[RFC PATCH net-next 14/22] nexthop: Emit a notification when a nexthop group is modified

[Ido Schimmel <idosch@idosch.org>]

From: Ido Schimmel <idosch@nvidia.com>

When a single nexthop is replaced, the configuration of all the groups
using the nexthop is effectively modified. In this case, emit a
notification in the nexthop notification chain for each modified group
so that listeners would not need to keep track of which nexthops are
member in which groups.

The notification can only be emitted after the new configuration (i.e.,
'struct nh_info') is pointed at by the old shell (i.e., 'struct
nexthop'). Before that the configuration of the nexthop groups is still
the same as before the replacement.

Signed-off-by: Ido Schimmel <idosch@nvidia.com>
---
 net/ipv4/nexthop.c | 32 ++++++++++++++++++++++++++++++--
 1 file changed, 30 insertions(+), 2 deletions(-)

diff --git a/net/ipv4/nexthop.c b/net/ipv4/nexthop.c
index b8a4abc00146..0edc3e73d416 100644
--- a/net/ipv4/nexthop.c
+++ b/net/ipv4/nexthop.c
@@ -1098,7 +1098,9 @@ static int replace_nexthop_single(struct net *net, struct nexthop *old,
 				  struct nexthop *new,
 				  struct netlink_ext_ack *extack)
 {
+	u8 old_protocol, old_nh_flags;
 	struct nh_info *oldi, *newi;
+	struct nh_grp_entry *nhge;
 	int err;
 
 	if (new->is_group) {
@@ -1121,18 +1123,29 @@ static int replace_nexthop_single(struct net *net, struct nexthop *old,
 	newi->nh_parent = old;
 	oldi->nh_parent = new;
 
+	old_protocol = old->protocol;
+	old_nh_flags = old->nh_flags;
+
 	old->protocol = new->protocol;
 	old->nh_flags = new->nh_flags;
 
 	rcu_assign_pointer(old->nh_info, newi);
 	rcu_assign_pointer(new->nh_info, oldi);
 
+	/* Send a replace notification for all the groups using the nexthop. */
+	list_for_each_entry(nhge, &old->grp_list, nh_list) {
+		struct nexthop *nhp = nhge->nh_parent;
+
+		err = call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, nhp,
+					     extack);
+		if (err)
+			goto err_notify;
+	}
+
 	/* When replacing an IPv4 nexthop with an IPv6 nexthop, potentially
 	 * update IPv4 indication in all the groups using the nexthop.
 	 */
 	if (oldi->family == AF_INET && newi->family == AF_INET6) {
-		struct nh_grp_entry *nhge;
-
 		list_for_each_entry(nhge, &old->grp_list, nh_list) {
 			struct nexthop *nhp = nhge->nh_parent;
 			struct nh_group *nhg;
@@ -1143,6 +1156,21 @@ static int replace_nexthop_single(struct net *net, struct nexthop *old,
 	}
 
 	return 0;
+
+err_notify:
+	rcu_assign_pointer(new->nh_info, newi);
+	rcu_assign_pointer(old->nh_info, oldi);
+	old->nh_flags = old_nh_flags;
+	old->protocol = old_protocol;
+	oldi->nh_parent = old;
+	newi->nh_parent = new;
+	list_for_each_entry_continue_reverse(nhge, &old->grp_list, nh_list) {
+		struct nexthop *nhp = nhge->nh_parent;
+
+		call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, nhp, extack);
+	}
+	call_nexthop_notifiers(net, NEXTHOP_EVENT_REPLACE, old, extack);
+	return err;
 }
 
 static void __nexthop_replace_notify(struct net *net, struct nexthop *nh,
-- 
2.26.2