4 files changed, 97 insertions, 6 deletions
diff --git a/lib/diameter/doc/src/diameter.xml b/lib/diameter/doc/src/diameter.xml
index 2cad70e3bc..43c497f50a 100644
--- a/lib/diameter/doc/src/diameter.xml
+++ b/lib/diameter/doc/src/diameter.xml
@@ -367,6 +367,19 @@ capabilities exchange message.
 Optional, defaults to the empty list.</p>
 </item>
 
+<tag><c>{'Inband-Security-Id', [Unsigned32()]}</c></tag>
+<item>
+<p>
+Values of Inband-Security-Id AVPs sent in an outgoing
+capabilities exchange message.
+Optional, defaults to the empty list, which is equivalent to a
+list containing only 0 (= NO_INBAND_SECURITY).</p>
+
+<p>
+If 1 (= TLS) is specified then TLS is selected if the CER/CEA received
+from the peer offers it.</p>
+</item>
+
 <tag><c>{'Acct-Application-Id', [Unsigned32()]}</c></tag>
 <item>
 <p>
@@ -683,6 +696,14 @@ in question.</p>
 AVP's used to construct outgoing CER/CEA messages.
 Any AVP specified takes precedence over a corresponding value specified
 for the service in question.</p>
+
+<p>
+Specifying a capability as a transport option
+may be particularly appropriate for Inband-Security-Id in case
+TLS is desired over TCP as implemented by
+<seealso marker="diameter_tcp">diameter_tcp(3)</seealso> but
+not over SCTP as implemented by
+<seealso marker="diameter_sctp">diameter_sctp(3)</seealso>.</p>
 </item>
 
 <tag><c>{watchdog_timer, TwInit}</c></tag>
diff --git a/lib/diameter/doc/src/diameter_soc.xml b/lib/diameter/doc/src/diameter_soc.xml
index 4f8581a904..6b9ef9f756 100644
--- a/lib/diameter/doc/src/diameter_soc.xml
+++ b/lib/diameter/doc/src/diameter_soc.xml
@@ -57,9 +57,13 @@ including the P Flag in the AVP header.</p>
 
 <item>
 <p>
-There is no TLS support.
-It's unclear (aka uninvestigated) how TLS would impact
-diameter but IPsec can be used without it needing to know.</p>
+There is no TLS support over SCTP.
+RFC 3588 requires that a Diameter server support TLS but in
+practise this seems to mean TLS over SCTP since there are limitations
+with running over SCTP: see RFC 6083 (DTLS over SCTP), which is a
+response to RFC 3436 (TLS over SCTP).
+The current RFC 3588 draft acknowledges this by equating
+TLS with TLS/TCP and DTLS/SCTP but we do not yet support DTLS.</p>
 </item>
 
 <item>
diff --git a/lib/diameter/doc/src/diameter_tcp.xml b/lib/diameter/doc/src/diameter_tcp.xml
index a502e53972..916700927f 100644
--- a/lib/diameter/doc/src/diameter_tcp.xml
+++ b/lib/diameter/doc/src/diameter_tcp.xml
@@ -43,7 +43,9 @@ It can be specified as the value of a transport_module option to
 <seealso
 marker="diameter#add_transport">diameter:add_transport/2</seealso>
 and implements the behaviour documented in
-<seealso marker="diameter_transport">diameter_transport(3)</seealso>.</p>
+<seealso marker="diameter_transport">diameter_transport(3)</seealso>.
+TLS security is supported, a connection being upgraded if
+TLS is negotiated during capabilities exchange.</p>
 
 <marker id="start"/>
 </description>
@@ -60,10 +62,14 @@ and implements the behaviour documented in
 <v>Type = connect | accept</v>
 <v>Ref = reference()</v>
 <v>Svc = #diameter_service{}</v>
-<v>Opt = {raddr, ip_address()} | {rport, integer()} | term()</v>
+<v>Opt = OwnOpt | TlsOpt | TcpOpt</v>
 <v>Pid = pid()</v>
 <v>LAddr = ip_address()</v>
 <v>Reason = term()</v>
+<v>OwnOpt = {raddr, ip_address()}
+          | {rport, integer()}</v>
+<v>TlsOpt = {ssl_options, list()}</v>
+<v>TcpOpt = term()</v>
 </type>
 <desc>
 
