sys/linux: add NDISC packet formats to vnet.txt

[dlrobertson]

Add the basic NDISC (RFC 4861) packet formats to sys/linux/vnet.txt.

[dvyukov]

Hi Dan,

While I am looking at the actual descriptions, you also need to generate *.const files, please see:
https://github.com/google/syzkaller/blob/master/docs/syscall_descriptions.md
In short:

make install_prerequisites
make extract SOURCEDIR=~/linux-next/checkout
make generate

and then add all changed files to this PR.

[dvyukov]

This does not look auto-formatted.
make generate will take care of formatting, or make format_sys will do it separately.

[dvyukov]

Perhaps this should be bytesize[data, int8]?

[dvyukov]

or bytesize[parent, int8]?

[dlrobertson]

I think bytesize8[data, int8bytesize8[parent, int8] is what we want. The length calculation for NDISC options is similar to that of the Hop-by-Hop options.

EDIT: s/data/parent/

[dvyukov]

If it's unused we could use const[0, int32]. Not that it's super important, but will fuzzer to not spend time mutating this a lot.

[dlrobertson]

👍 makes sense.

[dlrobertson]

@dvyukov thanks! Formatting etc now

[dlrobertson]

These constants are all just a single byte, so they'll be the same for all architectures regardless of endianness. Might be nice to add a vnet_any.const for constants like these?

[dvyukov]

These files are all auto-generated, so there is no cost in that duplication.

[dlrobertson]

👍

[dvyukov]

There is a problem with go fmt -- it changed format in between 1.10 and 1.11 (golang/go#25161) which creates problems.
We currently use format as produced by Go 1.9 and 1.10. You seems to use 1.11. I will reformat it now, but please use version 1.10 next time, for details see:
https://github.com/google/syzkaller/blob/master/docs/contributing.md#how-to-create-a-pull-request

[dlrobertson]

👍 yeah Gentoo uses 1.11.5.