[srslte-users] How can I access the pdu->msg.

[Paul Sutton]

Hi Raghav,

Instead of trying to print from within the
gtpu::handle_gtpu_s1u_rx_packet function, you can simply view the
message in hex format in the log file.
On line 225 of
https://github.com/srsLTE/srsLTE/blob/master/srsenb/src/stack/upper/gtpu.cc,
you will see that all GTPU data PDUs are logged with level INFO. You
simply need to configure srsENB logging for the GTPU layer to use log
level INFO (gtpu_level = info) and enable hex output (gtpu_hex_limit = 32).

Best regards,
Paul

On 04/06/2020 16:47, Raghav Rathi wrote:
> Hello Everyone,
>
> I am trying to understand how srsLTE handles IP packets. I am running
> the ping example mentioned in the srsLTE ZeroMQ documentation and I am
> focusing on the ENB part.
> From my understanding, when I call ping command, the flow of control
> goes to the 'gtpu.cc' file which makes sense as gtp is the GPRS
> tunneling protocol - U which carries user data from EPC to ENB.
> After looking at the gtpu.cc, i found that there is a function named 
> 'handle_gtpu_s1u_rx_packet' and every time i call ping, this function
> is called which i verified by adding a print statement.
>
> My aim here is to understand the IP packet which from my observation
> is the 'pdu' present in 'handle_gtpu_s1u_rx_packet' function. 
> pdu->N_bytes shows the byte size of the msg, but when I access the msg
> using pdu->msg, it gives me random characters.
> Since msg is a buffer I simply used a for loop of range pdu->n_byte
> and tried to access msg[i] but i am getting the following output. I
> think it is because the packet is encoded but I don't know how to
> decode. Can someone please help me with that?
>
> >>>> pdu -> n_byte84
> >>>>>>>>>> PDU->msg: E   T � � @  @ 
  � �   
 �      � %    N 
> � ^     � �
>                             
 
 
    ! " # $ % & ' ( ) *
> + , - . / 0 1 2 3 4 5 6 7
>
>
> Thank you,
>
> *Raghav Rathi*
>
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-- 
________________________________________________________________
Paul Sutton Ph.D.

Software Radio Systems (SRS)
http://www.softwareradiosystems.com
paul at softwareradiosystems.com

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