xenguestHelper.ml

(*
 * Copyright (C) 2006-2009 Citrix Systems Inc.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published
 * by the Free Software Foundation; version 2.1 only. with the special
 * exception on linking described in file LICENSE.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *)
open Fun
open Pervasiveext
open Xenops_task

module D = Debug.Debugger(struct let name = "xenguesthelper" end)
open D

(** Where to place the last xenguesthelper debug log (just in case) *)
let last_log_file = "/tmp/xenguesthelper-log"

(* Exceptions which may propagate from the xenguest binary *)
exception Xenctrl_dom_allocate_failure of int * string
exception Xenctrl_dom_linux_build_failure of int * string
exception Xenctrl_domain_save_failure of int * string
exception Xenctrl_domain_resume_failure of int * string
exception Xenctrl_domain_restore_failure of int * string

exception Domain_builder_error of string (* function name *) * int (* error code *) * string (* message *)

(** We do all our IO through the buffered channels but pass the 
    underlying fds as integers to the forked helper on the commandline. *)
type t = in_channel * out_channel * Unix.file_descr * Unix.file_descr * Forkhelpers.pidty

(** Fork and run a xenguest helper with particular args, leaving 'fds' open 
    (in addition to internal control I/O fds) *)
let connect path domid (args: string list) (fds: (string * Unix.file_descr) list) : t =
	debug "connect: args = [ %s ]" (String.concat " " args);
	(* Need to send commands and receive responses from the
	   slave process *)

	let using_xiu = false in 

	let last_log_file = Printf.sprintf "/tmp/xenguest.%d.log" domid in

	let slave_to_server_w_uuid = Uuid.to_string (Uuid.make_uuid ()) in
	let server_to_slave_r_uuid = Uuid.to_string (Uuid.make_uuid ()) in

	let slave_to_server_r, slave_to_server_w = Unix.pipe () in
	let server_to_slave_r, server_to_slave_w = Unix.pipe () in

	let args = [ "-controloutfd"; slave_to_server_w_uuid;
		     "-controlinfd"; server_to_slave_r_uuid;
		     "-debuglog";
		     last_log_file
	] @ (if using_xiu then [ "-fake" ] else []) @ args in
	let pid = Forkhelpers.safe_close_and_exec None None None 
	  ([ slave_to_server_w_uuid, slave_to_server_w;
	    server_to_slave_r_uuid, server_to_slave_r ] @ fds)
	  path args in
	
	Unix.close slave_to_server_w;
	Unix.close server_to_slave_r;

	Unix.in_channel_of_descr slave_to_server_r,
	Unix.out_channel_of_descr server_to_slave_w,
	slave_to_server_r,
	server_to_slave_w,
	pid

(** Wait for the (hopefully dead) child process *)
let disconnect (_, _, r, w, pid) =
	Unix.close r;
	Unix.close w;
	ignore(Forkhelpers.waitpid pid)

let with_connection (task: Xenops_task.t) path domid (args: string list) (fds: (string * Unix.file_descr) list) f =
	let t = connect path domid args fds in
	let cancelled = ref false in
	let cancel_cb () =
		let _, _, _, _, pid = t in
		let pid = Forkhelpers.getpid pid in
		cancelled := true;
		info "Cancelling task %s by killing xenguest subprocess pid: %d" task.Xenops_task.id pid;
		try Unix.kill pid Sys.sigkill with _ -> () in
	finally
		(fun () ->
			Xenops_task.with_cancel task cancel_cb
				(fun () ->
					try
						f t
					with e ->
						if !cancelled
						then Xenops_task.raise_cancelled task
						else raise e
				)
		) (fun () -> disconnect t)

(** immediately write a command to the control channel *)
let send (_, out, _, _, _) txt = output_string out txt; flush out

