[OpenWrt-Devel] dnsmasq stops receiving packets after network restart

[Kristian Evensen]

Hi Jo-Philipp,

On Tue, Sep 25, 2018 at 11:23 AM Jo-Philipp Wich <jo at mein.io> wrote:
> does the same happen without "bind-dynamic" ? My hunch is that dnsmasq
> fails to "resubscribe" to the socket after the ifindex of br-lan changed
> due to the network restart (which will destroy and recreate br-lan).

bind-dynamic seems indeed to be the trigger. Disabling bind-dynamic
makes the problem go away.

> Maybe netlink congestion or something related to privilege dropping? Can
> you manage to capture an strace log of the running dnsmasq instance
> while the network is getting restarted?

I have attached the strace.  My router only has one LAN interface
(br-lan), which has the correct index. However, looking at the trace,
it seems that no DHCP socket is created after network restart. When
compared to the trace produced when starting dnsmasq (with
bind-dynamic), then I see the expected socket calls. I will take a
look at the dnsmasq code and see if there has been any changes to
bind-dynamic/netlink/...

BR,
Kristian
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