LARTC - Jul 2007 - Hotplug and Multipath routes = lost route

I have 2 cable modems on a server (Linux 2.6.22). I use
multipath, so the route is something like this:

default 
        nexthop via 201.6.102.1  dev eth1 weight 256
        nexthop via 201.6.107.1  dev eth2 weight 128

	The first one (eth1) has a higher priority, then when it goes
down, I can "ifconfig" the interface eth1 down and Linux automatically
detects the "dead" gateway and change the route to the second one.

	Ok. The problem is that when one of the modems goes down, and
as they use the cdc_ether module to communicate via USB, the *entire*
route is erased because one of the devices doesn''t exist anymore. 

	It''s not a problem with hotplug, since it''s correct to remove
the device and the route that would go through it. But it would be nice
if the kernel just removed the specific "nexthop" which uses the
inactive device instead of removing the entire default route.

	Is there a way to tell the kernel to do that? Or to not remove
the route at all and just mark the "nexthop" with the inactive device
as dead and wait for it to come back alive?

	Thank you!

-- 
Linux 2.6.22: Holy Dancing Manatees, Batman!
http://www.lastfm.pt/user/danielfraga
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The Cranberries - "Dreams" (Everybody Else Is Doing It, So Why
Can''t
We?) Linux 2.6.22: Holy Dancing Manatees, Batman!
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On 7/23/2007 8:59 PM, Dâniel Fraga wrote:
> 	Is there a way to tell the kernel to do that? Or to not remove 
> the route at all and just mark the "nexthop" with the inactive
device
> as dead and wait for it to come back alive?
Do some reading about Julian Anastasov''s kernel patches, in particular 
the dead gateway detection patch (http://www.ssi.bg/~ja/dgd.txt).



Grant. . . .

On Mon, 23 Jul 2007 23:27:37 -0500
Grant Taylor <gtaylor@riverviewtech.net> wrote:
> Do some reading about Julian Anastasov''s kernel patches, in
> particular the dead gateway detection patch
> (http://www.ssi.bg/~ja/dgd.txt).
	Yes, I read that, but I don''t understand why those patches
aren''t merged in the kernel. Is there some kind of opposition to these
patches? Thanks.

-- 
Linux 2.6.22: Holy Dancing Manatees, Batman!
http://www.lastfm.pt/user/danielfraga
http://u-br.net
Sade - "Kiss of Life" (The Best of Sade - 2002)

On 07/25/07 01:58, Dâniel Fraga wrote:
> Yes, I read that, but I don''t understand why those patches
aren''t
> merged in the kernel. Is there some kind of opposition to these 
> patches?
Julian would be the better person to ask, but I''ll take a stab at it.

I don''t know of any opposition per say that is preventing the patches 
from going in to the main line kernel.  I think it has more to do with 
the need for the functionality verses the complexity both of which in 
conjunction with the fact that in the later 2.6 kernel networking and 
net filter code has undergone *MASSIVE* changes.  As such the demand to 
get the patches in to the kernel has probably not been high enough to 
warrant the effort, especially if the patches will apply cleanly to a 
stock kernel.
> Thanks.
*nod*



Grant. . . .