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Message-ID: <e5e0640094a4e594eda8c3f8a54eca6728e58510.camel@codeconstruct.com.au>
Subject: Re: [PATCH net-next v1] net: mctp: use deprecated parser in
 mctp_set_link_af
From: Jeremy Kerr <jk@codeconstruct.com.au>
To: Lin Ma <linma@zju.edu.cn>, Jakub Kicinski <kuba@kernel.org>
Cc: matt@codeconstruct.com.au, davem@davemloft.net, edumazet@google.com, 
	pabeni@redhat.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Date: Thu, 04 Jan 2024 14:43:38 +0800
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Hi Lin,

> (1) will get AF_MCTP with nla_type(...) call, and (2) will then
> passing `af` to `mctp_set_link_af`, which will expect the
> `NLA_F_NESTED` flag.

You could set that flag? It's not exclusive with the attribute type.
From netlink.h:

  /*
   * nla_type (16 bits)
   * +---+---+-------------------------------+
   * | N | O | Attribute Type                |
   * +---+---+-------------------------------+
   * N :=3D Carries nested attributes
   * O :=3D Payload stored in network byte order
   *
   * Note: The N and O flag are mutually exclusive.
   */

Which is what we do with existing userspace:

  https://github.com/CodeConstruct/mctp/blob/6aa4b052d/src/mctp.c#L569C1-L5=
69C1

Cheers,


Jeremy