Re: How to conditionally compile plug-in source file to only support dhcpcd or dhclient?

[Dan Williams <dcbw redhat com>]

On Fri, 2010-06-04 at 21:50 +0800, Mu Qiao wrote:
> Hi Dan,
> 
> Gentoo NM plugin has to read dhcp hostname and clientid from
> configuration file of dhcpcd or dhclient.
> 
> Currently I just test whether the configuration file of dhcpcd or
> dhclient exists to determine which one is used. Could I make use of the
> switch "--with-dhcpcd=yes" to enable conditional compilation?
> for example:
> #ifdef DHCPCD_PATH
> //handling dhcpcd configuration file
> #else
> //handling dhclient configuration file
> #endif
> 
> If this could be achieved, what should follow "#ifdef"? Should I include
> any header file?

I changed NM a few months ago to allow either DHCP client at runtime, so
it's possible that support for *both* is compiled in.  It's then
selectable via the config file /etc/NetworkManager/NetworkManager.conf
or (older name) /etc/NetworkManager/nm-system-settings.conf.  I think at
this point, you should probably look for that file and use the DHCP
client listed there.  The actual code that determines which DHCP client
to use at run time is in:

src/dhcp-manager/nm-dhcp-manager.c::get_client_type()

It's probably sufficient to grab the variable out of the .conf file, and
if that doesn't exist or isn't valid, use dhclient (if it's installed)
and then fallback dhcpcd (if it's installed).

Dan