[xen stable-4.4] oxenstored: refactor putting response on wire

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[xen stable-4.4] oxenstored: refactor putting response on wire

patchbot
commit 262754b45e1c1445af291e9c82c164f145e2b0e6
Author:     Jonathan Davies <[hidden email]>
AuthorDate: Thu Mar 23 17:40:00 2017 +0000
Commit:     Ian Jackson <[hidden email]>
CommitDate: Wed Apr 5 15:26:37 2017 +0100

    oxenstored: refactor putting response on wire
   
    Previously, the functions reply_{ack,data,data_or_ack} and input_handle_error
    put the response on the wire by invoking Connection.send_{ack,reply,error}.
   
    Instead, these functions now return a value indicating what needs to be put on
    the wire, and that action is done by a send_response function called
    afterwards.
   
    This refactoring gives us a chance to store the value of the response, useful
    for replaying transactions.
   
    Reported-by: Juergen Gross <[hidden email]>
    Signed-off-by: Jonathan Davies <[hidden email]>
    Reviewed-by: Andrew Cooper <[hidden email]>
    Reviewed-by: Jon Ludlam <[hidden email]>
    Reviewed-by: Euan Harris <[hidden email]>
    Acked-by: David Scott <[hidden email]>
---
 tools/ocaml/xenstored/Makefile   |  1 +
 tools/ocaml/xenstored/packet.ml  |  4 ++++
 tools/ocaml/xenstored/process.ml | 34 ++++++++++++++++++++++++----------
 3 files changed, 29 insertions(+), 10 deletions(-)

diff --git a/tools/ocaml/xenstored/Makefile b/tools/ocaml/xenstored/Makefile
index b18f190..7a4c317 100644
--- a/tools/ocaml/xenstored/Makefile
+++ b/tools/ocaml/xenstored/Makefile
@@ -17,6 +17,7 @@ OBJS = define \
  stdext \
  trie \
  config \
+ packet \
  logging \
  quota \
  perms \
diff --git a/tools/ocaml/xenstored/packet.ml b/tools/ocaml/xenstored/packet.ml
new file mode 100644
index 0000000..c8ecfe5
--- /dev/null
+++ b/tools/ocaml/xenstored/packet.ml
@@ -0,0 +1,4 @@
+type response =
+ | Ack of (unit -> unit)  (* function is the action to execute after sending the ack *)
+ | Reply of string
+ | Error of string
diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml
index 89db56c..8be2ff1 100644
--- a/tools/ocaml/xenstored/process.ml
+++ b/tools/ocaml/xenstored/process.ml
@@ -126,8 +126,7 @@ let do_watch con t rid domains cons data =
  | _                   -> raise Invalid_Cmd_Args
  in
  let watch = Connections.add_watch cons con node token in
- Connection.send_ack con (Transaction.get_id t) rid Xenbus.Xb.Op.Watch;
- Connection.fire_single_watch watch
+ Packet.Ack (fun () -> Connection.fire_single_watch watch)
 
 let do_unwatch con t domains cons data =
  let (node, token) =
@@ -284,20 +283,32 @@ let do_set_target con t domains cons data =
  | _                           -> raise Invalid_Cmd_Args
 
 (*------------- Generic handling of ty ------------------*)
+let send_response ty con t rid response =
+ match response with
+ | Packet.Ack f ->
+ Connection.send_ack con (Transaction.get_id t) rid ty;
+ (* Now do any necessary follow-up actions *)
+ f ()
+ | Packet.Reply ret ->
+ Connection.send_reply con (Transaction.get_id t) rid ty ret
+ | Packet.Error e ->
+ Connection.send_error con (Transaction.get_id t) rid e
+
 let reply_ack fct ty con t rid doms cons data =
  fct con t doms cons data;
- Connection.send_ack con (Transaction.get_id t) rid ty;
- if Transaction.get_id t = Transaction.none then
- process_watch (Transaction.get_ops t) cons
+ Packet.Ack (fun () ->
+ if Transaction.get_id t = Transaction.none then
+ process_watch (Transaction.get_ops t) cons
+ )
 
 let reply_data fct ty con t rid doms cons data =
  let ret = fct con t doms cons data in
- Connection.send_reply con (Transaction.get_id t) rid ty ret
+ Packet.Reply ret
 
 let reply_data_or_ack fct ty con t rid doms cons data =
  match fct con t doms cons data with
- | Some ret -> Connection.send_reply con (Transaction.get_id t) rid ty ret
- | None -> Connection.send_ack con (Transaction.get_id t) rid ty
+ | Some ret -> Packet.Reply ret
+ | None -> Packet.Ack (fun () -> ())
 
 let reply_none fct ty con t rid doms cons data =
  (* let the function reply *)
@@ -329,7 +340,7 @@ let function_of_type ty =
 
 let input_handle_error ~cons ~doms ~fct ~ty ~con ~t ~rid ~data =
  let reply_error e =
- Connection.send_error con (Transaction.get_id t) rid e in
+ Packet.Error e in
  try
  fct ty con t rid doms cons data
  with
@@ -362,7 +373,10 @@ let process_packet ~store ~cons ~doms ~con ~tid ~rid ~ty ~data =
  else
  Connection.get_transaction con tid
  in
- input_handle_error ~cons ~doms ~fct ~ty ~con ~t ~rid ~data;
+ let response = input_handle_error ~cons ~doms ~fct ~ty ~con ~t ~rid ~data in
+
+ (* Put the response on the wire *)
+ send_response ty con t rid response
  with exn ->
  error "process packet: %s" (Printexc.to_string exn);
  Connection.send_error con tid rid "EIO"
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.4

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