linux-kernel - Re: get device from file struct

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Date:	Wed, 13 Dec 2006 15:53:46 -0800
From:	Stephen Hemminger <shemminger@...l.org>
To:	linux-kernel@...r.kernel.org
Subject: Re: get device from file struct

On Wed, 13 Dec 2006 20:19:51 +0100 (MET)
Jan Engelhardt <jengelh@...ux01.gwdg.de> wrote:

> 
> >in fs/read_write.c, the vfs_read function does:
> >
> >file->f_op->read(file, buf, count, pos);
> >
> >after this call is it possible to determine where the
> >data is coming from?
> >e.g., the first hard disk, a pipe or from a socket.
> 
> For hard disks:
>   file->f_dentry->d_inode->d_sb->s_bdev gives you the block device
>   in case it is a non-virtual filesystem.
> 
> For pipes/sockets I do not know of a may to go from a filp to a
> struct sock or struct socket.
> 
> >If it is a socket we are interested
> >from which device (eth0, eth1, lo, ...) the data was received.
> 
> I do not think that is possible either.

The connection between file and network device is through many
layers and there is no direct binding. It could be 0 to N interfaces
and even be data dependent.

-- 
Stephen Hemminger <shemminger@...l.org>
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