nbd: new package nbd-server

Network block device server allows to export a block device from router
to remote host. This is particularly useful if no network filesystem
server is feasible or direct access to a block device is needed.

It's been tested for nearly a month on ar71xx (TL-WR842ND) and proved to
be very stable and efficient solution.
The package comes with init.d script and conf.d file allowing to
configure most nbd-server options using standard uci interface.

Signed-off-by: Marcin Jurkowski <marcin1j@gmail.com>

net/nbd/files/nbd-server.conf

@@ -0,0 +1,31 @@
+config nbd-server
+	option enabled 0
+#	option port 10809
+#	option user root
+#	option group root
+#	option allowlist 0
+#	option includedir '/etc/nbd-server/conf.d'
+#	option listenaddr '0.0.0.0'
+#	option oldstyle 0
+
+config share usb_sda1
+	option filename '/dev/sda1'
+#	option authfile '/etc/nbd-server/allow'
+#	option timeout 0
+#	option flush 0
+#	option fua 0
+#	option rotational 0
+#	option sync 0
+#	option discard 0
+#	option maxconnections 10
+#	option filesize 1000000
+#	option multifile 0
+#	option copyonwrite 0
+#	option sparse_cow 1
+#	option readonly 0
+#	option prerun '/bin/true'
+#	option postrun '/bin/true'
+#	option virtstyle 'ipliteral'
+#	option oldstyle_port 12345
+#	option oldstyle_listenaddr '0.0.0.0'
+