Re: Mobile Networking.

----- Bob Johnson's Original Message -----
> On Sunday 06 October 2002 03:13 pm, Eric Gebhart appears to have 
> written:
> > When I started using my laptop last year I was immediately annoyed
> > by my networking setup.  At home I have wireless.  At work I had
> > wire.
> >
> > But If I had fxp0=DHCP in my rc.conf then the etc/networking script
> > would always do dhclient with it.  Even if there was no connection on
> > it.
> 
> Does that mean it is built in to the laptop and is not a pccard?  It 
> won't try to use dhclient if it isn't in the system.

Yep.  Builtin.  So if I want to use the wireless pccard I have to
comment out the fxp0 entry in rc.conf.

> [...]
> >
> > Now I have wireless at work.  So now I have multiple access points
> > to deal with.  Each with it's own set of wep keys, channel, etc.
> [...]
> >
> > I have to think that these issues are common to most people who use
> > a laptop on more than one network.  So how does everyone else deal
> > with these problems?
> 
> In the past, I was fortunate to be able to use the simple expedient of 
> having a different pcmcia network card for each network I used my 
> laptop on.  So in pccard.conf I ran whatever scripts were necessary 
> to configure the system for the network that went with a particular 
> card.
> 
> I no longer take my laptop to work, and I'm not sure how I would deal 
> with it now because I'd be using the same wireless card I use at home.  
> It seems to me you are mostly on the right track.  A script executed 
> when your wireless card is inserted can do whatever it takes to figure 
> out what network it is on and configure accordingly.  Although I think 
> it would probably be better to use the hooks provided by dhclient so 
> that you won't run the script until after you have an IP number.  Then 
> your script can probably identify the network based on IP number, 
> and configure accordingly.

But you can't get your IP number until you have a network.  And you
can't have a network until you know which AP you are talking to, get
past WEP...  

> 
> See dhclient-script(8), and look at the HOOKS section.  Basically, 
> if you have an executable script named /etc/dhclient-exit-hooks, 
> dhclient will execute it after the interface is configured.  There are 
> also hooks for running things before dhcp configuration where you 
> might be able to set WEP keys and such.  E.g. it might ask you which 
> network you are on and then issue the appropriate ifconfig command 
> to set up the WEP keys, or it might even try the candidate keys in 
> sequence until it finds one that allows the wireless card to associate.  

I have used the dhclient hooks in the past.  It might be a good idea
to use them for this.

My current solution is to turn off dhcp.  That keeps rc.network from 
doing stupid things.

I have a script in /usr/local/etc/rc.d/ which is the important parts 
of rc.network surrounded by a little bit of intelligence.
It figures out which devices are active, and chooses the most preferred 
one.

Currently I have an additional loop that tries to detect known AP's if
the chosen device is wireless.  After all that I run dhclient on it.  

I think I got a better method off list.  It modifies the pccardd behavior 
to detect the AP's.  This is the flakey part of my system.  So anything
I can do to make it work better is a good thing.

After all that, I have another rc.d script that figures out the Network
location.  I attempt to locate a known machine on one of the known
networks.  if it finds it then it runs that networks's startup-hook.
Otherwise it runs a default startup-hook.

> There real solutiion to the WEP key problem is to not use WEP, 
> e.g. have an IPsec server on each network and tunnel all of your 
> traffic through it.  That has advantages for both you and the operator 
> of the network, but obviously you may not get to say how all of the 
> networks you use are operated.

I agree with that.  I hate WEP.  But at work they insist on it. Even
when we use tunnels. I like the tunnel method better.  WAR people may 
think it's an open AP.  But they won't get anywhere with it.

> - Bob

Eric

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