netdev - Re: [patch net-next v2] tools: ynl: introduce option to process unknown attributes or types

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Date: Tue, 17 Oct 2023 08:18:13 +0200
From: Jiri Pirko <jiri@...nulli.us>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, pabeni@...hat.com, davem@...emloft.net,
	edumazet@...gle.com
Subject: Re: [patch net-next v2] tools: ynl: introduce option to process
 unknown attributes or types

Tue, Oct 17, 2023 at 02:59:03AM CEST, kuba@...nel.org wrote:
>On Mon, 16 Oct 2023 13:02:22 +0200 Jiri Pirko wrote:
>> +class FakeSpecAttr:
>> +    def __init__(self, name):
>> +        self.dict = {"name": name, "type": None}
>> +        self.is_multi = False
>> +
>> +    def __getitem__(self, key):
>> +        return self.dict[key]
>> +
>> +    def __contains__(self, key):
>> +        return key in self.dict
>
>Why the new class? Why not attach the NlAttr object directly?

It's not NlAttr, it's SpecAttr. And that has a constructor with things I
cannot provide for fake object, that's why I did this dummy object.


>
>I have an idea knocking about in my head to support "polymorphic"
>nests (nests where decoding depends on value of another attr,
>link rtnl link attrs or tc object attrs). The way I'm thinking 
>about doing it is to return NlAttr / struct nla_attr back to the user.
>And let the users call a sub-parser of choice by hand.

Sounds parallel to this patch, isn't it?


>
>So returning a raw NlAttr appeals to me more.

Wait, you suggest not to print out attr.as_bin(), but something else?


>
>> +                if not self.process_unknown:
>> +                    raise Exception(f'Unknown {attr_spec["type"]} with name {attr_spec["name"]}')
>> +                if attr._type & Netlink.NLA_F_NESTED:
>> +                    subdict = self._decode(NlAttrs(attr.raw), None)
>> +                    decoded = subdict
>> +                else:
>> +                    decoded = attr.as_bin()
>
>Again, I wouldn't descend at all.

I don't care that much. I just thought it might be handy for the user to
understand the topology. Actually, I found it quite convenient already.
It's basically a direct dump. What is the reason not to do this exactly?