CP-45016: Implement get_nbd_server SMAPI{v1,v2,v3} calls

This new function returns the real nbd server of the underlying storage
backend. This nbd server will not accept any fd passing. This is in
contrast to import_activate, which returns a "special" nbd server that
will accept fds via SCM_RIGHTS.

Signed-off-by: Vincent Liu <[email protected]>

ocaml/xapi-idl/storage/storage_interface.ml

@@ -1093,7 +1093,19 @@ module StorageAPI (R : RPC) = struct
           @-> returning sock_path_p err
           )
 
-
+      (** [get_nbd_server dbg dp sr vdi vm] returns the address of a generic nbd
+      server that can be connected to. Depending on the backend, this will either
+      be a nbd server backed by tapdisk or qemu-dp. Note this is different 
+      from [import_activate] as the returned server does not accept fds. *)
+      let get_nbd_server =
+        declare "DATA.MIRROR.get_nbd_server" []
+          (dbg_p
+          @-> dp_p
+          @-> sr_p
+          @-> vdi_p
+          @-> vm_p
+          @-> returning sock_path_p err
+          )
     end
   end
 
@@ -1448,6 +1460,14 @@ module type Server_impl = sig
         -> vm:vm
         -> sock_path
 
+      val get_nbd_server :
+           context
+        -> dbg:debug_info
+        -> dp:dp
+        -> sr:sr
+        -> vdi:vdi
+        -> vm:vm
+        -> sock_path
     end
   end
 
@@ -1630,7 +1650,9 @@ module Server (Impl : Server_impl) () = struct
     S.DATA.MIRROR.import_activate (fun dbg dp sr vdi vm ->
         Impl.DATA.MIRROR.import_activate () ~dbg ~dp ~sr ~vdi ~vm
     ) ;
-
+    S.DATA.MIRROR.get_nbd_server (fun dbg dp sr vdi vm ->
+        Impl.DATA.MIRROR.get_nbd_server () ~dbg ~dp ~sr ~vdi ~vm
+    ) ;
     S.Policy.get_backend_vm (fun dbg vm sr vdi ->
         Impl.Policy.get_backend_vm () ~dbg ~vm ~sr ~vdi
     ) ;

ocaml/xapi-idl/storage/storage_skeleton.ml

@@ -180,6 +180,9 @@ module DATA = struct
 
     let import_activate ctx ~dbg ~dp ~sr ~vdi ~vm =
       u "DATA.MIRROR.import_activate"
+
+    let get_nbd_server ctx ~dbg ~dp ~sr ~vdi ~vm =
+      u "DATA.MIRROR.get_nbd_server"
   end
 end
 

ocaml/xapi-storage-script/main.ml

@@ -1819,7 +1819,44 @@ let bind ~volume_script_dir =
       fail (Storage_interface.Errors.Unimplemented _vdi_mirror_in)
   in
   S.DATA.MIRROR.import_activate data_import_activate_impl ;
-
+  let get_nbd_server_impl dbg _dp sr vdi' vm' =
+    wrap
+    @@
+    let vdi = Storage_interface.Vdi.string_of vdi' in
+    let domain = Storage_interface.Vm.string_of vm' in
+    vdi_attach_common dbg sr vdi domain >>>= function
+    | response -> (
+        let convert_implementation = function
+          | Xapi_storage.Data.XenDisk {params; extra; backend_type} ->
+              Storage_interface.XenDisk {params; extra; backend_type}
+          | BlockDevice {path} ->
+              BlockDevice {path}
+          | File {path} ->
+              File {path}
+          | Nbd {uri} ->
+              Nbd {uri}
+        in
+        let _, blockdevices, _, nbds =
+          Storage_interface.implementations_of_backend
+            {
+              Storage_interface.implementations=
+                List.map convert_implementation
+                  response.Xapi_storage.Data.implementations
+            }
+        in
+        match (blockdevices, nbds) with
+        | _, ({uri} as nbd) :: _ ->
+            info (fun m ->
+                m "%s qemu-dp nbd server address is %s" __FUNCTION__ uri
+            )
+            >>= fun () ->
+            let socket, _export = Storage_interface.parse_nbd_uri nbd in
+            return socket
+        | _ ->
+            fail (backend_error "No nbd server found" [])
+      )
+  in
+  S.DATA.MIRROR.get_nbd_server get_nbd_server_impl ;
   let u name _ = failwith ("Unimplemented: " ^ name) in
   S.get_by_name (u "get_by_name") ;
   S.VDI.get_by_name (u "VDI.get_by_name") ;

ocaml/xapi/storage_mux.ml

@@ -880,7 +880,14 @@ module Mux = struct
         end)) in
         C.DATA.MIRROR.import_activate (Debug_info.to_string di) dp sr vdi vm
 
-
+      let get_nbd_server () ~dbg ~dp ~sr ~vdi ~vm =
+        with_dbg ~name:"DATA.MIRROR.get_nbd_server" ~dbg @@ fun di ->
+        info "%s dbg:%s dp:%s sr:%s vdi:%s vm:%s" __FUNCTION__ dbg dp
+          (s_of_sr sr) (s_of_vdi vdi) (s_of_vm vm) ;
+        let module C = StorageAPI (Idl.Exn.GenClient (struct
+          let rpc = of_sr sr
+        end)) in
+        C.DATA.MIRROR.get_nbd_server (Debug_info.to_string di) dp sr vdi vm
     end
   end
 

ocaml/xapi/storage_smapiv1.ml

@@ -1238,6 +1238,7 @@ module SMAPIv1 : Server_impl = struct
       let import_activate _context ~dbg:_ ~dp:_ ~sr:_ ~vdi:_ ~vm:_ =
         assert false
 
+      let get_nbd_server _context ~dbg:_ ~dp:_ ~sr:_ ~vdi:_ ~vm:_ = assert false
     end
   end
 

ocaml/xapi/storage_smapiv1_wrapper.ml

@@ -1216,6 +1216,9 @@ functor
 
         let import_activate context ~dbg ~dp ~sr ~vdi ~vm =
           get_nbd_server_common context ~dbg ~dp ~sr ~vdi ~vm ~style:`oldstyle
+
+        let get_nbd_server context ~dbg ~dp ~sr ~vdi ~vm =
+          get_nbd_server_common context ~dbg ~dp ~sr ~vdi ~vm ~style:`real
       end
     end