[pkg-wpa-devel] Re: Patch: Support for mapping scripts, e.g. guessnet

[Felix Homann]

Hi Kel,

sorry for being a bit late in responding and big thanks for your enhancements! 
More details below:

On Saturday 05 August 2006 07:19, Kel Modderman wrote:
> Hi Felix and list,
>
> Okay, I spent quite some time looking at this, my observations follow, and
> my (current) version of this functionality is attached in patch form, and
> also I've uploaded the source and binary packages to my site for testing.

Great!

> Therefore, when adding a new network
> + mapping, it would be required to stop the daemon to add extra wpa-map*
> lines, so that the action script's environment is aware of the changes.

Yes, sure. We should mention it in the docs. BTW, I actually stop the daemon 
everytime I change something in /e/n/i just like you always should ifdown an 
interface before changing /e/n/i. It might not be necessary everytime, but 
it's safer. (E.g. if you delete the logical interface from /e/n/i that's 
currently up you'll have some trouble ifdowning it.)

> 2.  I would prefer to do sanity checking of IF_WPA_MAPPING_SCRIPT_PRIORITY
> and IF_WPA_MAPPING_SCRIPT in ifupdown.sh before allowing the action script
> to start, because later it would _always_ fail.

OK.

> 3. Use WPA_LOGICAL_IFACE instead of LOGICAL_IFACE to avoid similarities
> with ifupdown's LOGICAL env variable now, and in the future.

Yes, I originally  wanted to use that name, too. I've been lazy at typing 
though ;-)

> 4. Force the admin to give the absolute path to the (executable)
> wpa-mapping-script. /usr/bin/which may not be present when networking
> starts, and its not too much to ask, IMHO.

Here, I disagree. I would like to be as compatible to ifupdowns mapping as 
possible. Any script that can be found by ifupdown should be found by 
wpa_action. Maybe we should search the path without using 'which'?

> 5. Remove brace expansion. Instead use set and sed to get a list of all
> IF_WPA_MAP env variables and form a single string from then with a for
> loop. The string is then given as STDIN to the mapping script. This should
> also scale to allow as many IF_WPA_MAP lines as the shell can manage.

Great!!!!!!

> 6. Verify that the WPA_LOGICAL_IFACE returned by the mapping script is
> defined in /etc/network/interfaces with a quick grep.

I had this in an early version of my  patch, too. I removed it because I think 
a good mapping script should take care of this. If we do this check and then 
fallback to "none" or "default" it could hide the failing of a script from 
the user. 

Furthermore, it could even be wanted that a script returns a nonexistent 
logical interface name to make sure the interface won't ifup properly.

I think we should do it as ifupdown does: Let's just pass it through.

> 7. Don't always return with error in this function, but rather just unset
> WPA_LOGICAL_IFACE (or simply do not set it). ifupdown will not be called
> when it is not set.

OK.

> 8. Changed wpa-script-priority => wpa-mapping-script-priority. It can be
> set to any value to be active, but we'll document it as '1' to activate it.

OK.

> 9. Fallback to logical interface "none",

That's a good idea! I never liked falling back to "default" by default. IMO, 
there should be no hardcoded default that might be found in /e/n/i 
accidentally. 

To be more specific: guessnet uses "none" as the default fallback. I think 
it's rather unlikely that anyone has a "none" interface defined in his /e/n/i 
without using guessnet. And I don't think you should use a "none" iface if 
you _are_ using guessnet. You'd better specify a default one by a line "map 
default: default" or "map default: fallback".

Yes, it's partially about personal taste, but if the answer to "Which logical 
interface is up?" is "None!" it doesn't feel right. If "none" is returned by 
a script no logical interface should be brought up.

> but provide backwards 
> compatibility to the "default" action we have documented so far. This makes
> using wpa-roam with guessnet easier to follow.

Hmm, I guess this might cause some confusion. There should only be one default 
fallback, no matter what logical interfaces there are in /e/n/i. I would like 
falling back to "none" while introducing a "wpa-roam-default-iface" option.

> 10. I'm concerned that guessnet installs itself under /usr, this may not be
> mounted at the time networking wants it.

That's beyond our responsibility. We just provide the means to call mapping 
scripts just as you can from a mapping stanza. (Sure, I've had guessnet in 
mind when doing this, though.) But we could drop a note to the guessnet 
maintainer.

> Lets discuss the changes and make the code work exactly as it should. I
> like it. When we decide thats going to stick, lets document it together.

Sure.

I'm really looking forward to having this released!

Kind regards,

Felix