datapath: Consider tunnels to have no MTU, fixing jumbo frame support.

Until now, tunnel vports have had a specific MTU, in the same way that
ordinary network devices have an MTU, but treating them this way does not
always make sense.  For example, consider a datapath that has three ports:
the local port, a GRE tunnel to another host, and a physical port.  If
the physical port is configured with a jumbo MTU, it should be possible to
send jumbo packets across the tunnel: the tunnel can do fragmentation or
the physical port traversed by the tunnel might have a jumbo MTU.

However, until now, tunnels always had a 1500-byte MTU by default.  It
could be adjusted using ODP_VPORT_MTU_SET, but nothing actually did this.
One alternative would be to make ovs-vswitchd able to set the vport's MTU.
This commit, however, takes a different approach, of dropping the concept
of MTU entirely for tunnel vports.  This also solves the problem described
above, without making any additional work for anyone.

I tested that, without this change, I could not send 1600-byte "pings"
between two machines whose NICs had 2000-byte MTUs that were connected to
vswitches that were in turn connected over GRE tunnels with the default
1500-byte MTU.  With this change, it worked OK, regardless of the MTU of
the network traversed by the GRE tunnel.

This patch also makes "patch" ports MTU-less.

It might make sense to remove vport_set_mtu() and the associated callback
now, since ordinary network devices are the only vports that support it
now.

Signed-off-by: Ben Pfaff <blp@nicira.com>
Suggested-by: Jesse Gross <jesse@nicira.com>
Acked-by: Jesse Gross <jesse@nicira.com>
Bug #3728.

1 files changed, 0 insertions, 29 deletions

diff --git a/datapath/vport-patch.c b/datapath/vport-patch.c
index 7dfea6ba6..1c4d2c5e2 100644
--- a/datapath/vport-patch.c
+++ b/datapath/vport-patch.c
@@ -20,7 +20,6 @@ struct patch_config {
 
 	char peer_name[IFNAMSIZ];
 	unsigned char eth_addr[ETH_ALEN];
-	unsigned int mtu;
 };
 
 struct patch_vport {
@@ -148,10 +147,6 @@ static struct vport *patch_create(const struct vport_parms *parms)
 
 	vport_gen_rand_ether_addr(patchconf->eth_addr);
 
-	/* Make the default MTU fairly large so that it doesn't become the
-	 * bottleneck on systems using jumbo frames. */
-	patchconf->mtu = 65535;
-
 	rcu_assign_pointer(patch_vport->patchconf, patchconf);
 
 	peer_name = patchconf->peer_name;
@@ -236,22 +231,6 @@ static void update_peers(const char *name, struct vport *vport)
 	}
 }
 
-static int patch_set_mtu(struct vport *vport, int mtu)
-{
-	struct patch_vport *patch_vport = patch_vport_priv(vport);
-	struct patch_config *patchconf;
-
-	patchconf = kmemdup(rtnl_dereference(patch_vport->patchconf),
-			  sizeof(struct patch_config), GFP_KERNEL);
-	if (!patchconf)
-		return -ENOMEM;
-
-	patchconf->mtu = mtu;
-	assign_config_rcu(vport, patchconf);
-
-	return 0;
-}
-
 static int patch_set_addr(struct vport *vport, const unsigned char *addr)
 {
 	struct patch_vport *patch_vport = patch_vport_priv(vport);
@@ -289,12 +268,6 @@ static int patch_get_options(const struct vport *vport, struct sk_buff *skb)
 	return nla_put_string(skb, ODP_PATCH_ATTR_PEER, patchconf->peer_name);
 }
 
-static int patch_get_mtu(const struct vport *vport)
-{
-	const struct patch_vport *patch_vport = patch_vport_priv(vport);
-	return rcu_dereference_rtnl(patch_vport->patchconf)->mtu;
-}
-
 static int patch_send(struct vport *vport, struct sk_buff *skb)
 {
 	struct patch_vport *patch_vport = patch_vport_priv(vport);
@@ -319,7 +292,6 @@ const struct vport_ops patch_vport_ops = {
 	.exit		= patch_exit,
 	.create		= patch_create,
 	.destroy	= patch_destroy,
-	.set_mtu	= patch_set_mtu,
 	.set_addr	= patch_set_addr,
 	.get_name	= patch_get_name,
 	.get_addr	= patch_get_addr,
@@ -328,6 +300,5 @@ const struct vport_ops patch_vport_ops = {
 	.get_dev_flags	= vport_gen_get_dev_flags,
 	.is_running	= vport_gen_is_running,
 	.get_operstate	= vport_gen_get_operstate,
-	.get_mtu	= patch_get_mtu,
 	.send		= patch_send,
 };