[PATCH 6/8] oxenstored: enable domain connection indexing based on eventchn port

[Zheng Li <dev@zheng.li>]

Currently in xenstore connection database,  we use a hash table of
(domid -> connection) to store domain connections. This allows fast indexing
based on domids.

This patch adds another dimention of fast indexing which is based on the
eventchn port number. This is useful when doing selective connections
processing based on incoming events.

For memory efficiency, the implementation reuse the the existing domain
connections hash table, but use the negative of a port number as the index (to
distinguish from domid which always >= 0).

Signed-off-by: Zheng Li <dev@zheng.li>
---
 tools/ocaml/xenstored/connections.ml | 21 +++++++++++++++++----
 tools/ocaml/xenstored/domain.ml      |  1 +
 2 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/tools/ocaml/xenstored/connections.ml b/tools/ocaml/xenstored/connections.ml
index 59c5c1a..a0f1b89 100644
--- a/tools/ocaml/xenstored/connections.ml
+++ b/tools/ocaml/xenstored/connections.ml
@@ -19,6 +19,7 @@ let debug fmt = Logging.debug "connections" fmt
 
 type t = {
 	anonymous: (Unix.file_descr, Connection.t) Hashtbl.t;
+	(* the key of the domains table can be either a domid or a port number (taking negative) *)
 	domains: (int, Connection.t) Hashtbl.t;
 	mutable watches: (string, Connection.watch list) Trie.t;
 }
@@ -33,7 +34,10 @@ let add_anonymous cons fd can_write =
 let add_domain cons dom =
 	let xbcon = Xenbus.Xb.open_mmap (Domain.get_interface dom) (fun () -> Domain.notify dom) in
 	let con = Connection.create xbcon (Some dom) in
-	Hashtbl.add cons.domains (Domain.get_id dom) con
+	Hashtbl.add cons.domains (Domain.get_id dom) con;
+	match Domain.get_port dom with
+	| Some p -> Hashtbl.add cons.domains (-1 * Xeneventchn.to_int p) con;
+	| None -> ()
 
 let select cons =
 	Hashtbl.fold
@@ -45,8 +49,11 @@ let select cons =
 let find cons =
 	Hashtbl.find cons.anonymous
 
-let find_domain cons id =
-	Hashtbl.find cons.domains id
+let find_domain cons =
+	Hashtbl.find cons.domains
+
+let find_domain_by_port cons port =
+	Hashtbl.find cons.domains (-1 * Xeneventchn.to_int port)
 
 let del_watches_of_con con watches =
 	match List.filter (fun w -> Connection.get_con w != con) watches with
@@ -65,13 +72,19 @@ let del_domain cons id =
 	try
 		let con = find_domain cons id in
 		Hashtbl.remove cons.domains id;
+		(match Connection.get_domain con with
+		 | Some d ->
+		   (match Domain.get_port d with
+		    | Some p -> Hashtbl.remove cons.domains (-1 * Xeneventchn.to_int p)
+		    | None -> ())
+		 | None -> ());
 		cons.watches <- Trie.map (del_watches_of_con con) cons.watches;
 		Connection.close con
 	with exn ->
 		debug "del domain %u: %s" id (Printexc.to_string exn)
 
 let iter_domains cons fct =
-	Hashtbl.iter (fun k c -> fct c) cons.domains
+	Hashtbl.iter (fun k c -> if k >= 0 then fct c) cons.domains
 
 let iter_anonymous cons fct =
 	Hashtbl.iter (fun _ c -> fct c) cons.anonymous
diff --git a/tools/ocaml/xenstored/domain.ml b/tools/ocaml/xenstored/domain.ml
index 444069d..06d5749 100644
--- a/tools/ocaml/xenstored/domain.ml
+++ b/tools/ocaml/xenstored/domain.ml
@@ -35,6 +35,7 @@ let get_id domain = domain.id
 let get_interface d = d.interface
 let get_mfn d = d.mfn
 let get_remote_port d = d.remote_port
+let get_port d = d.port
 
 let is_bad_domain domain = domain.bad_client
 let mark_as_bad domain = domain.bad_client <- true
-- 
2.1.0