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Message-ID: <ZS+OpBfxCkX1hQAj@nanopsycho> Date: Wed, 18 Oct 2023 09:52:04 +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 05:50:53PM CEST, kuba@...nel.org wrote: >On Tue, 17 Oct 2023 08:18:13 +0200 Jiri Pirko wrote: >> 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. > >Just to be able to do spec["type"] on it? Nope. Need .is_multi() and spec["name"] as well. > >There is an if "ladder", just replace the first > > if attr_spec["type"] == ... > >with > if attr_spec is None: > # your code > elif attr_spec["type"] == ... > >hm? Well, I need the same processing for "else". Okay, I'll to this with local variables instead. Fake class looked a bit more elegant. > >> >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? > >I'm just giving you extra info to explain my thinking. >Given how we struggle to understand each other lately :S Yeah :/ > >> >So returning a raw NlAttr appeals to me more. >> >> Wait, you suggest not to print out attr.as_bin(), but something else? > >Yea, it should not be needed. NlAttr has a __repr__ which *I think* >should basically do the same thing? Or you may need to call that >__repr__ from __str__, I don't know what PrettyPrinter uses internally Instead of: {'129': {'0': b'\x00\x00\x00\x00\x00\x00\x00\x00', '1': b'\x00\x00\x00\x00\x00\x00\x00\x00', '2': b'(\x00\x00\x00\x00\x00\x00\x00'}, You'd get: {'129': {'0': [type:0 len:12] b'\x00\x00\x00\x00\x00\x00\x00\x00', '1': [type:1 len:12] b'\x00\x00\x00\x00\x00\x00\x00\x00', '2': [type:2 len:12] b'(\x00\x00\x00\x00\x00\x00\x00'}, Looks like unnecessary redundant info, I would rather stick with "as_bin()". __repr__() is printable representation of the whole object, we just need value here, already have that in a structured object. > >> >> + 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? > >No strong reason but you need to rewrite it to at least not access >attr._type directly. Okay. > >I have a weak preference for putting this code in NlAttr's __repr__, >could be more broadly useful? As I pointed out above, it's a different use case. Here we do decoding into structured object. __repr__() is fro plain str conversion.
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