[Xen-changelog] [xen stable-4.6] oxenstored: keep track of each transaction's operations

[patchbot@xxxxxxx]

commit ebb5a34e856a0173ee688bf1f8fcfd38e577e3d4
Author:     Jonathan Davies <jonathan.davies@xxxxxxxxxx>
AuthorDate: Thu Mar 23 16:27:58 2017 +0000
Commit:     Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
CommitDate: Wed Apr 5 15:19:02 2017 +0100

    oxenstored: keep track of each transaction's operations
    
    A list of (request, response) pairs from the operations performed within the
    transaction will be useful to support transaction replay.
    
    Since this consumes memory, the number of requests per transaction must not 
be
    left unbounded. Hence a new quota for this is introduced. This quota, 
configured
    via the configuration key 'quota-maxrequests', limits the size of 
transactions
    initiated by domUs.
    
    After the maximum number of requests has been exhausted, any further 
requests
    will result in EQUOTA errors. The client may then choose to end the 
transaction;
    a successful commit will result in the retention of only the prior requests.
    
    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/define.ml       |  1 +
 tools/ocaml/xenstored/oxenstored.conf |  1 +
 tools/ocaml/xenstored/process.ml      | 13 +++++++++++--
 tools/ocaml/xenstored/transaction.ml  | 21 +++++++++++++++------
 tools/ocaml/xenstored/xenstored.ml    |  1 +
 5 files changed, 29 insertions(+), 8 deletions(-)

diff --git a/tools/ocaml/xenstored/define.ml b/tools/ocaml/xenstored/define.ml
index 89a6aac..d60861c 100644
--- a/tools/ocaml/xenstored/define.ml
+++ b/tools/ocaml/xenstored/define.ml
@@ -27,6 +27,7 @@ let default_config_dir = "/etc/xen"
 
 let maxwatch = ref (50)
 let maxtransaction = ref (20)
+let maxrequests = ref (-1)   (* maximum requests per transaction *)
 
 let domid_self = 0x7FF0
 
diff --git a/tools/ocaml/xenstored/oxenstored.conf 
b/tools/ocaml/xenstored/oxenstored.conf
index dd20eda..ac60f49 100644
--- a/tools/ocaml/xenstored/oxenstored.conf
+++ b/tools/ocaml/xenstored/oxenstored.conf
@@ -18,6 +18,7 @@ quota-maxentity = 1000
 quota-maxsize = 2048
 quota-maxwatch = 100
 quota-transaction = 10
+quota-maxrequests = 1024
 
 # Activate filed base backend
 persistent = false
diff --git a/tools/ocaml/xenstored/process.ml b/tools/ocaml/xenstored/process.ml
index c92bec7..758ade1 100644
--- a/tools/ocaml/xenstored/process.ml
+++ b/tools/ocaml/xenstored/process.ml
@@ -155,7 +155,7 @@ let do_transaction_end con t domains cons data =
        if not success then
                raise Transaction_again;
        if commit then
-               process_watch (List.rev (Transaction.get_ops t)) cons
+               process_watch (List.rev (Transaction.get_paths t)) cons
 
 let do_introduce con t domains cons data =
        if not (Connection.is_dom0 con)
@@ -303,7 +303,7 @@ let reply_ack fct con t doms cons data =
        fct con t doms cons data;
        Packet.Ack (fun () ->
                if Transaction.get_id t = Transaction.none then
-                       process_watch (Transaction.get_ops t) cons
+                       process_watch (Transaction.get_paths t) cons
        )
 
 let reply_data fct con t doms cons data =
@@ -384,6 +384,15 @@ let process_packet ~store ~cons ~doms ~con ~req =
                        in
                let response = input_handle_error ~cons ~doms ~fct ~con ~t ~req 
in
 
+               let response = try
+                       if tid <> Transaction.none then
+                               (* Remember the request and response for this 
operation in case we need to replay the transaction *)
+                               Transaction.add_operation 
~perm:(Connection.get_perm con) t req response;
+                       response
+               with Quota.Limit_reached ->
+                       Packet.Error "EQUOTA"
+               in
+
                (* Put the response on the wire *)
                send_response ty con t rid response
        with exn ->
diff --git a/tools/ocaml/xenstored/transaction.ml 
b/tools/ocaml/xenstored/transaction.ml
index 77de4e8..6b37fc2 100644
--- a/tools/ocaml/xenstored/transaction.ml
+++ b/tools/ocaml/xenstored/transaction.ml
@@ -75,7 +75,8 @@ type t = {
        ty: ty;
        store: Store.t;
        quota: Quota.t;
-       mutable ops: (Xenbus.Xb.Op.operation * Store.Path.t) list;
+       mutable paths: (Xenbus.Xb.Op.operation * Store.Path.t) list;
+       mutable operations: (Packet.request * Packet.response) list;
        mutable read_lowpath: Store.Path.t option;
        mutable write_lowpath: Store.Path.t option;
 }
@@ -86,16 +87,24 @@ let make id store =
                ty = ty;
                store = if id = none then store else Store.copy store;
                quota = Quota.copy store.Store.quota;
-               ops = [];
+               paths = [];
+               operations = [];
                read_lowpath = None;
                write_lowpath = None;
        }
 
 let get_id t = match t.ty with No -> none | Full (id, _, _) -> id
 let get_store t = t.store
-let get_ops t = t.ops
-
-let add_wop t ty path = t.ops <- (ty, path) :: t.ops
+let get_paths t = t.paths
+
+let add_wop t ty path = t.paths <- (ty, path) :: t.paths
+let add_operation ~perm t request response =
+       if !Define.maxrequests >= 0
+               && not (Perms.Connection.is_dom0 perm)
+               && List.length t.operations >= !Define.maxrequests
+               then raise Quota.Limit_reached;
+       t.operations <- (request, response) :: t.operations
+let get_operations t = List.rev t.operations
 let set_read_lowpath t path = t.read_lowpath <- get_lowest path t.read_lowpath
 let set_write_lowpath t path = t.write_lowpath <- get_lowest path 
t.write_lowpath
 
@@ -141,7 +150,7 @@ let getperms t perm path =
        r
 
 let commit ~con t =
-       let has_write_ops = List.length t.ops > 0 in
+       let has_write_ops = List.length t.paths > 0 in
        let has_coalesced = ref false in
        let has_commited =
        match t.ty with
diff --git a/tools/ocaml/xenstored/xenstored.ml 
b/tools/ocaml/xenstored/xenstored.ml
index 42b8183..7d3df43 100644
--- a/tools/ocaml/xenstored/xenstored.ml
+++ b/tools/ocaml/xenstored/xenstored.ml
@@ -95,6 +95,7 @@ let parse_config filename =
                ("quota-transaction", Config.Set_int Define.maxtransaction);
                ("quota-maxentity", Config.Set_int Quota.maxent);
                ("quota-maxsize", Config.Set_int Quota.maxsize);
+               ("quota-maxrequests", Config.Set_int Define.maxrequests);
                ("test-eagain", Config.Set_bool Transaction.test_eagain);
                ("persistent", Config.Set_bool Disk.enable);
                ("xenstored-log-file", Config.String 
Logging.set_xenstored_log_destination);
--
generated by git-patchbot for /home/xen/git/xen.git#stable-4.6

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