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From:   Eyal Birger <eyal.birger@gmail.com>
Date:   Sat, 6 Feb 2021 17:42:54 +0200
Message-ID: <CAHsH6GuW-xYp01ovBBC7+j8_v_WfiDmYznxW3Ajzo_qSFLy93A@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>,
        Willem de Bruijn <willemdebruijn.kernel@gmail.com>,
        Eric Dumazet <edumazet@google.com>,
        John Ogness <john.ogness@linutronix.de>,
        Tanner Love <tannerlove@google.com>,
        Network Development <netdev@vger.kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>
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Hi,

On Sat, Feb 6, 2021 at 4:52 AM Willem de Bruijn
<willemdebruijn.kernel@gmail.com> wrote:
>
> 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.

As such, may I suggest making this explicit by making
dev_hard_header() use dev_has_header()?

Eyal.