Re: [PATCH net-next 2/3] tools: ynl: print some information about attribute we can't parse

[Donald Hunter <donald.hunter@gmail.com>]

Jakub Kicinski <kuba@kernel.org> writes:

> When parsing throws an exception one often has to figure out which
> attribute couldn't be parsed from first principles. For families
> with large message parsing trees like rtnetlink guessing the
> attribute can be hard.
>
> Print a bit of information as the exception travels out, e.g.:
>
>   # when dumping rt links
>   Error decoding 'flags' from 'linkinfo-ip6tnl-attrs'
>   Error decoding 'data' from 'linkinfo-attrs'
>   Error decoding 'linkinfo' from 'link-attrs'
>   Traceback (most recent call last):
>     File "/home/kicinski/linux/./tools/net/ynl/cli.py", line 119, in <module>
>       main()
>     File "/home/kicinski/linux/./tools/net/ynl/cli.py", line 100, in main
>       reply = ynl.dump(args.dump, attrs)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 1064, in dump
>       return self._op(method, vals, dump=True)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 1058, in _op
>       return self._ops(ops)[0]
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 1045, in _ops
>       rsp_msg = self._decode(decoded.raw_attrs, op.attr_set.name)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 738, in _decode
>       subdict = self._decode(NlAttrs(attr.raw), attr_spec['nested-attributes'], search_attrs)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 763, in _decode
>       decoded = self._decode_sub_msg(attr, attr_spec, search_attrs)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 714, in _decode_sub_msg
>       subdict = self._decode(NlAttrs(attr.raw, offset), msg_format.attr_set)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 749, in _decode
>       decoded = attr.as_scalar(attr_spec['type'], attr_spec.byte_order)
>     File "/home/kicinski/linux/tools/net/ynl/lib/ynl.py", line 147, in as_scalar
>       return format.unpack(self.raw)[0]
>   struct.error: unpack requires a buffer of 2 bytes
>
> The Traceback is what we would previously see, the "Error..."
> messages are new. We print a message per level (in the stack
> order). Printing single combined message gets tricky quickly
> given sub-messages etc.
>
> Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Reviewed-by: Donald Hunter <donald.hunter@gmail.com>