LINE_CALL: add detection of LINE voip calls (#1761)

These flows are classifed as `LINE_CALL`; another option was
`RTP/LINE_CALL`. No sure about the best solution...

Extend LINE domains list.

Remove RTP dead code.

1 files changed, 91 insertions, 0 deletions

diff --git a/src/lib/protocols/line.c b/src/lib/protocols/line.c
new file mode 100644
index 000000000..a94b39037
--- /dev/null
+++ b/src/lib/protocols/line.c
@@ -0,0 +1,91 @@
+/*
+ * line.c
+ *
+ * Copyright (C) 2022 - ntop.org
+ *
+ * nDPI is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * nDPI is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with nDPI.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+
+#include "ndpi_protocol_ids.h"
+
+#define NDPI_CURRENT_PROTO NDPI_PROTOCOL_LINE_CALL
+
+#include "ndpi_api.h"
+
+extern int is_valid_rtp_payload_type(uint8_t type);
+
+static void ndpi_int_line_add_connection(struct ndpi_detection_module_struct * const ndpi_struct,
+                                         struct ndpi_flow_struct * const flow)
+{
+  NDPI_LOG_INFO(ndpi_struct, "found LineCall\n");
+  ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_UNKNOWN,
+                             NDPI_PROTOCOL_LINE_CALL, NDPI_CONFIDENCE_DPI);
+}
+
+void ndpi_search_line(struct ndpi_detection_module_struct *ndpi_struct,
+                      struct ndpi_flow_struct *flow)
+{
+  struct ndpi_packet_struct const * const packet = &ndpi_struct->packet;
+
+  NDPI_LOG_DBG(ndpi_struct, "searching LineCall\n");
+
+  /* Some "random" UDP packets before the standard RTP stream:
+     it seems that the 4th bytes of these packets is some kind of packet
+     number. Look for 4 packets per direction with consecutive numbers. */
+
+  if(packet->payload_packet_len > 10) {
+    if(flow->l4.udp.line_pkts[packet->packet_direction] == 0) {
+      flow->l4.udp.line_base_cnt[packet->packet_direction] = packet->payload[3];
+      flow->l4.udp.line_pkts[packet->packet_direction] += 1;
+      return;
+    } else {
+      /* It might be a RTP/RTCP packet. Ignore it and keep looking for the
+         LINE packet numbers */
+      /* Basic RTP detection */
+      if((packet->payload[0] >> 6) == 2 && /* Version 2 */
+         (packet->payload[1] == 201 || /* RTCP, Receiver Report */
+          packet->payload[1] == 200 || /* RTCP, Sender Report */
+          is_valid_rtp_payload_type(packet->payload[1] & 0x7F)) /* RTP */) {
+        NDPI_LOG_DBG(ndpi_struct, "Probably RTP; keep looking for LINE");
+        return;
+      } else {
+        if((u_int8_t)(flow->l4.udp.line_base_cnt[packet->packet_direction] +
+                      flow->l4.udp.line_pkts[packet->packet_direction]) == packet->payload[3]) {
+          flow->l4.udp.line_pkts[packet->packet_direction] += 1;
+          if(flow->l4.udp.line_pkts[0] >= 4 && flow->l4.udp.line_pkts[1] >= 4)
+            ndpi_int_line_add_connection(ndpi_struct, flow);
+          return;
+        }
+      }
+    }
+  }
+
+  NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
+  return;
+}
+
+void init_line_dissector(struct ndpi_detection_module_struct *ndpi_struct,
+                         u_int32_t *id, NDPI_PROTOCOL_BITMASK *detection_bitmask)
+{
+  ndpi_set_bitmask_protocol_detection("LineCall", ndpi_struct, detection_bitmask, *id,
+				      NDPI_PROTOCOL_LINE_CALL,
+				      ndpi_search_line,
+				      NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
+				      SAVE_DETECTION_BITMASK_AS_UNKNOWN,
+				      ADD_TO_DETECTION_BITMASK);
+
+  *id += 1;
+}