[CRIU] [PATCH 0/10] add ability to set callbacks for external sockets (v6)

[Andrey Vagin]

We don't know a state behind an external socket. It depends on logic
of the program, which handles this socket.

The patch adds ability to load a library with callbacks for dumping
and restoring external sockets, character devices. In a future we can
add callbacks for other external objects.

Now a library can have:
* two functions cr_plugin_init and cr_plugin_fini, which are called
  on loading and unloading.
* two callbacks cr_plugin_{dump,restore}_unix_sk for dumping and restoring
  unix sockets.
* two callbacks cr_plugin_{dump,restore}_file for character devices.

If a callback can not handle an object, it must return CRIU_CB_SKIP.

v2: * Scan libraries in a predefined directory. The path cab be set by
      the -L option or the CRIU_LIBS_DIR environment
    * Look up all callbacks on loading of libraries
    * The test uses two libraries
v3: add callbacks for character devices.
v4: rework callbacks for dumping files.
v5: use -ENOTSUP instead of CRIU_CB_SKIP
    open files in the criu_plugin_restore_files() callbacks
v6: set USK_CALLBACK, if a socket was dumped by callback

Andrey Vagin (7):
  crtools: preload libraries (v2)
  unix: link a socket to its peer
  unix: add ability to set callbacks for external sockets (v2)
  plugin: allow to use logging function in plugins
  tests: check callback-s for dumping and restoring sockets (v2)
  files: add ability to set callbacks for character devices
  zdtm: test dumping character devices with help of custom callbacks

 Makefile                              |   4 +-
 Makefile.crtools                      |   1 +
 cr-dump.c                             |   6 +
 cr-restore.c                          |  27 ++--
 crtools.c                             |  14 ++-
 files-reg.c                           |  16 +++
 files.c                               |  14 +++
 include/cr_options.h                  |   1 +
 include/criu-plugin.h                 |  91 ++++++++++++++
 include/files.h                       |   2 +
 include/image.h                       |   1 +
 include/log-levels.h                  |  12 --
 include/log.h                         |  43 +------
 include/plugin.h                      |  18 +++
 pie/log-simple.c                      |   1 -
 plugin.c                              | 223 ++++++++++++++++++++++++++++++++++
 protobuf/regfile.proto                |   1 +
 sk-unix.c                             | 109 ++++++++++++-----
 test/unix-callback/Makefile           |  16 +++
 test/unix-callback/lib/syslog-lib.so  |   1 +
 test/unix-callback/lib/unix-lib.so    |   1 +
 test/unix-callback/run.sh             |  48 ++++++++
 test/unix-callback/syslog-lib.c       |  50 ++++++++
 test/unix-callback/unix-client.c      |  88 ++++++++++++++
 test/unix-callback/unix-lib.c         | 170 ++++++++++++++++++++++++++
 test/unix-callback/unix-server.c      | 102 ++++++++++++++++
 test/zdtm.sh                          |   6 +
 test/zdtm/live/static/Makefile        |   9 +-
 test/zdtm/live/static/criu-rtc.c      |  87 +++++++++++++
 test/zdtm/live/static/lib/criu-rtc.so |   1 +
 test/zdtm/live/static/rtc.c           |  57 +++++++++
 31 files changed, 1123 insertions(+), 97 deletions(-)
 create mode 100644 include/criu-plugin.h
 delete mode 100644 include/log-levels.h
 create mode 100644 include/plugin.h
 create mode 100644 plugin.c
 create mode 100644 test/unix-callback/Makefile
 create mode 120000 test/unix-callback/lib/syslog-lib.so
 create mode 120000 test/unix-callback/lib/unix-lib.so
 create mode 100755 test/unix-callback/run.sh
 create mode 100644 test/unix-callback/syslog-lib.c
 create mode 100644 test/unix-callback/unix-client.c
 create mode 100644 test/unix-callback/unix-lib.c
 create mode 100644 test/unix-callback/unix-server.c
 create mode 100644 test/zdtm/live/static/criu-rtc.c
 create mode 120000 test/zdtm/live/static/lib/criu-rtc.so
 create mode 100644 test/zdtm/live/static/rtc.c

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1.8.3.1:qa