[radvd-devel-l] Advertising interface is not "autoconfigured"

Pekka Savola radvd-devel-l@litech.org
Thu, 24 Jan 2002 17:10:14 +0200 (EET)

On Tue, 22 Jan 2002, Vincent Jardin wrote:

Nathan already answered to this, so I'll just respond to a few questions.. 
If anything was mised, please try again. :-)

> Now if eth0 is "autoconfigured" with the prefix:
> 2002:IPv4:/48
> The R's IPv6 routing table is like the previous one with one more entry:
> 2002:500d:e52d:beef::/64 dev eth0

You're supposed add this by the configuration; for example, in Red Hat 
Linux scripts, this can be done with:

IPV6TO4_ROUTING="eth0-:1::0/64" (which will configure 2002:IPV4:1::1/64 on 
the LAN interface).

> Thanks it works. But it would be niced if it was a RADVD option.
> I thought it was a kernel option:
> net.ipv6.conf.eth0.autoconf=1

I'm not sure if it's a good idea for routers to autoconfigure themselves.

> > Changes in radvd 0.7.1 probably kill this approach (if "all") is used --
> > radvd will not start unless "all" forwarding is enabled.
> Why ?

Because without "all" forwarding enabled, starting radvd is almost always 
a wrong operational procedure, and a cause for many weird errors.

> > Having conf/eth0/forwarding=0 is effectively a DoS for the clients for the
> > period it's 0, but in simple scenarios this may not be a problem.
> Which kind of DoS ?

a) all/forwarding is used

1) At first, all/forwarding=0 (and thus eth0/forwarding=0)
2) At time X, radvd is started
3) At time X+n, all/forwarding and eth0/forwarding are set to "1"

Between time ]X, X+n[ (for example 5s):
 - routing and addressing is advertised, and the client will configure the 
address adn the route, but the box will not forward any packets (gives 
back ICMP address unreachable error) until time 'X+n'.
 - any received router solicitations etc. will be silently discarded
   (see src/linux/Documentation/networking/ip-sysctl.txt more on this)

b) all/forwarding=1 all the time, only eth0/forwarding is toggled

1) At first, all/forwarding=1 (and eth0/forwarding=0 has been set)
2) At time X, radvd is started
3) At time X+n, eth0/forwarding are set to "1"

Now only the second point of above holds.

Pekka Savola                 "Tell me of difficulties surmounted,
Netcore Oy                   not those you stumble over and fall"
Systems. Networks. Security.  -- Robert Jordan: A Crown of Swords