1NBDKit(3) NBDKit(3)
2
6 NBDKit - Interface between plugins written in OCaml and the nbdkit
7 server.
8
10 Module NBDKit
11
13 Module NBDKit
14 : sig end
15 Interface between plugins written in OCaml and the nbdkit server.
18 Read nbdkit-ocaml-plugin(3) first.
20 type flags = flag list
26 Flags passed from the server to various callbacks.
29 type flag =
32 | May_trim
33 | FUA
34 | Req_one
35 type fua_flag =
40 | FuaNone
41 | FuaEmulate
42 | FuaNative
43 type cache_flag =
48 | CacheNone
49 | CacheEmulate
50 | CacheNop
51 type extent = {
56 offset : int64 ;
57 length : int64 ;
58 is_hole : bool ;
59 is_zero : bool ;
60 }
61 The type of the extent list returned by NBDKit.plugin.extents
64 type export = {
68 name : string ;
69 description : string option ;
70 }
71 The type of the export list returned by NBDKit.plugin.list_exports
74 type thread_model =
78 | THREAD_MODEL_SERIALIZE_CONNECTIONS
79 | THREAD_MODEL_SERIALIZE_ALL_REQUESTS
80 | THREAD_MODEL_SERIALIZE_REQUESTS
81 | THREAD_MODEL_PARALLEL
82 The type of the thread model returned by NBDKit.plugin.thread_model
85 type 'a plugin = {
89 name : string ; (* required field
90 *)
91 longname : string ;
92 version : string ;
93 description : string ;
94 load : (unit -> unit) option ;
95 get_ready : (unit -> unit) option ;
96 after_fork : (unit -> unit) option ;
97 cleanup : (unit -> unit) option ;
98 unload : (unit -> unit) option ;
99 config : (string -> string -> unit) option ;
100 config_complete : (unit -> unit) option ;
101 config_help : string ;
102 thread_model : (unit -> thread_model) option ;
103 preconnect : (bool -> unit) option ;
104 open_connection : (bool -> 'a) option ; (* required field
105 *)
106 close : ('a -> unit) option ;
107 get_size : ('a -> int64) option ; (* required field
108 *)
109 can_cache : ('a -> cache_flag) option ;
110 can_extents : ('a -> bool) option ;
111 can_fast_zero : ('a -> bool) option ;
112 can_flush : ('a -> bool) option ;
113 can_fua : ('a -> fua_flag) option ;
114 can_multi_conn : ('a -> bool) option ;
115 can_trim : ('a -> bool) option ;
116 can_write : ('a -> bool) option ;
117 can_zero : ('a -> bool) option ;
118 is_rotational : ('a -> bool) option ;
119 pread : ('a -> int32 -> int64 -> flags -> string) option ; (* re‐
120 quired field
121 *)
122 pwrite : ('a -> string -> int64 -> flags -> unit) option ;
123 flush : ('a -> flags -> unit) option ;
124 trim : ('a -> int32 -> int64 -> flags -> unit) option ;
125 zero : ('a -> int32 -> int64 -> flags -> unit) option ;
126 extents : ('a -> int32 -> int64 -> flags -> extent list) option ;
127 cache : ('a -> int32 -> int64 -> flags -> unit) option ;
128 dump_plugin : (unit -> unit) option ;
129 list_exports : (bool -> bool -> export list) option ;
130 default_export : (bool -> bool -> string) option ;
131 export_description : ('a -> string) option ;
132 }
133 The plugin fields and callbacks.
136 The 'a parameter is the handle type returned by your open_connection
138 method and passed back to all connected calls.
139 val default_callbacks : 'a plugin
143 The plugin with all fields set to None , so you can write { de‐
145 fault_callbacks with field1 = Some foo1; field2 = Some foo2 }
146 val register_plugin : 'a plugin -> unit
151 Register the plugin with nbdkit.
153 val set_error : Unix.error -> unit
157 Set the errno returned over the NBD protocol to the client.
159 Notice however that the NBD protocol only supports a small handful of
161 errno values. Any other errno will be translated into EINVAL .
162 val parse_size : string -> int64
166 Bindings for nbdkit_parse_size , nbdkit_parse_bool and nbd‐
168 kit_read_password . See nbdkit-plugin(3) for information about these
169 functions.
170 On error these functions all raise Invalid_argument . The actual error
172 is sent to the nbdkit error log and is not available from the OCaml
173 code. It is usually best to let the exception escape.
174 val parse_bool : string -> bool
178 val read_password : string -> string
183 val realpath : string -> string
188 Binding for nbdkit_realpath . Returns the canonical path from a path
190 parameter.
191 val nanosleep : int -> int -> unit
195 Binding for nbdkit_nanosleep . Sleeps for seconds and nanoseconds.
197 val export_name : unit -> string
201 Binding for nbdkit_export_name . Returns the name of the export as re‐
203 quested by the client.
204 val shutdown : unit -> unit
208 Binding for nbdkit_shutdown . Requests the server shut down.
210 val debug : ('a, unit, string, unit) Stdlib.format4 -> 'a
214 Print a debug message when nbdkit is in verbose mode.
216 val version : unit -> string
220 Return the version of nbdkit that the plugin was compiled with.
222 val peer_pid : unit -> int64
226 Binding for nbdkit_peer_pid .
228 val peer_uid : unit -> int64
232 Binding for nbdkit_peer_uid .
234 val peer_gid : unit -> int64
238 Binding for nbdkit_peer_gid .
240OCamldoc 2021-11-09 NBDKit(3)