[Dnsmasq-discuss] No more random source port

Risto Suominen risto.suominen at gmail.com
Thu Mar 23 16:40:10 GMT 2017

Hi Simon,

2017-03-23 0:04 UTC+02.00, Simon Kelley <simon at thekelleys.org.uk>:
> This indicates that dnsmasq has been configured to force the packets to
> the upstream server via eth0. To do that requires an operation on the
> socket which can only be done as root, so the socket has to be
> pre-allocated and there's no random source port.
>From the comments in the source code I got the impression that root
priviledges are held in pre_allocate_sfds(), but not in
check_servers(). The latter is where the socket is allocated.

> It looks like dnsmasq is being configured by networkmanager via the
> DBus, and I guess it's that which is doing the configuration of the
> upstream server.
Yes. And this same seems to happen in at least Lubuntu 14.04 with
dnsmasq 2.68 (now 16.04/2.75). But it uses random ports. So, something
has changed, if not in dnsmasq, then possibly in NetworkManager.


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