[Cerowrt-devel] Strange behavior with macbook and DNS

[Cerowrt-devel] Strange behavior with macbook and DNS

[Shannon Kendrick]

Whenever I switch from wired to wireless my Macbook pops up a dialog with a message similar to this:

"This computer’s local hostname “‫Shannon-Kendricks-MacBook-Pro-7.local‎‬” is already in use on this network. The name has been changed to “‫Shannon-Kendricks-MacBook-Pro-8.local‎‬”."

The number at the end of the hostname is incremented each time.

Any idea why this is happening and how to prevent it?  This was not a problem on any of the other routers I've used (Linksys, DD-WRT, m0n0wall).
Thanks,
Shannon

Re: [Cerowrt-devel] Strange behavior with macbook and DNS

[William Katsak]

I see this too, but mostly on my desktop  Mac when it wakes up from sleep.

I think something is up with the Avahi reflector, but haven't had time
to look into it.

Bill Katsak

Sent from my iPhone

On Oct 24, 2012, at 9:04 AM, Shannon Kendrick
<shannon@kendrickonline.org> wrote:

> Whenever I switch from wired to wireless my Macbook pops up a dialog with a message similar to this:
>
> "This computer’s local hostname “Shannon-Kendricks-MacBook-Pro-7.local” is already in use on this network. The name has been changed to “Shannon-Kendricks-MacBook-Pro-8.local”."
>
> The number at the end of the hostname is incremented each time.
>
> Any idea why this is happening and how to prevent it?  This was not a problem on any of the other routers I've used (Linksys, DD-WRT, m0n0wall).
> Thanks,
> Shannon
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel

Re: [Cerowrt-devel] Strange behavior with macbook and DNS

[Dave Taht]

On Wed, Oct 24, 2012 at 6:14 AM, William Katsak <wkatsak@gmail.com> wrote:
> I see this too, but mostly on my desktop  Mac when it wakes up from sleep.
>
> I think something is up with the Avahi reflector, but haven't had time
> to look into it.
>
> Bill Katsak
>
> Sent from my iPhone
>
> On Oct 24, 2012, at 9:04 AM, Shannon Kendrick
> <shannon@kendrickonline.org> wrote:
>
>> Whenever I switch from wired to wireless my Macbook pops up a dialog with a message similar to this:
>>
>> "This computer’s local hostname “Shannon-Kendricks-MacBook-Pro-7.local” is already in use on this network. The name has been changed to “Shannon-Kendricks-MacBook-Pro-8.local”."
>>
>> The number at the end of the hostname is incremented each time.
>>
>> Any idea why this is happening and how to prevent it?  This was not a problem on any of the other routers I've used (Linksys, DD-WRT, m0n0wall).

This is an issue with avahi's mdns tying names to mac addresses, and
this being a routed, rather than bridged, network. It's actually a
flaw in mdns's design which I hope will be worked on in the new dnsext
working group at the ietf.

There are worse issues with mdns than this in a routed environment.

>> Thanks,
>> Shannon
>> _______________________________________________
>> Cerowrt-devel mailing list
>> Cerowrt-devel@lists.bufferbloat.net
>> https://lists.bufferbloat.net/listinfo/cerowrt-devel
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel



-- 
Dave Täht

Fixing bufferbloat with cerowrt: http://www.teklibre.com/cerowrt/subscribe.html

Re: [Cerowrt-devel] Strange behavior with macbook and DNS

[Michael Richardson]

[-- Attachment #1: Type: text/plain, Size: 1089 bytes --]


Dave Taht <dave.taht@gmail.com> wrote:
    >> I think something is up with the Avahi reflector, but haven't had
    >> time to look into it.

    DT> This is an issue with avahi's mdns tying names to mac addresses,
    DT> and this being a routed, rather than bridged, network. It's
    DT> actually a flaw in mdns's design which I hope will be worked on
    DT> in the new dnsext working group at the ietf.

So, basically, each time the mac goes from wired to wireless, the
reflector sees the name, says, "hey, that name is in use over *THERE*",
and declares a conflict.

If tied to mac address, then I'd expect at most two names (one for the
wired mac, one for the wireless mac), which is also suboptimal, but
understandable.   SO I think you are saying that in addition to this
protocol problem, there is also some bug in the reflector causing all
previous names to be taken?

(I'm asking mostly so that I can make sure that mdnsext can capture this
as part of the problem statement.  BTW: who will be in Atlanta?)

-- 
Michael Richardson
-on the road-




[-- Attachment #2: Type: application/pgp-signature, Size: 489 bytes --]

Re: [Cerowrt-devel] Strange behavior with macbook and DNS

[Jim Gettys]

On 10/24/2012 08:06 PM, Michael Richardson wrote:
> Dave Taht <dave.taht@gmail.com> wrote:
>     >> I think something is up with the Avahi reflector, but haven't had
>     >> time to look into it.
>
>     DT> This is an issue with avahi's mdns tying names to mac addresses,
>     DT> and this being a routed, rather than bridged, network. It's
>     DT> actually a flaw in mdns's design which I hope will be worked on
>     DT> in the new dnsext working group at the ietf.
>
> So, basically, each time the mac goes from wired to wireless, the
> reflector sees the name, says, "hey, that name is in use over *THERE*",
> and declares a conflict.
>
> If tied to mac address, then I'd expect at most two names (one for the
> wired mac, one for the wireless mac), which is also suboptimal, but
> understandable.   SO I think you are saying that in addition to this
> protocol problem, there is also some bug in the reflector causing all
> previous names to be taken?
Dunno.  Kerry Lynn is probably in a better position to say.
>
> (I'm asking mostly so that I can make sure that mdnsext can capture this
> as part of the problem statement.  BTW: who will be in Atlanta?)
We have another problem to capture in mdnsext.

Multiple CeroWrt routers can mesh; so there can be loops, and mdns has
problems with that: it will forward things it's already heard.  I
observe Avahi in a hard loop (and probably flooding the network with
lots of messages).

So Avahi basically loops in that case forwarding announcements and
generating names.

Kerry and I got together a few weeks back and discussed this. I don't
know if he's had time to set up some routers to test and diagnose
exactly what is happening yet or not (I suspect not, that he's probably
been busy with the startup of the working group).

So this is a concrete example of the problems homenet faces with
multiple routers in the home.  Naive people (like my family) want their
printer discovery to "just work".
                        - Jim


>
>
>
> _______________________________________________
> Cerowrt-devel mailing list
> Cerowrt-devel@lists.bufferbloat.net
> https://lists.bufferbloat.net/listinfo/cerowrt-devel