Adapt to changed DiameterURI defaults in RFC 6733

Despite claims of full backwards compatibility, the text of RFC 6733
changes the interpretation of unspecified values in a DiameterURI. In
particular, 3588 says that the default port and transport are 3868 and
sctp respectively, while 6733 says it's either 3868/tcp (aaa) or
5658/tcp (aaas). The 3588 defaults were used regardless, but now use
them only if the common dictionary is diameter_gen_base_rfc3588. The
6733 defaults are used otherwise.

This kind of change in the standard can lead to interop problems, since
a node has to know which RFC its peer is following to know that it will
properly interpret missing URI components. Encode of a URI includes all
components to avoid such confusion.

That said, note that the defaults in the diameter_uri record have *not*
been changed. This avoids breaking code that depends on them, but the
risk is that such code sends inappropriate values. The record defaults
may be changed in a future release, to force values to be explicitly
specified.

1 files changed, 9 insertions, 0 deletions

diff --git a/lib/diameter/src/base/diameter_codec.erl b/lib/diameter/src/base/diameter_codec.erl
index cc0953f5d3..15a4c5e86f 100644
--- a/lib/diameter/src/base/diameter_codec.erl
+++ b/lib/diameter/src/base/diameter_codec.erl
@@ -81,6 +81,13 @@ setopts(Opts)
 setopt({string_decode = K, false = B}) ->
     setopt(K, B);
 
+%% Regard anything but the generated RFC 3588 dictionary as modern.
+%% This affects the interpretation of defaults during the decode
+%% of values of type DiameterURI, this having changed from RFC 3588.
+%% (So much for backwards compatibility.)
+setopt({common_dictionary, diameter_gen_base_rfc3588}) ->
+    setopt(rfc, 3588);
+
 setopt(_) ->
     ok.
 
@@ -91,6 +98,8 @@ getopt(Key) ->
     case get({diameter, Key}) of
         undefined when Key == string_decode ->
             true;
+        undefined when Key == rfc ->
+            6733;
         V ->
             V
     end.