bpf, xdp: Make bpf_redirect_map() a map operation

Currently the bpf_redirect_map() implementation dispatches to the
correct map-lookup function via a switch-statement. To avoid the
dispatching, this change adds bpf_redirect_map() as a map
operation. Each map provides its bpf_redirect_map() version, and
correct function is automatically selected by the BPF verifier.

A nice side-effect of the code movement is that the map lookup
functions are now local to the map implementation files, which removes
one additional function call.

Signed-off-by: Björn Töpel <bjorn.topel@intel.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210308112907.559576-2-bjorn.topel@gmail.com

1 files changed, 16 insertions, 0 deletions

diff --git a/net/xdp/xskmap.c b/net/xdp/xskmap.c
index 113fd9017203..fbeb4870f798 100644
--- a/net/xdp/xskmap.c
+++ b/net/xdp/xskmap.c
@@ -125,6 +125,16 @@ static int xsk_map_gen_lookup(struct bpf_map *map, struct bpf_insn *insn_buf)
 	return insn - insn_buf;
 }
 
+static void *__xsk_map_lookup_elem(struct bpf_map *map, u32 key)
+{
+	struct xsk_map *m = container_of(map, struct xsk_map, map);
+
+	if (key >= map->max_entries)
+		return NULL;
+
+	return READ_ONCE(m->xsk_map[key]);
+}
+
 static void *xsk_map_lookup_elem(struct bpf_map *map, void *key)
 {
 	WARN_ON_ONCE(!rcu_read_lock_held());
@@ -215,6 +225,11 @@ static int xsk_map_delete_elem(struct bpf_map *map, void *key)
 	return 0;
 }
 
+static int xsk_map_redirect(struct bpf_map *map, u32 ifindex, u64 flags)
+{
+	return __bpf_xdp_redirect_map(map, ifindex, flags, __xsk_map_lookup_elem);
+}
+
 void xsk_map_try_sock_delete(struct xsk_map *map, struct xdp_sock *xs,
 			     struct xdp_sock **map_entry)
 {
@@ -247,4 +262,5 @@ const struct bpf_map_ops xsk_map_ops = {
 	.map_check_btf = map_check_no_btf,
 	.map_btf_name = "xsk_map",
 	.map_btf_id = &xsk_map_btf_id,
+	.map_redirect = xsk_map_redirect,
 };