On Mon, Jul 20, 2020 at 08:20:12PM +0200, Andrea Bolognani wrote: > On Mon, 2020-07-20 at 18:21 +0100, Daniel P. Berrangé wrote: > > On Mon, Jul 20, 2020 at 07:18:55PM +0200, Andrea Bolognani wrote: > > > The other day I randomly realized the ssh-based transports already > > > accept a 'netcat' URI parameter which can be used to point libvirt > > > to a non-standard nc stand-in. With that in mind, is it really > > > necessary to introduce another URI parameter? Can't we just reuse > > > the existing one? > > > > Any binary provided there needs to implement netcat syntax. The whole > > point of this work is that we don't want to use the netcat syntax since > > it is impossible to know the correct socket path. > > We could special-case binaries called 'virt-nc' and use our internal > syntax for those. Having two separate URI parameters to control the > same knob sounds like trouble, especially since you can mix and > match: if you try to connect to > > qemu+ssh://host/system?proxy=virt-nc&netcat=my-cool-nc > > for example, what happens? As far as I can tell virt-nc will be used, > but it's certainly not as obvious as it would be if everything was > controlled by a single URI parameter. No, I really don't want to do magic based on the name of the binary. That is a recipe for long term pain. It never turns out well when we try to overload two distinct concepts onto a single tunable. That URL you illustrate should be reported as an error since it is using mutually exclusive args. > Actually, and I might be very well missing something because I looked > at the code rather quickly, from what I can tell the default value > for proxy will cause libvirt to always prefer virt-nc when available, > which means that the URI > > qemu+ssh://host/system?netcat=my-cool-nc > > will suddenly stop using my-cool-nc and start using virt-nc after > libvirt has been upgraded - a breaking change. It will only stop using my-cool-nc if you have upgraded the remote host to have virt-nc installed, and your local host also has the libvirt supporting virt-nc. I'd consider that desirable, as netcat is redundant once both sides are upgraded. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
