From: Jason Wang <jasowang@redhat.com>
To: David Woodhouse <dwmw2@infradead.org>, netdev@vger.kernel.org
Cc: "Eugenio Pérez" <eperezma@redhat.com>,
"Willem de Bruijn" <willemb@google.com>
Subject: Re: [PATCH v3 3/5] vhost_net: remove virtio_net_hdr validation, let tun/tap do it themselves
Date: Mon, 28 Jun 2021 12:23:13 +0800 [thread overview]
Message-ID: <1c6110d9-2a45-f766-9d9a-e2996c14b748@redhat.com> (raw)
In-Reply-To: <bfad641875aff8ff008dd7f9a072c5aa980703f4.camel@infradead.org>
在 2021/6/25 下午4:37, David Woodhouse 写道:
> On Fri, 2021-06-25 at 15:33 +0800, Jason Wang wrote:
>> 在 2021/6/24 下午8:30, David Woodhouse 写道:
>>> From: David Woodhouse<dwmw@amazon.co.uk>
>>>
>>> When the underlying socket isn't configured with a virtio_net_hdr, the
>>> existing code in vhost_net_build_xdp() would attempt to validate
>>> uninitialised data, by copying zero bytes (sock_hlen) into the local
>>> copy of the header and then trying to validate that.
>>>
>>> Fixing it is somewhat non-trivial because the tun device might put a
>>> struct tun_pi*before* the virtio_net_hdr, which makes it hard to find.
>>> So just stop messing with someone else's data in vhost_net_build_xdp(),
>>> and let tap and tun validate it for themselves, as they do in the
>>> non-XDP case anyway.
>>
>> Thinking in another way. All XDP stuffs for vhost is prepared for TAP.
>> XDP is not expected to work for TUN.
>>
>> So we can simply let's vhost doesn't go with XDP path is the underlayer
>> socket is TUN.
> Actually, IFF_TUN mode per se isn't that complex. It's fixed purely on
> the tun side by that first patch I posted, which I later expanded a
> little to factor out tun_skb_set_protocol().
>
> The next two patches in my original set were fixing up the fact that
> XDP currently assumes that the *socket* will be doing the vhdr, not
> vhost. Those two weren't tun-specific at all.
>
> It's supporting the PI header (which tun puts *before* the virtio
> header as I just said) which introduces a tiny bit more complexity.
This reminds me we need to fix tun_put_user_xdp(), but as we've
discussed, we need first figure out if PI is worth to support for vhost-net.
>
> So yes, avoiding the XDP path if PI is being used would make some
> sense.
>
> In fact I wouldn't be entirely averse to refusing PI mode completely,
> as long as we fail gracefully at setup time by refusing the
> SET_BACKEND. Not by just silently failing to receive packets.
That's another way. Actually, macvtap mandate IFF_TAP | IFF_NO_PI.
Thanks
>
> But then again, it's not actually *that* hard to support, and it's
> working fine in my selftests at the end of my patch series.
