[Dnsmasq-discuss] RA support in dnsmasq

Gene Czarcinski gene at czarc.net
Thu Nov 29 20:31:48 GMT 2012


On 11/29/2012 02:56 PM, Gene Czarcinski wrote:
> On 11/29/2012 02:08 PM, Gene Czarcinski wrote:
>> On 11/29/2012 11:28 AM, Simon Kelley wrote:
>>> On 29/11/12 16:06, Gene Czarcinski wrote:
>>>
>>>> Something is definitely not working correctly.  I do not know if you
>>>> have a qemu/kvm setup so duplicating the conditions that way will 
>>>> not work.
>>>>
>>>> Attached is a piece of syslog (before I patched things to suppress the
>>>> messages).  BTW, I also have no idea why anything is being done with
>>>> "p33p1" ... that is the real NIC on that system.  I have also attached
>>>> the dnsmasq conf file for that interface.
>>>>
>>>> I am willing to try any testing.  Unless I can get things to work as
>>>> they are suppose to, user reception of using dnsmasq to handle RA will
>>>> get support somewhere between zero and none :-)
>>> Another theory: a netlink NEWADDR event (ie assigning an address to a
>>> network interface) triggers the one minute of rapid advertisements.
>>> Maybe something on your system is doing that regularly?
>>>
>>> Can you try adding a logging line next to the call to
>>> ra_start_unsolicited() in nl_async() in netlink.c, to see how often 
>>> that
>>> gets called?
>>>
>>>
>> OK, rebuilt dnsmasq with the patch to limit RTR-ADVERT out and a 
>> patch added to issue a syslog message when ra_start_unsolicted is 
>> done.  It is installed on two systems which also run virtualization.  
>> They are both fairly new AMD-cpu systems and I have not had any 
>> problems with clocks.  One virtual network started on each and no 
>> other dnsmasq instances.
>>
>> I do wonder if this rapid issuing also takes place with radvd but has 
>> never been noticed because it does not issue log messages.
>>
>> BTW, on a system which does not have virtualization installed 
>> (because it cannot run it) but does have dnsmasq doing its thing 
>> including DHCPv6, there are RTR-ADVERT messages about every eight 
>> minutes per interface.
>>
> Have you ever felt really sick on a Friday but decided to wait until 
> Monday to see a Doctor and then, On Monday, when you see the Doctor 
> neither he nor you can find anything wrong.
>
> Well, I am not sure what was happening when I was getting all of those 
> RTR-ADVERT messages but they appear to be "normal" now.
>
> 1. Only a few ra-unsolicited occurred.
>
> 2. Although they start out frequent it settles down to about once 
> every none to ten minutes.
>
> 3. Starting another virtual network get the first one to get frequent 
> again but, after a while, they both settle down to about nine minutes.
>
> 4. I have not noticed any stuff with the real (p33p1) NIC.
>
> Note:
>
> 1. During the last month or so there have been some system updates 
> including the kernel.
>
> 2. Also over the last month or two I have been running "leading edge" 
> development versions of libvirt and NetworkManager.
>
> Right now all I can do is let it run and keep an eye on it.
>
>
I spoke too quickly.

The cause of the problem is libvirt related but I am not sure what just yet.

I was running a libvirt that had a lot of "stuff" on it but seemed to 
work OK.  Then, earlier today I update to a point that appears to be 
somewhat beyond the leading edge and, although I was not getting any 
RTR-ADVERT messages, it turned out that there were/are big-time problems 
running qemu-kvm.  So, back off/downgrade to the previous version.  
Qemu-kvm now works but the RTR-ADVERT messages are back.

This may be a bit time-consuming to debug!

Gene




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