netdev - [RFC PATCH] net: introduce IFF_NO_RX

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Message-Id: <ce8cd4c1f5150c9b913e81914f222a837c1bee54.1520351254.git.pabeni@redhat.com>
Date:   Tue,  6 Mar 2018 16:53:12 +0100
From:   Paolo Abeni <pabeni@...hat.com>
To:     netdev@...r.kernel.org
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Jiri Benc <jbenc@...hat.com>
Subject: [RFC PATCH] net: introduce IFF_NO_RX_HANDLER

Some network devices - notably ipvlan slave - are not compatible with
any kind of rx_handler. Currently the hook can be installed but any
configuration (bridge, bond, macsec, ...) is nonfunctional.

This change allocates a priv_flag bit to mark such devices and explicitly
forbid installing a rx_handler if such bit is set. The new bit is used
by ipvlan slave device.

Signed-off-by: Paolo Abeni <pabeni@...hat.com>
---
Notes:
- this is on top of "net: unpollute priv_flags space"
- accocating a new bit instead of reusing IFF_IPVLAN, to allow
  other driver leveraging it, if need arises
---
 drivers/net/ipvlan/ipvlan_main.c | 2 ++
 include/linux/netdevice.h        | 3 +++
 net/core/dev.c                   | 3 +++
 3 files changed, 8 insertions(+)

diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 23fd5ab180e8..743d37fb034a 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -604,6 +604,8 @@ int ipvlan_link_new(struct net *src_net, struct net_device *dev,
 	 */
 	memcpy(dev->dev_addr, phy_dev->dev_addr, ETH_ALEN);
 
+	dev->priv_flags |= IFF_NO_RX_HANDLER;
+
 	err = register_netdevice(dev);
 	if (err < 0)
 		return err;
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 95a613a7cc1c..4f3d2a0e2ad6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1390,6 +1390,7 @@ struct net_device_ops {
  * @IFF_PHONY_HEADROOM: the headroom value is controlled by an external
  *	entity (i.e. the master device for bridged veth)
  * @IFF_MACSEC: device is a MACsec device
+ * @IFF_NO_RX_HANDLER: device doesn't support the rx_handler hook
  */
 enum netdev_priv_flags {
 	IFF_802_1Q_VLAN			= 1<<0,
@@ -1418,6 +1419,7 @@ enum netdev_priv_flags {
 	IFF_RXFH_CONFIGURED		= 1<<23,
 	IFF_PHONY_HEADROOM		= 1<<24,
 	IFF_MACSEC			= 1<<25,
+	IFF_NO_RX_HANDLER		= 1<<26,
 };
 
 #define IFF_802_1Q_VLAN			IFF_802_1Q_VLAN
@@ -1445,6 +1447,7 @@ enum netdev_priv_flags {
 #define IFF_TEAM			IFF_TEAM
 #define IFF_RXFH_CONFIGURED		IFF_RXFH_CONFIGURED
 #define IFF_MACSEC			IFF_MACSEC
+#define IFF_NO_RX_HANDLER		IFF_NO_RX_HANDLER
 
 /**
  *	struct net_device - The DEVICE structure.
diff --git a/net/core/dev.c b/net/core/dev.c
index 5bdcc5a161fe..30078f69a571 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -4351,6 +4351,9 @@ int netdev_rx_handler_register(struct net_device *dev,
 	if (netdev_is_rx_handler_busy(dev))
 		return -EBUSY;
 
+	if (dev->priv_flags & IFF_NO_RX_HANDLER)
+		return -EINVAL;
+
 	/* Note: rx_handler_data must be set before rx_handler */
 	rcu_assign_pointer(dev->rx_handler_data, rx_handler_data);
 	rcu_assign_pointer(dev->rx_handler, rx_handler);
-- 
2.14.3