From: Jesper Dangaard Brouer <brouer@redhat.com>
To: Toshiaki Makita <toshiaki.makita1@gmail.com>
Cc: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>,
Alexei Starovoitov <ast@kernel.org>,
Daniel Borkmann <daniel@iogearbox.net>,
netdev@vger.kernel.org,
Jakub Kicinski <jakub.kicinski@netronome.com>,
John Fastabend <john.fastabend@gmail.com>,
brouer@redhat.com
Subject: Re: [PATCH v7 bpf-next 05/10] veth: Handle xdp_frames in xdp napi ring
Date: Thu, 2 Aug 2018 15:53:36 +0200 [thread overview]
Message-ID: <20180802155336.15169974@redhat.com> (raw)
In-Reply-To: <4402804f-bf7b-9ca0-baa9-1415884b0a80@gmail.com>
On Thu, 2 Aug 2018 22:17:53 +0900
Toshiaki Makita <toshiaki.makita1@gmail.com> wrote:
> On 18/08/02 (木) 20:45, Jesper Dangaard Brouer wrote:
> > On Thu, 2 Aug 2018 19:55:09 +0900
> > Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp> wrote:
> >
> >> + headroom = frame->data - delta - (void *)frame;
> >
> > Your calculation of headroom is still adding an assumption that
> > xdp_frame is located in the top of data area, that is unnecessary.
> >
> > The headroom can be calculated as:
> >
> > headroom = sizeof(struct xdp_frame) + frame->headroom - delta;
>
> Thanks. But I'm not sure I get what you are requesting.
I'm simply requesting you do not use the (void *)frame pointer address,
to calculate the headroom, as it can be calculated in another way.
> Supposing xdp_frame is not located in the top of data area, what ensures
> that additional sizeof(struct xdp_frame) can be used?
The calculation in convert_to_xdp_frame() assures this. If we later
add an xdp_frame that is not located in the top of data area, and want
to change the reserved headroom size, then we deal with it, and update
the code.
--
Best regards,
Jesper Dangaard Brouer
MSc.CS, Principal Kernel Engineer at Red Hat
LinkedIn: http://www.linkedin.com/in/brouer
next prev parent reply other threads:[~2018-08-02 15:45 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-02 10:55 [PATCH v7 bpf-next 00/10] veth: Driver XDP Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 01/10] net: Export skb_headers_offset_update Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 02/10] veth: Add driver XDP Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 03/10] veth: Avoid drops by oversized packets when XDP is enabled Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 04/10] xdp: Helper function to clear kernel pointers in xdp_frame Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 05/10] veth: Handle xdp_frames in xdp napi ring Toshiaki Makita
2018-08-02 11:45 ` Jesper Dangaard Brouer
2018-08-02 13:17 ` Toshiaki Makita
2018-08-02 13:53 ` Jesper Dangaard Brouer [this message]
2018-08-02 14:10 ` Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 06/10] veth: Add ndo_xdp_xmit Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 07/10] bpf: Make redirect_info accessible from modules Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 08/10] xdp: Helpers for disabling napi_direct of xdp_return_frame Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 09/10] veth: Add XDP TX and REDIRECT Toshiaki Makita
2018-08-02 10:55 ` [PATCH v7 bpf-next 10/10] veth: Support per queue XDP ring Toshiaki Makita
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