[CRIU] Diagnosing runaway socket error

[Dan Hatton]

I have a particular process, embodying some numerical calculations in
Octave, on which I'd like to perform a CRIU dump.  Having launched the
process (as normal user my_user_name) with

(setsid nice -n +19 octave my_octave_script.m) >& log.log &

and found out its PID, PID_x, I run (as root)

criu dump -t PID_x -D ~my_user_name/a_dir/dump

where the directory ~my_user_name/a_dir/dump already exists and is
owned by my_user_name.

The dump attempt consistently fails with an "External socket is used"
error.

If I crank up the verbosity, what happens just before the failure is

(02.636547) unix: Dumping external sockets
(02.636657) unix:       Dumping extern: ino 631338 peer_ino 632188 family    1 type    1 state  1 name 
(02.636787) unix:       Dumped extern: id 0x2a1 ino 631338 peer 0 type 2 state 10 name 21 bytes
(02.636873) unix:       Runaway socket: ino 631338 peer_ino 632188 family    1 type    1 state  1 name

If I then try (as root)

find / -inum 631338
find / -inum 632188

Nothing is found.  I'm left with no idea what this socket is or
whether it's of the type for which it's safe to use the --external
option to criu.  What should be my next step, please?

--

Kind regards,

Daniel