netfilter: xt_qtaguid: add some tagging/matching stats

/proc/net/xt_qtaguid/ctrl will now show:
  active tagged sockets: lines of "sock=%p tag=0x%llx (uid=%u)"
  sockets_tagged, : the number of sockets successfully tagged.
  sockets_untagged: the number of sockets successfully untagged.
  counter_set_changes: ctrl counter set change requests.
  delete_cmds: ctrl delete commands completed.
  iface_events: number of NETDEV_* events handled.
  match_found_sk: sk found in skbuff without ct assist.
  match_found_sk_in_ct: the number of times the connection tracker found
    a socket for us. This happens when the skbuff didn't have info.
  match_found_sk_none: the number of times no sk could be determined
    successfully looked up. This indicates we don't know who the
    data actually belongs to. This could be unsolicited traffic.

Change-Id: I3a65613bb24852e1eea768ab0320a6a7073ab9be
Signed-off-by: JP Abgrall <jpa@google.com>
netfilter: xt_qtaguid: fix dev_stats for missing NETDEV_UNREGISTER

Turns out that some devices don't call the notifier chains
with NETDEV_UNREGISTER.
So now we only track up/down as the points for tracking
active/inactive transitions and saving the get_dev_stats().

Change-Id: I948755962b4c64150b4d04f294fb4889f151e42b
Signed-off-by: JP Abgrall <jpa@google.com>
netfilter: qtaguid: fix proc/.../stats uid filtered output

"cat /proc/net/xt_qtaguid/stats"
for a non-priviledged UID would output multiple twice its own stats.
The fix tweaks the way lines are counted.

Non-root:
  idx iface acct_tag_hex uid_tag_int cnt_set ...
  2 wlan0 0x0 10022 0 ...
  3 wlan0 0x0 10022 1 ...
  4 wlan0 0x3010000000000000 10022 0 ...
  5 wlan0 0x3010000000000000 10022 1 ...

Root:
  idx iface acct_tag_hex uid_tag_int cnt_set
  2 wlan0 0x0 0 0 ...
  3 wlan0 0x0 0 1 ...
  4 wlan0 0x0 1000 0 ...
  ...
  12 wlan0 0x0 10022 0 ...
  13 wlan0 0x0 10022 1 ...
  ...
  18 wlan0 0x3010000000000000 10022 0 ...
  19 wlan0 0x3010000000000000 10022 1 ...

Change-Id: I3cae1f4fee616bc897831350374656b0c718c45b
Signed-off-by: JP Abgrall <jpa@google.com>
netfilter: xt_qtaguid: 1st pass at tracking tag based data resources

* Added global resource tracking based on tags.
 - Can be put into passive mode via
    /sys/modules/xt_qtaguid/params/tag_tracking_passive
 - The number of socket tags per UID is now limited
 - Adding /dev/xt_qtaguid that each process should open before starting
to tag sockets. A later change will make it a "must".
 - A process should not create new tags unless it has the dev open.
  A later change will make it a must.
 - On qtaguid_resources release, the process' matching socket tag info
  is deleted.
* Support run-time debug mask via /sys/modules parameter "debug_mask".
* split module into prettyprinting code, includes, main.
* Removed ptrdiff_t usage which didn't work in all cases.

Change-Id: I4a21d3bea55d23c1c3747253904e2a79f7d555d9
Signed-off-by: JP Abgrall <jpa@google.com>
netfilter: xt_qtaguid: warn only once for missing proc qtaguid data

When a process doesn't have /dev/xt_qtaguid open, only warn once
instead of for every ctrl access.

Change-Id: I98a462a8731254ddc3bf6d2fefeef9823659b1f0
Signed-off-by: JP Abgrall <jpa@google.com>
netfilter: xt_qtaguid: work around devices that reset their stats

Most net devs will not reset their stats when just going down/up,
unless a NETDEV_UNREGISTER was notified.
But some devs will not send out a NETDEV_UNREGISTER but still
reset their stats just before a NETDEV_UP.
Now we just track the dev stats during NETDEV_DOWN... just in case.
Then on NETDEV_UP we check the stats: if the device didn't do a
NETDEV_UNREGISTER and a prior NETDEV_DOWN captured stats, then we treat
it as an UNREGISTER and save the totals from the stashed values.

Added extra netdev event debugging.

Change-Id: Iec79e74bfd40269aa3e5892f161be71e09de6946
Signed-off-by: JP Abgrall <jpa@google.com>