NetworkManager shared connection and custom dnsmasq

[ibukanov]

Hello,

When I activate a shared connection in NetworkManager, it runs dnsmsq with an empty config file according to the ps axww output:

/usr/sbin/dnsmasq --conf-file --no-hosts --keep-in-foreground --bind-interfaces --except-interface=lo --clear-on-reload --strict-order --listen-address=10.42.0.1 --dhcp-range=10.42.0.10,10.42.0.100,60m --dhcp-option=option:router,10.42.0.1 --dhcp-lease-max=50 --pid-file=/var/run/nm-dnsmasq-em1.pid

How can I customize this dnsmasq instance and, for example, permanently bind a client with a particular MAC address to a given IP address?

[stevea]

permanently bind a client with a particular MAC address to a given IP address?

You are asking for a configuration that causes the dnsmasq server to offer a specific IP address to a dhcp client with a specific MAC address.

Normally dnsmasq can take this information from /etc/hosts but in this case "--no-hosts" prevents that.
The dnsmasq option --dhcp-host=MAC,name,IPaddr .

The options (not the specific option addresses) are compiled into the NetworkMananger binary.

Scanning the sources it seems you should be able put parameters in
/etc/dnsmasq.d/local (create the file). Something like
dhcp-host=00:11:22:33:44:55,fred,10.12.13.73

        if (getenv ("NM_DNSMASQ_DEBUG")) {
                nm_cmd_line_add_string (cmd, "--log-dhcp");
                nm_cmd_line_add_string (cmd, "--log-queries");
        }

        /* dnsmasq may read from it's default config file location, which if that
         * location is a valid config file, it will combine with the options here
         * and cause undesirable side-effects.  Like sending bogus IP addresses
         * as the gateway or whatever.  So tell dnsmasq not to use any config file
         * at all.
         */
        nm_cmd_line_add_string (cmd, "--conf-file");

        nm_cmd_line_add_string (cmd, "--no-hosts");
        nm_cmd_line_add_string (cmd, "--keep-in-foreground");
        nm_cmd_line_add_string (cmd, "--bind-interfaces");
        nm_cmd_line_add_string (cmd, "--except-interface=lo");
        nm_cmd_line_add_string (cmd, "--clear-on-reload");

[ibukanov]

The suggestion to check the source was a good advise . However, I do not see where NetworkManager 0.9.6 tells dnsmaq to read anything from /etc/dnsmasq.d/* as typically it is the config file itself that does that.

As a workaround I simply put into /usr/local/sbin/dnsmasq a script that calls /usr/sbin/dnsmasq. In the script I check for NetworkManager invocation corresponding to the shared connection setup and then simply add --dhcp-host=MAC,IP

Note that putting DNS information into --dhcp-host is useless for my purposes as NetworkmManager does not update resolve.conf with the dns server that dnsmasq provides. So any names that dnsmasq knows about are not visible on my computer. Instead I had to add the name to /etc/hosts