bpf: add bpf_redirect_map helper routine

BPF programs can use the devmap with a bpf_redirect_map() helper
routine to forward packets to netdevice in map.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 0 deletions

diff --git a/kernel/bpf/devmap.c b/kernel/bpf/devmap.c
index 1a878356bd37..36dc13deb2e1 100644
--- a/kernel/bpf/devmap.c
+++ b/kernel/bpf/devmap.c
@@ -159,6 +159,18 @@ static int dev_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
         return 0;
 }
 
+struct net_device  *__dev_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+        struct bpf_dtab *dtab = container_of(map, struct bpf_dtab, map);
+        struct bpf_dtab_netdev *dev;
+
+        if (key >= map->max_entries)
+                return NULL;
+
+        dev = READ_ONCE(dtab->netdev_map[key]);
+        return dev ? dev->dev : NULL;
+}
+
 /* rcu_read_lock (from syscall and BPF contexts) ensures that if a delete and/or
  * update happens in parallel here a dev_put wont happen until after reading the
  * ifindex.