Bug 554742 - Using other dhcp client than ISC dhclient
Using other dhcp client than ISC dhclient
Product: Fedora
Classification: Fedora
Component: dhcp (Show other bugs)
All Linux
low Severity high
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Assigned To: Jiri Popelka
Fedora Extras Quality Assurance
Depends On:
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Reported: 2010-01-12 09:40 EST by Aurélien Cedeyn
Modified: 2010-06-28 11:37 EDT (History)
5 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
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Clone Of:
Last Closed: 2010-06-28 11:37:03 EDT
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Attachments (Terms of Use)
Src rpm with ifup-eth/ifdown-eth patches (1.46 MB, application/x-rpm)
2010-01-12 09:40 EST, Aurélien Cedeyn
no flags Details
configuration with other dhcp client (dhcpcd) (57 bytes, text/plain)
2010-01-15 05:07 EST, Aurélien Cedeyn
no flags Details
configuration with dhclient (no changes) (38 bytes, text/plain)
2010-01-15 05:08 EST, Aurélien Cedeyn
no flags Details

  None (edit)
Description Aurélien Cedeyn 2010-01-12 09:40:37 EST
Created attachment 383249 [details]
Src rpm with ifup-eth/ifdown-eth patches

Description of problem:
dhclient-4.1.0 does not support infiniband hardware so I wanted to switch to another dhcp client. In fact, dhcpcd supports this hardware.
I started to build a package for dhcpcd. But here is the issue :
 It seems that /etc/sysconfig/network-scripts/{ifup,ifdown}-eth doesn't manage any other client than dhclient.

Version-Release number of selected component (if applicable):

How reproducible:
Trying to use another dhcp client.

Steps to Reproduce:
1. Install another dhcp client
2. Try to use it with ifup/ifdown
Actual results:
Doesn't work until rewriting all /etc/sysconfig/network-scripts/{ifup,down}-eth, so this file will conflict with any other package providing a dhcp client.

Expected results:
Only provide a script which will manage the installed client.

Additional info:
I send you patches to be able to use any other dhcp client inside the startup scripts ifup-eth.

What provides thoses patches :
- Split ifup-eth in ifup-eth and ifup-dhclient
- New option in ifcfg-${DEVICE}
  * DHCP_CLIENT : name of the dhcp client

How it works :
- if DHCP_CLIENT is specified, and /etc/sysconfig/network-scripts/ifup-${DHCLIENT} is runnable, launch it with ${DEVICE} as parameter
- else run etc/sysconfig/network-scripts/ifup-dhclient ${DEVICE}

I don't know if this is the good way to report this issue, if I'm wrong, let me know.


Comment 1 Bill Nottingham 2010-01-12 11:42:14 EST
The far far simpler solution would be to make dhclient work on infiniband hardware. Assigning there.
Comment 2 Aurélien Cedeyn 2010-01-13 05:05:33 EST
Yes, you're right, but patching dhclient is not so easy.
I used dhclient but the patching method provided by ofed is not working anymore for dhclient-4.1.0. That's why I wanted to use a infiniband compliant client.
Comment 3 Aurélien Cedeyn 2010-01-14 04:20:10 EST
I don't know if isc dhcp wants to support infiniband devices, so I think that what I proposed the src.rpm attached before does not change the default behaviour of the current initscripts and could help if the redhat community wants one day offer multiple dhcp client.
So please just look what changes in the patch that I sent and give me feedback.
The initscripts modification is not so hard and could give a new functionality.
Comment 4 Bill Nottingham 2010-01-14 11:07:45 EST
Supporting random different clients with disparate features is a good way to cause weird bugs that only happen with one or the other, and it's done in such a way that you're asking the users often for information that they don't necessarily know. Then you get in the question of do you install all clients just so it's there in case someone hits the one usage case that's only supported by one client, etc.
Comment 5 Aurélien Cedeyn 2010-01-15 05:04:52 EST
I do not ask to support random dhcp client, I just say that with a few changes in the initscripts, advanced users, by changing their /etc/sysconfig/network-scripts/ifcfg-${DEVICE} by hand and by installing a new dhcp client (of course), will be able to change the default dhcp client.

For a standard user which didn't change anything by hand, nothing will change.

My changes did not modify the default behaviour :
If there is no specified option, the default behaviour is kept (using dhclient) even if another dhcp client is installed.

With this, you just have to support dhclient and you will provide a clean way to manage the dynamic IP allocation.
Comment 6 Aurélien Cedeyn 2010-01-15 05:07:21 EST
Created attachment 384554 [details]
configuration with other dhcp client (dhcpcd)
Comment 7 Aurélien Cedeyn 2010-01-15 05:08:21 EST
Created attachment 384556 [details]
configuration with dhclient (no changes)
Comment 8 Bill Nottingham 2010-01-15 13:36:18 EST
This can be accomplished with no initscripts changes (AFAICT) by writing your own 'ifup-dhcpcd' and adding DEVICETYPE=dhcpcd to your ifcfg file.
Comment 9 Aurélien Cedeyn 2010-01-18 03:55:41 EST
Indeed, but DEVICETYPE=dhcpcd goes against the global meaning of this variable.
That's why I think that it would be better to split the dhcp management inside the ifup-eth script into two scripts.

Maybe if{up,down}-dhclient are not a good filenames, {start,stop}-dhclient would be better to respect the meaning of ifup-* scripts.

Another point is that if I copy/paste the ifup-eth in ifup-dhcpcd and modify what I need to manage dhcpcd, when ifup-eth will change, I will need to follow these changes and merge it inside this script (ifup-eth doesn't only dhcp requests, it also manages bridges and more)... The work will be done twice.
Comment 10 Bill Nottingham 2010-01-18 12:35:14 EST
The point is... supporting multiple DHCP clients in the main scripts is a fool's errand - you then have to manage the complexities of all of them, for a much higher engineering cost than just fixing the deficiencies of one. For example, what happens when you want to do DHCPv6 over IB?

(See https://www.redhat.com/archives/fedora-devel-list/2008-January/msg00861.html for more discussion of this.)

The DEVICETYPE=dhcpcd is meant as a band-aid that you can use while dhclient is getting fixed.
Comment 11 Aurélien Cedeyn 2010-01-19 06:00:31 EST
> The point is... supporting multiple DHCP clients in the main scripts is a
> fool's errand

Again : I do not ask to support multiple dhcp client in the initscripts. I just ask to split the big ifup-eth into ifup-eth (containing what depends on all eth setup except the dhcp allocation) and {ifup/start}-dhclient (containing what manages the dhcp part). There is no other cost but to package 2 more file...

> what happens when you want to do DHCPv6 over IB?
I don't get this point... On your side, nothing has to be done.
On the current script, dhclient AND dhcp6c will be launched. I don't know if dhcp6c supports IB hardware, but if I want to use dhcpcd and dhcp6c, it will be possible without any modification in the ifup-eth script.

If dhcp6c doesn't support IB but another one does, with this patch I will be able to switch to another dhcp6 client without modifying ifup-eth... And without bothering you...
Comment 12 Bug Zapper 2010-04-28 07:42:10 EDT
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Comment 13 Bug Zapper 2010-06-28 11:37:03 EDT
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