Merge branch 'bpf-allow-xdp_redirect-for-xdp-dev-bound-programs'

Lorenzo Bianconi says:

====================
bpf: Allow XDP_REDIRECT for XDP dev-bound programs

In the current implementation if the program is dev-bound to a specific
device, it will not be possible to perform XDP_REDIRECT into a DEVMAP or
CPUMAP even if the program is running in the driver NAPI context.
Fix the issue introducing __bpf_prog_map_compatible utility routine in
order to avoid bpf_prog_is_dev_bound() during the XDP program load.
Continue forbidding to attach a dev-bound program to XDP maps.
====================

Link: https://patch.msgid.link/[email protected]
Signed-off-by: Martin KaFai Lau <[email protected]>

Author: Martin KaFai Lau

kernel/bpf/core.c

@@ -2358,8 +2358,8 @@ static unsigned int __bpf_prog_ret0_warn(const void *ctx,
 	return 0;
 }
 
-bool bpf_prog_map_compatible(struct bpf_map *map,
-			     const struct bpf_prog *fp)
+static bool __bpf_prog_map_compatible(struct bpf_map *map,
+				      const struct bpf_prog *fp)
 {
 	enum bpf_prog_type prog_type = resolve_prog_type(fp);
 	bool ret;
@@ -2368,14 +2368,6 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
 	if (fp->kprobe_override)
 		return false;
 
-	/* XDP programs inserted into maps are not guaranteed to run on
-	 * a particular netdev (and can run outside driver context entirely
-	 * in the case of devmap and cpumap). Until device checks
-	 * are implemented, prohibit adding dev-bound programs to program maps.
-	 */
-	if (bpf_prog_is_dev_bound(aux))
-		return false;
-
 	spin_lock(&map->owner.lock);
 	if (!map->owner.type) {
 		/* There's no owner yet where we could check for
@@ -2409,6 +2401,19 @@ bool bpf_prog_map_compatible(struct bpf_map *map,
 	return ret;
 }
 
+bool bpf_prog_map_compatible(struct bpf_map *map, const struct bpf_prog *fp)
+{
+	/* XDP programs inserted into maps are not guaranteed to run on
+	 * a particular netdev (and can run outside driver context entirely
+	 * in the case of devmap and cpumap). Until device checks
+	 * are implemented, prohibit adding dev-bound programs to program maps.
+	 */
+	if (bpf_prog_is_dev_bound(fp->aux))
+		return false;
+
+	return __bpf_prog_map_compatible(map, fp);
+}
+
 static int bpf_check_tail_call(const struct bpf_prog *fp)
 {
 	struct bpf_prog_aux *aux = fp->aux;
@@ -2421,7 +2426,7 @@ static int bpf_check_tail_call(const struct bpf_prog *fp)
 		if (!map_type_contains_progs(map))
 			continue;
 
-		if (!bpf_prog_map_compatible(map, fp)) {
+		if (!__bpf_prog_map_compatible(map, fp)) {
 			ret = -EINVAL;
 			goto out;
 		}

tools/testing/selftests/bpf/prog_tests/xdp_metadata.c

@@ -351,9 +351,10 @@ void test_xdp_metadata(void)
 	struct xdp_metadata2 *bpf_obj2 = NULL;
 	struct xdp_metadata *bpf_obj = NULL;
 	struct bpf_program *new_prog, *prog;
+	struct bpf_devmap_val devmap_e = {};
+	struct bpf_map *prog_arr, *devmap;
 	struct nstoken *tok = NULL;
 	__u32 queue_id = QUEUE_ID;
-	struct bpf_map *prog_arr;
 	struct xsk tx_xsk = {};
 	struct xsk rx_xsk = {};
 	__u32 val, key = 0;
@@ -409,6 +410,13 @@ void test_xdp_metadata(void)
 	bpf_program__set_ifindex(prog, rx_ifindex);
 	bpf_program__set_flags(prog, BPF_F_XDP_DEV_BOUND_ONLY);
 
+	/* Make sure we can load a dev-bound program that performs
+	 * XDP_REDIRECT into a devmap.
+	 */
+	new_prog = bpf_object__find_program_by_name(bpf_obj->obj, "redirect");
+	bpf_program__set_ifindex(new_prog, rx_ifindex);
+	bpf_program__set_flags(new_prog, BPF_F_XDP_DEV_BOUND_ONLY);
+
 	if (!ASSERT_OK(xdp_metadata__load(bpf_obj), "load skeleton"))
 		goto out;
 
@@ -423,6 +431,18 @@ void test_xdp_metadata(void)
 			"update prog_arr"))
 		goto out;
 
+	/* Make sure we can't add dev-bound programs to devmaps. */
+	devmap = bpf_object__find_map_by_name(bpf_obj->obj, "dev_map");
+	if (!ASSERT_OK_PTR(devmap, "no dev_map found"))
+		goto out;
+
+	devmap_e.bpf_prog.fd = val;
+	if (!ASSERT_ERR(bpf_map__update_elem(devmap, &key, sizeof(key),
+					     &devmap_e, sizeof(devmap_e),
+					     BPF_ANY),
+			"update dev_map"))
+		goto out;
+
 	/* Attach BPF program to RX interface. */
 
 	ret = bpf_xdp_attach(rx_ifindex,

tools/testing/selftests/bpf/progs/xdp_metadata.c

@@ -19,6 +19,13 @@ struct {
 	__type(value, __u32);
 } prog_arr SEC(".maps");
 
+struct {
+	__uint(type, BPF_MAP_TYPE_DEVMAP);
+	__uint(key_size, sizeof(__u32));
+	__uint(value_size, sizeof(struct bpf_devmap_val));
+	__uint(max_entries, 1);
+} dev_map SEC(".maps");
+
 extern int bpf_xdp_metadata_rx_timestamp(const struct xdp_md *ctx,
 					 __u64 *timestamp) __ksym;
 extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, __u32 *hash,
@@ -95,4 +102,10 @@ int rx(struct xdp_md *ctx)
 	return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
 }
 
+SEC("xdp")
+int redirect(struct xdp_md *ctx)
+{
+	return bpf_redirect_map(&dev_map, ctx->rx_queue_index, XDP_PASS);
+}
+
 char _license[] SEC("license") = "GPL";