[P4-dev] clarify nested struct support in P4-16?

hemant at mnkcg.com hemant at mnkcg.com
Thu Aug 24 10:11:13 EDT 2017



Got it - thanks.




From: Mihai Budiu [mailto:mbudiu at vmware.com] 
Sent: Wednesday, August 23, 2017 11:11 PM
To: hemant at mnkcg.com; 'p4-dev lists.p4.org' <p4-dev at lists.p4.org>
Subject: RE: [P4-dev] clarify nested struct support in P4-16?


P4-16 allows nested structures to an arbitrary degree. Various targets and
back-ends may introduce additional restrictions. Some restrictions are due
to target limitations, and may never be lifted, some are due to code
immaturity in the compilers.


The bmv2 backend removes nested structs that do not appear in control apis
(arguments),because bmv does not support nested structs.  More work is
needed to remove the other ones. In principle ebpf does not need to remove
nested structs, because it generates c, which supports nested structs.
However, there are currently no tests with nested structs, so it is possible
that they don't work.




From: hemant at mnkcg.com <mailto:hemant at mnkcg.com> 
Sent: Wednesday, August 23, 2017 16:47
To: 'p4-dev lists.p4.org' <mailto:p4-dev at lists.p4.org> 
Subject: [P4-dev] clarify nested struct support in P4-16?


I don't see any text in the P4-16 spec that says nested struct is not
supported.  At least, when I use p4test, I see a nested struct pass
compilation.  When folks get a chance, the EBPF backend could use the same
behavior because p4c-ebpf does not support a nested struct.



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