From: Toshiaki Makita <toshiaki.makita1@gmail.com>
To: Jesper Dangaard Brouer <brouer@redhat.com>
Cc: Mao Wenan <maowenan@huawei.com>,
davem@davemloft.net, ast@kernel.org, daniel@iogearbox.net,
kuba@kernel.org, hawk@kernel.org, john.fastabend@gmail.com,
kafai@fb.com, songliubraving@fb.com, yhs@fb.com, andriin@fb.com,
jwi@linux.ibm.com, jianglidong3@jd.com, edumazet@google.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
bpf@vger.kernel.org, kernel-janitors@vger.kernel.org
Subject: Re: [PATCH net v2] veth: xdp: use head instead of hard_start
Date: Thu, 2 Apr 2020 09:47:03 +0900 [thread overview]
Message-ID: <ede2f407-839e-d29e-0ebe-aa39dd461bfd@gmail.com> (raw)
In-Reply-To: <20200401181419.7acd2aa6@carbon>
On 2020/04/02 1:15, Jesper Dangaard Brouer wrote:
...
> [PATCH RFC net-next] veth: adjust hard_start offset on redirect XDP frames
>
> When native XDP redirect into a veth device, the frame arrives in the
> xdp_frame structure. It is then processed in veth_xdp_rcv_one(),
> which can run a new XDP bpf_prog on the packet. Doing so requires
> converting xdp_frame to xdp_buff, but the tricky part is that
> xdp_frame memory area is located in the top (data_hard_start) memory
> area that xdp_buff will point into.
>
> The current code tried to protect the xdp_frame area, by assigning
> xdp_buff.data_hard_start past this memory. This results in 32 bytes
> less headroom to expand into via BPF-helper bpf_xdp_adjust_head().
>
> This protect step is actually not needed, because BPF-helper
> bpf_xdp_adjust_head() already reserve this area, and don't allow
> BPF-prog to expand into it. Thus, it is safe to point data_hard_start
> directly at xdp_frame memory area.
>
> Cc: Toshiaki Makita <makita.toshiaki@lab.ntt.co.jp>
FYI: This mail address is deprecated.
> Fixes: 9fc8d518d9d5 ("veth: Handle xdp_frames in xdp napi ring")
> Reported-by: Mao Wenan <maowenan@huawei.com>
> Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
FWIW,
Acked-by: Toshiaki Makita <toshiaki.makita1@gmail.com>
next prev parent reply other threads:[~2020-04-02 0:47 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-30 10:26 [PATCH net] veth: xdp: use head instead of hard_start Mao Wenan
2020-03-30 11:34 ` Jesper Dangaard Brouer
2020-03-30 23:35 ` Toshiaki Makita
2020-03-31 3:56 ` maowenan
2020-03-31 5:45 ` Toshiaki Makita
2020-03-31 6:06 ` [PATCH net v2] " Mao Wenan
2020-03-31 6:16 ` Toshiaki Makita
2020-04-01 16:15 ` Jesper Dangaard Brouer
2020-04-02 0:47 ` Toshiaki Makita [this message]
2020-04-02 9:06 ` Jesper Dangaard Brouer
2020-04-02 15:40 ` Alexei Starovoitov
2020-04-03 7:58 ` Jesper Dangaard Brouer
2020-04-03 21:12 ` Alexei Starovoitov
2020-04-02 1:23 ` maowenan
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