linux-kernel - Re: [PATCH v2 07/18] xen/pvcalls: implement socket command

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Message-ID: <alpine.DEB.2.10.1706021137060.18759@sstabellini-ThinkPad-X260>
Date:   Fri, 2 Jun 2017 11:41:16 -0700 (PDT)
From:   Stefano Stabellini <sstabellini@...nel.org>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
cc:     Stefano Stabellini <sstabellini@...nel.org>,
        xen-devel@...ts.xen.org, linux-kernel@...r.kernel.org,
        jgross@...e.com, Stefano Stabellini <stefano@...reto.com>
Subject: Re: [PATCH v2 07/18] xen/pvcalls: implement socket command

On Fri, 26 May 2017, Boris Ostrovsky wrote:
> On 05/19/2017 07:22 PM, Stefano Stabellini wrote:
> > Just reply with success to the other end for now. Delay the allocation
> > of the actual socket to bind and/or connect.
> >
> > Signed-off-by: Stefano Stabellini <stefano@...reto.com>
> > CC: boris.ostrovsky@...cle.com
> > CC: jgross@...e.com
> > ---
> >  drivers/xen/pvcalls-back.c | 29 ++++++++++++++++++++++++++++-
> >  1 file changed, 28 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/xen/pvcalls-back.c b/drivers/xen/pvcalls-back.c
> > index 9dc8a28..fed54bf 100644
> > --- a/drivers/xen/pvcalls-back.c
> > +++ b/drivers/xen/pvcalls-back.c
> > @@ -12,12 +12,17 @@
> >   * GNU General Public License for more details.
> >   */
> >  
> > +#include <linux/inet.h>
> >  #include <linux/kthread.h>
> >  #include <linux/list.h>
> >  #include <linux/radix-tree.h>
> >  #include <linux/module.h>
> >  #include <linux/semaphore.h>
> >  #include <linux/wait.h>
> > +#include <net/sock.h>
> > +#include <net/inet_common.h>
> > +#include <net/inet_connection_sock.h>
> > +#include <net/request_sock.h>
> >  
> >  #include <xen/events.h>
> >  #include <xen/grant_table.h>
> > @@ -55,7 +60,29 @@ struct pvcalls_back_priv {
> >  static int pvcalls_back_socket(struct xenbus_device *dev,
> >  		struct xen_pvcalls_request *req)
> >  {
> > -	return 0;
> > +	struct pvcalls_back_priv *priv;
> > +	int ret;
> > +	struct xen_pvcalls_response *rsp;
> > +
> > +	priv = dev_get_drvdata(&dev->dev);
> > +
> > +	if (req->u.socket.domain != AF_INET ||
> > +	    req->u.socket.type != SOCK_STREAM ||
> > +	    (req->u.socket.protocol != 0 &&
> > +	     req->u.socket.protocol != AF_INET))
> > +		ret = -EAFNOSUPPORT;
> > +	else
> > +		ret = 0;
> > +
> > +	/* leave the actual socket allocation for later */
> 
> Why is this allocation deferred (to connect and bind)? Doesn't it in
> some way violate semantics of socket call?

For convenience: this way we can easily distinguish active sockets from
passive sockets when we do the allocation. I don't think it violates the
semantics, as in pvcalls the socket identifier is chosen ("allocated")
by the frontend anyway.


> > +
> > +	rsp = RING_GET_RESPONSE(&priv->ring, priv->ring.rsp_prod_pvt++);
> > +	rsp->req_id = req->req_id;
> > +	rsp->cmd = req->cmd;
> > +	rsp->u.socket.id = req->u.socket.id;
> > +	rsp->ret = ret;
> > +
> > +	return ret;
> >  }
> >  
> >  static int pvcalls_back_connect(struct xenbus_device *dev,