linux-kernel - Re: [RFC net-next v1 4/5] net: macsec: introduce mdo_insert_tx

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Message-ID: <6eccb80a-a03c-4944-b7ac-e79e191802e6@oss.nxp.com>
Date:   Wed, 16 Aug 2023 13:12:26 +0300
From:   "Radu Pirea (OSS)" <radu-nicolae.pirea@....nxp.com>
To:     Andrew Lunn <andrew@...n.ch>
Cc:     hkallweit1@...il.com, linux@...linux.org.uk, davem@...emloft.net,
        edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com,
        richardcochran@...il.com, sd@...asysnail.net,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC net-next v1 4/5] net: macsec: introduce mdo_insert_tx_tag



On 11.08.2023 20:42, Andrew Lunn wrote:
> On Fri, Aug 11, 2023 at 06:32:48PM +0300, Radu Pirea (NXP OSS) wrote:
> 
>> +	if (macsec->offload == MACSEC_OFFLOAD_OFF) {
>> +		dev->needed_headroom -= ops->needed_headroom;
>> +		dev->needed_headroom += MACSEC_NEEDED_HEADROOM;
>> +		dev->needed_tailroom -= ops->needed_tailroom;
>> +		dev->needed_tailroom += MACSEC_NEEDED_TAILROOM;
>> +	} else {
>> +		dev->needed_headroom -= MACSEC_NEEDED_HEADROOM;
>> +		dev->needed_headroom += ops->needed_headroom;
>> +		dev->needed_tailroom -= MACSEC_NEEDED_TAILROOM;
>> +		dev->needed_tailroom += ops->needed_tailroom;
>> +	}
> 
> It is not obvious to me what this is doing. Should this actually be in
> macsec_dev_init()? My main problem is why there is an else condition?

The user can enable/disable offloading after the interface is created, 
that's why the else condition is needed.

>> +static struct sk_buff *insert_tx_tag(struct sk_buff *skb,
>> +				     struct net_device *dev)
>> +{
>> +	struct macsec_dev *macsec = macsec_priv(dev);
>> +	const struct macsec_ops *ops;
>> +	struct macsec_context ctx;
>> +	int err;
>> +
>> +	if (!macsec_is_offloaded(macsec))
>> +		return ERR_PTR(-EINVAL);
> 
> Hasn't this already been checked in macsec_start_xmit()
Yes. This check is useless.

> 
>> +
>> +	ops = macsec_get_ops(macsec, &ctx);
>> +	if (!ops)
>> +		return ERR_PTR(-EINVAL);
>> +
>> +	if (!ops->mdo_insert_tx_tag)
>> +		return skb;
> 
> You are in the hot path here. You don't expect this to change from
> frame to frame. So could you evaluate this once and store it
> somewhere? Maybe in macsec_dev ?

The macsec_dev struct seems to be the right place.

> 
> 	Andrew

-- 
Radu P.