Commit fc38b283 authored by Eric Dumazet's avatar Eric Dumazet Committed by Jakub Kicinski
Browse files

ipv4: use rcu in ip_fib_check_default() 



fib_info_devhash[] is not resized in fib_info_hash_move().

fib_nh structs are already freed after an rcu grace period.

This will allow to remove fib_info_lock in the following patch.

Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Reviewed-by: default avatarKuniyuki Iwashima <kuniyu@amazon.com>
Reviewed-by: default avatarDavid Ahern <dsahern@kernel.org>
Link: https://patch.msgid.link/20241004134720.579244-3-edumazet@google.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 8a0f62fd

net/ipv4/fib_semantics.c

+4 −9
Original line number Diff line number Diff line
@@ -275,7 +275,7 @@ void fib_release_info(struct fib_info *fi) 
			change_nexthops(fi) {

				if (!nexthop_nh->fib_nh_dev)

					continue;

				hlist_del(&nexthop_nh->nh_hash);

				hlist_del_rcu(&nexthop_nh->nh_hash);

			} endfor_nexthops(fi)

		}

		/* Paired with READ_ONCE() from fib_table_lookup() */
@@ -431,28 +431,23 @@ static struct fib_info *fib_find_info(struct fib_info *nfi) 
}



/* Check, that the gateway is already configured.

 * Used only by redirect accept routine.

 * Used only by redirect accept routine, under rcu_read_lock();

 */

int ip_fib_check_default(__be32 gw, struct net_device *dev)

{

	struct hlist_head *head;

	struct fib_nh *nh;



	spin_lock(&fib_info_lock);



	head = fib_info_devhash_bucket(dev);



	hlist_for_each_entry(nh, head, nh_hash) {

	hlist_for_each_entry_rcu(nh, head, nh_hash) {

		if (nh->fib_nh_dev == dev &&

		    nh->fib_nh_gw4 == gw &&

		    !(nh->fib_nh_flags & RTNH_F_DEAD)) {

			spin_unlock(&fib_info_lock);

			return 0;

		}

	}



	spin_unlock(&fib_info_lock);



	return -1;

}
@@ -1606,7 +1601,7 @@ struct fib_info *fib_create_info(struct fib_config *cfg, 
			if (!nexthop_nh->fib_nh_dev)

				continue;

			head = fib_info_devhash_bucket(nexthop_nh->fib_nh_dev);

			hlist_add_head(&nexthop_nh->nh_hash, head);

			hlist_add_head_rcu(&nexthop_nh->nh_hash, head);

		} endfor_nexthops(fi)

	}

	spin_unlock_bh(&fib_info_lock);