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

Kristian Evensen kristian.evensen at gmail.com
Mon Sep 24 14:12:25 EDT 2018


I have some routers running OpenWRT (latest nightly) and that I have
to access remotely (using reverse SSH). When I restart networking
(/etc/init.d/network restart), clients on the LAN can no longer obtain
an IP address using DHCP. If I restart networking locally, DHCP works
as expected after the network is back up.

In order to try and figure out what is going on, I have checked/tried
the following:

* I started out by checking if dnsmasq has been restarted and if the
DHCP socket has been created. I can always see the socket in netstat.
* I then took a look at the firewall. I can see the DHCP packets in
the INPUT chain in filter, which according to my understanding of
Netfilter-internals is the last stop before a packet is delivered to a
* I then instrumented dnsmasq and added some logging in dhcp_packet()
in dhcp.c. This function is never called, as none of my log-messages
are written to syslog. I checked that the logging works by checking
for my messages when DHCP is working.
* Restarting dnsmasq makes DHCP work again. I can't see any difference
in for example netstat-output.

Does anyone have any idea on what to try or where to look next? After
having spent a couple of days on this issue, I am quickly starting to
run out of ideas.

Thanks in advance for any help,

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