dhclient raw socket?

David W. Hankins David_Hankins at isc.org
Fri Jan 26 17:24:53 UTC 2007


On Fri, Jan 26, 2007 at 10:57:33AM -0500, Schmidt, Jolynn wrote:
> I have my new dhclient-script written and I have recompiled the kernel
> but want to make sure all of the parts are correct.  Once I have enabled
> netfilters I have various other options that are available.  Do I need
> any of these?  I have an embedded system so keeping the kernel small is
> important.  Can I get away with just netfilter?
> 
> > CONFIG_NETFILTER=y

Our README says CONFIG_PACKET and CONFIG_FILTER.  I think
CONFIG_FILTER went away.  I don't think any of the NETFILTER
suboptions are necc'y (at least they're built as modules on my
machine, isc dhcp is running, and none of them are loaded).

> When looking at the dhclient-script used by Fedora it sources files and
> uses outside functions so it was hard for me to trace down where the [

Oh, well, sure, you could /make/ it complicated if you really tried!

> x$var = x ] syntax comes from since I had never seen it before.  I never

This is a shell scripting convention.  "if [ $var = foo ]" fails with
a shell-level error in some shells where $var is empty (the parser
tries to read this as "if [ = foo ]").  So "x$foo = xbar" is
the canonical way to deal with this and all other edge cases.

I believe the linux dhclient-script started as a copy of one of the
bourne (not again) shell versions, and then developed some aspects
that relied on bash (I remember changing it to #!/bin/bash) through
submitted patches.

So if you're using the package's script as a starting point, and
not using bash in your initrd, you might want to look carefully
to make sure it's all bourne (not again) shell syntax.

-- 
David W. Hankins	"If you don't do it right the first time,
Software Engineer		you'll just have to do it again."
Internet Systems Consortium, Inc.	-- Jack T. Hankins


More information about the dhcp-users mailing list