From aa5d9c9fae29c09eeba72305a274f37e79bf089f Mon Sep 17 00:00:00 2001 From: Jonathan Davies Date: Thu, 23 Mar 2017 17:40:35 +0000 Subject: [PATCH] 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 Signed-off-by: Jonathan Davies Reviewed-by: Andrew Cooper Reviewed-by: Jon Ludlam Reviewed-by: Euan Harris Acked-by: David Scott --- 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 89a6aacc88..d60861ca34 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 dd20eda140..ac60f49df8 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 b8bcb46628..34fb66c374 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) @@ -298,7 +298,7 @@ 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 = @@ -378,6 +378,15 @@ 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 77de4e8ac1..6b37fc2ad0 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 58a1ffc407..656a79b2ff 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); -- 2.39.5