2018-07 - packet dropping - fix ETH_P_8021AD IEEE_802.1ad QinQ or dou…

…ble vlan encoding
cloudflare · Jul 15, 2018 · 765d4b6 · 765d4b6 · X-Cli · Jul 15, 2018
1 parent a0c86a9
commit 765d4b6
Showing 1 changed file with 12 additions and 7 deletions.
diff --git a/2018-07-dropping-packets/xdp-drop-ebpf.c b/2018-07-dropping-packets/xdp-drop-ebpf.c
@@ -30,15 +30,20 @@ int xdp_drop_benchmark_traffic(struct xdp_md *ctx)
 	}
 
 	uint16_t h_proto = eth->h_proto;
-	if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
-		struct vlan_hdr *vhdr;
+	int i;
 
-		vhdr = data + nh_off;
-		nh_off += sizeof(struct vlan_hdr);
-		if (data + nh_off > data_end) {
-			return XDP_PASS;
+	/* Handle double VLAN tagged packet. See https://en.wikipedia.org/wiki/IEEE_802.1ad */
+	for (i = 0; i < 2; i++) {
+		if (h_proto == htons(ETH_P_8021Q) || h_proto == htons(ETH_P_8021AD)) {
+			struct vlan_hdr *vhdr;
+
+			vhdr = data + nh_off;
+			nh_off += sizeof(struct vlan_hdr);
+			if (data + nh_off > data_end) {
+				return XDP_PASS;
+			}
+			h_proto = vhdr->h_vlan_encapsulated_proto;
 		}
-		h_proto = vhdr->h_vlan_encapsulated_proto;
 	}
 
 	if (h_proto == htons(ETH_P_IP)) {