Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Date:   Tue, 16 Aug 2022 11:07:17 -0700
From:   Jakub Kicinski <kuba@kernel.org>
To:     Bobby Eshleman <bobby.eshleman@gmail.com>
Cc:     "Michael S. Tsirkin" <mst@redhat.com>,
        Bobby Eshleman <bobbyeshleman@gmail.com>,
        Bobby Eshleman <bobby.eshleman@bytedance.com>,
        Cong Wang <cong.wang@bytedance.com>,
        Jiang Wang <jiang.wang@bytedance.com>,
        Stefan Hajnoczi <stefanha@redhat.com>,
        Stefano Garzarella <sgarzare@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>,
        Eric Dumazet <edumazet@google.com>,
        Paolo Abeni <pabeni@redhat.com>, kvm@vger.kernel.org,
        virtualization@lists.linux-foundation.org, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 3/6] vsock: add netdev to vhost/virtio vsock
Message-ID: <20220816110717.5422e976@kernel.org>
In-Reply-To: <20220816123701-mutt-send-email-mst@kernel.org>
References: <cover.1660362668.git.bobby.eshleman@bytedance.com>
        <5a93c5aad99d79f028d349cb7e3c128c65d5d7e2.1660362668.git.bobby.eshleman@bytedance.com>
        <20220816123701-mutt-send-email-mst@kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Content-Transfer-Encoding: quoted-printable
Precedence: bulk

On Tue, 16 Aug 2022 12:38:52 -0400 Michael S. Tsirkin wrote:
> On Mon, Aug 15, 2022 at 10:56:06AM -0700, Bobby Eshleman wrote:
> > In order to support usage of qdisc on vsock traffic, this commit
> > introduces a struct net_device to vhost and virtio vsock.
> >=20
> > Two new devices are created, vhost-vsock for vhost and virtio-vsock
> > for virtio. The devices are attached to the respective transports.
> >=20
> > To bypass the usage of the device, the user may "down" the associated
> > network interface using common tools. For example, "ip link set dev
> > virtio-vsock down" lets vsock bypass the net_device and qdisc entirely,
> > simply using the FIFO logic of the prior implementation. =20
>=20
> Ugh. That's quite a hack. Mark my words, at some point we will decide to
> have down mean "down".  Besides, multiple net devices with link up tend
> to confuse userspace. So might want to keep it down at all times
> even short term.

Agreed!

=46rom a cursory look (and Documentation/ would be nice..) it feels
very wrong to me. Do you know of any uses of a netdev which would=20
be semantically similar to what you're doing? Treating netdevs as
buildings blocks for arbitrary message passing solutions is something=20
I dislike quite strongly.

Could you recommend where I can learn more about vsocks?