[RFC PATCH net-next 03/15] ipv4: Notify route if replacing currently offloaded one

[Ido Schimmel <idosch@idosch.org>]

From: Ido Schimmel <idosch@mellanox.com>

When replacing a route, its replacement should only be notified in case
the replaced route is of any interest to listeners. In other words, if
the replaced route is currently used in the data path, which means it is
the first route in the FIB alias list with the given {prefix, prefix
length, table ID}.

Signed-off-by: Ido Schimmel <idosch@mellanox.com>
---
 net/ipv4/fib_trie.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 3ba63ebcfeef..8387b275721c 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c
@@ -978,6 +978,27 @@ static struct key_vector *fib_find_node(struct trie *t,
 	return n;
 }
 
+/* Return the first fib alias matching prefix length and table ID. */
+static struct fib_alias *fib_find_first_alias(struct hlist_head *fah, u8 slen,
+					      u32 tb_id)
+{
+	struct fib_alias *fa;
+
+	hlist_for_each_entry(fa, fah, fa_list) {
+		if (fa->fa_slen < slen)
+			continue;
+		if (fa->fa_slen != slen)
+			break;
+		if (fa->tb_id > tb_id)
+			continue;
+		if (fa->tb_id != tb_id)
+			break;
+		return fa;
+	}
+
+	return NULL;
+}
+
 /* Return the first fib alias matching TOS with
  * priority less than or equal to PRIO.
  */
@@ -1217,6 +1238,17 @@ int fib_table_insert(struct net *net, struct fib_table *tb,
 			new_fa->tb_id = tb->tb_id;
 			new_fa->fa_default = -1;
 
+			if (fib_find_first_alias(&l->leaf, fa->fa_slen,
+						 tb->tb_id) == fa) {
+				enum fib_event_type fib_event;
+
+				fib_event = FIB_EVENT_ENTRY_REPLACE_TMP;
+				err = call_fib_entry_notifiers(net, fib_event,
+							       key, plen,
+							       new_fa, extack);
+				if (err)
+					goto out_free_new_fa;
+			}
 			err = call_fib_entry_notifiers(net,
 						       FIB_EVENT_ENTRY_REPLACE,
 						       key, plen, new_fa,
-- 
2.21.0