Re: [net PATCH 1/2] ipv4: Restore fib_trie_flush_external function and fix call ordering

Fixes: 347e3b28c1ba2 ("switchdev: remove FIB offload infrastructure")
Reported-by: Eric Dumazet <edumazet@google.com>
Cc: Jiri Pirko <redacted>
Signed-off-by: Alexander Duyck <redacted>
---
include/net/ip_fib.h    |    1 +
net/ipv4/fib_frontend.c |   20 +++++++++++---
net/ipv4/fib_trie.c     |   65 +++++++++++++++++++++++++++++++++++++++++++++++
3 files changed, 81 insertions(+), 5 deletions(-)

diff --git a/include/net/ip_fib.h b/include/net/ip_fib.h
index b9314b4..f390c3b 100644
--- a/include/net/ip_fib.h
+++ b/include/net/ip_fib.h

@@ -243,6 +243,7 @@ int fib_table_dump(struct fib_table *table, struct sk_buff *skb,

		   struct netlink_callback *cb);
int fib_table_flush(struct net *net, struct fib_table *table);
struct fib_table *fib_trie_unmerge(struct fib_table *main_tb);
+void fib_table_flush_external(struct fib_table *table);
void fib_free_table(struct fib_table *tb);

#ifndef CONFIG_IP_MULTIPLE_TABLES

diff --git a/net/ipv4/fib_frontend.c b/net/ipv4/fib_frontend.c
index c3b8047..161fc0f 100644
--- a/net/ipv4/fib_frontend.c
+++ b/net/ipv4/fib_frontend.c

@@ -151,7 +151,7 @@ static void fib_replace_table(struct net *net, struct fib_table *old,

int fib_unmerge(struct net *net)
{
-	struct fib_table *old, *new;
+	struct fib_table *old, *new, *main_table;

	/* attempt to fetch local table if it has been allocated */
	old = fib_get_table(net, RT_TABLE_LOCAL);

@@ -162,11 +162,21 @@ int fib_unmerge(struct net *net)

	if (!new)
		return -ENOMEM;

+	/* table is already unmerged */
+	if (new == old)
+		return 0;
+
	/* replace merged table with clean table */
-	if (new != old) {
-		fib_replace_table(net, old, new);
-		fib_free_table(old);
-	}
+	fib_replace_table(net, old, new);
+	fib_free_table(old);
+
+	/* attempt to fetch main table if it has been allocated */
+	main_table = fib_get_table(net, RT_TABLE_MAIN);
+	if (!main_table)
+		return 0;
+
+	/* flush local entries from main table */
+	fib_table_flush_external(main_table);

	return 0;
}

diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
index 4cff74d..735edc9 100644
--- a/net/ipv4/fib_trie.c
+++ b/net/ipv4/fib_trie.c

@@ -1760,6 +1760,71 @@ struct fib_table *fib_trie_unmerge(struct fib_table *oldtb)

	return NULL;
}

+/* Caller must hold RTNL */
+void fib_table_flush_external(struct fib_table *tb)
+{
+	struct trie *t = (struct trie *)tb->tb_data;
+	struct key_vector *pn = t->kv;
+	unsigned long cindex = 1;
+	struct hlist_node *tmp;
+	struct fib_alias *fa;
+
+	/* walk trie in reverse order */
+	for (;;) {
+		unsigned char slen = 0;
+		struct key_vector *n;
+
+		if (!(cindex--)) {
+			t_key pkey = pn->key;
+
+			/* cannot resize the trie vector */
+			if (IS_TRIE(pn))
+				break;
+
+			/* resize completed node */
+			pn = resize(t, pn);
+			cindex = get_index(pkey, pn);
+
+			continue;
+		}
+
+		/* grab the next available node */
+		n = get_child(pn, cindex);
+		if (!n)
+			continue;
+
+		if (IS_TNODE(n)) {
+			/* record pn and cindex for leaf walking */
+			pn = n;
+			cindex = 1ul << n->bits;
+
+			continue;
+		}
+
+		hlist_for_each_entry_safe(fa, tmp, &n->leaf, fa_list) {
+			/* if alias was cloned to local then we just
+			 * need to remove the local copy from main
+			 */
+			if (tb->tb_id != fa->tb_id) {
+				hlist_del_rcu(&fa->fa_list);
+				alias_free_mem_rcu(fa);
+				continue;
+			}
+
+			/* record local slen */
+			slen = fa->fa_slen;
+		}
+
+		/* update leaf slen */
+		n->slen = slen;
+
+		if (hlist_empty(&n->leaf)) {
+			put_child_root(pn, n->key, NULL);
+			node_free(n);
+		}
+	}
+}
+
/* Caller must hold RTNL. */
int fib_table_flush(struct net *net, struct fib_table *tb)
{