selftests/bpf: Allow VLAN packets in xdp_hw_metadata

Make VLAN c-tag and s-tag XDP hint testing more convenient
by not skipping VLAN-ed packets.

Allow both 802.1ad and 802.1Q headers.
Acked-by: Stanislav Fomichev <sdf@google.com>
Signed-off-by: Larysa Zaremba <larysa.zaremba@intel.com>
Link: https://lore.kernel.org/r/20231205210847.28460-16-larysa.zaremba@intel.comSigned-off-by: Alexei Starovoitov <ast@kernel.org>

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

@@ -26,15 +26,23 @@ int rx(struct xdp_md *ctx)
 {
 	void *data, *data_meta, *data_end;
 	struct ipv6hdr *ip6h = NULL;
-	struct ethhdr *eth = NULL;
 	struct udphdr *udp = NULL;
 	struct iphdr *iph = NULL;
 	struct xdp_meta *meta;
+	struct ethhdr *eth;
 	int err;
 
 	data = (void *)(long)ctx->data;
 	data_end = (void *)(long)ctx->data_end;
 	eth = data;
+
+	if (eth + 1 < data_end && (eth->h_proto == bpf_htons(ETH_P_8021AD) ||
+				   eth->h_proto == bpf_htons(ETH_P_8021Q)))
+		eth = (void *)eth + sizeof(struct vlan_hdr);
+
+	if (eth + 1 < data_end && eth->h_proto == bpf_htons(ETH_P_8021Q))
+		eth = (void *)eth + sizeof(struct vlan_hdr);
+
 	if (eth + 1 < data_end) {
 		if (eth->h_proto == bpf_htons(ETH_P_IP)) {
 			iph = (void *)(eth + 1);

tools/testing/selftests/bpf/xdp_metadata.h

@@ -9,6 +9,14 @@
 #define ETH_P_IPV6 0x86DD
 #endif
 
+#ifndef ETH_P_8021Q
+#define ETH_P_8021Q 0x8100
+#endif
+
+#ifndef ETH_P_8021AD
+#define ETH_P_8021AD 0x88A8
+#endif
+
 struct xdp_meta {
 	__u64 rx_timestamp;
 	__u64 xdp_timestamp;