Add transport_opt() length_errors

The value determines whether or not an unexpected message length in the
header of an incoming messages causes the peer process to exit, the
message to be discarded or handled as usual. The latter may only be
appropriate for message-oriented transport (eg. SCTP) since
stream-oriented transport (eg. TCP) may not be able to recover the
message boundary once a length error has occurred.

1 files changed, 36 insertions, 0 deletions

diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 7e50f338d3..ba9225da8b 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -975,6 +975,42 @@ configured them.</p>
 Defaults to a single callback returning <c>dpr</c>.</p>
 </item>
 
+<marker id="length_errors"/>
+<tag><c>{length_errors, exit|handle|discard}</c></tag>
+<item>
+<p>
+Specifies how to deal with errors in the Message Length field of the
+Diameter Header in an incoming message.
+An error in this context is that the length is not at least 20 bytes
+(the length of a Header), is not a multiple of 4 (a valid length) or
+is not the length of the message in question, as received over the
+transport interface documented in &man_transport;.</p>
+
+<p>
+If <c>exit</c> then a warning report is emitted and the parent of the
+transport process in question exits, which causes the transport
+process itself to exit as described in &man_transport;.
+If <c>handle</c> then the message is processed as usual, a resulting
+&app_handle_request; or &app_handle_answer; callback (if one takes
+place) indicating the <c>5015</c> error (DIAMETER_INVALID_MESSAGE_LENGTH).
+If <c>discard</c> then the message in question is silently discarded.</p>
+
+<p>
+Defaults to <c>exit</c>.</p>
+
+<note>
+<p>
+The default value reflects the fact that a transport module for a
+stream-oriented transport like TCP may not be able to recover from a
+message length error since such a transport must use the Message
+Length header to divide the incoming byte stream into individual
+Diameter messages.
+An invalid length leaves it with no reliable way to rediscover message
+boundaries, which may result in the failure of subsequent messages.
+See &man_tcp; for the behaviour of that module.</p>
+</note>
+</item>
+
 <marker id="reconnect_timer"/>
 <tag><c>{reconnect_timer, Tc}</c></tag>
 <item>