netdev - Re: Multicast routing stops functioning after 4G multicast packets recived.

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Message-ID: <20140104233840.GD25828@order.stressinduktion.org>
Date:	Sun, 5 Jan 2014 00:38:40 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	Julian Anastasov <ja@....bg>
Cc:	Bob Falken <NetFestivalHaveFun@....com>, netdev@...r.kernel.org
Subject: Re: Multicast routing stops functioning after 4G multicast packets recived.

On Sat, Jan 04, 2014 at 09:55:51PM +0200, Julian Anastasov wrote:
> 
> 	Hello,
> 
> On Thu, 19 Dec 2013, Bob Falken wrote:
> 
> > Hello, I have an issue after kernel 2.6.37 and above.
> > If i roll back to kernel 2.6.36.4 everything is fine.
> > if recive more than 4294967295 multicast packets, the kernel does not register the multicast packets. and multicast routing does not functioning.
> 
> ...
> 
> > I think there might be a variable in the kernel that get overflown. though i cannot be sure as im not a programmer. 
> > 
> > Let me know if you need more debug information.
> > 
> > Please help.  
> 
> 	As Hannes guessed, may be it is really the missing
> flags = FIB_LOOKUP_NOREF in ipmr_fib_lookup() when calling
> fib_rules_lookup(), we have an atomic_inc_not_zero() there that
> can stop to work after 4G lookups when rule's refcnt reaches 0.
> As result, fib_rules_lookup() can start to return -ESRCH.

I guess we should just try. I somehow forgot to look after that. Thanks
for reminding, Julian.

Bob, can you try with this patch again?

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index 421a249..b9b3472 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -157,9 +157,12 @@ static struct mr_table *ipmr_get_table(struct net *net, u32 id)
 static int ipmr_fib_lookup(struct net *net, struct flowi4 *flp4,
 			   struct mr_table **mrt)
 {
-	struct ipmr_result res;
-	struct fib_lookup_arg arg = { .result = &res, };
 	int err;
+	struct ipmr_result res;
+	struct fib_lookup_arg arg = {
+		.result = &res,
+		.flags = FIB_LOOKUP_NOREF,
+	};
 
 	err = fib_rules_lookup(net->ipv4.mr_rules_ops,
 			       flowi4_to_flowi(flp4), 0, &arg);
--
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