diff mbox

[net] vlan: use a valid default mtu value for vlan over macsec

Message ID 909348fc51775dc7070b528a7492632e53400412.1468511497.git.pabeni@redhat.com
State Accepted, archived
Delegated to: David Miller
Headers show

Commit Message

Paolo Abeni July 14, 2016, 4 p.m. UTC 
macsec can't cope with mtu frames which need vlan tag insertion, and
vlan device set the default mtu equal to the underlying dev's one.
By default vlan over macsec devices use invalid mtu, dropping
all the large packets.
This patch adds a netif helper to check if an upper vlan device
needs mtu reduction. The helper is used during vlan devices
initialization to set a valid default and during mtu updating to
forbid invalid, too bit, mtu values.
The helper currently only check if the lower dev is a macsec device,
if we get more users, we need to update only the helper (possibly
reserving an additional IFF bit).

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 include/linux/netdevice.h |  7 +++++++
 net/8021q/vlan_dev.c      | 10 ++++++----
 net/8021q/vlan_netlink.c  |  7 +++++--
 3 files changed, 18 insertions(+), 6 deletions(-)

Comments

David Miller July 17, 2016, 3:16 a.m. UTC | #1 
From: Paolo Abeni <pabeni@redhat.com>
Date: Thu, 14 Jul 2016 18:00:10 +0200

> macsec can't cope with mtu frames which need vlan tag insertion, and
> vlan device set the default mtu equal to the underlying dev's one.
> By default vlan over macsec devices use invalid mtu, dropping
> all the large packets.
> This patch adds a netif helper to check if an upper vlan device
> needs mtu reduction. The helper is used during vlan devices
> initialization to set a valid default and during mtu updating to
> forbid invalid, too bit, mtu values.
> The helper currently only check if the lower dev is a macsec device,
> if we get more users, we need to update only the helper (possibly
> reserving an additional IFF bit).
> 
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

Applied and queued up for -stable.
diff mbox

Patch

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 49736a3..8b24952 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -4175,6 +4175,13 @@  static inline void netif_keep_dst(struct net_device *dev)
 	dev->priv_flags &= ~(IFF_XMIT_DST_RELEASE | IFF_XMIT_DST_RELEASE_PERM);
 }
 
+/* return true if dev can't cope with mtu frames that need vlan tag insertion */
+static inline bool netif_reduces_vlan_mtu(struct net_device *dev)
+{
+	/* TODO: reserve and use an additional IFF bit, if we get more users */
+	return dev->priv_flags & IFF_MACSEC;
+}
+
 extern struct pernet_operations __net_initdata loopback_net_ops;
 
 /* Logging, debugging and troubleshooting/diagnostic helpers. */
diff --git a/net/8021q/vlan_dev.c b/net/8021q/vlan_dev.c
index c8f422c..fbfacd5 100644
--- a/net/8021q/vlan_dev.c
+++ b/net/8021q/vlan_dev.c
@@ -146,10 +146,12 @@  static netdev_tx_t vlan_dev_hard_start_xmit(struct sk_buff *skb,
 
 static int vlan_dev_change_mtu(struct net_device *dev, int new_mtu)
 {
-	/* TODO: gotta make sure the underlying layer can handle it,
-	 * maybe an IFF_VLAN_CAPABLE flag for devices?
-	 */
-	if (vlan_dev_priv(dev)->real_dev->mtu < new_mtu)
+	struct net_device *real_dev = vlan_dev_priv(dev)->real_dev;
+	unsigned int max_mtu = real_dev->mtu;
+
+	if (netif_reduces_vlan_mtu(real_dev))
+		max_mtu -= VLAN_HLEN;
+	if (max_mtu < new_mtu)
 		return -ERANGE;
 
 	dev->mtu = new_mtu;
diff --git a/net/8021q/vlan_netlink.c b/net/8021q/vlan_netlink.c
index c92b52f..1270207 100644
--- a/net/8021q/vlan_netlink.c
+++ b/net/8021q/vlan_netlink.c
@@ -118,6 +118,7 @@  static int vlan_newlink(struct net *src_net, struct net_device *dev,
 {
 	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
 	struct net_device *real_dev;
+	unsigned int max_mtu;
 	__be16 proto;
 	int err;
 
@@ -144,9 +145,11 @@  static int vlan_newlink(struct net *src_net, struct net_device *dev,
 	if (err < 0)
 		return err;
 
+	max_mtu = netif_reduces_vlan_mtu(real_dev) ? real_dev->mtu - VLAN_HLEN :
+						     real_dev->mtu;
 	if (!tb[IFLA_MTU])
-		dev->mtu = real_dev->mtu;
-	else if (dev->mtu > real_dev->mtu)
+		dev->mtu = max_mtu;
+	else if (dev->mtu > max_mtu)
 		return -EINVAL;
 
 	err = vlan_changelink(dev, tb, data);