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/*
* rtp.c
*
* Copyright (C) 2009-11 - ipoque GmbH
* Copyright (C) 2011-22 - ntop.org
*
* This file is part of nDPI, an open source deep packet inspection
* library based on the OpenDPI and PACE technology by ipoque GmbH
*
* 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_RTP
#include "ndpi_api.h"
#include "ndpi_private.h"
#define RTP_MIN_HEADER 12
#define RTCP_MIN_HEADER 8
/* https://www.iana.org/assignments/rtp-parameters/rtp-parameters.xhtml */
int is_valid_rtp_payload_type(uint8_t type)
{
if(!(type <= 34 || (type >= 96 && type <= 127)))
return 0;
return 1;
}
u_int8_t rtp_get_stream_type(u_int8_t payloadType, ndpi_multimedia_flow_type *s_type)
{
switch(payloadType) {
case 0: /* G.711 u-Law */
case 3: /* GSM 6.10 */
case 4: /* G.723.1 */
case 8: /* G.711 A-Law */
case 9: /* G.722 */
case 13: /* Comfort Noise */
case 96: /* Dynamic RTP */
case 97: /* Redundant Audio Data Payload */
case 98: /* DynamicRTP-Type-98 (Zoom) */
case 101: /* DTMF */
case 103: /* SILK Narrowband */
case 104: /* SILK Wideband */
case 111: /* Siren */
case 112: /* G.722.1 */
case 114: /* RT Audio Wideband */
case 115: /* RT Audio Narrowband */
case 116: /* G.726 */
case 117: /* G.722 */
case 118: /* Comfort Noise Wideband */
*s_type = ndpi_multimedia_audio_flow;
return(1);
case 34: /* H.263 [MS-H26XPF] */
case 121: /* RT Video */
case 122: /* H.264 [MS-H264PF] */
case 123: /* H.264 FEC [MS-H264PF] */
case 127: /* x-data */
*s_type = ndpi_multimedia_video_flow;
return(1);
default:
*s_type = ndpi_multimedia_unknown_flow;
return(0);
}
}
static int is_valid_rtcp_payload_type(uint8_t type)
{
return (type >= 192 && type <= 213);
}
int is_rtp_or_rtcp(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
u_int8_t padding, csrc_count, ext_header;
u_int16_t ext_len;
u_int32_t min_len;
const u_int8_t *payload = packet->payload;
const u_int16_t payload_len = packet->payload_packet_len;
if(payload_len < 2)
return NO_RTP_RTCP;
if((payload[0] & 0xC0) != 0x80) { /* Version 2 */
NDPI_LOG_DBG(ndpi_struct, "Not version 2\n");
return NO_RTP_RTCP;
}
if(is_valid_rtp_payload_type(payload[1] & 0x7F) &&
payload_len >= RTP_MIN_HEADER) {
/* RTP */
csrc_count = payload[0] & 0x0F;
padding = payload[0] & 0x20;
ext_header = !!(payload[0] & 0x10);
min_len = RTP_MIN_HEADER + 4 * csrc_count + 4 * ext_header;
if(ext_header) {
if(min_len > payload_len) {
NDPI_LOG_DBG(ndpi_struct, "Too short (a) %d vs %d\n", min_len, payload_len);
return NO_RTP_RTCP;
}
ext_len = ntohs(*(unsigned short *)&payload[min_len - 2]);
min_len += ext_len * 4;
}
if(min_len > payload_len) {
NDPI_LOG_DBG(ndpi_struct, "Too short (b) %d vs %d\n", min_len, payload_len);
return NO_RTP_RTCP;
}
/* TODO: this check doesn't work if we have multiple RTP packets in the
same UDP datagram */
if(padding &&
min_len + payload[payload_len - 1] > payload_len) {
NDPI_LOG_DBG(ndpi_struct, "Invalid padding len %d\n", payload[payload_len - 1]);
return NO_RTP_RTCP;
}
return IS_RTP;
} else if(is_valid_rtcp_payload_type(payload[1]) &&
payload_len >= RTCP_MIN_HEADER) {
min_len = (ntohs(*(unsigned short *)&payload[2]) + 1) * 4;
if(min_len > payload_len) {
NDPI_LOG_DBG(ndpi_struct, "Too short (c) %d vs %d\n", min_len, payload_len);
return NO_RTP_RTCP;
}
return IS_RTCP;
}
NDPI_LOG_DBG(ndpi_struct, "not RTP/RTCP\n");
return NO_RTP_RTCP;
}
/* *************************************************************** */
static void ndpi_rtp_search(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow) {
u_int8_t is_rtp;
u_int16_t d_port = ntohs(ndpi_struct->packet.udp->dest);
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
const u_int8_t *payload = packet->payload;
NDPI_LOG_DBG(ndpi_struct, "search RTP\n");
if(d_port == 5355 || /* LLMNR_PORT */
d_port == 5353 || /* MDNS_PORT */
d_port == 9600 /* FINS_PORT */) {
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
/* * Let some "unknown" packets at the beginning
* search for 3 consecutive RTP/RTCP packets
*/
if(flow->packet_counter > 3 &&
flow->l4.udp.rtp_stage == 0) {
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
return;
}
is_rtp = is_rtp_or_rtcp(ndpi_struct, flow);
if(is_rtp == IS_RTP) {
if(flow->l4.udp.rtp_stage == 2) {
if(flow->l4.udp.line_pkts[0] >= 2 && flow->l4.udp.line_pkts[1] >= 2) {
/* It seems that it is a LINE stuff; let its dissector to evaluate */
} else if(flow->l4.udp.epicgames_stage > 0) {
/* It seems that it is a EpicGames stuff; let its dissector to evaluate */
} else {
rtp_get_stream_type(payload[1] & 0x7F, &flow->flow_multimedia_type);
NDPI_LOG_INFO(ndpi_struct, "Found RTP\n");
ndpi_set_detected_protocol(ndpi_struct, flow,
NDPI_PROTOCOL_UNKNOWN, NDPI_PROTOCOL_RTP,
NDPI_CONFIDENCE_DPI);
}
return;
}
flow->l4.udp.rtp_stage += 1;
} else if(is_rtp == IS_RTCP && flow->l4.udp.rtp_stage > 0) {
/* RTCP after (some) RTP. Keep looking for RTP */
} else {
if(flow->l4.udp.rtp_stage) {
flow->l4.udp.rtp_stage = 0;
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}
}
}
/* *************************************************************** */
static void ndpi_search_rtp(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &ndpi_struct->packet;
u_int16_t source = ntohs(packet->udp->source);
u_int16_t dest = ntohs(packet->udp->dest);
// printf("==> %s()\n", __FUNCTION__);
/* printf("*** %s(pkt=%d)\n", __FUNCTION__, flow->packet_counter); */
if((source != 30303) && (dest != 30303 /* Avoid to mix it with Ethereum that looks alike */)
&& (dest > 1023)
)
ndpi_rtp_search(ndpi_struct, flow);
else
NDPI_EXCLUDE_PROTO(ndpi_struct, flow);
}
/* *************************************************************** */
void init_rtp_dissector(struct ndpi_detection_module_struct *ndpi_struct,
u_int32_t *id) {
ndpi_set_bitmask_protocol_detection("RTP", ndpi_struct, *id,
NDPI_PROTOCOL_RTP,
ndpi_search_rtp,
NDPI_SELECTION_BITMASK_PROTOCOL_V4_V6_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
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