Speed up ejabberd_s2s:is_service/2, allow_host/2 (thanks to Andreas Köhler)(EJAB-1319)

Iterating through the list of possible parent domains of a given domain
and comparing with the list of hosts or routes is almost always faster
than doing it the other way around. It naturally returns the shortest or
longest parent domain satisfying a predicate, whereas the possibly long
list compared with would need to be sorted by length first.

1 files changed, 18 insertions, 18 deletions

diff --git a/src/ejabberd_s2s.erl b/src/ejabberd_s2s.erl
index 8ab520f56..4d32ef66d 100644
--- a/src/ejabberd_s2s.erl
+++ b/src/ejabberd_s2s.erl
@@ -408,22 +408,21 @@ needed_connections_number(Ls, MaxS2SConnectionsNumber,
 is_service(From, To) ->
     LFromDomain = From#jid.lserver,
     case ejabberd_config:get_local_option({route_subdomains, LFromDomain}) of
-        s2s -> % bypass RFC 3920 10.3
-            false;
-        _ ->
-            LDstDomain = To#jid.lserver,
-            P = fun(Domain) -> is_subdomain(LDstDomain, Domain) end,
-            lists:any(P, ?MYHOSTS)
+	s2s -> % bypass RFC 3920 10.3
+	    false;
+	_ ->
+	    Hosts = ?MYHOSTS,
+	    P = fun(ParentDomain) -> lists:member(ParentDomain, Hosts) end,
+	    lists:any(P, parent_domains(To#jid.lserver))
     end.
 
-%%--------------------------------------------------------------------
-%% Function: is_subdomain(Domain1, Domain2) -> true | false
-%% Description: Return true if Domain1 (a string representing an
-%% internet domain name) is a subdomain (or the same domain) of
-%% Domain2
-%% --------------------------------------------------------------------
-is_subdomain(Domain1, Domain2) ->
-    lists:suffix(string:tokens(Domain2, "."), string:tokens(Domain1, ".")).
+parent_domains(Domain) ->
+    lists:foldl(
+      fun(Label, []) ->
+	      [Label];
+	 (Label, [Head | Tail]) ->
+	      [Label ++ "." ++ Head, Head | Tail]
+      end, [], lists:reverse(string:tokens(Domain, "."))).
 
 send_element(Pid, El) ->
     Pid ! {send_element, El}.
@@ -486,10 +485,11 @@ update_tables() ->
 
 %% Check if host is in blacklist or white list
 allow_host(MyServer, S2SHost) ->
-    case lists:filter(
-	   fun(Host) ->
-		   is_subdomain(MyServer, Host)
-	   end, ?MYHOSTS) of
+    Hosts = ?MYHOSTS,
+    case lists:dropwhile(
+	   fun(ParentDomain) ->
+		   not lists:member(ParentDomain, Hosts)
+	   end, parent_domains(MyServer)) of
 	[MyHost|_] ->
 	    allow_host1(MyHost, S2SHost);
 	[] ->