Connecting to public wifi hotspots

[Karl Auer]

On Sun, 2013-02-17 at 13:09 -0700, JD wrote:
> On Sun, Feb 17, 2013 at 1:01 PM, Karl Auer <kauer at biplane.com.au> wrote:
> > You can check the DNS situation using dig:
> Well, apparently, you are not aware of the entire thread.
> [etc]

"When you have eliminated the impossible, whatever remains, *however
improbable* must be the truth" - Sherlock Holmes.

> The problem I presented is that Using Ubuntu and firefox,
> I am unable to connect with open hotspots because most
> of these hotspots require that you open the browser, which
> automagically to the hotspat's start page (I do nto not know how, perhaps
> via a directive from the hotspot's server),

Exactly. You do not know. So the starting point is to find out what
exactly works, and what exactly does not work, as expected. If you
replace the word "because" in your sentence with a full stop, you have
several facts. But the statement that some of those facts are related is
not yet known to be true. Plausible - yes. True - maybe.

The first thing your browser - any browser! - does is to resolve the
given URL host into an IP address. This may be IPv4 or IPv6, and it may
be multiple addresses. If you actually do "dig www.google.com any" you
will see quite a few addresses for Google.

   www.google.com. 300 IN AAAA 2404:6800:4006:804::1014
   www.google.com. 300 IN A    74.125.237.144
   www.google.com. 300 IN A    74.125.237.145
   www.google.com. 300 IN A    74.125.237.146
   www.google.com. 300 IN A    74.125.237.147
   www.google.com. 300 IN A    74.125.237.148

The browser then starts at the top of this list and works through them,
trying for a connection (that's a simplification, as that list may be
reorganised by the resolver, and some browsers get tricky with what they
try, but it's good enough for now).

A lot of hot spots work by faking initial DNS responses - the browser
looks up www.google.com (or anything else) and the hotspot nameserver
returns some completely other address which is the local address of
their login page. Others capture the actual connection - the browser
gets the correct addresses back from the DNS, but any attempt to
actually connect is "diverted" to the login page.

So the *first thing* to check is whether your Linux host can and does
correctly resolve the target URL. If it does, then we move on. If it
does not, then we have something we can work with. Doing "dig" at the
hotspot tells you what the hotspot returns; putting literal addresses
into a browser tells you what you connect to (if anything) when you use
those addresses.

> So my problem has nothing to do with getting to me browser's
> default home page.

Clear the mind of preconceptions and assumptions. Work only with what
you know to be fact (because you have actually checked it), not with
what you assume, presume or hope. Maybe the above assumption is
absolutely correct! But right now you don't actually know that.

> firefox does not behave as it behaves on windows when it comes
> to connecting through hotspots.

There are many differences between the two environments you are using.
You may take a short cut and get lucky - or you may end up thrashing
about. By all means take those short cuts (like checking for that cert
problem someone mentioned), and if they work, that's great - lots of
time saved. But if they do not, get ready to go back to first
principles. That way lies almost certain success, though it may take a
little longer.

Regards, K.

-- 
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Karl Auer (kauer at biplane.com.au)
http://www.biplane.com.au/kauer
http://www.biplane.com.au/blog

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