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Date:   Tue, 19 Jul 2022 17:37:26 +0200
From:   Andrew Lunn <andrew@lunn.ch>
To:     Antonio Quartulli <antonio@openvpn.net>
Cc:     netdev@vger.kernel.org, David Miller <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [RFC 1/1] net: introduce OpenVPN Data Channel Offload (ovpn-dco)
Message-ID: <YtbPtkF1Ah9xrBam@lunn.ch>
References: <20220719014704.21346-1-antonio@openvpn.net>
 <20220719014704.21346-2-antonio@openvpn.net>
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> +static int ovpn_net_change_mtu(struct net_device *dev, int new_mtu)
> +{
> +	if (new_mtu < IPV4_MIN_MTU ||
> +	    new_mtu + dev->hard_header_len > IP_MAX_MTU)
> +		return -EINVAL;

If you set dev->min_mtu and dev->max_mtu, the core will validate this
for you, see dev_validate_mtu().

> +static int ovpn_get_link_ksettings(struct net_device *dev,
> +				   struct ethtool_link_ksettings *cmd)
> +{
> +	ethtool_convert_legacy_u32_to_link_mode(cmd->link_modes.supported, 0);
> +	ethtool_convert_legacy_u32_to_link_mode(cmd->link_modes.advertising, 0);

These two should not be needed. Look at tun, veth etc, they don't set
them.

	Andrew