We need to check that we are able to create large enough file which is
used as an export base rather than connection URL. Unfortunately, there
are cases when the TEST_IMG_FILE is not defined. We should fallback to
TEST_IMG in that case.

This problem has been detected when running
    ./check -nbd 5
The test should be able to run while it does not.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230906140917.559129-2-den@openvz.org>
Tested-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

The test actually requires Python bindings to libnbd rather than libnbd
itself. Clarify that inside the message.

Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Hanna Reitz <hreitz@redhat.com>
CC: Eric Blake <eblake@redhat.com>
CC: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230906140917.559129-3-den@openvz.org>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

The upcoming patches for 64-bit extensions requires various points in
the protocol to make decisions based on what was negotiated.  While we
could easily add a 'bool extended_headers' alongside the existing
'bool structured_reply', this does not scale well if more modes are
added in the future.  Better is to expose the mode enum added in the
recent commit bfe04d0 out to a wider use in the code base.

Where the code previously checked for structured_reply being set or
clear, it now prefers checking for an inequality; this works because
the nodes are in a continuum of increasing abilities, and allows us to
touch fewer places if we ever insert other modes in the middle of the
enum.  There should be no semantic change in this patch.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230829175826.377251-20-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Once the 64-bit headers extension is enabled, the data layout we send
over the wire for a client request depends on the mode negotiated with
the server.  Rather than adding a parameter to nbd_send_request, we
can add a member to struct NBDRequest, since it already does not
reflect on-wire format.  Some callers initialize it directly; many
others rely on a common initialization point during
nbd_co_send_request().  At this point, there is no semantic change.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230829175826.377251-21-eblake@redhat.com>

Add the constants and structs necessary for later patches to start
implementing the NBD_OPT_EXTENDED_HEADERS extension in both the client
and server, matching recent upstream nbd.git (through commit
e6f3b94a934).  This patch does not change any existing behavior, but
merely sets the stage for upcoming patches.

This patch does not change the status quo that neither the client nor
server use a packed-struct representation for the request header.
While most of the patch adds new types, there is also some churn for
renaming the existing NBDExtent to NBDExtent32 to contrast it with
NBDExtent64, which I thought was a nicer name than NBDExtentExt.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>
Message-ID: <20230829175826.377251-22-eblake@redhat.com>

Widen the length field of NBDRequest to 64-bits, although we can
assert that all current uses are still under 32 bits: either because
of NBD_MAX_BUFFER_SIZE which is even smaller (and where size_t can
still be appropriate, even on 32-bit platforms), or because nothing
ever puts us into NBD_MODE_EXTENDED yet (and while future patches will
allow larger transactions, the lengths in play here are still capped
at 32-bit).  There are no semantic changes, other than a typo fix in a
couple of error messages.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230829175826.377251-23-eblake@redhat.com>
[eblake: fix assertion bug in nbd_co_send_simple_reply]
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

Upcoming additions to support NBD 64-bit effect lengths will add a new
command flag NBD_CMD_FLAG_PAYLOAD_LEN that needs to be considered in
our sanity checks of the client's messages (that is, more than just
CMD_WRITE have the potential to carry a client payload when extended
headers are in effect).  But before we can start to support that, it
is easier to first refactor the existing set of various if statements
over open-coded combinations of request->type to instead be a single
switch statement over all command types that sets witnesses, then
straight-line processing based on the witnesses.  No semantic change
is intended.

Signed-off-by: Eric Blake <eblake@redhat.com>
Message-ID: <20230829175826.377251-24-eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru>

… staging

NBD patches through 2023-09-25

- Denis V. Lunev: iotest improvements
- Eric Blake: further work towards 64-bit NBD extensions

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* tag 'pull-nbd-2023-09-25' of https://repo.or.cz/qemu/ericb:
  nbd/server: Refactor handling of command sanity checks
  nbd: Prepare for 64-bit request effect lengths
  nbd: Add types for extended headers
  nbd/client: Pass mode through to nbd_send_request
  nbd: Replace bool structured_reply with mode enum
  iotests: improve 'not run' message for nbd-multiconn test
  iotests: use TEST_IMG_FILE instead of TEST_IMG in _require_large_file

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>