I got tired of debugging whether a server was advertising the correct things during negotiation by inspecting the trace logs of qemu-io as client - not to mention that without SOME sort of client tracing particular commands, we can't easily regression test the server for correct behavior. The final straw was at KVM Forum, when Nir asked me to make sure there was a way to easily determine if an NBD server is exposing what we really want (and fixing x-dirty-bitmap to behave saner fell out as a result of answering that question).
I note that upstream NBD has 'nbd-client -l $host' for querying just export names (with no quoting, so you have to know that a blank line means the default export), but it wasn't powerful enough, so I implemented 'qemu-nbd -L' to document everything. Upstream NBD has separate 'nbd-client' and 'nbd-server' binaries, while we only have 'qemu-nbd' (which is normally just a server, but 'qemu-nbd -c' also operates a second thread as a client). Our other uses of qemu as NBD client are for consuming a block device (as in qemu-io, qemu-img, or a drive to qemu) - but those binaries are less suited to something so specific to the NBD protocol. Bonus: As a result of my work on this series, nbdkit now supports NBD_OPT_INFO (my interoperability testing between server implementations has been paying off, both at fixing server bugs, and at making this code more reliable across difference in valid servers). Also available at: https://repo.or.cz/qemu/ericb.git qemu-nbd-list-v4 Currently based on master. Since v3: - 1 new patch (1/21) - split old patch 15/19 into two (16,17/21) - retitle two patches (git backport-diff doesn't do too well at showing the diff on a retitled patch; 5,11/21) - fix review comments from Rich, Vladimir 001/21:[down] 'iotests: Make 233 output more reliable' 002/21:[----] [--] 'maint: Allow for EXAMPLES in texi2pod' 003/21:[----] [--] 'qemu-nbd: Enhance man page' 004/21:[0006] [FC] 'qemu-nbd: Sanity check partition bounds' 005/21:[down] 'nbd/server: Hoist length check to qmp_nbd_server_add' 006/21:[0025] [FC] 'nbd/server: Favor [u]int64_t over off_t' 007/21:[----] [-C] 'qemu-nbd: Avoid strtol open-coding' 008/21:[----] [--] 'nbd/client: Refactor nbd_receive_list()' 009/21:[----] [--] 'nbd/client: Move export name into NBDExportInfo' 010/21:[----] [--] 'nbd/client: Change signature of nbd_negotiate_simple_meta_context()' 011/21:[down] 'nbd/client: Split out nbd_send_meta_query()' 012/21:[0003] [FC] 'nbd/client: Split out nbd_receive_one_meta_context()' 013/21:[----] [--] 'nbd/client: Refactor return of nbd_receive_negotiate()' 014/21:[0003] [FC] 'nbd/client: Split handshake into two functions' 015/21:[----] [-C] 'nbd/client: Pull out oldstyle size determination' 016/21:[down] 'nbd/client: Refactor nbd_opt_go() to support NBD_OPT_INFO' 017/21:[0032] [FC] 'nbd/client: Add nbd_receive_export_list()' 018/21:[0006] [FC] 'nbd/client: Add meta contexts to nbd_receive_export_list()' 019/21:[0014] [FC] 'qemu-nbd: Add --list option' 020/21:[0004] [FC] 'nbd/client: Work around 3.0 bug for listing meta contexts' 021/21:[0002] [FC] 'iotests: Enhance 223, 233 to cover 'qemu-nbd --list'' Eric Blake (21): iotests: Make 233 output more reliable maint: Allow for EXAMPLES in texi2pod qemu-nbd: Enhance man page qemu-nbd: Sanity check partition bounds nbd/server: Hoist length check to qmp_nbd_server_add nbd/server: Favor [u]int64_t over off_t qemu-nbd: Avoid strtol open-coding nbd/client: Refactor nbd_receive_list() nbd/client: Move export name into NBDExportInfo nbd/client: Change signature of nbd_negotiate_simple_meta_context() nbd/client: Split out nbd_send_meta_query() nbd/client: Split out nbd_receive_one_meta_context() nbd/client: Refactor return of nbd_receive_negotiate() nbd/client: Split handshake into two functions nbd/client: Pull out oldstyle size determination nbd/client: Refactor nbd_opt_go() to support NBD_OPT_INFO nbd/client: Add nbd_receive_export_list() nbd/client: Add meta contexts to nbd_receive_export_list() qemu-nbd: Add --list option nbd/client: Work around 3.0 bug for listing meta contexts iotests: Enhance 223, 233 to cover 'qemu-nbd --list' qemu-nbd.texi | 116 +++++- Makefile | 2 + include/block/nbd.h | 31 +- block/nbd-client.c | 9 +- blockdev-nbd.c | 10 +- nbd/client.c | 775 ++++++++++++++++++++++++++----------- nbd/server.c | 24 +- qemu-nbd.c | 224 ++++++++--- nbd/trace-events | 17 +- scripts/texi2pod.pl | 2 +- tests/qemu-iotests/223 | 2 + tests/qemu-iotests/223.out | 20 + tests/qemu-iotests/233 | 30 +- tests/qemu-iotests/233.out | 19 +- 14 files changed, 942 insertions(+), 339 deletions(-) -- 2.20.1
