linux-kernel - RE: [PATCH net-next 3/6] vsock: add local transport support in the vsock core

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Message-ID: <MWHPR05MB3376F4452F0CF38C1AFABA2EDA4E0@MWHPR05MB3376.namprd05.prod.outlook.com>
Date:   Thu, 21 Nov 2019 15:04:18 +0000
From:   Jorgen Hansen <jhansen@...are.com>
To:     'Stefano Garzarella' <sgarzare@...hat.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>
CC:     "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        Dexuan Cui <decui@...rosoft.com>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kvm@...r.kernel.org" <kvm@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>
Subject: RE: [PATCH net-next 3/6] vsock: add local transport support in the
 vsock core

> From: Stefano Garzarella [mailto:sgarzare@...hat.com]
> Sent: Tuesday, November 19, 2019 12:01 PM
> To: netdev@...r.kernel.org
>
> This patch allows to register a transport able to handle
> local communication (loopback).
> 
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
>  include/net/af_vsock.h   |  2 ++
>  net/vmw_vsock/af_vsock.c | 17 ++++++++++++++++-
>  2 files changed, 18 insertions(+), 1 deletion(-)
> 
> diff --git a/include/net/af_vsock.h b/include/net/af_vsock.h
> index 4206dc6d813f..b1c717286993 100644
> --- a/include/net/af_vsock.h
> +++ b/include/net/af_vsock.h
> @@ -98,6 +98,8 @@ struct vsock_transport_send_notify_data {
>  #define VSOCK_TRANSPORT_F_G2H		0x00000002
>  /* Transport provides DGRAM communication */
>  #define VSOCK_TRANSPORT_F_DGRAM		0x00000004
> +/* Transport provides local (loopback) communication */
> +#define VSOCK_TRANSPORT_F_LOCAL		0x00000008
> 
>  struct vsock_transport {
>  	struct module *module;
> diff --git a/net/vmw_vsock/af_vsock.c b/net/vmw_vsock/af_vsock.c
> index cc8659838bf2..c9e5bad59dc1 100644
> --- a/net/vmw_vsock/af_vsock.c
> +++ b/net/vmw_vsock/af_vsock.c
> @@ -136,6 +136,8 @@ static const struct vsock_transport *transport_h2g;
>  static const struct vsock_transport *transport_g2h;
>  /* Transport used for DGRAM communication */
>  static const struct vsock_transport *transport_dgram;
> +/* Transport used for local communication */
> +static const struct vsock_transport *transport_local;
>  static DEFINE_MUTEX(vsock_register_mutex);
> 
>  /**** UTILS ****/
> @@ -2130,7 +2132,7 @@ EXPORT_SYMBOL_GPL(vsock_core_get_transport);
> 
>  int vsock_core_register(const struct vsock_transport *t, int features)
>  {
> -	const struct vsock_transport *t_h2g, *t_g2h, *t_dgram;
> +	const struct vsock_transport *t_h2g, *t_g2h, *t_dgram, *t_local;
>  	int err = mutex_lock_interruptible(&vsock_register_mutex);
> 
>  	if (err)
> @@ -2139,6 +2141,7 @@ int vsock_core_register(const struct
> vsock_transport *t, int features)
>  	t_h2g = transport_h2g;
>  	t_g2h = transport_g2h;
>  	t_dgram = transport_dgram;
> +	t_local = transport_local;
> 
>  	if (features & VSOCK_TRANSPORT_F_H2G) {
>  		if (t_h2g) {
> @@ -2164,9 +2167,18 @@ int vsock_core_register(const struct
> vsock_transport *t, int features)
>  		t_dgram = t;
>  	}
> 
> +	if (features & VSOCK_TRANSPORT_F_LOCAL) {
> +		if (t_local) {
> +			err = -EBUSY;
> +			goto err_busy;
> +		}
> +		t_local = t;
> +	}
> +
>  	transport_h2g = t_h2g;
>  	transport_g2h = t_g2h;
>  	transport_dgram = t_dgram;
> +	transport_local = t_local;
> 
>  err_busy:
>  	mutex_unlock(&vsock_register_mutex);
> @@ -2187,6 +2199,9 @@ void vsock_core_unregister(const struct
> vsock_transport *t)
>  	if (transport_dgram == t)
>  		transport_dgram = NULL;
> 
> +	if (transport_local == t)
> +		transport_local = NULL;
> +
>  	mutex_unlock(&vsock_register_mutex);
>  }
>  EXPORT_SYMBOL_GPL(vsock_core_unregister);
> --
> 2.21.0

Having loopback support as a separate transport fits nicely, but do we need to support
different variants of loopback? It could just be built in.

Thanks,
Jorgen