1 files changed, 66 insertions, 7 deletions
diff --git a/src/gun_tcp.erl b/src/gun_tcp.erl
index 72e5681..2d091a0 100644
--- a/src/gun_tcp.erl
+++ b/src/gun_tcp.erl
@@ -16,23 +16,82 @@
 
 -export([name/0]).
 -export([messages/0]).
--export([connect/4]).
+-export([domain_lookup/4]).
+-export([connect/2]).
 -export([send/2]).
 -export([setopts/2]).
 -export([sockname/1]).
 -export([close/1]).
 
+-type lookup_info() :: #{
+	ip_addresses := [inet:ip_address()],
+	port := inet:port_number(),
+	tcp_module := module(),
+	tcp_opts := [gen_tcp:connect_option()] | [ssl:connect_option()]
+}.
+-export_type([lookup_info/0]).
+
 name() -> tcp.
 
 messages() -> {tcp, tcp_closed, tcp_error}.
 
--spec connect(inet:ip_address() | inet:hostname(),
-	inet:port_number(), any(), timeout())
+%% The functions domain_lookup/4 and connect/2 are very similar
+%% to gen_tcp:connect/4 except the logic is split in order to
+%% be able to trigger events between the domain lookup step
+%% and the actual connect step.
+
+-spec domain_lookup(inet:ip_address() | inet:hostname(),
+	inet:port_number(), [gen_tcp:connect_option()] | [ssl:connect_option()], timeout())
+	-> {ok, lookup_info()} | {error, atom()}.
+domain_lookup(Address, Port0, Opts0, Timeout) ->
+	{Mod, Opts} = inet:tcp_module(Opts0, Address),
+	Timer = inet:start_timer(Timeout),
+	try Mod:getaddrs(Address, Timer) of
+		{ok, IPs} ->
+			case Mod:getserv(Port0) of
+				{ok, Port} ->
+					{ok, #{
+						ip_addresses => IPs,
+						port => Port,
+						tcp_module => Mod,
+						tcp_opts => Opts ++ [binary, {active, false}, {packet, raw}]
+					}};
+				Error ->
+					maybe_exit(Error)
+			end;
+		Error ->
+			maybe_exit(Error)
+	after
+		_ = inet:stop_timer(Timer)
+	end.
+
+-spec connect(lookup_info(), timeout())
 	-> {ok, inet:socket()} | {error, atom()}.
-connect(Host, Port, Opts, Timeout) when is_integer(Port) ->
-	gen_tcp:connect(Host, Port,
-		Opts ++ [binary, {active, false}, {packet, raw}],
-		Timeout).
+connect(#{ip_addresses := IPs, port := Port, tcp_module := Mod, tcp_opts := Opts}, Timeout) ->
+	Timer = inet:start_timer(Timeout),
+	Res = try
+		try_connect(IPs, Port, Opts, Timer, Mod, {error, einval})
+	after
+		_ = inet:stop_timer(Timer)
+	end,
+	case Res of
+		{ok, S} -> {ok, S};
+		Error -> maybe_exit(Error)
+	end.
+
+try_connect([IP|IPs], Port, Opts, Timer, Mod, _) ->
+	Timeout = inet:timeout(Timer),
+	case Mod:connect(IP, Port, Opts, Timeout) of
+		{ok, S} -> {ok, S};
+		{error, einval} -> {error, einval};
+		{error, timeout} -> {error, timeout};
+		Error -> try_connect(IPs, Port, Opts, Timer, Mod, Error)
+	end;
+try_connect([], _, _, _, _, Error) ->
+	Error.
+
+maybe_exit({error, einval}) -> exit(badarg);
+maybe_exit(Error) -> Error.
 
 -spec send(inet:socket(), iodata()) -> ok | {error, atom()}.
 send(Socket, Packet) ->