selftests/bpf: Check VLAN tag and proto in xdp_metadata

Verify, whether VLAN tag and proto are set correctly.

To simulate "stripped" VLAN tag on veth, send test packet from VLAN
interface.

Also, add TO_STR() macro for convenience.

Acked-by: Stanislav Fomichev <[e-mail]>
Signed-off-by: Larysa Zaremba <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Alexei Starovoitov <[e-mail]>

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

···
 #define TX_MAC "00:00:00:00:00:01"
 #define RX_MAC "00:00:00:00:00:02"
 
+#define VLAN_ID 59
+#define VLAN_PROTO "802.1Q"
+#define VLAN_PID htons(ETH_P_8021Q)
+#define TX_NAME_VLAN TX_NAME "." TO_STR(VLAN_ID)
+
 #define XDP_RSS_TYPE_L4 BIT(3)
+#define VLAN_VID_MASK 0xfff
 
 struct xsk {
 	void *umem_area;
···
 	if (!sent_from_af_xdp) {
 		if (!ASSERT_NEQ(meta->rx_hash_type & XDP_RSS_TYPE_L4, 0, "rx_hash_type"))
 			return -1;
+
+		if (!ASSERT_EQ(meta->rx_vlan_tci & VLAN_VID_MASK, VLAN_ID, "rx_vlan_tci"))
+			return -1;
+
+		if (!ASSERT_EQ(meta->rx_vlan_proto, VLAN_PID, "rx_vlan_proto"))
+			return -1;
 		goto done;
 	}
 
···
 
 	SYS(out, "ip link set dev " TX_NAME " address " TX_MAC);
 	SYS(out, "ip link set dev " TX_NAME " up");
-	SYS(out, "ip addr add " TX_ADDR "/" PREFIX_LEN " dev " TX_NAME);
+
+	SYS(out, "ip link add link " TX_NAME " " TX_NAME_VLAN
+		 " type vlan proto " VLAN_PROTO " id " TO_STR(VLAN_ID));
+	SYS(out, "ip link set dev " TX_NAME_VLAN " up");
+	SYS(out, "ip addr add " TX_ADDR "/" PREFIX_LEN " dev " TX_NAME_VLAN);
 
 	/* Avoid ARP calls */
-	SYS(out, "ip -4 neigh add " RX_ADDR " lladdr " RX_MAC " dev " TX_NAME);
+	SYS(out, "ip -4 neigh add " RX_ADDR " lladdr " RX_MAC " dev " TX_NAME_VLAN);
 
 	switch_ns_to_rx(&tok);
 

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

···
 					 __u64 *timestamp) __ksym;
 extern int bpf_xdp_metadata_rx_hash(const struct xdp_md *ctx, __u32 *hash,
 				    enum xdp_rss_hash_type *rss_type) __ksym;
+extern int bpf_xdp_metadata_rx_vlan_tag(const struct xdp_md *ctx,
+					__be16 *vlan_proto,
+					__u16 *vlan_tci) __ksym;
 
 SEC("xdp")
 int rx(struct xdp_md *ctx)
···
 		meta->rx_timestamp = 1;
 
 	bpf_xdp_metadata_rx_hash(ctx, &meta->rx_hash, &meta->rx_hash_type);
+	bpf_xdp_metadata_rx_vlan_tag(ctx, &meta->rx_vlan_proto,
+				     &meta->rx_vlan_tci);
 
 	return bpf_redirect_map(&xsk, ctx->rx_queue_index, XDP_PASS);
 }

tools/testing/selftests/bpf/testing_helpers.h

···
 #include <bpf/libbpf.h>
 #include <time.h>
 
+#define __TO_STR(x) #x
+#define TO_STR(x) __TO_STR(x)
+
 int parse_num_list(const char *s, bool **set, int *set_len);
 __u32 link_info_prog_id(const struct bpf_link *link, struct bpf_link_info *info);
 int bpf_prog_test_load(const char *file, enum bpf_prog_type type,