net: Initial nexthop code

Barebones start point for nexthops. Implementation for RTM commands,
notifications, management of rbtree for holding nexthops by id, and
kernel side data structures for nexthops and nexthop config.

Nexthops are maintained in an rbtree sorted by id. Similar to routes,
nexthops are configured per namespace using netns_nexthop struct added
to struct net.

Nexthop notifications are sent when a nexthop is added or deleted,
but NOT if the delete is due to a device event or network namespace
teardown (which also involves device events). Applications are
expected to use the device down event to flush nexthops and any
routes used by the nexthops.

Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/net/netns/nexthop.h b/include/net/netns/nexthop.h
new file mode 100644
index 000000000000..c712ee5eebd9
--- /dev/null
+++ b/include/net/netns/nexthop.h
@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * nexthops in net namespaces
+ */
+
+#ifndef __NETNS_NEXTHOP_H__
+#define __NETNS_NEXTHOP_H__
+
+#include <linux/rbtree.h>
+
+struct netns_nexthop {
+	struct rb_root		rb_root;	/* tree of nexthops by id */
+	struct hlist_head	*devhash;	/* nexthops by device */
+
+	unsigned int		seq;		/* protected by rtnl_mutex */
+	u32			last_id_allocated;
+};
+#endif