Max Reitz <mre...@redhat.com> writes: > On 08.04.19 19:22, Richard W.M. Jones wrote: >> I don't know much about this patch which looks like internal qemu >> rearrangements so I guess fine. However I do have a few things to say >> about the ssh driver ... >> >> As you know I wrote this a few years ago, and it uses libssh2. >> libssh2 has not evolved as quickly as we'd like and it may be better >> to use libssh instead -- despite the names, these are two separate and >> unrelated libraries. libssh supports a wider range of SSH encryption >> and has more features. It's generally more likely to work against a >> random SSH server. It has also been through the FIPS process. Indeed >> Red Hat made the decision to switch exclusively to libssh in RHEL 8, >> if that carries any weight. >> >> Pino posted a libssh2 -> libssh conversion patch a while back, but it >> has been somewhat stuck in review. If I recall the latest concern was >> whether it performs as well as the libssh2 version. >> >> https://lists.gnu.org/archive/html/qemu-devel/2018-06/msg07267.html >> >> In the meantime I added libssh support to nbdkit. nbdkit can be used >> as a complete replacement for qemu's ssh driver. >> >> nbdkit ssh host=foo.example.com disk.img -U tmpdirXXXXXX/sock >> qemu -hda nbd:unix:tmpdirXXXXXX/sock >> >> In fact it's somewhat superior (IMHO) because all of the tricky code >> handling libssh runs outside qemu in a separate process, improving >> isolation and potentially allowing separate, restrictive security >> policies to be applied. For example it would no longer be necessary >> to give qemu permission to connect to remote SSH servers. >> >> Could we make this really smooth somehow? nbdkit has a concept >> [https://www.mankier.com/1/nbdkit-captive] where we make it easy to >> manage external commands owned by nbdkit. Is there an equivalent >> feature of qemu where: >> >> qemu -object exec,id=nbd1,cmd='nbdkit -f -U $sock ssh ...' \ >> -drive file.driver=nbd,file.socket=nbd1 >> >> would run the command but also allocate a socket and kill the >> subcommand on exit (of qemu)? >> >> Basically I'm trying to think about how to make this a reality: >> >> https://rwmj.files.wordpress.com/2018/10/drawing2-svg.png >> >> Rich. > > I don’t disagree with anything you say. I would prefer to move the less > well maintained drivers (for which there is no strict performance > requirement) into a separate process. nbdkit is perfectly suited for > that, and the drivers are there, as you say (ssh, curl, vvfat). > > Having a nicer interface in qemu would make the transition simple, > because we could tell users exactly how to change their command line so > their use case continues to work. I’m not sure whether it really works, > though, because I don’t think there is such a simple replacement for > being able to simply pass "ssh://host/path" to qemu and have it work. > > But I think it’s still worth it.
I guess that boils down to "patches welcome". For v1, I wouldn't worry about making the transition simple. Just show us some working code.