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use a fresh client for requesting vif and ip

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in the callback to "Xs_client.wait", all operations are tracked and new watches
are installed (that are never removed, due to xenstore's xs_handle
"accessed_path" never removes any elements of the "accessed_paths" (a mutable
StringSet). So, whatever is done in the callback of wait needs to take care
(if returning EAGAIN and thus forcing xenstore to continue waiting/watching)
that accesses are tracked.

Our way out is to create a fresh client and read the IP address with that new
client -> the watcher isn't extended -> no dangling (leaking) watches, and no
leaking only-expanding StringSet.
This commit is contained in:
Hannes Mehnert 2022-11-10 23:08:21 +01:00
parent 0e0917f4fe
commit d094b20950
1 changed files with 36 additions and 34 deletions
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dao.ml
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@ -65,11 +65,12 @@ let read_rules rules client_ip =
icmp_type = None; icmp_type = None;
number = 0;})] number = 0;})]
let vifs ~handle domid = let vifs client domid =
match String.to_int domid with match String.to_int domid with
| None -> Log.err (fun f -> f "Invalid domid %S" domid); Lwt.return [] | None -> Log.err (fun f -> f "Invalid domid %S" domid); Lwt.return []
| Some domid -> | Some domid ->
let path = Printf.sprintf "backend/vif/%d" domid in let path = Printf.sprintf "backend/vif/%d" domid in
Xen_os.Xs.immediate client (fun handle ->
directory ~handle path >>= directory ~handle path >>=
Lwt_list.filter_map_p (fun device_id -> Lwt_list.filter_map_p (fun device_id ->
match String.to_int device_id with match String.to_int device_id with
@ -101,7 +102,7 @@ let vifs ~handle domid =
ClientVif.pp vif (Printexc.to_string ex)); ClientVif.pp vif (Printexc.to_string ex));
Lwt.return None Lwt.return None
) )
) ))
let watch_clients fn = let watch_clients fn =
Xen_os.Xs.make () >>= fun xs -> Xen_os.Xs.make () >>= fun xs ->
@ -114,7 +115,8 @@ let watch_clients fn =
| Xs_protocol.Enoent _ -> Lwt.return [] | Xs_protocol.Enoent _ -> Lwt.return []
| ex -> Lwt.fail ex) | ex -> Lwt.fail ex)
end >>= fun items -> end >>= fun items ->
Lwt_list.map_p (vifs ~handle) items >>= fun items -> Xen_os.Xs.make () >>= fun xs ->
Lwt_list.map_p (vifs xs) items >>= fun items ->
fn (List.concat items |> VifMap.of_list); fn (List.concat items |> VifMap.of_list);
(* Wait for further updates *) (* Wait for further updates *)
Lwt.fail Xs_protocol.Eagain Lwt.fail Xs_protocol.Eagain