[Commotion-dev] DNS Update

[Will Hawkins]

I uploaded a set of patches to redmine that should implement this.
Please take a look at your convenience and provide feedback. I am eager
to hear what you think.

To get the new feature, follow the instructions in the README (basically
update android.env and run ./build_external.sh).

As an overview, here's how the new dns setup works:

On connection to the mesh,
1. the user's DNS server preference is taken from the preferences and
stashed in app_bin/resolv.conf
2. The system-wide dns server is set to 127.0.0.1
3. adsuck (the name of the dns server binary) is launched. Its pid is
stored in the app_bin/adsuck.pid file.
4. olsrd is started with a properly configured nameservice plug-in.
At this point, adsuck is now ready to do .mesh -> address translations.

When olsrd receives an updated DNS entry,
1. The mapping is automatically reflected in
app_bin/chroot/hosts.android.small.
2. The adsuck process (whose pid is found in app_bin/adsuck.pid) is
signalled with HUP to indicate that there were changes to its data source.
3. adsuck rereads app_bin/chroot/hosts.android.small.

On disconnection from the mesh,
1. The application resets the system-wide dns server to what it was
before connecting.

Please let me know if this makes sense. I am eager to get feedback on
the approach and how it works. It's pretty cool to be able to go to
http://commotion-xxxx.mesh from the Android browser.

Will


On 05/15/2012 03:30 PM, Will Hawkins wrote:
> You can now find discussion of this item on Redmine in the
> commotion-android project under Feature #300.
> 
> https://code.commotionwireless.net/issues/300
> 
> Will
> 
> On 05/15/2012 01:25 PM, Will Hawkins wrote:
>> Thanks for this Hans.
>>
>> This setup is meant now only for Android, but it could be useful for
>> other platforms that do not readily support /etc/hosts-formatted files.
>> In all honesty I never considered a Java DNS implementation that could
>> simply run in a separate thread. That is something that I will
>> definitely look into.
>>
>> As for the files themselves, these do go into the app-local data
>> directories. The installation definitely does not pollute the OS file
>> system beyond that. I'm sorry if there was confusion in my previous
>> email regarding that point.
>>
>> Will
>>
>> On 05/15/2012 12:09 PM, Hans-Christoph Steiner wrote:
>>>
>>> Sounds good.  Is this setup meant to be only for Android or other platforms too?  I ask because it'll probably be easier to manage a pure Java DNS server as an Android Service than adding another C binary.
>>>
>>> As for writing out a non-standard file like /etc/hosts-formatted, if you are writing a custom file, then it should go into the app's file hierarchy.  It is important to avoid touching the filesystem as much as possible.  This file could go into /data/data/net.szym.barnacle/app_bin or we could create ...../app_etc or something like that.
>>>
>>> .hc
>>>
>>> On May 14, 2012, at 4:22 PM, Will Hawkins wrote:
>>>
>>>> Hello all!
>>>>
>>>> I just wanted to give everyone an update on what's going on here: I am
>>>> working on adding capability to the client to handle DNS entries
>>>> distributed in the mesh (via olsr nameservice plugin). Because Android's
>>>> /etc/hosts file is on the readonly file system, simply telling olsrd to
>>>> write out an /etc/hosts file (like it would normally do on a *nix host)
>>>> does not work.
>>>>
>>>> So, I cross-compiled a small (300k) DNS server that the app invokes when
>>>> the user connects to the mesh. This server answers queries by first
>>>> looking for an answer in an /etc/hosts-formatted file. If there are no
>>>> matches, the DNS server forwards the request.
>>>>
>>>> In my testing it works fairly well. I am still integrating it into the
>>>> build but I wanted to give everyone an update.
>>>>
>>>> Talk to you all soon!
>>>> Will
>>>> _______________________________________________
>>>> Commotion-dev mailing list
>>>> Commotion-dev at lists.chambana.net
>>>> http://lists.chambana.net/mailman/listinfo/commotion-dev
>>>>
>>>
>>>
>>
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