Re: [PATCH] Disable multipath cache routing

Re: [PATCH] Disable multipath cache routing

[pravin b shelar]

Chris Wedgwood wrote:
> Apparently IP_ROUTE_MULTIPATH_CACHED isn't entirely safe to use and
> will oops the kernel "sooner or later".  The Kconfig comment says
> EXPERIMENTAL but it's not.
>
> Let's go further and mark it BROKEN for now (leaving the comment as-is
> though).  If nobody steps up to resurrect this code we can discuss
> removing it entirely.
I am working on Linux multipath networking and I will like to fix bugs 
related to equal cost multipath caching support.

So can u send me following information about the oops :-

kernel version
config file
routing table setup ( any multipath setup information. e.g. multipath 
algorithm options)
iptable configuration
forwarding information
what was the oops message & what triggered that?

This will help me understand the problem.

Thanks & Regards,
Pravin.

Re: [PATCH] Disable multipath cache routing

[Chris Wedgwood]

(cc' list exploded to include various people who might not be reading
     netdev, sorry about that)

On Sat, May 20, 2006 at 03:11:20PM +0530, pravin b shelar wrote:
> I am working on Linux multipath networking and I will like to fix
> bugs related to equal cost multipath caching support.

My experience here is limited to having been using as and finding it
was creating erroneous routes which DaveM correctly guessed was the
result of CONFIG_IP_MULTIPATH_CACHED being enabled.

Looking over ipv4/route.c there is a fair bit of complex code to audit
(fib_semantics.c also needs to be checked, but it's not very involved)
so perhaps if you or someone else who understand this code well is
interested that would be a good place to start a code audit?

I see also a patch from Herbert Xu about disabling this on the input
path (the patch isn't present in the tree right now, I'm not sure if
it was revert/fixed or just never merged).  Perhaps he can also point
out what wrong here?

  http://oss.sgi.com/archives/netdev/2005-04/msg00232.html

Anyhow, the code as-is hasn't been maintained for a long time except
for a few minor blips (I'm using hg's annotate to find those and have
included those people on the cc' list as presumably there are using
these features and might have useful input).

[CFT] CONFIG_IP_ROUTE_MULTIPATH_CACHED [was Re: [PATCH] Disable multipath cache routing ]

[Ravikiran G Thirumalai]

On Sat, May 20, 2006 at 01:51:45PM -0700, Chris Wedgwood wrote:
> ...
> Anyhow, the code as-is hasn't been maintained for a long time except
> for a few minor blips (I'm using hg's annotate to find those and have
> included those people on the cc' list as presumably there are using
> these features and might have useful input).

We are interested in keeping CONFIG_IP_ROUTE_MULTIPATH_CACHED,
as this enables us to do node aware multipathing
	http://lkml.org/lkml/2006/3/22/13
Hence, we are also interested in stabilizing MULTIPATH_CACHED.  Please send
bug reports with the test case scenario to myself and Pravin at 
kiran@scalex86.org and pravin.shelar@calsoftinc.com

Thanks,
Kiran

[PATCH] Disable multipath cache routing

[Chris Wedgwood]

Apparently IP_ROUTE_MULTIPATH_CACHED isn't entirely safe to use and
will oops the kernel "sooner or later".  The Kconfig comment says
EXPERIMENTAL but it's not.

Let's go further and mark it BROKEN for now (leaving the comment as-is
though).  If nobody steps up to resurrect this code we can discuss
removing it entirely.


Signed-off-by: Chris Wedgwood <cw@f00f.org>

diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig
index 011cca7..3a08b9e 100644
--- a/net/ipv4/Kconfig
+++ b/net/ipv4/Kconfig
@@ -124,7 +124,7 @@ config IP_ROUTE_MULTIPATH
 
 config IP_ROUTE_MULTIPATH_CACHED
 	bool "IP: equal cost multipath with caching support (EXPERIMENTAL)"
-	depends on IP_ROUTE_MULTIPATH
+	depends on IP_ROUTE_MULTIPATH && BROKEN
 	help
 	  Normally, equal cost multipath routing is not supported by the
 	  routing cache. If you say Y here, alternative routes are cached