[CRIU] [PATCH 0/4] add join-ns option to criu restore

[Dengguangxing]

This patch add join-ns option to criu restore.

join-ns can be used in this fomat:
    --join-ns NS:PID|NS_FILE
for example --join-ns net:12345 or --join-ns net:/foo/bar.

pid namespaces is not supported yet. As fork() is needed to make
new pid-namespace work. That makes it hard for criu to track the
child-process through pid because another child process has been
created after fork().

patches:
 join-ns: add join-ns option to criu CLI and RPC
 join-ns: perform join_namespace according to join-ns opts
 join-ns: skip prepare_net_ns when join net ns flag set
 join-ns: add join-ns zdtm test

 criu/cr-restore.c         |   5 +++
 criu/cr-service.c         |  10 +++++
 criu/crtools.c            |  43 ++++++++++++++++++-
 criu/include/cr_options.h |   1 +
 criu/include/namespaces.h |  24 +++++++++++
 criu/namespaces.c         | 273 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-
 criu/net.c                |   3 +-
 images/rpc.proto          |   7 +++
 test/zdtm.py              |  30 ++++++++++++-