Debugging SLAAC

[Alexander Koeppe]

Hello list,

just recently I've had issues that SLAAC didn't worked out for a while
and started working again w/o knowing the reason.

I tried to sniff ICMPv6 packets, saw the RAs coming around every 5-6
minutes, but my net adapter didn't configured itself with a GUA derived
from the prefix in the RA.

Is there any possiblitiy to increase the debug level to troubleshoot
issues with the address generation?

Checked dmesg, but didn't relveal much.

Regards - Alex

[Pascal-liste]

Hello,

Le 12/11/2017 à 13:28, Alexander Koeppe a écrit :
>
> just recently I've had issues that SLAAC didn't worked out for a while
> and started working again w/o knowing the reason.
>
> I tried to sniff ICMPv6 packets, saw the RAs coming around every 5-6
> minutes, but my net adapter didn't configured itself with a GUA derived
> from the prefix in the RA.

Did you see Router Solicitation packets sent by the interface after the
link was activated ?
Did the host set at least prefixes/routes from the RAs ?

What manages the interface ? Is SLAAC enabled for the interface in
/proc/sys/net/ipv6/conf/ ?
Are NDP ICMPv6 packets allowed by the firewall rules ?

> Is there any possiblitiy to increase the debug level to troubleshoot
> issues with the address generation?
>
> Checked dmesg, but didn't relveal much.

Did you see the message saying that no IPv6 routers were found ?

[Alexander Koeppe]

Am 12.11.2017 um 15:38 schrieb Pascal-liste:
> Hello,
>

Hi

> Did you see Router Solicitation packets sent by the interface after the
> link was activated ?
> Did the host set at least prefixes/routes from the RAs ?

I also thought about it. No router solicitations seen, going out from my
host on which i ran Wireshark. So seem really pointing to a local issue
on my Debian machine. The only IPv6 prefix on the interface was the
link-local.

> What manages the interface ? Is SLAAC enabled for the interface in
> /proc/sys/net/ipv6/conf/ ?
> Are NDP ICMPv6 packets allowed by the firewall rules ?

The interface is configured in /etc/network/interfaces.d/, so
NetworkManager is out of the game. At the time the issue was present, I
missed to check /proc, however nothing changed and AFAICS everything
necessary is enabled. There is also no filtering between the host and
the router.

> Did you see the message saying that no IPv6 routers were found ?

Nothing like that. That's actuall I hoped to see.

So essentialy that's what I'm looking for. Maybe a /proc or /sys entry
to be modified to increase the kernel logging for the SLAAC process. Or
maybe a kernel parameter set at boot.....

Thanks
- Alex

[Marc Haber]

On Sun, Nov 12, 2017 at 01:28:54PM +0100, Alexander Koeppe wrote:
> just recently I've had issues that SLAAC didn't worked out for a while
> and started working again w/o knowing the reason.

There is the rdisc6 tool that I have used quite some times to debug
SLAAC issues. You can use it to send out your own router solicitations,
and to see what's in the advertisement.

Greetings
Marc

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[Alexander Koeppe]

Am 15.11.2017 um 08:58 schrieb Hagen Paul Pfeifer:
>
>
> You are using the stock Debian Kernel - right? No self-backed version.
>
> Hagen
>

Yes, but I've no issues in making up a custom kernel.
Anything to enabled there to increase verbosity?

[Alexander Koeppe]

Am 15.11.2017 um 09:48 schrieb Marc Haber:
>
> There is the rdisc6 tool that I have used quite some times to debug
> SLAAC issues. You can use it to send out your own router solicitations,
> and to see what's in the advertisement.
>
> Greetings
> Marc
>

Thanks. Will take a look at rdisc6.

- Alex