Getting wrong UPD checksum using update_checksum_with_payload function

[ABHIK BOSE]

Hello everyone,

I'm trying to use "update_checksum_with_payload" function to recalculate UDP checksum in P4-16. My code snippet is as follows:

update_checksum_with_payload(hdr.udp.isValid(),{

    hdr.ipv4.srcAddr,

    hdr.ipv4.dstAddr,

    8w0,

    hdr.ipv4.protocol,

    hdr.udp.len,

    hdr.udp.srcPort,

    hdr.udp.dstPort,

    hdr.udp.len},

    hdr.udp.checksum,

    HashAlgorithm.csum16

);

The code is compiling correctly. Unfortunately, it's not updating the UDP checksum.

If I replace the update_checksum_with_payload with update_checksum, I'm getting same incorrect checksum (NOTE: I'm using the same source and destination IP and UDP port for the entire experiment). From this, it's looking like the update_checksum_with_payload is skipping the payload while UDP checksum calculation.

Any help regarding this will be very helpful.

Thanks and regards

Abhik Bose

Research scholar

CSE, IIT Bombay