Re: spamming router with router solicitations

On Tue, Jun 25, 2019 at 10:20:54AM -0400, Brian J. Murrell wrote:
On Mon, 2019-06-24 at 08:52 +0200, Beniamino Galvani via
networkmanager-list wrote:


Hi Beniamino,

I checked again the log you sent and I see the problem now. When NM
receives a RA, it checks whether the parameters

Which parameters exactly?  Because I might be able to shed some light
on this now that this is known.

Basically everything in the RA. See how the 'changed' variable is set in:

changed compared to
the previous RA and if so it applies the new configuration. When it
does so, it also reapplies the token; this triggers a new router
solicitation from kernel due to:


The new RA received is:

  neighbor discovery configuration changed [R]:
    dhcp-level none
    gateway fe80::6eb0:ceff:fef5:1e4a pref high exp 1799.2317
    address 2001:123:ab:123::2 exp permanent
    route 2001:123:ab:123::/64 via fe80::6eb0:ceff:fef5:1e4a pref
high exp permanent
    dns_server fd31:aeb1:48df::2 exp 7199.2317

Note the "changed [R]" part which means that routes changed. This is
strange because according to log there was no change from previous
RA. This causes the reapply of token, a new RS, a RA and so on ...

Here is what an RA from my router looks like:


But three things that the above is not saying:

   1. Until yesterday, the Router Lifetime of one of those RAs was 0 and
      the other was 1800 (I don't recall which was which).
   2. Until the last week or two, the first prefix was being advertised
      with a Router preference of high and the other was medium.
   3. Each of those two RAs come in two different packets, one for each
      prefix rather than them both being in the same RA which I think is
      the typical behaviour.

I think all these should be handled well. But perhaps older versions
of NM had issues with the 0 lifetime of point 1.

Apart from this, I think NM should not apply the token when it's
already set;

That seems reasonable.

This is now fixed in master:

and stable branches nm-1-18, nm-1-16.


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