netdev - [PATCH net-next v4 10/10] netdev: update comments and explain idempotency and rtnl locking

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Message-Id: <1452352052-27574-11-git-send-email-hannes@stressinduktion.org>
Date:	Sat,  9 Jan 2016 16:07:32 +0100
From:	Hannes Frederic Sowa <hannes@...essinduktion.org>
To:	netdev@...r.kernel.org
Cc:	jesse@...nel.org
Subject: [PATCH net-next v4 10/10] netdev: update comments and explain idempotency and rtnl locking

Signed-off-by: Hannes Frederic Sowa <hannes@...essinduktion.org>
---
 include/linux/netdevice.h | 40 +++++++++++++++++++++++-----------------
 1 file changed, 23 insertions(+), 17 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 4d93d474f1cd44..0dc3e4617db6ef 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1006,31 +1006,36 @@ typedef u16 (*select_queue_fallback_t)(struct net_device *dev,
  *	not implement this, it is assumed that the hw is not able to have
  *	multiple net devices on single physical port.
  *
+ *	*** Offloading callbacks: ***
+ *
+ *	Notify drivers about a new type of offloading being requested
+ *	or removed from the driver. The type is based on the function
+ *	name, sa_family distinguishes between ipv4 and ipv6 and the
+ *	corresponding port number (for now only being UDP tunnel
+ *	protocol numbers) is signaled down to the driver.
+ *
+ *	Calls into the offloading callback functions are always done
+ *	with rtnl_lock held.
+ *
+ *	Further more, the callbacks can happen multiple times for the
+ *	same primitive to be installed, so it is forbidden to use
+ *	reference counting on the {offload_type, sa_family, port}
+ *	tuple because the driver might see multiple calls to those
+ *	functions for one installed primitive.
+ *
+ *	If the driver wants to get the current ports reprogrammed it
+ *	can simply call netdev_refresh_offloads with rtnl_lock held.
+ *
  * void (*ndo_add_vxlan_port)(struct  net_device *dev,
  *			      sa_family_t sa_family, __be16 port);
- *	Called by vxlan to notiy a driver about the UDP port and socket
- *	address family that vxlan is listnening to. It is called only when
- *	a new port starts listening. The operation is protected by the
- *	vxlan_net->sock_lock.
- *
  * void (*ndo_add_geneve_port)(struct net_device *dev,
  *			      sa_family_t sa_family, __be16 port);
- *	Called by geneve to notify a driver about the UDP port and socket
- *	address family that geneve is listnening to. It is called only when
- *	a new port starts listening. The operation is protected by the
- *	geneve_net->sock_lock.
- *
  * void (*ndo_del_geneve_port)(struct net_device *dev,
  *			      sa_family_t sa_family, __be16 port);
- *	Called by geneve to notify the driver about a UDP port and socket
- *	address family that geneve is not listening to anymore. The operation
- *	is protected by the geneve_net->sock_lock.
- *
  * void (*ndo_del_vxlan_port)(struct  net_device *dev,
  *			      sa_family_t sa_family, __be16 port);
- *	Called by vxlan to notify the driver about a UDP port and socket
- *	address family that vxlan is not listening to anymore. The operation
- *	is protected by the vxlan_net->sock_lock.
+ *
+ *
  *
  * void* (*ndo_dfwd_add_station)(struct net_device *pdev,
  *				 struct net_device *dev)
@@ -2224,6 +2229,7 @@ netdev_notifier_info_to_dev(const struct netdev_notifier_info *info)
 
 int call_netdevice_notifiers(unsigned long val, struct net_device *dev);
 
+/* Obviously the driver needs to hold rtnl_lock while calling this function. */
 static inline void netdev_refresh_offloads(struct net_device *netdev)
 {
 	call_netdevice_notifiers(NETDEV_REFRESH_OFFLOADS, netdev);
-- 
2.5.0