LVS
lvs-users
Google
 
Web LinuxVirtualServer.org

Re: [lvs-users] annoying routing problem with a lvs cluster

To: LinuxVirtualServer.org users mailing list. <lvs-users@xxxxxxxxxxxxxxxxxxxxxx>, David Coulson <david@xxxxxxxxxxxxxxxx>
Subject: Re: [lvs-users] annoying routing problem with a lvs cluster
From: Dean Scothern <dean.scothern@xxxxxxxxxxxxxx>
Date: Thu, 8 Mar 2012 12:45:23 +0000
Hi,

It seems that the solution to my problem involves the use of 
/proc/sys/net/ipv4/conf/eth<n>/accept_local
For test purposes I've installed a more recent kernel that offers this 
functionality and I've been able to test it with a simple
Eth to eth external test.
So far I've been unsuccessful with the more complicated policy routing  
scenario.
Has anyone used accept_local with lvs nat to make something like the scenario I 
outlined  earlier work?

Best Regards


-----Original Message-----
From: lvs-users-bounces@xxxxxxxxxxxxxxxxxxxxxx 
[mailto:lvs-users-bounces@xxxxxxxxxxxxxxxxxxxxxx] On Behalf Of Dean Scothern
Sent: 02 March 2012 10:12
To: David Coulson
Cc: LinuxVirtualServer.org users mailing list.
Subject: Re: [lvs-users] annoying routing problem with a lvs cluster

Thanks,

It's worth a try but I think it will fall foul of the host route in the local 
table, which will apply first.

Best Regards



From: David Coulson [mailto:david@xxxxxxxxxxxxxxxx]
Sent: 01 March 2012 21:36
To: Dean Scothern
Cc: LinuxVirtualServer.org users mailing list.
Subject: Re: [lvs-users] annoying routing problem with a lvs cluster

Had a thought on this - You could use iptables to mark your return packet, then 
run it through a separate routing table based on a 'i ip ru add fwmark x table 
y' option. Your separate routing table would just have a default gw pointing to 
the VIP from your LVS cluster.


Not sure if that would work well, but it's worth a shot.


On Mar 1, 2012, at 8:59 AM, Dean Scothern wrote:


Thank you for your quick reply.

Whilst snat would work I would prefer not to use it as it hides the source ip 
of the packets, making applications that use ip access lists more problem atic 
to configure, eg mailservers. Eventually I would expand the clients to include 
other networks (internet), and would like log analysis to work.
I would prefer not to use a proxy and pass magic headers with the remote ip 
them either.
The link in question also probably cannot easily apply to redhat/centos 6 as 
they are based on 2.6.32 kernel and the link mentions 2.6.35, 2.6.36.
Reading further it might be possible to apply the patch set and rebuild the 
associated kernel modules.

To be honest I hoping for some route configuration magicry, I feel so close and 
surely there must be a way.

Many Thanks


From: David Coulson 
[mailto:david@xxxxxxxxxxxxxxxx]<mailto:[mailto:david@xxxxxxxxxxxxxxxx]>
Sent: 01 March 2012 13:04
To: LinuxVirtualServer.org<http://LinuxVirtualServer.org> users mailing list.
Cc: Dean Scothern
Subject: Re: [lvs-users] annoying routing problem with a lvs cluster

You need to SNAT real server traffic going to your real servers.

Quick google found this:

http://blog.loadbalancer.org/enabling-snat-in-lvs-xt_ipvs-and-iptables/

I'm presuming it's in mainline by now, but I know it's not in RHEL/SuSE yet.

David

On 3/1/12 7:55 AM, Dean Scothern wrote:

Hi,



I've been experimenting with a slightly non standard lvs cluster arrangement.



I have a set of combined real servers/real clients (each machine has both 
services and clients) and two machines running lvs as a cluster.



All machines are connected directly to the same two networks: frontend and 
backend.



The real servers/real clients connect to a service ip on the lvs machines on 
the frontend network.

The lvs machines run in masq mode and connect to the real servers/real clients 
on the backend network.

I've configured policy routing on the real servers/real clients backend 
interfaces to return traffic via a second gateway on the lvs hosts.



This works very well except when a real server/real client connects to its own 
backend interface via the lvs cluster ip.

I guessing that the local host route means that instead of returning the 
traffic via the backend gateway on the lvs it tries to go directly locally.

Tcpdump appears to support this guess and if I turn on martian logging  I can 
see the  traffic.



Initially I thought that reverse path filtering was preventing operation but 
the problem remained when it was disabled.

Turning on routing had not beneficial effect either.



Ideally I would like to setup routing to override the local table when the 
policy routing rules are applied, but I'm not sure how.

So far attempts to to do this have failed



Has anyone managed to  do this?



Its more of a routing question so apologies for being slightly off topic.



Best Regards



Dean Scothern

Dr Dean Scothern

Infrastructure

[Description: Eduserv]

E: 
dean.scothern@xxxxxxxxxxxxxx<mailto:dean.scothern@xxxxxxxxxxxxxx><mailto:forename.surname@xxxxxxxxxxxxxx><mailto:forename.surname@xxxxxxxxxxxxxx>



T: +44 (0)1225 474379



F: +44 (0)1225 474301



www.eduserv.org.uk<http://www.eduserv.org.uk><http://www.eduserv.org.uk/><http://www.eduserv.org.uk/>

Eduserv is a company limited by guarantee (registered in England & Wales, 
company number: 3763109) and a charity (charity number 1079456), whose 
registered office is at Royal Mead, Railway Place, Bath, BA1 1SR.











_______________________________________________

Please read the documentation before posting - it's available at:

http://www.linuxvirtualserver.org/



LinuxVirtualServer.org<http://LinuxVirtualServer.org> mailing list - 
lvs-users@xxxxxxxxxxxxxxxxxxxxxx<mailto:lvs-users@xxxxxxxxxxxxxxxxxxxxxx>

Send requests to 
lvs-users-request@xxxxxxxxxxxxxxxxxxxxxx<mailto:lvs-users-request@xxxxxxxxxxxxxxxxxxxxxx>

or go to http://lists.graemef.net/mailman/listinfo/lvs-users

_______________________________________________
Please read the documentation before posting - it's available at:
http://www.linuxvirtualserver.org/

LinuxVirtualServer.org mailing list - lvs-users@xxxxxxxxxxxxxxxxxxxxxx Send 
requests to lvs-users-request@xxxxxxxxxxxxxxxxxxxxxx
or go to http://lists.graemef.net/mailman/listinfo/lvs-users

_______________________________________________
Please read the documentation before posting - it's available at:
http://www.linuxvirtualserver.org/

LinuxVirtualServer.org mailing list - lvs-users@xxxxxxxxxxxxxxxxxxxxxx
Send requests to lvs-users-request@xxxxxxxxxxxxxxxxxxxxxx
or go to http://lists.graemef.net/mailman/listinfo/lvs-users

<Prev in Thread] Current Thread [Next in Thread>