I haven't dug very deep yet, but I can comment on the intent of the particular commit: without it, dnsmasq didn't do any unsolicited RAs on interfaces that are created after dnsmasq was started. It definitely should do unsolicited RAs on those interfaces too, although obviously not quite so many so often. I'm not sure why that happens. Note that the commit didn't introduce the fast RAs, it only enabled unsolicited RAs (including fast) for newly created interfaces too.

I wonder why this happens in those test cases and at-least one Raspberry Pi, but not on my server. Is there any information you could provide to pinpoint when exactly this bug triggers and when not? For example: what happens if the virtual interface is created before dnsmasq starts? Does it also trigger on bridge interfaces (which is what I personally tested the commit with) for you?

I will attempt to investigate too, but I'm somewhat swamped for time so I can't promise fast results.

Kinds regards,


On 27-08-2019 10:45, Iain Lane wrote:
On Wed, Aug 21, 2019 at 08:59:07PM +0200, Petr Mensik wrote:
Hi Simon and Maarten,

we discovered when playing with NetworkManager-ci [1], that lastest
release is somehow broken. Test running dnsmasq are quite slow on latest

I have created repeatable started script that reproduces it. Then used
git bisect to find when it was broken. It seems fast sending were
intentional in commit 0a496f059c1e9 [2], but maybe way it affects the
system were underestimated. It is significant for systems that hit such
issue. I think it has to be fixed to slow it down to short time
interval, not endless loop. Reported as Fedora bug [3].
Thanks for this Petr. Would you be able to share the script you've used,
so that perhaps an upstream developer could recreate the bug?

Mainly I wanted to chime in and say that (in addition to the other
instance referenced), we found this in the NetworkManager testsuite in
Ubuntu. I didn't come up with a nice reproducer at the time, but we did
identify the same commit and we've reverted it in Ubuntu. I posted on
the ML back then but we didn't get much traction and I didn't follow up
very aggressively.


   (the commit ID referenced in the changelog there seems or from
   somewhere else, it's the same patch)


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