>
next prev parent reply other threads:[~2021-06-28 4:27 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-19 13:33 [PATCH] net: tun: fix tun_xdp_one() for IFF_TUN mode David Woodhouse
2021-06-21 7:00 ` Jason Wang
2021-06-21 10:52 ` David Woodhouse
2021-06-21 14:50 ` David Woodhouse
2021-06-21 20:43 ` David Woodhouse
2021-06-22 4:52 ` Jason Wang
2021-06-22 7:24 ` David Woodhouse
2021-06-22 7:51 ` Jason Wang
2021-06-22 8:10 ` David Woodhouse
2021-06-22 11:36 ` David Woodhouse
2021-06-22 4:34 ` Jason Wang
2021-06-22 4:34 ` Jason Wang
2021-06-22 7:28 ` David Woodhouse
2021-06-22 8:00 ` Jason Wang
2021-06-22 8:29 ` David Woodhouse
2021-06-23 3:39 ` Jason Wang
2021-06-24 12:39 ` David Woodhouse
2021-06-22 16:15 ` [PATCH v2 1/4] " David Woodhouse
2021-06-22 16:15 ` [PATCH v2 2/4] net: tun: don't assume IFF_VNET_HDR in tun_xdp_one() tx path David Woodhouse
2021-06-23 3:46 ` Jason Wang
2021-06-22 16:15 ` [PATCH v2 3/4] vhost_net: validate virtio_net_hdr only if it exists David Woodhouse
2021-06-23 3:48 ` Jason Wang
2021-06-22 16:15 ` [PATCH v2 4/4] vhost_net: Add self test with tun device David Woodhouse
2021-06-23 4:02 ` Jason Wang
2021-06-23 16:12 ` David Woodhouse
2021-06-24 6:12 ` Jason Wang
2021-06-24 10:42 ` David Woodhouse
2021-06-25 2:55 ` Jason Wang
2021-06-25 7:54 ` David Woodhouse
2021-06-23 3:45 ` [PATCH v2 1/4] net: tun: fix tun_xdp_one() for IFF_TUN mode Jason Wang
2021-06-23 8:30 ` David Woodhouse
2021-06-23 13:52 ` David Woodhouse
2021-06-23 17:31 ` David Woodhouse
2021-06-23 22:52 ` David Woodhouse
2021-06-24 6:37 ` Jason Wang
2021-06-24 7:23 ` David Woodhouse
2021-06-24 6:18 ` Jason Wang
2021-06-24 7:05 ` David Woodhouse
2021-06-24 12:30 ` [PATCH v3 1/5] net: add header len parameter to tun_get_socket(), tap_get_socket() David Woodhouse
2021-06-24 12:30 ` [PATCH v3 2/5] net: tun: don't assume IFF_VNET_HDR in tun_xdp_one() tx path David Woodhouse
2021-06-25 6:58 ` Jason Wang
2021-06-24 12:30 ` [PATCH v3 3/5] vhost_net: remove virtio_net_hdr validation, let tun/tap do it themselves David Woodhouse
2021-06-25 7:33 ` Jason Wang
2021-06-25 8:37 ` David Woodhouse
2021-06-28 4:23 ` Jason Wang [this message]
2021-06-28 11:23 ` David Woodhouse
2021-06-28 23:29 ` David Woodhouse
2021-06-29 3:43 ` Jason Wang
2021-06-29 6:59 ` David Woodhouse
2021-06-29 10:49 ` David Woodhouse
2021-06-29 13:15 ` David Woodhouse
2021-06-30 4:39 ` Jason Wang
2021-06-30 10:02 ` David Woodhouse
2021-07-01 4:13 ` Jason Wang
2021-07-01 17:39 ` David Woodhouse
2021-07-02 3:13 ` Jason Wang
2021-07-02 8:08 ` David Woodhouse
2021-07-02 8:50 ` Jason Wang
2021-07-09 15:04 ` Eugenio Perez Martin
2021-06-29 3:21 ` Jason Wang
2021-06-24 12:30 ` [PATCH v3 4/5] net: tun: fix tun_xdp_one() for IFF_TUN mode David Woodhouse
2021-06-25 7:41 ` Jason Wang
2021-06-25 8:51 ` David Woodhouse
2021-06-28 4:27 ` Jason Wang
2021-06-28 10:43 ` David Woodhouse
2021-06-25 18:43 ` Willem de Bruijn
2021-06-25 19:00 ` David Woodhouse
2021-06-24 12:30 ` [PATCH v3 5/5] vhost_net: Add self test with tun device David Woodhouse
2021-06-25 5:00 ` [PATCH v3 1/5] net: add header len parameter to tun_get_socket(), tap_get_socket() Jason Wang
2021-06-25 8:23 ` David Woodhouse
2021-06-28 4:22 ` Jason Wang
2021-06-25 18:13 ` Willem de Bruijn
2021-06-25 18:55 ` David Woodhouse
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