Linux Virtualization - Nov 2019 - [PATCH net-next 3/6] vsock: add local transport support in the vsock core

> From: Stefano Garzarella [mailto:sgarzare at redhat.com]
> Sent: Tuesday, November 19, 2019 12:01 PM
> To: netdev at vger.kernel.org
>
> This patch allows to register a transport able to handle
> local communication (loopback).
> 
> Signed-off-by: Stefano Garzarella <sgarzare at redhat.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

On Thu, Nov 21, 2019 at 03:04:18PM +0000, Jorgen Hansen
wrote:
> > From: Stefano Garzarella [mailto:sgarzare at redhat.com]
> > Sent: Tuesday, November 19, 2019 12:01 PM
> > To: netdev at vger.kernel.org
> >
> > This patch allows to register a transport able to handle
> > local communication (loopback).
> > 
> > Signed-off-by: Stefano Garzarella <sgarzare at redhat.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.
I agree with you, indeed initially I developed it as built in, but
DEPMOD found a cyclic dependency because vsock_transport use
virtio_transport_common that use vsock, so if I include vsock_transport
in the vsock module, DEPMOD is not happy.

I don't know how to break this cyclic dependency, do you have any ideas?

Thanks,
Stefano

> From: Stefano Garzarella [mailto:sgarzare at redhat.com]
> Sent: Thursday, November 21, 2019 4:22 PM
> 
> On Thu, Nov 21, 2019 at 03:04:18PM +0000, Jorgen Hansen wrote:
> > > From: Stefano Garzarella [mailto:sgarzare at redhat.com]
> > > Sent: Tuesday, November 19, 2019 12:01 PM
> > > To: netdev at vger.kernel.org
> > >
> > > This patch allows to register a transport able to handle
> > > local communication (loopback).
> > >
> > > Signed-off-by: Stefano Garzarella <sgarzare at redhat.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.
> 
> I agree with you, indeed initially I developed it as built in, but
> DEPMOD found a cyclic dependency because vsock_transport use
> virtio_transport_common that use vsock, so if I include vsock_transport
> in the vsock module, DEPMOD is not happy.
> 
> I don't know how to break this cyclic dependency, do you have any
ideas?
One way to view this would be that the loopback transport and the support
it uses from virtio_transport_common are independent of virtio as such,
and could be part of  the af_vsock module if loopback is configured. So
in a way, the virtio g2h and h2g transports would be extensions of the
built in loopback transport. But that brings in quite a bit of code so
it could be better to just keep it as is.

Thanks,
Jorgen