[CRIU] c/r support for cgroup namespaces

[Tycho Andersen]

Hi guys,

Here's a draft set for supporting cgroup namespaces. The one obvious nit I can
think of is in include/namespaces.h, although there are probably others. I
haven't done extenstive testing on this, but I'm hoping to bang on it more next
week.

Also, when running the test in a user ns, I get what I think is an unrelated
network failure due to the way 4.4 does things, but I haven't looked into it
yet. If anyone has any ideas about this that would be great, but I'll take a
look now.

$ sudo ./zdtm.py run -t zdtm/live/static/cgroupns
Checking feature cgroupns
=== Run 1/1 ================

====================== Run zdtm/live/static/cgroupns in h ======================
Start test
Test is SUID
./cgroupns --pidfile=cgroupns.pid --outfile=cgroupns.out --dirname=cgroupns.test
Run criu dump
Run criu restore
Wait for zdtm/live/static/cgroupns to die for 0.100000
Removing dump/zdtm/live/static/cgroupns/62
===================== Test zdtm/live/static/cgroupns PASS ======================

===================== Run zdtm/live/static/cgroupns in ns ======================
Start test
Test is SUID
./cgroupns --pidfile=cgroupns.pid --outfile=cgroupns.out --dirname=cgroupns.test
Run criu dump
=[log]=> dump/zdtm/live/static/cgroupns/130/1/dump.log
------------------------ grep Error ------------------------
(00.015021) Error (net.c:228): Unsupported link 2 (type 776 kind sit)
(00.018762) Error (namespaces.c:829): Namespaces dumping finished with error 65280
(00.021230) Error (cr-dump.c:1580): Dumping FAILED.
------------------------ ERROR OVER ------------------------
############### Test zdtm/live/static/cgroupns FAIL at CRIU dump ###############
Wait for zdtm/live/static/cgroupns to die for 0.100000
##################################### FAIL #####################################

Thoughts welcome!

Tycho