Re: spamming router with router solicitations

On Fri, Jun 21, 2019 at 01:03:11PM -0400, Brian J. Murrell wrote:
On Fri, 2019-06-21 at 17:58 +0200, Beniamino Galvani via
networkmanager-list wrote:

Sounds ok.


Which kernel version do you have on the EL 7.6 machine?



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

If you are not able to reproduce the problem with a newer NM version,
this means that probably the wrong comparison of RAs was fixed in the
meantime. I don't see any commit that seems to directly fix that,

Apart from this, I think NM should not apply the token when it's
already set; and also I'm not sure why it keeps the accept_ra sysctl
enabled these days, that allows the kernel to send RAs in parallel
with NM. I will check if this can be improved.


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