Subject: Re: [PATCH RFC] tun: export underlying socket

From: Eric Dumazet <[email-masked]>
Date: Fri, 11 Sep 2009 08:10:27 +0200

Michael S. Tsirkin a écrit :
> On Fri, Sep 11, 2009 at 07:59:43AM +0300, Michael S. Tsirkin wrote:
>> On Fri, Sep 11, 2009 at 12:17:27AM -0400, Paul Moore wrote:
>>> On Thursday 10 September 2009 08:59:29 am Michael S. Tsirkin wrote:
>>>> Tun device looks similar to a packet socket
>>>> in that both pass complete frames from/to userspace.
>>>>
>>>> This patch fills in enough fields in the socket underlying tun driver
>>>> to support sendmsg/recvmsg operations, and exports access to this socket
>>>> to modules.
>>>>
>>>> This way, code using raw sockets to inject packets
>>>> into a physical device, can support injecting
>>>> packets into host network stack almost without modification.
>>>>
>>>> First user of this interface will be vhost virtualization
>>>> accelerator.
>>> No comments on the code at this point - I'm just trying to understand the 
>>> intended user right now which I'm assuming is the vhost-net bits you sent 
>>> previously? 
>> Yes - these now use raw socket,
> 
> More specifically, vhost would then be patched with:
> 
> diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
> index aeffb3a..b54f9d6 100644
> --- a/drivers/vhost/net.c
> +++ b/drivers/vhost/net.c
> @@ -331,15 +331,26 @@ err:
>  	return ERR_PTR(r);
>  }
>  
> +static struct socket *get_tun_socket(int fd)
> +{
> +	struct file *file = fget(fd);
> +	if (!file)
> +		return ERR_PTR(-EBADF);
> +	return tun_get_socket(file);

This would leak a reference on file, if it happens not being a tun file 

> +}
> +
>  static struct socket *get_socket(int fd)
>  {
>  	struct socket *sock;
>  	sock = get_raw_socket(fd);
>  	if (!IS_ERR(sock))
>  		return sock;
> +	sock = get_tun_socket(fd);
> +	if (!IS_ERR(sock))
> +		return sock;
>  	return ERR_PTR(-ENOTSOCK);
>  }
>  
>  static long vhost_net_set_socket(struct vhost_net *n, int fd)
>  {
>  	struct socket *sock, *oldsock = NULL;