[PATCH net-next v2 3/5] nexthop: add support for notifiers

[Roopa Prabhu]

From: Roopa Prabhu <ro...@cumulusnetworks.com>

This patch adds nexthop add/del notifiers. To be used by
vxlan driver in a later patch. Could possibly be used by
switchdev drivers in the future.

Signed-off-by: Roopa Prabhu <ro...@cumulusnetworks.com>
---
 include/net/netns/nexthop.h |  1 +
 include/net/nexthop.h       | 12 ++++++++++++
 net/ipv4/nexthop.c          | 26 ++++++++++++++++++++++++++
 3 files changed, 39 insertions(+)

diff --git a/include/net/netns/nexthop.h b/include/net/netns/nexthop.h
index c712ee5..1937476 100644
--- a/include/net/netns/nexthop.h
+++ b/include/net/netns/nexthop.h
@@ -14,5 +14,6 @@ struct netns_nexthop {
 
        unsigned int            seq;            /* protected by rtnl_mutex */
        u32                     last_id_allocated;
+       struct atomic_notifier_head notifier_chain;
 };
 #endif
diff --git a/include/net/nexthop.h b/include/net/nexthop.h
index d929c98..4c95168 100644
--- a/include/net/nexthop.h
+++ b/include/net/nexthop.h
@@ -10,6 +10,7 @@
 #define __LINUX_NEXTHOP_H
 
 #include <linux/netdevice.h>
+#include <linux/notifier.h>
 #include <linux/route.h>
 #include <linux/types.h>
 #include <net/ip_fib.h>
@@ -102,6 +103,17 @@ struct nexthop {
        };
 };
 
+enum nexthop_event_type {
+       NEXTHOP_EVENT_ADD,
+       NEXTHOP_EVENT_DEL
+};
+
+int call_nexthop_notifier(struct notifier_block *nb, struct net *net,
+                         enum nexthop_event_type event_type,
+                         struct nexthop *nh);
+int register_nexthop_notifier(struct net *net, struct notifier_block *nb);
+int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb);
+
 /* caller is holding rcu or rtnl; no reference taken to nexthop */
 struct nexthop *nexthop_find_by_id(struct net *net, u32 id);
 void nexthop_free_rcu(struct rcu_head *head);
diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index bf91edc..39f4957 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -36,6 +36,17 @@ static const struct nla_policy rtm_nh_policy[NHA_MAX + 1] = {
        [NHA_FDB]               = { .type = NLA_FLAG },
 };
 
+static int call_nexthop_notifiers(struct net *net,
+                                 enum fib_event_type event_type,
+                                 struct nexthop *nh)
+{
+       int err;
+
+       err = atomic_notifier_call_chain(&net->nexthop.notifier_chain,
+                                        event_type, nh);
+       return notifier_to_errno(err);
+}
+
 static unsigned int nh_dev_hashfn(unsigned int val)
 {
        unsigned int mask = NH_DEV_HASHSIZE - 1;
@@ -826,6 +837,8 @@ static void __remove_nexthop_fib(struct net *net, struct 
nexthop *nh)
        bool do_flush = false;
        struct fib_info *fi;
 
+       call_nexthop_notifiers(net, NEXTHOP_EVENT_DEL, nh);
+
        list_for_each_entry(fi, &nh->fi_list, nh_list) {
                fi->fib_flags |= RTNH_F_DEAD;
                do_flush = true;
@@ -1865,6 +1878,19 @@ static struct notifier_block nh_netdev_notifier = {
        .notifier_call = nh_netdev_event,
 };
 
+int register_nexthop_notifier(struct net *net, struct notifier_block *nb)
+{
+       return atomic_notifier_chain_register(&net->nexthop.notifier_chain, nb);
+}
+EXPORT_SYMBOL(register_nexthop_notifier);
+
+int unregister_nexthop_notifier(struct net *net, struct notifier_block *nb)
+{
+       return atomic_notifier_chain_unregister(&net->nexthop.notifier_chain,
+                                               nb);
+}
+EXPORT_SYMBOL(unregister_nexthop_notifier);
+
 static void __net_exit nexthop_net_exit(struct net *net)
 {
        rtnl_lock();
-- 
2.1.4