See the cross-post cover letter for details:
https://www.redhat.com/archives/libguestfs/2019-August/msg00322.html

Eric Blake (1):
  api: Add support for FAST_ZERO flag

 lib/nbd-protocol.h     |  2 ++
 generator/generator    | 29 +++++++++++++++++++++++------
 lib/flags.c            | 12 ++++++++++++
 lib/protocol.c         |  1 +
 lib/rw.c               |  9 ++++++++-
 tests/Makefile.am      | 20 ++++++++++++++++++++
 tests/eflags-plugin.sh |  5 +++++
 7 files changed, 71 insertions(+), 7 deletions(-)

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2.21.0