Rename reconnect_timer -> connect_timer

The former was misleading since the timer only applies to initial
connection attempts, reconnection attempts being governed by
watchdog_timer. The name is a historic remnant from a (dark, pre-OTP)
time in which RFC 3539 was followed less slavishly than it is now, and
the timer actually did apply to reconnection attempts.

Note that connect_timer corresponds to RFC 6733 Tc, while watchdog_timer
corresponds to RFC 3539 TwInit. The latter RFC makes clear that TwInit
should apply to reconnection attempts. It's less clear if only RFC 6733
is read.

Note also that reconnect_timer is still accepted for backwards
compatibility. It would be possible to add an option to make
reconnect_timer behave strictly as the name suggests (ie. ignore RFC 3539
and interpret RFC 6733 at face value; something that has some value for
testing at least) but no such option is implemented in this commit.

7 files changed, 51 insertions, 42 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index db19fbb271..06278d1a55 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -599,7 +599,7 @@ Opts = [&transport_opt;]
 
 <p>
 A connecting transport is attempting to establish/reestablish a
-transport connection with a peer following &reconnect_timer; or
+transport connection with a peer following &connect_timer; or
 &watchdog_timer; expiry.</p>
 </item>
 
@@ -1022,13 +1022,43 @@ The number of milliseconds after which a transport process having an
 established transport connection will be terminated if the expected
 capabilities exchange message (CER or CEA) is not received from the peer.
 For a connecting transport, the timing of reconnection attempts is
-governed by &watchdog_timer; or &reconnect_timer; expiry.
+governed by &watchdog_timer; or &connect_timer; expiry.
 For a listening transport, the peer determines the timing.</p>
 
 <p>
 Defaults to 10000.</p>
 </item>
 
+<marker id="connect_timer"/>
+<tag><c>{connect_timer, Tc}</c></tag>
+<item>
+<pre>
+Tc = &dict_Unsigned32;
+</pre>
+
+<p>
+For a connecting transport, the &the_rfc; Tc timer, in milliseconds.
+Note that this timer determines the frequency with which a transport
+will attempt to establish an initial connection with its peer
+following transport configuration: once an initial connection has been
+established it's &watchdog_timer; that determines the frequency of
+reconnection attempts, as required by RFC 3539.</p>
+
+<p>
+For a listening transport, the timer specifies the time after which a
+previously connected peer will be forgotten: a connection after this time is
+regarded as an initial connection rather than a reestablishment,
+causing the RFC 3539 state machine to pass to state OKAY rather than
+REOPEN.
+Note that these semantics are not governed by the RFC and
+that a listening transport's &connect_timer; should be greater
+than its peer's Tw plus jitter.</p>
+
+<p>
+Defaults to 30000 for a connecting transport and 60000 for a listening
+transport.</p>
+</item>
+
 <marker id="disconnect_cb"/>
 <tag><c>{disconnect_cb, &evaluable;}</c></tag>
 
@@ -1145,36 +1175,6 @@ See &man_tcp; for the behaviour of that module.</p>
 </note>
 </item>
 
-<marker id="reconnect_timer"/>
-<tag><c>{reconnect_timer, Tc}</c></tag>
-<item>
-<pre>
-Tc = &dict_Unsigned32;
-</pre>
-
-<p>
-For a connecting transport, the &the_rfc; Tc timer, in milliseconds.
-Note that this timer determines the frequency with which a transport
-will attempt to establish a connection with its peer only <em>before</em>
-an initial connection is established: once there is an initial
-connection it's &watchdog_timer; that determines the
-frequency of reconnection attempts, as required by RFC 3539.</p>
-
-<p>
-For a listening transport, the timer specifies the time after which a
-previously connected peer will be forgotten: a connection after this time is
-regarded as an initial connection rather than a reestablishment,
-causing the RFC 3539 state machine to pass to state OKAY rather than
-REOPEN.
-Note that these semantics are not governed by the RFC and
-that a listening transport's &reconnect_timer; should be greater
-than its peer's Tw plus jitter.</p>
-
-<p>
-Defaults to 30000 for a connecting transport and 60000 for a listening
-transport.</p>
-</item>
-
 <marker id="spawn_opt"/>
 <tag><c>{spawn_opt, [term()]}</c></tag>
 <item>
diff --git a/lib/diameter/doc/src/diameter_soc_rfc6733.xml b/lib/diameter/doc/src/diameter_soc_rfc6733.xml
index 8d85569650..deb4d05b0f 100644
--- a/lib/diameter/doc/src/diameter_soc_rfc6733.xml
+++ b/lib/diameter/doc/src/diameter_soc_rfc6733.xml
@@ -1272,7 +1272,7 @@ during capabilities exchange.)</p>
 
 <p>
 The frequency of reconnection attempts is configured with the
-&mod_transport_opt; <c>reconnect_timer</c> and
+&mod_transport_opt; <c>connect_timer</c> and
 <c>watchdog_timer</c>.</p>
 
