[Dnsmasq-discuss] No more random source port

Albert ARIBAUD albert.aribaud at free.fr
Mon Mar 20 19:05:40 GMT 2017


Bonjour,

Le Mon, 20 Mar 2017 20:54:51 +0200
Risto Suominen <risto.suominen at gmail.com> a écrit:

> Hi Albert,
> 
> 2017-03-20 20:30 UTC+02.00, Albert ARIBAUD <albert.aribaud at free.fr>:
> >
> > I don't kow about dnsmasq per se, but the range of ports an
> > application can use is controlled by the kernel -- on my 16.04
> > Xubuntu, that is defined by /proc/sys/net/ipv4/ip_local_port_range.
> > Does your system limit this range?
> >  
> 32768 60999
> >
> > Not sure what you mean exactly. "Same port" as what?
> >  
> Same as in previous request. The router is another forwarder for the
> DNS requests (dnsmasq is the first).

(I don't see the point of this restruction but hey, that's TP-Link's
choice.)

> To give an example:
> 
> - $ host xxx 127.0.1.1 -> no response (via dnsmasq to router)
> - $ host xxx 192.168.1.1 -> response (directly to router)
> 
> The difference is that 'host' uses varying random source ports, and
> 'dnsmasq' uses one preallocated random source port.

Ok, so the OS is not limiting the ports per se.

You said the command line did not change. Which is it exactly? I
usually do a "cat /proc/<pid-of-dnsmasq>/cmdline | tr '\0' '\n' to make
sure I see the real command line of the running dnsmasq.

> Risto

Amicalement,
-- 
Albert.



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