linux-kernel - Re: [PATCH net] ethtool: add and use message type for tunnel info reply

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Message-ID: <20200917014151.GK3463198@lunn.ch>
Date:   Thu, 17 Sep 2020 03:41:51 +0200
From:   Andrew Lunn <andrew@...n.ch>
To:     Michal Kubecek <mkubecek@...e.cz>
Cc:     David Miller <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net] ethtool: add and use message type for tunnel info
 reply

On Thu, Sep 17, 2020 at 01:04:10AM +0200, Michal Kubecek wrote:
> Tunnel offload info code uses ETHTOOL_MSG_TUNNEL_INFO_GET message type (cmd
> field in genetlink header) for replies to tunnel info netlink request, i.e.
> the same value as the request have. This is a problem because we are using
> two separate enums for userspace to kernel and kernel to userspace message
> types so that this ETHTOOL_MSG_TUNNEL_INFO_GET (28) collides with
> ETHTOOL_MSG_CABLE_TEST_TDR_NTF which is what message type 28 means for
> kernel to userspace messages.

>  
>  	rskb = ethnl_reply_init(reply_len, req_info.dev,
> -				ETHTOOL_MSG_TUNNEL_INFO_GET,
> +				ETHTOOL_MSG_TUNNEL_INFO_GET_REPLY,
>  				ETHTOOL_A_TUNNEL_INFO_HEADER,
>  				info, &reply_payload);

Michal

Maybe it would make sense to change the two enums from anonymous to
tagged. We can then make ethnl_reply_init() do type checking and
hopefully catch such problems earlier?

I just wonder if we then run into ABI problems?

	  Andrew