netdev - Re: [PATCH net-next v3 03/10] net/sched: cls_flower: prepare fl_{set,dump}_key_flags() for ENC

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Message-ID: <84b4b03d-3ec5-48cc-a889-bbeaaf3ceb0c@fiberby.net>
Date: Sat, 13 Jul 2024 01:14:57 +0000
From: Asbjørn Sloth Tønnesen <ast@...erby.net>
To: Jakub Kicinski <kuba@...nel.org>
Cc: netdev@...r.kernel.org, Davide Caratti <dcaratti@...hat.com>,
 Ilya Maximets <i.maximets@....org>, Jamal Hadi Salim <jhs@...atatu.com>,
 Cong Wang <xiyou.wangcong@...il.com>, Jiri Pirko <jiri@...nulli.us>,
 "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Paolo Abeni <pabeni@...hat.com>, David Ahern <dsahern@...nel.org>,
 Simon Horman <horms@...nel.org>, Ratheesh Kannoth <rkannoth@...vell.com>,
 Florian Westphal <fw@...len.de>,
 Alexander Lobakin <aleksander.lobakin@...el.com>,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next v3 03/10] net/sched: cls_flower: prepare
 fl_{set,dump}_key_flags() for ENC_FLAGS

Hi Jakub,

On 7/12/24 1:54 AM, Jakub Kicinski wrote:
> On Tue,  9 Jul 2024 16:38:17 +0000 Asbjørn Sloth Tønnesen wrote:
>> +	if (NL_REQ_ATTR_CHECK(extack, NULL, tb, fl_mask)) {
> 
> Does this work with nest as NULL?

It does, but it gives less information:

  * struct netlink_ext_ack - netlink extended ACK report struct
  [..]
  * @miss_nest: nest missing an attribute (%NULL if missing top level attr)

NL_REQ_ATTR_CHECK() doesn't check the value of nest, it just sets it.

That line originates from Davide's patch and is already in net-next:
1d17568e74de ("net/sched: cls_flower: add support for matching tunnel control flags")

It was added to that patch, after Jamal requested it.
https://lore.kernel.org/CAM0EoMkE3kzL28jg-nZiwQ0HnrFtm9HNBJwU1SJk7Z++yHzrMw@mail.gmail.com/

> tb here is corresponding to attrs from tca[TCA_OPTIONS], so IIRC we need
> to pass tca[TCA_OPTIONS] as nest here. Otherwise the decoder will look
> for attribute with ID fl_mask at the root level, and the root attrs are
> from the TCA_ enum.
> 
> Looks like Donald covered flower in Documentation/netlink/specs/tc.yaml
> so you should be able to try to hit this using the Python ynl CLI:
> https://docs.kernel.org/next/userspace-api/netlink/intro-specs.html#simple-cli
> But to be honest I'm not 100% sure if the YNL reverse parser works with
> TC and its "sub-message" polymorphism ;)

After extending the spec to know about the enc_flags keys, I get this:

$ sudo ./tools/net/ynl/cli.py --spec Documentation/netlink/specs/tc.yaml --do newtfilter --json '{"chain": 0, "family": 
0, "handle": 4, "ifindex": 22, "info": 262152, "kind": "flower", "options": { "flags": 0, "key-enc-flags": 8, 
"key-eth-type": 2048}, "parent": 4294967283}'
Netlink error: Invalid argument
nl_len = 68 (52) nl_flags = 0x300 nl_type = 2
         error: -22
         extack: {'msg': 'Missing flags mask', 'miss-type': 111}

After propagating tca[TCA_OPTIONS] through:

Netlink error: Invalid argument
nl_len = 76 (60) nl_flags = 0x300 nl_type = 2
         error: -22
         extack: {'msg': 'Missing flags mask', 'miss-type': 111, 'miss-nest': 56}

In v4, I have added the propagation as the last patch.

-- 
Best regards
Asbjørn Sloth Tønnesen
Network Engineer
Fiberby - AS42541