc_thresh1
root@target1:~# echo 200000 > /proc/sys/net/ipv6/neigh/default/gc_thresh2
root@target1:~# echo 200000 > /proc/sys/net/ipv6/neigh/default/gc_thresh3

But it seems to be a losing battle since the client has a delegated prefix of 
/64.