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References: <20210205224124.21345-1-xie.he.0141@gmail.com>
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From:   Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date:   Fri, 5 Feb 2021 21:51:36 -0500
Message-ID: <CA+FuTScLTZqZhNU7bWEw4OMTQzcKV106iRLwA--La0uH+JrTtg@mail.gmail.com>
Subject: Re: [PATCH net-next] net/packet: Improve the comment about LL header
 visibility criteria
To:     Xie He <xie.he.0141@gmail.com>
Cc:     "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        Eric Dumazet <edumazet@google.com>,
        John Ogness <john.ogness@linutronix.de>,
        Tanner Love <tannerlove@google.com>,
        Eyal Birger <eyal.birger@gmail.com>,
        Network Development <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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On Fri, Feb 5, 2021 at 5:42 PM Xie He <xie.he.0141@gmail.com> wrote:
>
> The "dev_has_header" function, recently added in
> commit d549699048b4 ("net/packet: fix packet receive on L3 devices
> without visible hard header"),
> is more accurate as criteria for determining whether a device exposes
> the LL header to upper layers, because in addition to dev->header_ops,
> it also checks for dev->header_ops->create.
>
> When transmitting an skb on a device, dev_hard_header can be called to
> generate an LL header. dev_hard_header will only generate a header if
> dev->header_ops->create is present.
>
> Signed-off-by: Xie He <xie.he.0141@gmail.com>

Acked-by: Willem de Bruijn <willemb@google.com>

Indeed, existence of dev->header_ops->create is the deciding factor. Thanks Xie.