[CRIU] Dumping of stream unix connection

[Artem Kuzmitskiy]

2015-06-04 23:30 GMT+03:00 Pavel Emelyanov <xemul at parallels.com>:

> On 06/04/2015 07:35 PM, Artem Kuzmitskiy wrote:
> >
> >
> > 2015-06-04 16:42 GMT+03:00 Pavel Emelyanov <xemul at parallels.com <mailto:
> xemul at parallels.com>>:
> >
> >     > Hi all,
> >     >
> >     > We're returned back at this problem..
> >
> >     Cool :)
> >
> >     >>     >     > The usage scenario is following: I'm having a parent
> process and a child processes bidirectonal communicating
> >     >>     >     > via stream Unix socket. The idea is to dump child
> process when it's not needed and to restore it
> >     >>     >     > again later
> >     >
> >     > This task still need for us and we did some test with upstream
> version of CRIU.
> >     > Code of test stub here -> http://pastebin.com/tLnRdE3K
> >     > CRIU called with next params:
> >     > for dump -> ${CRIU_bin} dump -vvvv -o <PID>.log -D ${DIR} -t <PID>
> -d --shell-job --ext-unix-sk
> >     > for restore -> ${CRIU_bin} restore -vvvv -o <PID>.log -D ${DIR}
> -d --shell-job --ext-unix-sk
> >     >
> >     > Test case: child write in a unix sock, parent read from unix sock.
> >     > Child proccess dumped&restored, but
> >     >  - only if we don't close sockets after fork (sock[0] in child and
> sock[1] in parent respectively) otherwise restore process failed
> >
> >     Can you share the restore logs?
> >
> >
> > yes sure:
> > test stub -> http://pastebin.com/iBuQy0CL
> > dump log -> http://pastebin.com/9ysvQ69m
> > restorel log ->  http://pastebin.com/HR459Diu
>
> Heh :) This is external dgram socket w/o a name. Can happen if it's a
> socketpair, but
> criu errorneously tries to connect() them back. Bug in CRIU, thanks!


yep.....also we tested same scenario but using named unix socket for IPC
with SOCK_DGRAM param (test stub code -> http://pastebin.com/QRYrV3LW) and
it works fine.
If sockets has SOCK_SEQPACKET or SOCK_STREAM dump failed(sk-unix.c:546 )
and it's current limitation of CRIU.


> >     > 3. Do you have any ideas which can help us make a dump\restore of
> child proccess with CRIU?
> >
> >     Not sure I understand this correctly, would you describe in more
> details, please?
> >
> >
> > We have parent process which forks few child processes and exchange with
> child processes using pair of sockets returned from socketpair(with option
> SOCK_SEQPACKET or SOCK_STREAM).
> > We would like to dump child(s) and  full-featured restore them.
>
> Ah, I see. Such sockets should be dumped and restored using the
> --inherit-fd option [1].
> We don't yet have it working with unix sockets, only regular files and
> pipes, but adding
> unix sockets should be not extremely hard.
>

Thx.


> [1] http://criu.org/Inheriting_FDs_on_restore
>
>
> -- Pavel
>
>


-- 
Best regards,
Artem Kuzmitskiy
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