Re: Automatically assign link local ipv4 address if dhcp fails



On Mon, Mar 20, 2017 at 11:21:22AM +0100, Viktor S. Wold Eide wrote:
On Wed, Mar 15, 2017 at 7:22 PM, Beniamino Galvani <bgalvani redhat com>
wrote:
I did install and test dhcpcd separately. It seems like dhcpcd works as
expected and provides ipv4 link local addresses when no dhcp reply is
received, as expected.
dhcpcd --version
dhcpcd 6.10.1
Copyright (c) 2006-2016 Roy Marples

I know that dhcpcd is no longer supported by NetworkManager, but I did test
anyway. I changed the dhcp client for NetworkManager by configuring
NetworkManager.conf:
dhcp=dhcpcd

The log reports the following, even if dhcpcd is installed and should be
available:
DHCP client 'dhcpcd' not available

Probably NM was not compiled with dhcpcd support.

As an alternative approach, I tried the NetworkManager hooking support, by
scripts in NetworkManager/dispatcher.d/
It does not seem possible to have a script invoked when for example dhcp
fails (only pre-up, up, dhcp renew, etc.). In other words, it seems a
script is only invoked when configuration is successful or renewed. Did I
overlook something?

AFAIK, it's not possible to implement such functionality using
dispatcher scripts because they are called after the connection
succeeds.

We have an open bugzilla [1] about supporting multiple IP methods
(DHCP, link-local, static) at the same type for a connection. Probably
that enhancement would solve your case, but at the moment I don't
think anybody is working on it.


Thanks for the info and the reference. Yes, that appears to be a reasonable
enhancement to resolve the issue.

It seems this issue with ipv4 link local addresses pops up from time to
time. I was hoping for some way to achieve the behavior, which from what I
understand is standard on (some) other platforms.

I agree, it's a useful feature, but the implementation will probably
require a rework of the device state machine, which I suspect is not
trivial.

Beniamino

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