linux-kernel - [ 69/85] ipv4: Dont create nh exeption when the device mtu is smaller than the reported pmtu

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Date:	Thu, 25 Oct 2012 17:06:27 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	alan@...rguk.ukuu.org.uk,
	Steffen Klassert <steffen.klassert@...unet.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [ 69/85] ipv4: Dont create nh exeption when the device mtu is smaller than the reported pmtu

3.6-stable review patch.  If anyone has any objections, please let me know.

------------------


From: Steffen Klassert <steffen.klassert@...unet.com>

[ Upstream commit 7f92d334ba19a0d8e96f8f8f092219553367d921 ]

When a local tool like tracepath tries to send packets bigger than
the device mtu, we create a nh exeption and set the pmtu to device
mtu. The device mtu does not expire, so check if the device mtu is
smaller than the reported pmtu and don't crerate a nh exeption in
that case.

Signed-off-by: Steffen Klassert <steffen.klassert@...unet.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/route.c |    3 +++
 1 file changed, 3 insertions(+)

--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -909,6 +909,9 @@ static void __ip_rt_update_pmtu(struct r
 	struct dst_entry *dst = &rt->dst;
 	struct fib_result res;
 
+	if (dst->dev->mtu < mtu)
+		return;
+
 	if (mtu < ip_rt_min_pmtu)
 		mtu = ip_rt_min_pmtu;
 


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