(** Keep this in sync with xenguest_main *)
type message =
    | Stdout of string (* captured stdout from libxenguest *)
    | Stderr of string (* captured stderr from libxenguest *)
    | Error of string  (* an actual error that we detected *)
    | Suspend          (* request the caller suspends the domain *)
    | Info of string   (* some info that we want to send back *)
    | Result of string (* the result of the operation *)

let string_of_message = function
  | Stdout x -> "stdout:" ^ (String.escaped x)
  | Stderr x -> "stderr:" ^ (String.escaped x)
  | Error x  -> "error:" ^ (String.escaped x)
  | Suspend  -> "suspend:"
  | Info x   -> "info:" ^ (String.escaped x)
  | Result x -> "result:" ^ (String.escaped x)

let message_of_string x =
  if not(String.contains x ':') 
  then failwith (Printf.sprintf "Failed to parse message from xenguesthelper [%s]" x);
  let i = String.index x ':' in
  let prefix = String.sub x 0 i
  and suffix = String.sub x (i + 1) (String.length x - i - 1) in match prefix with
    | "stdout" -> Stdout suffix
    | "stderr" -> Stderr suffix
    | "error" -> Error suffix
    | "suspend" -> Suspend
    | "info" -> Info suffix
    | "result" -> Result suffix
    | _ -> Error "uncaught exception"

(** return the next output line from the control channel *)
let receive (infd, _, _, _, _) = message_of_string (input_line infd)

(** return the next output line which is not a debug: line *)
let rec non_debug_receive ?(debug_callback=(fun s -> debug "%s" s)) cnx = match receive cnx with
  | Stdout x -> debug_callback x; non_debug_receive ~debug_callback cnx
  | Stderr x -> debug_callback x; non_debug_receive ~debug_callback cnx
  | Info x -> debug_callback x; non_debug_receive ~debug_callback cnx
  | x -> x (* Error or Result or Suspend *)

(* Dump memory statistics on failure *)
let non_debug_receive ?debug_callback cnx = 
	let debug_memory () = 
		Xenctrl.with_intf (fun xc ->
			let open Memory in
			let open Int64 in
			let open Xenctrl in
			let p = Xenctrl.physinfo xc in
			let open Xenctrl in
			error "Memory F %Ld KiB S %Ld KiB T %Ld MiB"
				(p.free_pages |> of_nativeint |> kib_of_pages)
				(p.scrub_pages |> of_nativeint |> kib_of_pages)
				(p.total_pages |> of_nativeint |> mib_of_pages_free)
		) in
  try
    match non_debug_receive ?debug_callback cnx with
    | Error y as x -> 
	error "Received: %s" y;
	debug_memory (); x
    | x -> x
  with e ->
    debug_memory ();
    raise e

(** For the simple case where we just want the successful result, return it.
    If we get an error message (or suspend) then throw an exception. *)
let receive_success ?(debug_callback=(fun s -> debug "%s" s)) cnx =
	match non_debug_receive ~debug_callback cnx with
	| Error x ->
		(* These error strings match those in xenguest_stubs.c *)
		begin
			match Stringext.String.split ~limit:3 ' ' x with
			| [ "hvm_build"         ; code; msg ] -> raise (Domain_builder_error       ("hvm_build", int_of_string code, msg))
			| [ "xc_dom_allocate"   ; code; msg ] -> raise (Xenctrl_dom_allocate_failure    (int_of_string code, msg))
			| [ "xc_dom_linux_build"; code; msg ] -> raise (Xenctrl_dom_linux_build_failure (int_of_string code, msg))
			| [ "hvm_build_params"  ; code; msg ] -> raise (Domain_builder_error       ("hvm_build_params", int_of_string code, msg))
			| [ "hvm_build_mem"     ; code; msg ] -> raise (Domain_builder_error       ("hvm_build_mem", int_of_string code, msg))
			| [ "xc_domain_save"    ; code; msg ] -> raise (Xenctrl_domain_save_failure     (int_of_string code, msg))
			| [ "xc_domain_resume"  ; code; msg ] -> raise (Xenctrl_domain_resume_failure   (int_of_string code, msg))
			| [ "xc_domain_restore" ; code; msg ] -> raise (Xenctrl_domain_restore_failure  (int_of_string code, msg))
			| _ -> failwith (Printf.sprintf "Error from xenguesthelper: " ^ x)
		end
	| Suspend -> failwith "xenguesthelper protocol failure; not expecting Suspend"
	| Result x -> x
	| Stdout _ | Stderr _ | Info _ -> assert false