[Libguestfs] [PATCH v4 0/3] v2v: Add -o rhv-upload output mode.

Previous versions: v3: https://www.redhat.com/archives/libguestfs/2018-March/msg00000.html v2: https://www.redhat.com/archives/libguestfs/2018-February/msg00177.html v1: https://www.redhat.com/archives/libguestfs/2018-February/msg00139.html This completely rethinks the approach taken by the previous patches. Instead of trying to involve qemu's curl driver, this uses a small Python 3 nbdkit plugin to interface between qemu and the oVirt server. The data path is: qemu-img convert -------> nbdkit -------> oVirt imageio nbd https There are two Python scripts included. One is the nbdkit plugin. The other creates the VM. As with the previous patches, these scripts get embeded in virt-v2v at compile time, so effectively there is no API contract between virt-v2v & the Python code. With this patch series I am able to (mostly) successfully convert VMs from local disk to oVirt 4.2, with full end-to-end streaming. There is some room for optimization -- in particular uploads are currently rather slow because we rely on qemu-img batching small requests into large ones which it doesn't do well, and instead the nbdkit plugin could batch small writes into larger ones. Also I noticed (but only one time) that very long transfers would cause the oVirt ticket to expire, even though we were writing the whole time. There are still a few unresolved issues (see patch 3/3) so this is not quite ready to go upstream yet, but can still be reviewed. Patches 1 & 2 are the same as posted before. I did not yet test qcow2 uploads. Those are "interestingly" different because qcow2 will require us to read from the remote oVirt server as well as just stream/write to it. The pread method for that is written but has not been tested. Rich.