bhyve/snapshot: use SOCK_DGRAM instead of SOCK_STREAM

[rew]

Summary

The unix domain socket that the save/restore feature uses is a stream
socket, switch to using a datagram socket instead.

• change socket type from SOCK_STREAM to SOCK_DGRAM

Currently, struct checkpoint_op is the data that gets sent across the
socket. My idea (at the moment) is that checkpoint_op will be swapped
out for a more generic approach - I'm planning to do that in a separate
review.

[jhb]

Generally looks good, just a minor nit about displaying errors.

usr.sbin/bhyve/snapshot.c

1489

This probably needs to use the helper macro for errors which adds \r when needed if bhyve's stdin/stdout are in raw mode for use as the serial console. It's true that the perror's in this file are also broken for the same reason, but it would be good to fix this in the new changes at least. I think the macro is something like EPRINTLN() IIRC.

[rew]

use EPRINTLN for display error messages..

changed fprintf and perror to use EPRINTLN, I only changed them in
the areas where I was close to a fprintf/perror.

[jhb]

usr.sbin/bhyvectl/bhyvectl.c

1716

Maybe fix this one as well since you are already touching the line.

[rew]

usr.sbin/bhyvectl/bhyvectl.c

1716

perror() is only broken for bhyve(8), no?

This one is in bhyvectl(8).

[jhb]

usr.sbin/bhyvectl/bhyvectl.c

1716

Oh yes, my bad!