 <pre>
diff --git a/lib/diameter/doc/src/seealso.ent b/lib/diameter/doc/src/seealso.ent
index 76b9823f79..3ec13477ab 100644
--- a/lib/diameter/doc/src/seealso.ent
+++ b/lib/diameter/doc/src/seealso.ent
@@ -66,7 +66,7 @@ significant.
 <!ENTITY disconnect_cb '<seealso marker="#disconnect_cb">disconnect_cb</seealso>'>
 <!ENTITY transport_config '<seealso marker="#transport_config">transport_config</seealso>'>
 <!ENTITY transport_module '<seealso marker="#transport_module">transport_module</seealso>'>
-<!ENTITY reconnect_timer '<seealso marker="#reconnect_timer">reconnect_timer</seealso>'>
+<!ENTITY connect_timer '<seealso marker="#connect_timer">connect_timer</seealso>'>
 <!ENTITY watchdog_timer '<seealso marker="#watchdog_timer">watchdog_timer</seealso>'>
 
 <!-- diameter_app -->
diff --git a/lib/diameter/src/base/diameter.erl b/lib/diameter/src/base/diameter.erl
index 77200cc7d0..d74e091e11 100644
--- a/lib/diameter/src/base/diameter.erl
+++ b/lib/diameter/src/base/diameter.erl
@@ -343,7 +343,7 @@ call(SvcName, App, Message) ->
     | {capx_timeout, 'Unsigned32'()}
     | {disconnect_cb, evaluable()}
     | {length_errors, exit | handle | discard}
-    | {reconnect_timer, 'Unsigned32'()}
+    | {connect_timer, 'Unsigned32'()}
     | {watchdog_timer, 'Unsigned32'() | {module(), atom(), list()}}
     | {watchdog_config, [{okay|suspect, non_neg_integer()}]}
     | {spawn_opt, list()}
diff --git a/lib/diameter/src/base/diameter_config.erl b/lib/diameter/src/base/diameter_config.erl
index 34b40c3a29..f5ea459fd0 100644
--- a/lib/diameter/src/base/diameter_config.erl
+++ b/lib/diameter/src/base/diameter_config.erl
@@ -537,7 +537,9 @@ opt({capx_timeout, Tmo}) ->
 opt({length_errors, T}) ->
     lists:member(T, [exit, handle, discard]);
 
-opt({reconnect_timer, Tmo}) ->
+opt({K, Tmo})
+  when K == reconnect_timer;  %% deprecated
+       K == connect_timer ->
     ?IS_UINT32(Tmo);
 
 opt({watchdog_timer, {M,F,A}})
diff --git a/lib/diameter/src/base/diameter_service.erl b/lib/diameter/src/base/diameter_service.erl
index 47e03cd0a0..70e66537ed 100644
--- a/lib/diameter/src/base/diameter_service.erl
+++ b/lib/diameter/src/base/diameter_service.erl
@@ -1143,10 +1143,17 @@ q_restart(false, _) ->
 %%   communicate.
 
 default_tc(connect, Opts) ->
-    proplists:get_value(reconnect_timer, Opts, ?DEFAULT_TC);
+    connect_timer(Opts, ?DEFAULT_TC);
 default_tc(accept, _) ->
     0.
 
+%% Accept both connect_timer and the (older) reconnect_timer, the
+%% latter being a remnant from a time in which the timer did apply to
+%% reconnect attempts.
+connect_timer(Opts, Def0) ->
+    Def = proplists:get_value(reconnect_timer, Opts, Def0),
+    proplists:get_value(connect_timer, Opts, Def).
+
 %% Bound tc below if the watchdog was restarted recently to avoid
 %% continuous restarted in case of faulty config or other problems.
 tc(Time, Tc) ->
@@ -1181,7 +1188,7 @@ tc(false = No, _, _) ->  %% removed
 %% another watchdog to be able to detect that it should transition
 %% from initial into reopen rather than okay. That someone is either
 %% the accepting watchdog upon reception of a CER from the previously
-%% connected peer, or us after reconnect_timer timeout.
+%% connected peer, or us after connect_timer timeout.
 
 close(#watchdog{type = connect}, _) ->
     ok;
@@ -1194,16 +1201,16 @@ close(#watchdog{type = accept,
 
 %% Tell watchdog to (maybe) die later ...
 c(Pid, true, Opts) ->
-    Tc = proplists:get_value(reconnect_timer, Opts, 2*?DEFAULT_TC),
+    Tc = connect_timer(Opts, 2*?DEFAULT_TC),
     erlang:send_after(Tc, Pid, close);
 
 %% ... or now.
 c(Pid, false, _Opts) ->
     Pid ! close.
 
-%% The RFC's only document the behaviour of Tc, our reconnect_timer,
+%% The RFC's only document the behaviour of Tc, our connect_timer,
 %% for the establishment of connections but we also give
-%% reconnect_timer semantics for a listener, being the time within
+%% connect_timer semantics for a listener, being the time within
 %% which a new connection attempt is expected of a connecting peer.
 %% The value should be greater than the peer's Tc + jitter.
 
diff --git a/lib/diameter/src/base/diameter_watchdog.erl b/lib/diameter/src/base/diameter_watchdog.erl
index 7e75801718..55d46fadea 100644
--- a/lib/diameter/src/base/diameter_watchdog.erl
+++ b/lib/diameter/src/base/diameter_watchdog.erl
@@ -329,7 +329,7 @@ code_change(_, State, _) ->
 %% the commentary is ours.
 
 %% Service or watchdog is telling the watchdog of an accepting
-%% transport to die after reconnect_timer expiry or reestablished
+%% transport to die after connect_timer expiry or reestablished
 %% connection (in another transport process) respectively.
 transition(close, #watchdog{status = down}) ->
     {{accept, _}, _, _} = getr(restart), %% assert