[Qemu-devel] [PATCH 2/2] qapi: Allow blockdev-add for NBD

[Max Reitz <mreitz@redhat.com>]

We have to introduce a new object (BlockdevOptionsNbd) for several
reasons:
- Neither of InetSocketAddress nor UnixSocketAddress alone is
  sufficient, because both are supported
- We cannot use SocketAddress because NBD does not support an fd,
  and because it is not a flat union which BlockdevOptionsNbd is
- We cannot use a flat union of InetSocketAddress and
  UnixSocketAddress because we would need some kind of discriminator
  which we do not have; we could inline the UnixSocketAddress as a
  string and then make it an 'alternate' type instead of a union, but
  this will not work either, because:
- InetSocketAddress itself is not suitable for NBD because the port is
  not optional (which it is for NBD) and because it offers more options
  (like choosing between ipv4 and ipv6) which NBD does not support.

Signed-off-by: Max Reitz <mreitz@redhat.com>
---
 qapi/block-core.json | 28 ++++++++++++++++++++++++++--
 1 file changed, 26 insertions(+), 2 deletions(-)

diff --git a/qapi/block-core.json b/qapi/block-core.json
index 33012b8..e1b8543 100644
--- a/qapi/block-core.json
+++ b/qapi/block-core.json
@@ -1567,13 +1567,14 @@
 # Drivers that are supported in block device operations.
 #
 # @host_device, @host_cdrom: Since 2.1
+# @nbd: Since 2.6
 #
 # Since: 2.0
 ##
 { 'enum': 'BlockdevDriver',
   'data': [ 'archipelago', 'blkdebug', 'blkverify', 'bochs', 'cloop',
             'dmg', 'file', 'ftp', 'ftps', 'host_cdrom', 'host_device',
-            'http', 'https', 'null-aio', 'null-co', 'parallels',
+            'http', 'https', 'nbd', 'null-aio', 'null-co', 'parallels',
             'qcow', 'qcow2', 'qed', 'quorum', 'raw', 'tftp', 'vdi', 'vhdx',
             'vmdk', 'vpc', 'vvfat' ] }
 
@@ -2002,6 +2003,29 @@
             '*read-pattern': 'QuorumReadPattern' } }
 
 ##
+# @BlockdevOptionsNbd
+#
+# Driver specific block device options for NBD. Either of @host or @path must be
+# specified, but not both.
+#
+# @host:    #optional Connects to the given host using TCP.
+#
+# @port:    #optional Specifies the TCP port to connect to; may be used only in
+#           conjunction with @host. Defaults to 10809.
+#
+# @path:    #optional Connects to the given Unix socket path.
+#
+# @export:  #optional Name of the NBD export to open.
+#
+# Since: 2.6
+##
+{ 'struct': 'BlockdevOptionsNbd',
+  'data': { '*host':    'str',
+            '*port':    'str',
+            '*path':    'str',
+            '*export':  'str' } }
+
+##
 # @BlockdevOptions
 #
 # Options for creating a block device.
@@ -2027,7 +2051,7 @@
       'http':       'BlockdevOptionsFile',
       'https':      'BlockdevOptionsFile',
 # TODO iscsi: Wait for structured options
-# TODO nbd: Should take InetSocketAddress for 'host'?
+      'nbd':        'BlockdevOptionsNbd',
 # TODO nfs: Wait for structured options
       'null-aio':   'BlockdevOptionsNull',
       'null-co':    'BlockdevOptionsNull',
-- 
2.7.0