From f4330e9ed3e457be9b8993b13798dd0acb5de5aa Mon Sep 17 00:00:00 2001
From: Geoff Cant <geoff.cant@process-one.net>
Date: Thu, 30 Jul 2009 12:34:59 +0000
Subject: [PATCH] EJAB-994: Implements DNS timeouts and retries.

SVN Revision: 2404
---
 src/ejabberd_config.erl  |  2 ++
 src/ejabberd_s2s_out.erl | 34 +++++++++++++++++++++++++++++-----
 2 files changed, 31 insertions(+), 5 deletions(-)

diff --git a/src/ejabberd_config.erl b/src/ejabberd_config.erl
index 70d7b5dc7..d673818c1 100644
--- a/src/ejabberd_config.erl
+++ b/src/ejabberd_config.erl
@@ -343,6 +343,8 @@ process_term(Term, State) ->
 	    add_option(outgoing_s2s_port, Port, State);
 	{outgoing_s2s_options, Methods, Timeout} ->
 	    add_option(outgoing_s2s_options, {Methods, Timeout}, State);
+        {s2s_dns_options, PropList} ->
+            add_option(s2s_dns_options, PropList, State);
 	{s2s_use_starttls, Port} ->
 	    add_option(s2s_use_starttls, Port, State);
 	{s2s_certfile, CertFile} ->
diff --git a/src/ejabberd_s2s_out.erl b/src/ejabberd_s2s_out.erl
index 338bc9669..4bd92dc09 100644
--- a/src/ejabberd_s2s_out.erl
+++ b/src/ejabberd_s2s_out.erl
@@ -995,11 +995,7 @@ is_verify_res(_) ->
 -include_lib("kernel/include/inet.hrl").
 
 get_addr_port(Server) ->
-    Res = case inet_res:getbyname("_xmpp-server._tcp." ++ Server, srv) of
-	      {error, _Reason1} ->
-		  inet_res:getbyname("_jabber._tcp." ++ Server, srv);
-	      {ok, _HEnt} = R -> R
-	  end,
+    Res = srv_lookup(Server),
     case Res of
 	{error, Reason} ->
 	    ?DEBUG("srv lookup of '~s' failed: ~p~n", [Server, Reason]),
@@ -1036,6 +1032,34 @@ get_addr_port(Server) ->
 	    end
     end.
 
+srv_lookup(Server) ->
+    Options = case ejabberd_config:get_local_option(s2s_dns_options) of
+                  L when is_list(L) -> L;
+                  _ -> []
+              end,
+    Timeout = proplists:get_value(timeout, Options, timer:seconds(10)),
+    Retries = proplists:get_value(retries, Options, 2),
+    srv_lookup(Server, Timeout, Retries).
+
+%% XXX - this behaviour is suboptimal in the case that the domain
+%% has a "_xmpp-server._tcp." but not a "_jabber._tcp." record and
+%% we don't get a DNS reply for the "_xmpp-server._tcp." lookup. In this
+%% case we'll give up when we get the "_jabber._tcp." nxdomain reply.
+srv_lookup(_Server, _Timeout, Retries) when Retries < 1 ->
+    {error, timeout};
+srv_lookup(Server, Timeout, Retries) ->
+    case inet_res:getbyname("_xmpp-server._tcp." ++ Server, srv, Timeout) of
+        {error, _Reason} ->
+            case inet_res:getbyname("_jabber._tcp." ++ Server, srv, Timeout) of
+                {error, timeout} ->
+                    ?ERROR_MSG("Couldn't resolve SRV records for ~p via nameservers ~p.",
+                               [Server, inet_db:res_option(nameserver)]),
+                    srv_lookup(Server, Timeout, Retries - 1);
+                R -> R
+            end;
+        {ok, _HEnt} = R -> R
+    end.
+
 test_get_addr_port(Server) ->
     lists:foldl(
       fun(_, Acc) ->