Calling MAC-LTE Dissectors using LUA

Hello,

I am trying to call dissector for mac-lte using lua. But getting error "Lua Error: ...logCapture.lua:27: attempt to call field 'get_mac_lte_proto_data' (a nil value)". I am passing the buffer as per the framing pattern for heuristic dissector.

Here below is the lua script snippet:

do
   print("hello Lua!!!")
local uelog_proto = Proto("uelog","UE Log Protocol")
– create a function to dissect it
function uelog_proto.dissector(buffer,pinfo,tree)
  local dissector = Dissector.get("mac-lte")
  if dissector ~= nil then
 print("Buffer %x,%x,%x \n",buffer(0,1):uint(),buffer(1,1):uint(),buffer(2,1):uint())
     --dissector:call(buffer(0):tvb(),pinfo,tree)
 --pinfo.proto_data=NULL
print("Value %s",buffer(0,7):string())

--pinfo.cols.info:set(buffer(0,7):string()) 
    --pinfo.cols.protocol = "udp"
 local mac_lte_info = dissector.get_mac_lte_proto_data(pinfo)
 mac_lte_info.radioType = buffer(8,1):uint()
 mac_lte_info.direction = buffer(9,1):uint()
 mac_lte_info.rntiType  = buffer(10,1):uint()
     dissector.set_mac_lte_proto_data(pinfo,mac_lte_info)
     dissector:call(buffer(14):tvb(),pinfo,tree)
  else 
     print(string.format("dissector not found, pkt number = %d", pinfo.number ))
  end

end

– load the udp.port table
udp_table = DissectorTable.get("udp.port")
– register our protocol to handle udp port 5001
udp_table:add(5003,uelog_proto)
end

C code for framing Mac-Lte PDU :

void SendMACFrame(guint8 radioType, guint8 direction, guint8 rntiType,
guint16 rnti, guint16 ueid, guint16 subframeNumber,
guint8 isPredefinedData, guint8 retx, guint8 crcStatus,char macpdu,guint8 length,struct UE_LogHeader uelog )
{
ssize_t bytesSent;
unsigned int  g_frameOffset = 0; 

unsigned short tmp16;
char g_frameBuffer = &uelog->data[0];
/********************************************************************/
/ Fixed start to each frame (allowing heuristic dissector to work) /
/ Not NULL terminated /
memcpy(g_frameBuffer+g_frameOffset, MAC_LTE_START_STRING,
strlen(MAC_LTE_START_STRING));
g_frameOffset += strlen(MAC_LTE_START_STRING);
TRACE_LOG("MAC PUD Direction %d ,length %d rntiType %d\n",direction ,length,rntiType );
/**************************************************************************/
/ Now write out fixed fields (the mandatory elements of struct mac_lte_info) */
g_frameBuffer[g_frameOffset++] = radioType;
g_frameBuffer[g_frameOffset++] = direction;
g_frameBuffer[g_frameOffset++] = rntiType;

/*************************************/
/* Now optional fields               */

/* Subframe number */
g_frameBuffer[g_frameOffset++] = MAC_LTE_FRAME_SUBFRAME_TAG;
tmp16 = htons(subframeNumber);
memcpy(g_frameBuffer+g_frameOffset, &tmp16, 2);
g_frameOffset += 2;
#if 0
/* RNTI */
g_frameBuffer[g_frameOffset++] = MAC_LTE_RNTI_TAG;
tmp16 = htons(rnti);
memcpy(g_frameBuffer+g_frameOffset, &tmp16, 2);
g_frameOffset += 2;
/* UEId */
g_frameBuffer[g_frameOffset++] = MAC_LTE_UEID_TAG;
tmp16 = htons(ueid);
memcpy(g_frameBuffer+g_frameOffset, &tmp16, 2);
g_frameOffset += 2;

/* Subframe number */
g_frameBuffer[g_frameOffset++] = MAC_LTE_SUBFRAME_TAG;
tmp16 = htons(ueid);
memcpy(g_frameBuffer+g_frameOffset, &tmp16, 2);
g_frameOffset += 2;

g_frameBuffer[g_frameOffset++] = MAC_LTE_CRC_STATUS_TAG;
g_frameBuffer[g_frameOffset++] = crcStatus;

/***********************************************************/
/* For these optional fields, no need to encode if value is default */
if (!isPredefinedData) {
    g_frameBuffer[g_frameOffset++] = MAC_LTE_PREDFINED_DATA_TAG;
    g_frameBuffer[g_frameOffset++] = isPredefinedData;
}

if (retx != 0) {
    g_frameBuffer[g_frameOffset++] = MAC_LTE_RETX_TAG;
    g_frameBuffer[g_frameOffset++] = retx;
}

#endif
/***************************************/
/* Now write the MAC PDU               */
g_frameBuffer[g_frameOffset++] = MAC_LTE_PAYLOAD_TAG;

/* Append actual PDU  */
memcpy(g_frameBuffer+g_frameOffset, macpdu, length);
g_frameOffset += length;

destination.sin_port = htons(5003);

/* Send out the data over the UDP socket */
bytesSent = sendto(rrcSockFd , uelog->data, g_frameOffset ,
SEND_FLAG, (struct sockaddr *)&destination, sizeof(destination));
if (bytesSent != g_frameOffset) {
    fprintf(stderr, "sendto() failed - expected %d bytes, got %d (errno=%d)\n",
            g_frameOffset, bytesSent, errno);
    exit(1);
}

}

Above mentioned C code works fine for wireshark If I disable lua script and simply enable heuristic dissector in wireshark. But I want to call dissector through lua as I have written some addtional dissectors related to generic UE specific information.

I am new to lua scripting, please help me out .