[CRIU] [PATCH 0/5] Add support to migrate processes

[Adrian Reber]

In order to migrate a process instead of writing the checkpoint
image to disk this patchset introduces the functionality to
listen on a network socket in the restore part to read the
checkpoint image over the network. Right now this works for
simple processes. To test this restore over the network
functionality the different image files are right now just piped
through netcat for the network transfer.
A future patchset will provide the functionality to directly dump
the checkpoint image to a network socket completely bypassing the
disk during checkpoint and restore.

Still not using the 
 # crtools dump -t 1234 | ssh root at restore.node crtools restore -t 1234
approach as I also see a value having it implemented the way
this patchset does it by opening a listen socket and waiting
for a checkpoint image to be transmitted.

v2:
- do not close and reopen the socket for FDs to be out of the
  way of FDs which are going to be restored. Just move the
  network listen socket to a free FD
- do not use a temporary file to store the pages-*.img but
  just pass the socket FD into restorer.c. For this to work
  the PAGE_SIZE'd read() in restorer.c had to be changed
  to read in a loop until PAGE_SIZE has actually been read