STEP 2, fixing dhclient behaviour with multiple interfaces

Dominic Mitchell dom at
Tue Jul 29 04:51:08 PDT 2003

On Tue, Jul 29, 2003 at 09:56:48AM +0200, Martin Blapp wrote:
> I't is my goal to make dhclient really functional, so it can not only
> be used with one interface, but several.

Yay!  This bites me badly on my laptop with a permanent fxp0 and a
sometimes-present wi0.

> On a well known OS this works just fine. A first interface gets
> initialized and the GW gets set as usual. But if a second interface
> gets added, and the first one is still active and has a working lease,
> the GW will not be overwriten. If you remove now the first interface,
> the default GW changes to the one of the second interface.
> "X" = Link on IF
> "+" = Interface gets added or has new link
> "-" = Interface gets removed or lost link
> IF1 IF2 GW1 GW2
> ---------------
> X       X
> X   +   X
> -   X       X
> +   X       X
> Too this functionality to dhclient, there is only one way to do it. the
> ISC-dhclient package offers a OMAPI Command Shell omsshell(1). There you
> can add new interfaces or even remove existing ones.
> The work that needs to be done is:
> - Adding a unix domain socket to OMAPI, so root (or a choosen user)
>   can access dhclient (or dhcpd) on the local machine without authentification.

You can get omshell working without auth over tcp/ip - I managed this
today when playing.  But a unix domain socket would be nicer because the
dhclient server binds to INADDR_ANY by default.

> - Providing the omshell scripts for adding and removing interfaces, adding
>   new default gateways on interface removal etc ...
> - Change our infrastructure (devd, rc.d/dhclient script) to use them.
> If there are other ideas, I'm open to them.

At present, dhclient gets given a list of interfaces at startup-time.
Would it be better to start it in "no-interfaces" mode (-n -w) and
dynamically add /all/ interfaces using omshell?

Another (loosely related) thing is that we should be able to use omshell
to tell dhclient to pause before going into suspend.  This is hinted at
in the dhclient man page, but it would be good to get it into the
standard infrastructure.


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