ipv4: Send a netevent whenever multipath hash policy is changed

Devices performing IPv4 forwarding need to update their multipath hash
policy whenever it is changed.

Inform these devices by generating a netevent.
Signed-off-by: NIdo Schimmel <idosch@mellanox.com>
Reviewed-by: NPetr Machata <petrm@mellanox.com>
Signed-off-by: NJiri Pirko <jiri@mellanox.com>
Acked-by: NDavid Ahern <dsahern@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

include/net/netevent.h

@@ -25,6 +25,7 @@ enum netevent_notif_type {
 	NETEVENT_NEIGH_UPDATE = 1, /* arg is struct neighbour ptr */
 	NETEVENT_REDIRECT,	   /* arg is struct netevent_redirect ptr */
 	NETEVENT_DELAY_PROBE_TIME_UPDATE, /* arg is struct neigh_parms ptr */
+	NETEVENT_MULTIPATH_HASH_UPDATE, /* arg is struct net ptr */
 };
 
 int register_netevent_notifier(struct notifier_block *nb);

net/ipv4/sysctl_net_ipv4.c

@@ -25,6 +25,7 @@
 #include <net/inet_frag.h>
 #include <net/ping.h>
 #include <net/protocol.h>
+#include <net/netevent.h>
 
 static int zero;
 static int one = 1;
@@ -385,6 +386,23 @@ static int proc_tcp_available_ulp(struct ctl_table *ctl,
 	return ret;
 }
 
+#ifdef CONFIG_IP_ROUTE_MULTIPATH
+static int proc_fib_multipath_hash_policy(struct ctl_table *table, int write,
+					  void __user *buffer, size_t *lenp,
+					  loff_t *ppos)
+{
+	struct net *net = container_of(table->data, struct net,
+	    ipv4.sysctl_fib_multipath_hash_policy);
+	int ret;
+
+	ret = proc_dointvec_minmax(table, write, buffer, lenp, ppos);
+	if (write && ret == 0)
+		call_netevent_notifiers(NETEVENT_MULTIPATH_HASH_UPDATE, net);
+
+	return ret;
+}
+#endif
+
 static struct ctl_table ipv4_table[] = {
 	{
 		.procname	= "tcp_max_orphans",
@@ -907,7 +925,7 @@ static struct ctl_table ipv4_net_table[] = {
 		.data		= &init_net.ipv4.sysctl_fib_multipath_hash_policy,
 		.maxlen		= sizeof(int),
 		.mode		= 0644,
-		.proc_handler	= proc_dointvec_minmax,
+		.proc_handler	= proc_fib_multipath_hash_policy,
 		.extra1		= &zero,
 		.extra2		= &one,
 	},