netdev - Re: [PATCH] net/netlink: how to deal with the problem of exceeding the maximum reach of nlattr's nla

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Message-ID: <20240321073045.3ee6127d@kernel.org>
Date: Thu, 21 Mar 2024 07:30:45 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: renmingshuai <renmingshuai@...wei.com>
Cc: <davem@...emloft.net>, <edumazet@...gle.com>, <pabeni@...hat.com>,
 <idosch@...dia.com>, <netdev@...r.kernel.org>, <yanan@...wei.com>,
 <chenzhen126@...wei.com>, <liaichun@...wei.com>
Subject: Re: [PATCH] net/netlink: how to deal with the problem of exceeding
 the maximum reach of nlattr's nla_len

On Thu, 21 Mar 2024 22:14:00 +0800 renmingshuai wrote:
> RTM_GETLINK for greater than about 220 VFs truncates IFLA_VFINFO_LIST
> due to the maximum reach of nlattr's nla_len being exceeded. As a result,
> the value of nla_len overflows in nla_nest_end(). According to [1],
> changing the type of nla_len is not possible, but how can we deal with this
> overflow problem? The nla_len is constantly set to the
> maximum value when it overflows? Or some better ways?

It's a known limitation of the legacy SRIOV VF API.
Use switchdev mode instead, please.