Answer 5xxx errors with application_opt() request_errors = answer

RFC 3588 allowed only 3xxx result codes in an answer-message (that is,
an answer that sets the E-bit) while RFC 6733 also allows 5xxx result
codes. Setting request_errors = answer tells diameter to answer 5xxx
errors itself. Returning {answer_message, integer()} from a
handle_request callback allows both 3xxx and 5xxx result codes to be
set. {protocol_error, integer()} is retained for 3xxx result codes.

2 files changed, 44 insertions, 16 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index accf21cf98..379e9f0738 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -188,7 +188,7 @@ Defaults to the value of the <c>alias</c> option if unspecified.</p>
 <item>
 <p>
 Specifies whether or not the &app_pick_peer;
-application callback can modify the application state,
+application callback can modify the application state.
 Defaults to <c>false</c> if unspecified.</p>
 
 <note>
@@ -226,22 +226,37 @@ question is as if a callback had taken place and returned
 Defaults to <c>report</c> if unspecified.</p>
 </item>
 
-<tag><c>{request_errors, answer_3xxx|callback}</c></tag>
+<tag><c>{request_errors, answer_3xxx|answer|callback}</c></tag>
 <item>
 <p>
 Determines the manner in which incoming requests are handled when an
-error other than 3007, DIAMETER_APPLICATION_UNSUPPORTED. (With which no
-application callback module can be associated.)</p>
+error other than 3007, DIAMETER_APPLICATION_UNSUPPORTED (which cannot
+be associated with an application callback module), is detected.</p>
 
 <p>
-If <c>answer_3xxx</c> then the request is answered by diameter
-without a &app_handle_request; callback taking place if a 3xxx series
-error (protocol errors) is detected.
-If <c>callback</c> then even 3xxx errors result in an application
-&app_handle_request; callback.</p>
+If <c>answer_3xxx</c> then requests are answered without a
+&app_handle_request; callback taking place.
+If <c>answer</c> then even 5xxx errors are answered without a
+callback unless the connection in question has configured the RFC 3588
+common dictionary as noted below.
+If <c>callback</c> then a &app_handle_request; callback always takes
+place and the return value determines the answer sent to the peer.</p>
 
 <p>
 Defaults to <c>answer_3xxx</c> if unspecified.</p>
+
+<note>
+<p>
+Answers sent by diameter set the E-bit in the Diameter Header.
+Since RFC 3588 allowed only 3xxx result codes in an
+<c>answer-message</c>, <c>answer</c> has the same semantics as
+<c>answer_3xxx</c> if the peer connection in question has configured
+the RFC 3588 common dictionary, <c>diameter_gen_base_rfc3588</c>.
+RFC 6733 allows both 3xxx and 5xxx result codes in an
+<c>answer-message</c> so a connection configured with the RFC 6733
+common dictionary, <c>diameter_gen_base_rfc6733</c>, does
+distinguish between <c>answer_3xxx</c> and <c>answer</c>.</p>
+</note>
 </item>
 
 </taglist>
diff --git a/lib/diameter/doc/src/diameter_app.xml b/lib/diameter/doc/src/diameter_app.xml
index 5c23c9d683..d0f1b22ebd 100644
--- a/lib/diameter/doc/src/diameter_app.xml
+++ b/lib/diameter/doc/src/diameter_app.xml
@@ -475,6 +475,7 @@ not selected.</p>
            | discard
            | {eval|eval_packet, Action, PostF}</v>
 <v>Reply   = {reply, &packet; | &message;}
+           | {answer_message, 3000..3999|5000..5999}
            | {protocol_error, 3000..3999}</v>
 <v>Opt     = &mod_call_opt;</v>
 <v>PostF   = &mod_evaluable;</v>
@@ -545,22 +546,25 @@ preserved in the outgoing answer, appropriate values otherwise
 being set by diameter.</p>
 </item>
 
-<tag><c>{protocol_error, 3000..3999}</c></tag>
+<tag><c>{answer_message, 3000..3999|5000..5999}</c></tag>
 <item>
 <p>
 Send an answer message to the peer containing the specified
-protocol error.
+Result-Code.
 Equivalent to</p>
 <pre>
 {reply, ['answer-message' | Avps]
 </pre>
 <p>
 where <c>Avps</c> sets the Origin-Host, Origin-Realm, the specified
-Result-Code and (if the request sent one) Session-Id AVP's.</p>
+Result-Code and (if the request contained one) Session-Id AVP's.</p>
 
 <p>
-Returning a non-3xxx value in a <c>protocol_error</c> tuple
-will cause the request process in question to fail.</p>
+Returning a value other than 3xxx or 5xxx will cause the request
+process in question to fail, as will returning a 5xxx value if the
+peer connection in question has been configured with the RFC 3588
+common dictionary <c>diameter_gen_base_rfc3588</c>.
+(Since RFC 3588 only allows 3xxx values in an answer-message.)</p>
 </item>
 
 <tag><c>{relay, Opts}</c></tag>
@@ -613,11 +617,20 @@ containing the encoded binary.
 The return value is ignored.</p>
 </item>
 
+<tag><c>{protocol_error, 3000..3999}</c></tag>
+<item>
+<p>
+Equivalent to <c>{answer_message, 3000..3999}</c>.</p>
+</item>
+
 </taglist>
 
+<note>
 <p>
-Note that protocol errors detected by diameter will result in an
-answer message without <c>handle_request/3</c> being invoked.</p>
+Requests containing errors may be answered by diameter, without a
+callback taking place, depending on the value of the
+&mod_application_opt; <c>request_errors</c>.</p>
+</note>
 
 </desc>
 </func>