Re: [PATCH 2/7][RFC] netfilter: add xt_qtaguid matching module

Hi John,

Cc'ing netfilter-devel (better than only netdev, to attract the
attention from other Netfilter hacker fellows).

Some comments on this:

On Fri, Sep 21, 2012 at 10:10:48PM -0400, John Stultz wrote:

From: JP Abgrall <redacted>

This module allows tracking stats at the socket level for given UIDs.
It replaces xt_owner.
If the --uid-owner is not specified, it will just count stats based on
who the skb belongs to. This will even happen on incoming skbs as it
looks into the skb via xt_socket magic to see who owns it.
If an skb is lost, it will be assigned to uid=0.

To control what sockets of what UIDs are tagged by what, one uses:
  echo t $sock_fd $accounting_tag $the_billed_uid \
     > /proc/net/xt_qtaguid/ctrl
 So whenever an skb belongs to a sock_fd, it will be accounted against
   $the_billed_uid
  and matching stats will show up under the uid with the given
   $accounting_tag.

Because the number of allocations for the stats structs is not that big:
  ~500 apps * 32 per app
we'll just do it atomic. This avoids walking lists many times, and
the fancy worker thread handling. Slabs will grow when needed later.

It use netdevice and inetaddr notifications instead of hooks in the core dev
code to track when a device comes and goes. This removes the need for
exposed iface_stat.h.

Put procfs dirs in /proc/net/xt_qtaguid/
  ctrl
  stats
  iface_stat/<iface>/...
The uid stats are obtainable in ./stats.

Unless I'm missing anything worth in this patch, this seems to me like
a combo match of owner + nfacct infrastructure.

I guess you can probably get all done with one single rule, but that
is not enough to justify its inclusion in mainline.

In case you are not familiar with the nfacct infrastructure:

http://lwn.net/Articles/472094/

I'd be happy anyway if you provide more examples on you use this, so I
can assure you we can do this with the existing infrastructure in
mainstream.

Thanks!