Make explicit local address to diameter_tcp:start/3 optional

Use the default address address (as selected by gen_tcp) if none is
configured, passing it in the new 'connected' message introduced by the
previous commit.

The corresponding update to diameter_sctp has to wait until problems
with inet:sockname/1 are resolved: the function currently only returns
one address, and sometimes {0,0,0,0}. See OTP-11018.

3 files changed, 72 insertions, 32 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 7ea93d480b..97071ff323 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -343,8 +343,9 @@ Has one of the following types.</p>
 An address list is available to the start function of a
 &transport_module;, which
 can return a new list for use in the subsequent CER or CEA.
-Host-IP-Address need not be specified if the transport start function
-returns an address list.</p>
+Host-IP-Address need not be specified if the transport module in
+question communicates an address list as described in
+&man_transport;</p>
 </item>
 
 <tag><c>{'Vendor-Id', &dict_Unsigned32;}</c></tag>
diff --git a/lib/diameter/doc/src/diameter_tcp.xml b/lib/diameter/doc/src/diameter_tcp.xml
index 01c781d553..8e509aa829 100644
--- a/lib/diameter/doc/src/diameter_tcp.xml
+++ b/lib/diameter/doc/src/diameter_tcp.xml
@@ -1,5 +1,6 @@
 <?xml version="1.0" encoding="latin1" ?>
 <!DOCTYPE erlref SYSTEM "erlref.dtd" [
+  <!ENTITY start '<seealso marker="#start-3">start/3</seealso>'>
   <!ENTITY gen_tcp_connect3
   '<seealso marker="kernel:gen_tcp#connect-3">gen_tcp:connect/3</seealso>'>
   <!ENTITY gen_tcp_listen2
@@ -81,7 +82,9 @@ before configuring TLS capability on diameter transports.</p>
 
 <func>
 <name>start({Type, Ref}, Svc, [Opt])
-         -> {ok, Pid, [LAddr]} | {error, Reason}</name>
+         -> {ok, Pid}
+          | {ok, Pid, [LAddr]}
+          | {error, Reason}</name>
 <fsummary>Start a transport process.</fsummary>
 <type>
 <v>Type = connect | accept</v>
@@ -153,13 +156,14 @@ that will not be forthcoming, which will eventually cause the RFC 3539
 watchdog to take down the connection.</p>
 
 <p>
-If the <c>#diameter_service{}</c> record has more than one
-<c>Host-IP-Address</c> and option <c>ip</c> is unspecified then the
-first of the these addresses is used as the local address.</p>
-
-<p>
-The returned local address list has length one.</p>
-
+If an <c>ip</c> option is not specified then the first element of a
+non-empty <c>Host-IP-Address</c> list in <c>Svc</c> provides the local
+IP address.
+If neither is specified then the default address selected by &gen_tcp;
+is used.
+In all cases, the selected address is either returned from
+&start; or passed in a <c>connected</c> message over the transport
+interface.</p>
 </desc>
 </func>
 
diff --git a/lib/diameter/src/transport/diameter_tcp.erl b/lib/diameter/src/transport/diameter_tcp.erl
index 132088b514..cbbba714ac 100644
--- a/lib/diameter/src/transport/diameter_tcp.erl
+++ b/lib/diameter/src/transport/diameter_tcp.erl
@@ -100,6 +100,18 @@
 %% # start/3
 %% ---------------------------------------------------------------------------
 
+-spec start({accept, Ref}, Svc, [Opt])
+   -> {ok, pid(), [inet:ip_address()]}
+ when Ref :: diameter:transport_ref(),
+      Svc :: #diameter_service{},
+      Opt :: diameter:transport_opt();
+           ({connect, Ref}, Svc, [Opt])
+   -> {ok, pid(), [inet:ip_address()]}
+    | {ok, pid()}
+ when Ref :: diameter:transport_ref(),
+      Svc :: #diameter_service{},
+      Opt :: diameter:transport_opt().
+                   
 start({T, Ref}, #diameter_service{capabilities = Caps}, Opts) ->
     diameter_tcp_sup:start(),  %% start tcp supervisors on demand
     {Mod, Rest} = split(Opts),
@@ -172,7 +184,7 @@ i({T, Ref, Mod, Pid, Opts, Addrs})
                               OwnOpts,
                               ?DEFAULT_FRAGMENT_TIMEOUT),
     ?IS_TIMEOUT(Tmo) orelse ?ERROR({fragment_timer, Tmo}),
-    Sock = i(T, Ref, Mod, Pid, SslOpts, Rest, Addrs),
+    Sock = init(T, Ref, Mod, Pid, SslOpts, Rest, Addrs),
     MPid ! {stop, self()},  %% tell the monitor to die
     M = if SslOpts -> ssl; true -> Mod end,
     setopts(M, Sock),
@@ -199,14 +211,21 @@ i(#monitor{parent = Pid, transport = TPid} = S) ->
 
 i({listen, LRef, APid, {Mod, Opts, Addrs}}) ->
     {[LA, LP], Rest} = proplists:split(Opts, [ip, port]),
-    LAddr = get_addr(LA, Addrs),
+    LAddrOpt = get_addr(LA, Addrs),
     LPort = get_port(LP),
-    {ok, LSock} = Mod:listen(LPort, gen_opts(LAddr, Rest)),
+    {ok, LSock} = Mod:listen(LPort, gen_opts(LAddrOpt, Rest)),
+    LAddr = laddr(LAddrOpt, Mod, LSock),
     true = diameter_reg:add_new({?MODULE, listener, {LRef, {LAddr, LSock}}}),
     proc_lib:init_ack({ok, self(), {LAddr, LSock}}),
     erlang:monitor(process, APid),
     start_timer(#listener{socket = LSock}).
 
