captive portal detection in Thunderbird

Bryan Clark clarkbw at
Tue Jun 28 16:24:13 UTC 2011

On Mon, Jun 27, 2011 at 6:07 PM, Siddharth Agarwal <sid at
> wrote:

>  On 27-06-2011 16:02, Bryan Clark wrote:
> Hey -
>  I've been working on a Thunderbird add-on that tries to detect captive
> portals <>.  For Thunderbird
> (compared to Firefox) I think this is a fairly straightforward problem to
> solve.  I wanted to talk a bit about my solution to the problem and what
> issues still exist. I'm not sure if this is something that could be merged
> into Thunderbird in the future but I think that's a conversation that makes
> sense to have; it also makes sense to have someone else write that code. ;-)
> I think doing something like what Microsoft does to detect captive portals
> in Windows 7 is the sanest approach to the problem. See
> and

These are about the same as I'm doing now.  First bit is getting a known
static file and watching for redirects.  They claim to also examine the file
to ensure it has the correct content, that is something I had tried with the
hash of the file but was a bit concerned about the file possibly changing.
 So far I haven't changed the file at all so it might not be a real concern,
once it's in version control and I'm checking the contents with tests it's
likely not an issue.

I'm not doing the DNS query which is also possible to do within an add-on
but I'm relying on the the platform network connection for that information.
 This piece seems like it could make sense for the future elements where we
want to help people diagnose their connection issues however the previous
steps already detected a captive portal so it's a bit unnecessary for
solving the problem.

> I don't think the privacy implications to this are anything beyond those of
> displaying the Thunderbird start page.

Agreed, given the same approach I think there is nothing to worry about.
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