[SRU][F:linux-bluefield][PATCH 2/4] net: introduce per-netns netdevice notifiers

[Bodong Wang]

From: Jiri Pirko <jiri at mellanox.com>

BugLink: https://bugs.launchpad.net/bugs/2002361

Often the code for example in drivers is interested in getting notifier
call only from certain network namespace. In addition to the existing
global netdevice notifier chain introduce per-netns chains and allow
users to register to that. Eventually this would eliminate unnecessary
overhead in case there are many netdevices in many network namespaces.

Signed-off-by: Jiri Pirko <jiri at mellanox.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
(Backported from commit a30c7b429f2dd980202c912fcb76442364937b4d)
Signed-off-by: Bodong Wang <bodong at nvidia.com>
[Bodong: ignore dev_base_seq/ifindex/dev_unreg_count]

---
 include/linux/netdevice.h   |  3 ++
 include/net/net_namespace.h |  2 +
 net/core/dev.c              | 87 +++++++++++++++++++++++++++++++++++++
 3 files changed, 92 insertions(+)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 9936a946d6e8..73a0c82a2621 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2540,6 +2540,9 @@ const char *netdev_cmd_to_name(enum netdev_cmd cmd);
 
 int register_netdevice_notifier(struct notifier_block *nb);
 int unregister_netdevice_notifier(struct notifier_block *nb);
+int register_netdevice_notifier_net(struct net *net, struct notifier_block *nb);
+int unregister_netdevice_notifier_net(struct net *net,
+				      struct notifier_block *nb);
 
 struct netdev_notifier_info {
 	struct net_device	*dev;
diff --git a/include/net/net_namespace.h b/include/net/net_namespace.h
index 444af82e46da..cc20e2e14940 100644
--- a/include/net/net_namespace.h
+++ b/include/net/net_namespace.h
@@ -36,6 +36,7 @@
 #include <linux/ns_common.h>
 #include <linux/idr.h>
 #include <linux/skbuff.h>
+#include <linux/notifier.h>
 
 struct user_namespace;
 struct proc_dir_entry;
@@ -110,6 +111,7 @@ struct net {
 	u32			hash_mix;
 
 	struct net_device       *loopback_dev;          /* The loopback */
+	struct raw_notifier_head	netdev_chain;
 
 	/* core fib_rules */
 	struct list_head	rules_ops;
diff --git a/net/core/dev.c b/net/core/dev.c
index 9e7ef73679b7..58cf313c6bea 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1680,6 +1680,80 @@ int unregister_netdevice_notifier(struct notifier_block *nb)
 }
 EXPORT_SYMBOL(unregister_netdevice_notifier);
 
+/**
+ * register_netdevice_notifier_net - register a per-netns network notifier block
+ * @net: network namespace
+ * @nb: notifier
+ *
+ * Register a notifier to be called when network device events occur.
+ * The notifier passed is linked into the kernel structures and must
+ * not be reused until it has been unregistered. A negative errno code
+ * is returned on a failure.
+ *
+ * When registered all registration and up events are replayed
+ * to the new notifier to allow device to have a race free
+ * view of the network device list.
+ */
+
+int register_netdevice_notifier_net(struct net *net, struct notifier_block *nb)
+{
+	int err;
+
+	rtnl_lock();
+	err = raw_notifier_chain_register(&net->netdev_chain, nb);
+	if (err)
+		goto unlock;
+	if (dev_boot_phase)
+		goto unlock;
+
+	err = call_netdevice_register_net_notifiers(nb, net);
+	if (err)
+		goto chain_unregister;
+
+unlock:
+	rtnl_unlock();
+	return err;
+
+chain_unregister:
+	raw_notifier_chain_unregister(&netdev_chain, nb);
+	goto unlock;
+}
+EXPORT_SYMBOL(register_netdevice_notifier_net);
+
+/**
+ * unregister_netdevice_notifier_net - unregister a per-netns
+ *                                     network notifier block
+ * @net: network namespace
+ * @nb: notifier
+ *
+ * Unregister a notifier previously registered by
+ * register_netdevice_notifier(). The notifier is unlinked into the
+ * kernel structures and may then be reused. A negative errno code
+ * is returned on a failure.
+ *
+ * After unregistering unregister and down device events are synthesized
+ * for all devices on the device list to the removed notifier to remove
+ * the need for special case cleanup code.
+ */
+
+int unregister_netdevice_notifier_net(struct net *net,
+				      struct notifier_block *nb)
+{
+	int err;
+
+	rtnl_lock();
+	err = raw_notifier_chain_unregister(&net->netdev_chain, nb);
+	if (err)
+		goto unlock;
+
+	call_netdevice_unregister_net_notifiers(nb, net);
+
+unlock:
+	rtnl_unlock();
+	return err;
+}
+EXPORT_SYMBOL(unregister_netdevice_notifier_net);
+
 /**
  *	call_netdevice_notifiers_info - call all network notifier blocks
  *	@val: value passed unmodified to notifier function
@@ -1692,7 +1766,18 @@ EXPORT_SYMBOL(unregister_netdevice_notifier);
 static int call_netdevice_notifiers_info(unsigned long val,
 					 struct netdev_notifier_info *info)
 {
+	struct net *net = dev_net(info->dev);
+	int ret;
+
 	ASSERT_RTNL();
+
+	/* Run per-netns notifier block chain first, then run the global one.
+	 * Hopefully, one day, the global one is going to be removed after
+	 * all notifier block registrators get converted to be per-netns.
+	 */
+	ret = raw_notifier_call_chain(&net->netdev_chain, val, info);
+	if (ret & NOTIFY_STOP_MASK)
+		return ret;
 	return raw_notifier_call_chain(&netdev_chain, val, info);
 }
 
@@ -10149,6 +10234,8 @@ static int __net_init netdev_init(struct net *net)
 	if (net->dev_index_head == NULL)
 		goto err_idx;
 
+	RAW_INIT_NOTIFIER_HEAD(&net->netdev_chain);
+
 	return 0;
 
 err_idx:
-- 
2.27.0