Re: Is there a way to pass my script to the DHCP client in NetworkManager?

[Dan Williams <dcbw redhat com>]

On Wed, 2012-06-27 at 16:14 -0600, Chengyu Fan wrote:
> 
> 
> On Wed, Jun 27, 2012 at 3:09 PM, Dan Williams <dcbw redhat com> wrote:
>         On Tue, 2012-06-26 at 11:34 -0600, Chengyu Fan wrote:
>         > Hi~
>         > I want to assign some job to my DHCP client (not just
>         configure the
>         > network interface). Ex: I let my DHCP client request some
>         private
>         > options(224-254), if I get those options another program
>         should run,
>         > otherwise just do the regular IP configuration.
>         >
>         >
>         > But the DHCP client is under the control of NetworkManager.
>         Does
>         > anyone know that if there is a way to pass a new script to
>         the DHCP
>         > client in the NetworkManager? Or if I can configure the
>         NetworkManager
>         > to create a new script?
>         
>         
>         If you have interface-specific options and you're on Fedora,
>         you can put
>         those options into interface config files,
>         eg /etc/dhclient-eth0.conf
>         or /etc/dhcp/dhclient-eth0.conf.  The other distros, for
>         whatever
>         reason, don't have interface-specific config files by
>         tradition, so you
>         all your interfaces have to share the config for your specific
>         options.
>         That goes in /etc/dhcp/dhclient.conf (Debian, Gentoo)
>         or /etc/dhclient.conf (SUSE).
>         
>         NM reads this file and copies its contents to the actual
>         config file it
>         sends to dhclient.  So feel free to drop your custom 'also
>         request'
>         stuff and custom 'option' formats there, and NM will use them.
>         
>         NM will call various scripts called "dispatcher" scripts on
>         network
>         events, like network up and network down.  So if you'd like
>         your script
>         to run when the network is ready (IP addressing complete) you
>         can do
>         that, and you'll also get all your DHCP options including the
>         private
>         ones in the script's environment.  See 'man NetworkManager'
>         for that.
> 
> 
> Thanks for your answer.
> I think this is what I need.
> 
> 
> One more question: 
> In DHCP, it is the "script-file" ( which is specified by -sf) to get
> the parameters and commit the actual configuration. I'd like to run my
> script or program after the network is ready, but how can I get the
> new DHCP options in "dispatcher"? Ex: $new_domain_name,
> $new_ip_address, et al.

They are given in the environment of the script, as described by 'man
NetworkManager', which says:

---
If the connection used DHCP for address configuration,  the  received
DHCP configuration is passed in the environment using standard DHCP
option names, prefixed with "DHCP4_", like "DHCP4_HOST_NAME=foobar".
---

The same also happens for DHCPv6, but obviously with a different prefix.

Dan