netfilter: add xt_qtaguid matching module

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.

Change-Id: I01af4fd91c8de651668d3decb76d9bdc1e343919
Signed-off-by: JP Abgrall <jpa@google.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
index e9410d17619..7a49f414c13 100644
--- a/net/netfilter/Kconfig
+++ b/net/netfilter/Kconfig
@@ -1231,6 +1231,8 @@ config NETFILTER_XT_MATCH_OWNER
 	based on who created the socket: the user or group. It is also
 	possible to check whether a socket actually exists.
 
+	Conflicts with '"quota, tag, uid" match'
+
 config NETFILTER_XT_MATCH_POLICY
 	tristate 'IPsec "policy" match support'
 	depends on XFRM
@@ -1264,6 +1266,22 @@ config NETFILTER_XT_MATCH_PKTTYPE
 
 	  To compile it as a module, choose M here.  If unsure, say N.
 
+config NETFILTER_XT_MATCH_QTAGUID
+	bool '"quota, tag, owner" match and stats support'
+        depends on NETFILTER_XT_MATCH_SOCKET
+	depends on NETFILTER_XT_MATCH_OWNER=n
+	help
+	  This option replaces the `owner' match. In addition to matching
+	  on uid, it keeps stats based on a tag assigned to a socket.
+	  The full tag is comprised of a UID and an accounting tag.
+	  The tags are assignable to sockets from user space (e.g. a download
+	  manager can assign the socket to another UID for accounting).
+	  Stats and control are done via /proc/net/xt_qtaguid/.
+	  It replaces owner as it takes the same arguments, but should
+	  really be recognized by the iptables tool.
+
+	  If unsure, say `N'.
+
 config NETFILTER_XT_MATCH_QUOTA
 	tristate '"quota" match support'
 	depends on NETFILTER_ADVANCED