[Dnsmasq-discuss] Debugging dnsmasq on Ubuntu

Joel Whitehouse code at joelwhitehouse.com
Thu Mar 30 08:43:30 BST 2017

I had tried dbus-monitor but message sniffing was disabled on my system 
and it gave me no useful information.

I also considered tcpdump/wireshark to watch for outbound traffic on 
port 53 but I also wanted to know when queries were being resolved from 
cache, not just when they were resolved through external dns servers.

Syslog was exactly what I needed.

Thanks Pali!


On 03/29/2017 10:11 AM, Pali Rohár wrote:
> On Wednesday 29 March 2017 09:43:33 Joel Whitehouse wrote:
>> Both the file /var/run/NetworkManager/dnsmasq.conf and the directory
>> /etc/NetworkManager/dnsmasq.d/ are empty, so it's likely that dnsmasq is
>> receiving its resovlers from Network Manager over the dbus interface.
> Right.
>> Is there any way to get dnsmasq to log when it issues a new query to a
>> resolver?
> I have all information in syslog.
> dhclient: DHCPDISCOVER on wlan0 to port 67 interval 21
> dhclient: DHCPREQUEST of X.X.X.X on wlan0 to port 67
> dhclient: DHCPOFFER of X.X.X.X from X.X.X.X
> dhclient: DHCPACK of X.X.X.X from X.X.X.X
> dhclient: bound to X.X.X.X -- renewal in X seconds.
> NetworkManager[1977]: <info> (wlan0): DHCPv4 state changed preinit -> bound
> NetworkManager[1977]: <info>   address X.X.X.X
> NetworkManager[1977]: <info>   prefix X (X.X.X.X)
> NetworkManager[1977]: <info>   gateway X.X.X.X
> NetworkManager[1977]: <info>   nameserver 'X.X.X.X'
> NetworkManager[1977]: <info>   domain name 'X'
> NetworkManager[1977]: <info> Activation (wlan0) Stage 5 of 5 (IPv4 Configure Commit) scheduled...
> NetworkManager[1977]: <info> Activation (wlan0) Stage 5 of 5 (IPv4 Commit) started...
> NetworkManager[1977]: <info> (wlan0): writing resolv.conf to /sbin/resolvconf
> dnsmasq[4160]: setting upstream servers from DBus
> dnsmasq[4160]: using nameserver X.X.X.X#53
> So when NetworkManager via dbus reconfigure list of nameservers then
> dnsmasq logs them into syslog.

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