Patch "geneve: Relax MTU constraints" has been added to the 4.4-stable tree

Patch "geneve: Relax MTU constraints" has been added to the 4.4-stable tree

[gregkh]

This is a note to let you know that I've just added the patch titled

    geneve: Relax MTU constraints

to the 4.4-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     geneve-relax-mtu-constraints.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@vger.kernel.org> know about it.


>From foo@baz Fri Jun 17 11:18:18 PDT 2016
From: David Wragg <david@weave.works>
Date: Fri, 3 Jun 2016 18:58:14 -0400
Subject: geneve: Relax MTU constraints

From: David Wragg <david@weave.works>

[ Upstream commit 55e5bfb53cff286c1c1ff49f51325dc15c7fea63 ]

Allow the MTU of geneve devices to be set to large values, in order to
exploit underlying networks with larger frame sizes.

GENEVE does not have a fixed encapsulation overhead (an openvswitch
rule can add variable length options), so there is no relevant maximum
MTU to enforce.  A maximum of IP_MAX_MTU is used instead.
Encapsulated packets that are too big for the underlying network will
get dropped on the floor.

Signed-off-by: David Wragg <david@weave.works>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/net/geneve.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -994,6 +994,17 @@ static netdev_tx_t geneve_xmit(struct sk
 	return geneve_xmit_skb(skb, dev, info);
 }
 
+static int geneve_change_mtu(struct net_device *dev, int new_mtu)
+{
+	/* GENEVE overhead is not fixed, so we can't enforce a more
+	 * precise max MTU.
+	 */
+	if (new_mtu < 68 || new_mtu > IP_MAX_MTU)
+		return -EINVAL;
+	dev->mtu = new_mtu;
+	return 0;
+}
+
 static int geneve_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb)
 {
 	struct ip_tunnel_info *info = skb_tunnel_info(skb);
@@ -1038,7 +1049,7 @@ static const struct net_device_ops genev
 	.ndo_stop		= geneve_stop,
 	.ndo_start_xmit		= geneve_xmit,
 	.ndo_get_stats64	= ip_tunnel_get_stats64,
-	.ndo_change_mtu		= eth_change_mtu,
+	.ndo_change_mtu		= geneve_change_mtu,
 	.ndo_validate_addr	= eth_validate_addr,
 	.ndo_set_mac_address	= eth_mac_addr,
 	.ndo_fill_metadata_dst	= geneve_fill_metadata_dst,


Patches currently in stable-queue which might be from david@weave.works are

queue-4.4/geneve-relax-mtu-constraints.patch
queue-4.4/vxlan-relax-mtu-constraints.patch
queue-4.4/vxlan-gre-geneve-set-a-large-mtu-on-ovs-created-tunnel-devices.patch