linux-kernel - Re: get device from file struct

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Date:	Wed, 13 Dec 2006 13:28:59 +0100
From:	Silviu Craciunas <silviu.craciunas@....ac.at>
To:	Jan Engelhardt <jengelh@...ux01.gwdg.de>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: get device from file struct

On Wed, 2006-12-13 at 12:03 +0100, Jan Engelhardt wrote:
> >> >thanks for the reply, the block device can be determined with the major
> >> >and minor numbers , what I would be more interested in is if one can get
> >> >the net_device struct from the file struct
> >> 
> >> Just how are you supposed to match files and network devices?
> >> 
> >
> >from the struct file you can get the struct socket and from there to the
> >struct sock .
> 
> That only applies when using PF_LOCAL sockets.
> 
> >What I would like to find out is where the data is coming
> >from (read) and where it is going to(write) or if it is even possible to
> >find the net device out using the struct file.
> 
> I really don't get what you want.
> 
> Suppose a daemon reads from a socket (PF_INET), then there is a file descriptor
> to sockfs (look into /proc/$$/fd/). Well, then you may be able to get the
> struct file for that socket, but it does not connect to a regular file
> (S_IFREG) at all.
> 
> 
> 	-`J'

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. If it is a socket we are interested
from which device (eth0, eth1, lo, ...) the data was received.

silviu

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