RTP: remove dead-code (#1953)

The checks `isValidMSRTPType(..) == 1` is a subset of
`is_valid_rtp_payload_type()` so this if-branch is never reached.

More importantly, the article describing how to detect Microsoft Lync and
Skype for Business is from 2014. These payload types are static or they
are in the dynamic range: in both cases, these values might be used (and
they are used indeed) pretty much by every application.
Bottom line: we can't use PT alone to identify a specific protocol.

Keep the list, since it is used to tell audio streams from video ones.

1 files changed, 3 insertions, 14 deletions

diff --git a/src/lib/protocols/rtp.c b/src/lib/protocols/rtp.c
index b90941bbb..218895679 100644
--- a/src/lib/protocols/rtp.c
+++ b/src/lib/protocols/rtp.c
@@ -165,8 +165,8 @@ static u_int8_t isZoom(u_int16_t sport, u_int16_t dport,
 
 static void ndpi_rtp_search(struct ndpi_detection_module_struct *ndpi_struct,
 			    struct ndpi_flow_struct *flow,
-			    u_int8_t * payload, u_int16_t payload_len) {
-  u_int8_t payloadType, payload_type;
+			    const u_int8_t * payload, u_int16_t payload_len) {
+  u_int8_t payload_type;
   u_int16_t s_port = ntohs(ndpi_struct->packet.udp->source), d_port = ntohs(ndpi_struct->packet.udp->dest), payload_offset;
   u_int8_t is_rtp, zoom_stream_type;
 
@@ -241,17 +241,6 @@ static void ndpi_rtp_search(struct ndpi_detection_module_struct *ndpi_struct,
 				 NDPI_CONFIDENCE_DPI);
       return;
     }
-  } else if((payload_len >= 12)
-	    && (((payload[0] & 0xFF) == 0x80)
-		|| ((payload[0] & 0xFF) == 0xA0)
-		|| ((payload[0] & 0xFF) == 0x90)
-		) /* RTP magic byte[1] */
-	    && (payloadType = isValidMSRTPType(payload[1] & 0xFF, &flow->protos.rtp.stream_type))) {
-    if(payloadType == 1 /* RTP */) {
-      NDPI_LOG_INFO(ndpi_struct, "Found Skype for Business (former MS Lync)\n");
-      ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_SKYPE_TEAMS, NDPI_PROTOCOL_UNKNOWN, NDPI_CONFIDENCE_DPI);
-      return;
-    }
   }
 
   /* No luck this time */
@@ -273,7 +262,7 @@ static void ndpi_search_rtp(struct ndpi_detection_module_struct *ndpi_struct, st
   if((source != 30303) && (dest != 30303 /* Avoid to mix it with Ethereum that looks alike */)
      && (dest > 1023)
      )
-    ndpi_rtp_search(ndpi_struct, flow, (u_int8_t*)packet->payload, packet->payload_packet_len);
+    ndpi_rtp_search(ndpi_struct, flow, packet->payload, packet->payload_packet_len);
   else
     NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
 }