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open Lwt.Infix
open Formats.QubesDB
let (>>!=) x f =
x >>= function
| `Ok y -> f y
| `Eof -> failwith "qubesdb-agent: end-of-file from QubesDB!"
| `Error (`Unknown msg) -> Fmt.failwith "qubesdb-agent: %s" msg
let starts_with str prefix =
let ls = String.length str in
let lp = String.length prefix in
if lp > ls then false else
let rec loop i =
if i = lp then true
else if str.[i] <> prefix.[i] then false
else loop (i + 1)
in loop 0
module QV = Msg_chan.Make(Framing)
let src = Logs.Src.create "qubes.db" ~doc:"QubesDB agent"
module Log = (val Logs.src_log src : Logs.LOG)
module KeyMap = Map.Make(String)
type t = {
vchan : QV.t;
notify : unit Lwt_condition.t;
commit : string Lwt_condition.t;
mutable store : string KeyMap.t;
mutable committed_store : string KeyMap.t KeyMap.t;
}
let update t bindings =
t.store <- bindings;
Lwt_condition.broadcast t.notify ()
let qubesdb_vchan_port =
match Vchan.Port.of_string "111" with
| Error (`Msg msg) -> failwith msg
| Ok port -> port
let send t ?(path="") ?(data="") ty =
let hdr = make_msg_header ~ty ~path ~data_len:(String.length data) in
QV.send t [hdr; data]
let recv t =
QV.recv t >>!= fun (hdr, data) ->
let ty =
let ty = get_msg_header_ty hdr in
match int_to_qdb_msg ty with
| None -> Fmt.failwith "Invalid message type %d" ty
| Some ty -> ty in
let path = get_msg_header_path hdr in
let path = String.sub path 0 (String.index path '\x00') in
Lwt.return (ty, path, data)
let values_for_key store key =
KeyMap.filter (fun k _ -> starts_with k (key ^ "/")) store
let full_db_sync t =
send t.vchan QDB_CMD_MULTIREAD >>!= fun () ->
let rec loop () =
recv t.vchan >>= function
| QDB_RESP_MULTIREAD, "", _ -> Lwt.return `Done
| QDB_RESP_MULTIREAD, path, data ->
Log.debug (fun f -> f "%S = %S" path data);
t.store <- t.store |> KeyMap.add path data;
loop ()
| ty, _, _ -> Fmt.failwith "Unexpected QubesDB message: %s" (qdb_msg_to_string ty) in
loop () >>= fun `Done ->
Lwt_condition.broadcast t.notify ();
KeyMap.iter (fun k v ->
if v = "" then
t.committed_store <- KeyMap.add k (values_for_key t.store k) t.committed_store)
t.store;
Lwt.return_unit
let rm t path =
let len = String.length path in
if len > 0 && path.[len - 1] = '/' then (
t.store
|> KeyMap.filter (fun key _ ->
if starts_with key path then (
Log.debug (fun f -> f "(rm %S)" key);
false
) else true
)
|> update t ;
let path_without_slash = String.sub path 0 (len - 1) in
t.committed_store <- KeyMap.remove path_without_slash t.committed_store;
) else (
if not (KeyMap.mem path t.store) then
Log.err (fun f -> f "%S not found (fatal database de-synchronization)" path);
t.store |> KeyMap.remove path |> update t
)
let listen t =
let rec loop () =
let ack path =
send t.vchan ~path QDB_RESP_OK >|= function
| `Eof -> failwith "End-of-file sending OK"
| `Ok () -> () in
recv t.vchan >>= function
| QDB_CMD_WRITE, path, value ->
Log.info (fun f -> f "got update: %S = %S" path value);
t.store |> KeyMap.add path value |> update t;
ack path >>= fun () ->
if value = "" then (
t.committed_store <- KeyMap.add path (values_for_key t.store path) t.committed_store;
Lwt_condition.broadcast t.commit path
);
loop ()
| QDB_RESP_OK, path, _ ->
Log.debug (fun f -> f "OK %S" path);
loop ()
| QDB_CMD_RM, path, _ ->
Log.info (fun f -> f "got rm %S" path);
rm t path;
ack path >>= loop
| QDB_RESP_ERROR, path, _ ->
Log.err (fun f -> f "Error from peer (for %S)" path);
loop ()
| ty, _, _ ->
Fmt.failwith "Unexpected QubesDB message: %s" (qdb_msg_to_string ty) in
loop () >|= fun `Done -> ()
let connect ~domid () =
Log.info (fun f -> f "connecting to server...");
QV.client ~domid ~port:qubesdb_vchan_port () >>= fun vchan ->
Log.info (fun f -> f "connected");
let t = {vchan; store = KeyMap.empty; committed_store = KeyMap.empty; notify = Lwt_condition.create (); commit = Lwt_condition.create ()} in
full_db_sync t >>= fun () ->
Lwt.async (fun () -> listen t);
Lwt.return t
let disconnect t : unit Lwt.t = QV.disconnect t.vchan
let read t key =
try Some (KeyMap.find key t.store)
with Not_found -> None
let write t key value =
send t.vchan QDB_CMD_WRITE ~path:key ~data:value >>!= fun () ->
Lwt.return_unit
let bindings t = t.store
let rec after t prev =
let current = t.store in
if KeyMap.equal (=) prev current then (
Lwt_condition.wait t.notify >>= fun () ->
after t prev
) else Lwt.return current
let find_committed_key t key =
match KeyMap.find_opt key t.committed_store with
| None -> KeyMap.empty
| Some map -> map
let rec got_new_commit t key prev =
let values = find_committed_key t key in
if KeyMap.equal (=) prev values then (
Lwt_condition.wait t.commit >>= fun key' ->
if String.equal key key' then
let values = find_committed_key t key in
Lwt.return values
else
got_new_commit t key prev
) else Lwt.return values