[P4-EBPF] Computation of more than 128 bits not supported in EBPF.

[komaljai]

For header fields more than 128 bits, compiler throw errors as computation not supported

error: (bit<128>)hdr.ipv4.dst_addr: Computations on 128 bits not supported
meta.dst_ip_addr = (bit<128>)hdr.ipv4.dst_addr;

[jafingerhut]

P4-DPDK has a similar limitation today: #4174

As I mention there, I would strongly recommend that all P4 implementation consider supporting arithmetic operations up to 128-bit wide values, because IPv6 is a fairly commonly used header, and although you do not often want to do arithmetic on IPv6 addresses, in the few cases that you do, it is very helpful, and you really miss it if you do not have it.

I cannot think of any strong reason to support arithmetic on values wider than 128 bits. At least, there would be diminishing returns there in terms of common use cases.