Function "truncate" problem

[tomyhu1995]

Hi all,
I am trying to use truncate to eliminate payload of packet. The following is the code I use:

   action no_payload() {
        truncate(0);
    }
    apply {
            if (standard_metadata.enq_qdepth >= ECN_THRESHOLD){
                no_payload();
            }
    }

In my opinion, the packet's payload will be eliminate when queue length is larger than ECN_THRESHOLD. However, it doesn't work. Receiver can't receive any packet. And I change the parameter of truncate( change 0 to 34). Receiver can receive packet which only include mac+ipv4 header.

My question is: what is the detail definition of truncate on bmv2? How to eliminate payload by using truncate?

[antoninbas]

What you are describing makes sense to me. The bmv2 truncate primitive applies to the deparsed packet I believe, not to the payload specifically. So if you truncate to 0, the packet is dropped.

[tomyhu1995]

@antoninbas It is real make sense to me, too.
I was confused by this issue #303. I do believe your explanation is correct and make sense. Thanks a lot