Let an 8-tuple given as ip_address() for gen_tcp/gen_udp/gen_sctp imply 'inet6'

Currently an 8-tuple representing an IPv6 address is not accepted by
gen_tcp:listen/2, gen_tcp:connect/3,4, gen_udp:open/2, or
gen_sctp:open/1,2, unless the 'inet6' option is also given. This means
that an application that has obtained the address, e.g. from
configuration that allows for either IPv4 or IPv6, must always check the
type of the address before passing it to these functions. Letting the
functions infer 'inet6' from the 8-tuple, in case other options do not
override this choice, improves usability.

1 files changed, 20 insertions, 10 deletions

diff --git a/lib/kernel/src/gen_sctp.erl b/lib/kernel/src/gen_sctp.erl
index a1542ab507..cccfa75005 100644
--- a/lib/kernel/src/gen_sctp.erl
+++ b/lib/kernel/src/gen_sctp.erl
@@ -39,7 +39,7 @@ open() ->
     open([]).
 
 open(Opts) when is_list(Opts) ->
-    Mod = mod(Opts),
+    Mod = mod(Opts, undefined),
     case Mod:open(Opts) of
 	{error,badarg} ->
 	    erlang:error(badarg, [Opts]);
@@ -234,17 +234,27 @@ controlling_process(S, Pid) ->
 %% Utilites
 %%
 
-%% Get the SCTP moudule
-mod() -> inet_db:sctp_module().
+%% Get the SCTP module, but IPv6 address overrides default IPv4
+mod(Address) ->
+    case inet_db:sctp_module() of
+	inet_sctp when tuple_size(Address) =:= 8 ->
+	    inet6_sctp;
+	Mod ->
+	    Mod
+    end.
 
 %% Get the SCTP module, but option sctp_module|inet|inet6 overrides
-mod([{sctp_module,Mod}|_]) ->
+mod([{sctp_module,Mod}|_], _Address) ->
     Mod;
-mod([inet|_]) ->
+mod([inet|_], _Address) ->
     inet_sctp;
-mod([inet6|_]) ->
+mod([inet6|_], _Address) ->
     inet6_sctp;
-mod([_|Opts]) ->
-    mod(Opts);
-mod([]) ->
-    mod().
+mod([{ip, Address}|Opts], _) ->
+    mod(Opts, Address);
+mod([{ifaddr, Address}|Opts], _) ->
+    mod(Opts, Address);
+mod([_|Opts], Address) ->
+    mod(Opts, Address);
+mod([], Address) ->
+    mod(Address).