mpls: Allow MPLS after vlan.

Fixes #2771

src/decode-vlan.c

@@ -130,6 +130,11 @@ int DecodeVLAN(ThreadVars *tv, DecodeThreadVars *dtv, Packet *p,
             break;
         case ETHERNET_TYPE_ARP:
             break;
+        case ETHERNET_TYPE_MPLS_UNICAST:
+        case ETHERNET_TYPE_MPLS_MULTICAST:
+            DecodeMPLS(tv, dtv, p, pkt + VLAN_HEADER_LEN,
+                       len - VLAN_HEADER_LEN, pq);
+            break;
         default:
             SCLogDebug("unknown VLAN type: %" PRIx32 "", proto);
             ENGINE_SET_INVALID_EVENT(p, VLAN_UNKNOWN_TYPE);