[Dnsmasq-discuss] dnsmasq using 100% cpu on router

[David Joslin]

Thanks Simon.

In your earlier message you said you thought this is probably dhcp related.
I did manage to retrieve some logs from the time of the problem and there
was a great deal of dhcp happening on the network at the time. I haven't
had time to go over them yet but I can see repeated dhcp requests from the
same clients over and over again and often only a few minutes (or less)
apart. Our network is only lightly loaded at the moment and I can't
reproduce the problem on any client. Does this sound like the same bug?
Would the logs be useful to you?

Cheers

David


On 28 April 2014 18:36, Simon Kelley <simon at thekelleys.org.uk> wrote:

> Note that this bug appears to be a hard lockup.
>
> https://bugs.launchpad.net/ubuntu/+source/dnsmasq/+bug/1313393
>
> investigations are continuing.....
>
>
> Simon.
>
>
>
>
> On 28/04/14 12:18, Kevin Darbyshire-Bryant wrote:
> > On 25/04/2014 09:37, David Joslin wrote:
> >> Hi Kevin and thanks for the help.
> >>
> > Apologies for delay in reply.
> >> Is it possible to upgrade the dnsmasq version on the router without
> >> waiting for the author of the tomato firmware to include a later
> >> version in a release of his firmware (and you mentioned that dnsmasq
> >> in tomato isn't a clean pull of Simon's release)?
> > Probably, but as you'd have to cross compile it to MIPS and 'Tomato'
> > environment you might as well try to rebuild the entire firmware.  I
> > loosely 'maintain' a shadow of Simon's git repo of dnsmasq with the
> > Tomato/Asuswrt tweaks here
> > https://github.com/kdarbyshirebryant/dnsmasq   - No guarantees etc etc,
> > but I personally try to keep up to date with both 'Merlin's
> > Asuswrt/rmerlin and put current dnsmasq in there too.
> >>
> >> Why would changing the location of the leasefile to a usb stick make a
> >> difference? If the issue, as Simon suggests, is caused by the constant
> >> rewriting of the lease database, then wouldn't its current location
> >> (which on a router would be RAM) be a faster/better option than a usb
> >> stick? Or is there another possible issue here that I've missed?
> > Agree, RAM should be faster but there is a finite amount of it and it's
> > volatile...I quite like to store the database on something that survives
> > reboots.  Also, as tomato is compiled with 'no rtc', the code tries to
> > minimise the number of writes to the leasefile on the basis it thinks it
> > likely that flash memory is involved, so better to reduce the wear.
> >>
> >> The only recent change I've made to the router was the addition of a
> >> usb stick as the location for the writing of system logs and bandwidth
> >> and IP traffic usage logs (so that they weren't lost on a reboot). I
> >> had wondered if the cause of the problem was related to the speed of
> >> writing this stuff (which obviously includes dnsmasq logging) to the
> >> usb stick rather than RAM. That's why I turned off dnsmasq logging at
> >> one point but it didn't seem to make any difference.
> >>
> >> Thanks again for your help and I'll wait for your comments on the above.
> > I'm not sure I've helped really.
> >
> > Kevin
> >
> >
> >
> > _______________________________________________
> > Dnsmasq-discuss mailing list
> > Dnsmasq-discuss at lists.thekelleys.org.uk
> > http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
> >
>
>
> _______________________________________________
> Dnsmasq-discuss mailing list
> Dnsmasq-discuss at lists.thekelleys.org.uk
> http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/attachments/20140429/766ad47e/attachment.html>