[Xen-changelog] [xen stable-4.6] oxenstored: refactor putting response on wire

[patchbot@xxxxxxx]

commit a57a99ae0f90ad9237869b962067c7a77190bf4c
Author:     Jonathan Davies <jonathan.davies@xxxxxxxxxx>
AuthorDate: Thu Mar 23 16:27:23 2017 +0000
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Wed Apr 5 15:19:02 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 <jgross@xxxxxxxx>
    Signed-off-by: Jonathan Davies <jonathan.davies@xxxxxxxxxx>
    Reviewed-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
    Reviewed-by: Jon Ludlam <jonathan.ludlam@xxxxxxxxxx>
    Reviewed-by: Euan Harris <euan.harris@xxxxxxxxxx>
    Acked-by: David Scott <dave@xxxxxxxxxx>
---
 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 59875f7..dce9e70 100644
--- a/tools/ocaml/xenstored/Makefile
+++ b/tools/ocaml/xenstored/Makefile
@@ -36,6 +36,7 @@ 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 e827678..3377966 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) =
@@ -289,20 +288,32 @@ 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 *)
@@ -335,7 +346,7 @@ 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
@@ -368,7 +379,10 @@ 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-4.6

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