+laddr([], Mod, Sock) ->
+    {ok, {Addr, _Port}} = sockname(Mod, Sock),
+    Addr;
+laddr([{ip, Addr}], _, _) ->
+    Addr.
+    
 own(Opts) ->
     {Own, Rest} = proplists:split(Opts, [fragment_timer]),
     {lists:append(Own), Rest}.
@@ -225,17 +244,19 @@ ssl_opts([{ssl_options, Opts}])
 ssl_opts(L) ->
     ?ERROR({ssl_options, L}).
 
-%% i/7
+%% init/7
 
 %% Establish a TLS connection before capabilities exchange ...
-i(Type, Ref, Mod, Pid, true, Opts, Addrs) ->
-    i(Type, Ref, ssl, Pid, [{cb_info, ?TCP_CB(Mod)} | Opts], Addrs);
+init(Type, Ref, Mod, Pid, true, Opts, Addrs) ->
+    init(Type, Ref, ssl, Pid, [{cb_info, ?TCP_CB(Mod)} | Opts], Addrs);
 
 %% ... or not.
-i(Type, Ref, Mod, Pid, _, Opts, Addrs) ->
-    i(Type, Ref, Mod, Pid, Opts, Addrs).
+init(Type, Ref, Mod, Pid, _, Opts, Addrs) ->
+    init(Type, Ref, Mod, Pid, Opts, Addrs).
+
+%% init/6
 
-i(accept = T, Ref, Mod, Pid, Opts, Addrs) ->
+init(accept = T, Ref, Mod, Pid, Opts, Addrs) ->
     {LAddr, LSock} = listener(Ref, {Mod, Opts, Addrs}),
     proc_lib:init_ack({ok, self(), [LAddr]}),
     Sock = ok(accept(Mod, LSock)),
@@ -243,17 +264,28 @@ i(accept = T, Ref, Mod, Pid, Opts, Addrs) ->
     diameter_peer:up(Pid),
     Sock;
 
-i(connect = T, Ref, Mod, Pid, Opts, Addrs) ->
+init(connect = T, Ref, Mod, Pid, Opts, Addrs) ->
     {[LA, RA, RP], Rest} = proplists:split(Opts, [ip, raddr, rport]),
-    LAddr = get_addr(LA, Addrs),
-    RAddr = get_addr(RA, []),
+    LAddrOpt = get_addr(LA, Addrs),
+    RAddr = get_addr(RA),
     RPort = get_port(RP),
-    proc_lib:init_ack({ok, self(), [LAddr]}),
-    Sock = ok(connect(Mod, RAddr, RPort, gen_opts(LAddr, Rest))),
+    proc_lib:init_ack(init_rc(LAddrOpt)),
+    Sock = ok(connect(Mod, RAddr, RPort, gen_opts(LAddrOpt, Rest))),
     publish(Mod, T, Ref, Sock),
-    diameter_peer:up(Pid, {RAddr, RPort}),
+    up(Pid, {RAddr, RPort}, LAddrOpt, Mod, Sock),
     Sock.
 
+init_rc([{ip, Addr}]) ->
+    {ok, self(), [Addr]};
+init_rc([]) ->
+    {ok, self()}.
+
+up(Pid, Remote, [{ip, _Addr}], _, _) ->
+    diameter_peer:up(Pid, Remote);
+up(Pid, Remote, [], Mod, Sock) -> 
+    {Addr, _Port} = ok(sockname(Mod, Sock)),
+    diameter_peer:up(Pid, Remote, [Addr]).
+
 publish(Mod, T, Ref, Sock) ->
     true = diameter_reg:add_new({?MODULE, T, {Ref, Sock}}),
     putr(?INFO_KEY, {Mod, Sock}).  %% for info/1
@@ -281,10 +313,17 @@ l([], LRef, T) ->
     {ok, _, AS} = diameter_tcp_sup:start_child({listen, LRef, self(), T}),
     AS.
 
+%% get_addr/1
+
+get_addr(As) ->
+    diameter_lib:ipaddr(addr(As, [])).
+
 %% get_addr/2
 
+get_addr([], []) ->
+    [];
 get_addr(As, Def) ->
-    diameter_lib:ipaddr(addr(As, Def)).
+    [{ip, diameter_lib:ipaddr(addr(As, Def))}].
 
 %% Take the first address from the service if several are unspecified.
 addr([], [Addr | _]) ->
@@ -305,14 +344,10 @@ get_port(Ps) ->
 
 %% gen_opts/2
 
-gen_opts(LAddr, Opts) ->
+gen_opts(LAddrOpt, Opts) ->
     {L,_} = proplists:split(Opts, [binary, packet, active]),
     [[],[],[]] == L orelse ?ERROR({reserved_options, Opts}),
-    [binary,
-     {packet, 0},
-     {active, once},
-     {ip, LAddr}
-     | Opts].
+    [binary, {packet, 0}, {active, once}] ++ LAddrOpt ++ Opts.
 
 %% ---------------------------------------------------------------------------
 %% # ports/1