@@ -74,8 +80,11 @@ marker="diameter_transport#start">diameter_transport(3)</seealso>.</p>
 <p>
 The only diameter_tcp-specific argument is the options list.
 Options <c>raddr</c> and <c>rport</c> specify the remote address
-and port for a connecting transport and not valid for a listening
+and port for a connecting transport and are not valid for a listening
 transport.
+Option <c>ssl_options</c> specifies options to be passed
+to ssl:connect/2 of ssl:ssl_accept/2 in case capabilities exchange
+results in TLS being chosen for inband security.
 Remaining options are any accepted by gen_tcp:connect/3 for
 a connecting transport, or gen_tcp:listen/2 for a listening transport,
 with the exception of <c>binary</c>, <c>packet</c> and <c>active</c>.
@@ -85,6 +94,24 @@ to specify the local listening port, the default being the standardized
 Note that option <c>ip</c> specifies the local address.</p>
 
 <p>
+The <c>ssl_options</c> option must be specified if and only if
+the transport in question has specified an Inband-Security-Id
+AVP with value TLS on the relevant call to
+<seealso
+marker="diameter#start_service">start_service/2</seealso> or
+<seealso
+marker="diameter#add_transport">add_transport/2</seealso>,
+so that the transport process will receive notification of
+whether or not to commence with a TLS handshake following capabilities
+exchange.
+Failing to specify <c>ssl_options</c> on a TLS-capable transport
+for which TLS is negotiated will cause TLS handshake to fail.
+Failing to specify TLS capability when <c>ssl_options</c> has been
+specified will cause the transport process to wait for a notification
+that will not be forthcoming, which will eventually cause the RFC 3539
+watchdog to take down the connection.</p>
+
+<p>
 If the service specifies more than one Host-IP-Address and
 option <c>ip</c> is unspecified then then the
 first of the service's addresses is used as the local address.</p>
@@ -104,6 +131,7 @@ The returned local address list has length one.</p>
 <title>SEE ALSO</title>
 
 <p>
+<seealso marker="diameter">diameter(3)</seealso>,
 <seealso marker="diameter_transport">diameter_transport(3)</seealso></p>
 
 </section>
diff --git a/lib/diameter/doc/src/diameter_transport.xml b/lib/diameter/doc/src/diameter_transport.xml
index 37cc871e75..087a90b099 100644
--- a/lib/diameter/doc/src/diameter_transport.xml
+++ b/lib/diameter/doc/src/diameter_transport.xml
@@ -143,6 +143,34 @@ connection.
 Pid is the pid() of the parent process.</p>
 </item>
 
+<tag><c>{diameter, {tls, Ref, Type, Bool}}</c></tag>
+<item>
+<p>
+Indication of whether or not capabilities exchange has selected
+inband security using TLS.
+Ref is a reference() that must be included in the
+<c>{diameter, {tls, Ref}}</c> reply message to the transport's
+parent process (see below).
+Type is either <c>connect</c> or <c>accept</c> depending on
+whether the process has been started for a connecting or listening
+transport respectively.
+Bool is a boolean() indicating whether or not the transport connection
+should be upgraded to TLS.</p>
+
+<p>
+If TLS is requested (Bool = true) then a connecting process should
+initiate a TLS handshake with the peer and an accepting process should
+prepare to accept a handshake.
+A successful handshake should be followed by a <c>{diameter, {tls, Ref}}</c>
+message to the parent process.
+A failed handshake should cause the process to exit.</p>
+
+<p>
+This message is only sent to a transport process over whose
+<c>Inband-Security-Id</c> configuration has indicated support for
+TLS.</p>
+</item>
+
 </taglist>
 
 <p>
@@ -184,6 +212,16 @@ How the <c>transport_data</c> is used/interpreted is up to the
 transport module.</p>
 </item>
 
+<tag><c>{diameter, {tls, Ref}}</c></tag>
+<item>
+<p>
+Acknowledgment of a successful TLS handshake.
+Ref is the reference() received in the
+<c>{diameter, {tls, Ref, Type, Bool}}</c> message in response
+to which the reply is sent.
+A transport must exit if a handshake is not successful.</p>
+</item>
+
 </taglist>
 
 </section>