decode/vntag: Add VNTag decoder logic

(cherry picked from commit 0f0cb5169f)

src/decode.h

@@ -961,6 +961,7 @@ int DecodeUDP(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint1
 int DecodeSCTP(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint16_t);
 int DecodeGRE(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeVLAN(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
+int DecodeVNTag(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeIEEE8021ah(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeGeneve(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
 int DecodeVXLAN(ThreadVars *, DecodeThreadVars *, Packet *, const uint8_t *, uint32_t);
@@ -1280,6 +1281,9 @@ static inline bool DecodeNetworkLayer(ThreadVars *tv, DecodeThreadVars *dtv,
                 DecodeEthernet(tv, dtv, p, data, len);
             }
             break;
+        case ETHERNET_TYPE_VNTAG:
+            DecodeVNTag(tv, dtv, p, data, len);
+            break;
         default:
             SCLogDebug("unknown ether type: %" PRIx16 "", proto);
             return false;