rtpengine: added support for DTLS transports

- added ability to explicitly request DTLS transports:
  UDP/TLS/RTP/SAVP and UDP/TLS/RTP/SAVPF

(cherry picked from commit 99695c2827d0ff6e3d25f144678f07548016415d)

src/modules/rtpengine/doc/rtpengine_admin.xml

@@ -2159,7 +2159,7 @@ rtpengine_offer();
 				&sdp; substitutions (c=, m=, etc) are unaffected by this flag.
 				</para></listitem>
 				<listitem><para>
-				<emphasis>RTP, SRTP, AVP, AVPF</emphasis> - These flags control the &rtp;
+				<emphasis>RTP, SRTP, DTLS, AVP, AVPF</emphasis> - These flags control the &rtp;
 				transport protocol that should be used towards the recipient of
 				the &sdp;. If none of them are specified, the protocol given in
 				the &sdp; is left untouched. Otherwise, the <quote>SRTP</quote> flag indicates that
@@ -2169,8 +2169,8 @@ rtpengine_offer();
 				should be used. See also the next set of flags below.
 				</para></listitem>
 				<listitem><para>
-				<emphasis>RTP/AVP, RTP/SAVP, RTP/AVPF, RTP/SAVPF</emphasis> - these serve as
-				an alternative, more explicit way to select between the different &rtp; protocols
+				<emphasis>RTP/AVP, RTP/SAVP, UDP/TLS/RTP/SAVP, RTP/AVPF, RTP/SAVPF, UDP/TLS/RTP/SAVPF</emphasis> - these 
+				serve as an alternative, more explicit way to select between the different &rtp; protocols
 				and profiles supported by the &rtp; proxy. For example, giving the flag
 				<quote>RTP/SAVPF</quote> has the same effect as giving the two flags
 				<quote>SRTP AVPF</quote>.

src/modules/rtpengine/rtpengine.c

@@ -1871,6 +1871,8 @@ static const char *transports[] = {
 	[0x01]	= "RTP/SAVP",
 	[0x02]	= "RTP/AVPF",
 	[0x03]	= "RTP/SAVPF",
+	[0x04]	= "UDP/TLS/RTP/SAVP",
+	[0x06]	= "UDP/TLS/RTP/SAVPF",
 };
 
 static int parse_flags(struct ng_flags_parse *ng_flags, struct sip_msg *msg, enum rtpe_operation *op,
@@ -1946,6 +1948,8 @@ static int parse_flags(struct ng_flags_parse *ng_flags, struct sip_msg *msg, enu
 					ng_flags->transport |= 0x101;
 				else if (str_eq(&key, "AVPF"))
 					ng_flags->transport |= 0x102;
+				else if (str_eq(&key, "DTLS"))
+					ng_flags->transport |= 0x104;
 				else
 					goto generic;
 				goto next;
@@ -2048,6 +2052,23 @@ static int parse_flags(struct ng_flags_parse *ng_flags, struct sip_msg *msg, enu
 					goto next;
 				}
 				break;
+
+			case 16:
+				if (str_eq(&key, "UDP/TLS/RTP/SAVP"))
+					ng_flags->transport = 0x104;
+				else
+					goto generic;
+				goto next;
+				break;
+
+			case 17:
+				if (str_eq(&key, "UDP/TLS/RTP/SAVPF"))
+					ng_flags->transport = 0x106;
+				else
+					goto generic;
+				goto next;
+				break;
+
 		}
 
 generic:
@@ -2148,7 +2169,7 @@ static bencode_item_t *rtpp_function_call(bencode_buffer_t *bencbuf, struct sip_
 		bencode_dictionary_add(ng_flags.dict, "replace", ng_flags.replace);
 	if ((ng_flags.transport & 0x100))
 		bencode_dictionary_add_string(ng_flags.dict, "transport-protocol",
-				transports[ng_flags.transport & 0x003]);
+				transports[ng_flags.transport & 0x007]);
 	if (ng_flags.rtcp_mux && ng_flags.rtcp_mux->child)
 		bencode_dictionary_add(ng_flags.dict, "rtcp-mux", ng_flags.rtcp_mux);