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/*
* mdns.c
*
* Copyright (C) 2009-2011 by ipoque GmbH
* Copyright (C) 2011-15 - 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_protocols.h"
#ifdef NDPI_PROTOCOL_MDNS
#define NDPI_MAX_MDNS_REQUESTS 128
/*
This module should detect MDNS
*/
static void ndpi_int_mdns_add_connection(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow)
{
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_MDNS, NDPI_PROTOCOL_UNKNOWN);
}
static int ndpi_int_check_mdns_payload(struct ndpi_detection_module_struct
*ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
if ((packet->payload[2] & 0x80) == 0 &&
ntohs(get_u_int16_t(packet->payload, 4)) <= NDPI_MAX_MDNS_REQUESTS &&
ntohs(get_u_int16_t(packet->payload, 6)) <= NDPI_MAX_MDNS_REQUESTS) {
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct, NDPI_LOG_DEBUG, "found MDNS with question query.\n");
return 1;
} else if ((packet->payload[2] & 0x80) != 0 &&
ntohs(get_u_int16_t(packet->payload, 4)) == 0 &&
ntohs(get_u_int16_t(packet->payload, 6)) <= NDPI_MAX_MDNS_REQUESTS &&
ntohs(get_u_int16_t(packet->payload, 6)) != 0) {
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct, NDPI_LOG_DEBUG, "found MDNS with answer query.\n");
return 1;
}
return 0;
}
void ndpi_search_mdns(struct ndpi_detection_module_struct *ndpi_struct, struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
// struct ndpi_id_struct *src=ndpi_struct->src;
// struct ndpi_id_struct *dst=ndpi_struct->dst;
u_int16_t dport;
// const u_int16_t sport=ntohs(packet->udp->source);
/* check if UDP and */
if (packet->udp != NULL) {
/*read destination port */
dport = ntohs(packet->udp->dest);
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct, NDPI_LOG_DEBUG, "MDNS udp start \n");
/*check standard MDNS to port 5353 */
/*took this information from http://www.it-administrator.de/lexikon/multicast-dns.html */
if (dport == 5353 && packet->payload_packet_len >= 12) {
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct, NDPI_LOG_DEBUG, "found MDNS with destination port 5353\n");
/* MDNS header is similar to dns header */
/* dns header
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ID |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|QR| Opcode |AA|TC|RD|RA| Z | RCODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| QDCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ANCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| NSCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| ARCOUNT |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
*
* dns query check: query: QR set, ancount = 0, nscount = 0, QDCOUNT < MAX_MDNS, ARCOUNT < MAX_MDNS
*
*/
/* mdns protocol must have destination address 224.0.0.251 */
/* took this information from http://www.it-administrator.de/lexikon/multicast-dns.html */
if (packet->iph != NULL && ntohl(packet->iph->daddr) == 0xe00000fb) {
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct,
NDPI_LOG_DEBUG, "found MDNS with destination address 224.0.0.251 (=0xe00000fb)\n");
if (ndpi_int_check_mdns_payload(ndpi_struct, flow) == 1) {
ndpi_int_mdns_add_connection(ndpi_struct, flow);
return;
}
}
#ifdef NDPI_DETECTION_SUPPORT_IPV6
if (packet->iphv6 != NULL) {
const u_int32_t *daddr = packet->iphv6->daddr.ndpi_v6_u.u6_addr32;
if (daddr[0] == htonl(0xff020000) && daddr[1] == 0 && daddr[2] == 0 && daddr[3] == htonl(0xfb)) {
NDPI_LOG(NDPI_PROTOCOL_MDNS, ndpi_struct,
NDPI_LOG_DEBUG, "found MDNS with destination address ff02::fb\n");
if (ndpi_int_check_mdns_payload(ndpi_struct, flow) == 1) {
ndpi_int_mdns_add_connection(ndpi_struct, flow);
return;
}
}
}
#endif
}
}
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_MDNS);
}
#endif
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