[Buildroot] [PATCH 1/1] busybox: udhcpc create leases file

[Arnout Vandecappelle <arnout@mind.be>]

On 04/30/15 16:59, Peter Korsgaard wrote:
>>>>>> "Matthew" == Matthew Weber <matthew.weber@rockwellcollins.com> writes:
> 
> Hi,
> 
>  >> > +            # Based on http://sourceforge.net/p/kboot/mailman/message/1168535/
>  >> 
>  >> A more detailed commit message would be good. After looking at that URL
>  >> I'm still not quite sure what this is needed for? It doesn't seem to be
>  >> read again anywhere.
> 
>  > Sorry, I can add that.  In general, it adds the leases functionality
>  > that mimics full dhclient behavior.  This file can then be used at a
>  > system level to know least expiration and other server provided
>  > information.
> 
> Ok, good. Is that really something we want to enforce for everyone using
> udhcpc with Buildroot?

 I don't see why not. It's creating a small file in /tmp, that's all. Except for
the appending, of course, otherwise a long-running system could just fill up
/tmp with leases. Overwriting has the disadvantage that there's a race condition
when the file is truncated at the same time that another process is reading from
it, but I don't think the complexity of fixing that race is worth the bother.


 Regards,
 Arnout

> 
>  >>> +             } >> /var/lib/misc/udhcpc-$interface.leases
>  >> 
>  >> Are you sure this should append the file and not overwrite it? Why would
>  >> you want to keep older lease info around when you receive a new one?
> 
>  > I just mimic'd dhclient but I could see in a embedded space you might
>  > only want to keep the latest and when a lease expires, removing this
>  > file.  I think the full client usually used this file to set an
>  > interface after reboot to the previous lease if one was still valid.
>  > I wasn't going to keep this behavior since for embedded devices it
>  > doesn't make sense.
> 
> Ok.
> 
>  >> 
>  >> Perhaps this belongs in a hook in your rootfs overlay?
> 
>  > Right now there isn't any way to get dhcp lease information after a
>  > lease is provided.  It seemed this should be a standard capability of
>  > the script.  I do agree I should make it not append and clean up when
>  > there isnt' a lease.
> 
> I'm still not convinced this isn't something that belongs in a project
> specific rootfs overlay instead. That's part of the reason why we now
> support custom hooks in the udhcpc script.
> 


-- 
Arnout Vandecappelle                          arnout at mind be
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