netdev - Re: [PATCH net] macsec: Fix header length if SCI is added if explicitily disabled

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Message-ID: <20161024112822.GA28497@bistromath.localdomain>
Date:   Mon, 24 Oct 2016 13:28:22 +0200
From:   Sabrina Dubroca <sd@...asysnail.net>
To:     Tobias Brunner <tobias@...ongswan.org>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH net] macsec: Fix header length if SCI is added if
 explicitily disabled

2016-10-21, 13:11:37 +0200, Tobias Brunner wrote:
> Even if sending SCIs is explicitly disabled, the code that creates the
> Security Tag might still decide to add it (e.g. if multiple RX SCs are
> defined on the MACsec interface).
> But because the header length so far only depended on the configuration
> option the SCI might not actually have ended up in the packet, while the
> SC flag in the TCI field of the Security Tag was still set, resulting
> in invalid MACsec frames.

Or overwriting the original frame's contents (ethertype and eg
beginning of the IP header) if !encrypt.

Fixes: c09440f7dcb3 ("macsec: introduce IEEE 802.1AE driver")

[snip]
> @@ -440,12 +448,12 @@ static void macsec_fill_sectag(struct macsec_eth_header *h,
>  			       const struct macsec_secy *secy, u32 pn)
>  {
>  	const struct macsec_tx_sc *tx_sc = &secy->tx_sc;
> +	bool sci_present = send_sci(secy);

You're already computing this in macsec_encrypt() just before calling
macsec_fill_sectag(), so you could pass it as argument instead of
recomputing it.

Other than that, LGTM, thanks!

-- 
Sabrina