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/*
* rx.c
*
* Copyright (C) 2012-16 - ntop.org
*
* Giovanni Mascellani <gio@debian.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_api.h"
#ifdef NDPI_PROTOCOL_RX
/* See http://web.mit.edu/kolya/afs/rx/rx-spec for procotol description. */
/* The should be no need for explicit packing, but just in case... */
struct __attribute__((__packed__)) ndpi_rx_header {
u_int32_t conn_epoch;
u_int32_t conn_id;
u_int32_t call_number;
u_int32_t sequence_number;
u_int32_t serial_number;
u_int8_t type;
u_int8_t flags;
u_int8_t status;
u_int8_t security;
u_int16_t checksum;
u_int16_t service_id;
};
void ndpi_check_rx(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
u_int32_t payload_len = packet->payload_packet_len;
int exclude = 0;
int found = 0;
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "RX: pck: %d, dir[0]: %d, dir[1]: %d\n",
flow->packet_counter, flow->packet_direction_counter[0], flow->packet_direction_counter[1]);
/* Check that packet is long enough. */
if (payload_len < sizeof(struct ndpi_rx_header)) {
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "short packet\n");
exclude = 1;
goto end;
}
/* Check whether the packet has counters beginning from one; the
Sequence Number can be zero if the packet is just an ACK. */
struct ndpi_rx_header *header = (struct ndpi_rx_header*) packet->payload;
if ((ntohl(header->sequence_number) | 1) != 1 || ntohl(header->serial_number) != 1) {
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "wrong counters\n");
exclude = 1;
goto end;
}
/* If we have already seen one packet in the other direction, then
the two must have matching connection numbers. Otherwise store
them. */
if (flow->packet_direction_counter[!packet->packet_direction] != 0) {
if (flow->l4.udp.rx_conn_epoch == header->conn_epoch &&
flow->l4.udp.rx_conn_id == header->conn_id) {
found = 1;
/* In theory we could inspect the service_id field of the header
to know exactly which service is being used; see
https://www.central.org/frameless/numbers/rxservice.html. */
} else {
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "IDs not matching\n");
exclude = 1;
}
goto end;
} else {
flow->l4.udp.rx_conn_epoch = header->conn_epoch;
flow->l4.udp.rx_conn_id = header->conn_id;
}
end:
if (found) {
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "found RX\n");
ndpi_set_detected_protocol(ndpi_struct, flow, NDPI_PROTOCOL_RX, NDPI_PROTOCOL_UNKNOWN);
}
else if (exclude) {
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "excluding RX\n");
NDPI_ADD_PROTOCOL_TO_BITMASK(flow->excluded_protocol_bitmask, NDPI_PROTOCOL_RX);
}
}
void ndpi_search_rx(struct ndpi_detection_module_struct *ndpi_struct,
struct ndpi_flow_struct *flow)
{
struct ndpi_packet_struct *packet = &flow->packet;
NDPI_LOG(NDPI_PROTOCOL_RX, ndpi_struct, NDPI_LOG_DEBUG, "entering RX search\n");
if (packet->detected_protocol_stack[0] != NDPI_PROTOCOL_RX) {
ndpi_check_rx(ndpi_struct, flow);
}
}
void init_rx_dissector(struct ndpi_detection_module_struct *ndpi_struct,
u_int32_t *id,
NDPI_PROTOCOL_BITMASK *detection_bitmask)
{
ndpi_set_bitmask_protocol_detection("RX", ndpi_struct, detection_bitmask, *id,
NDPI_PROTOCOL_RX,
ndpi_search_rx,
NDPI_SELECTION_BITMASK_PROTOCOL_UDP_WITH_PAYLOAD,
SAVE_DETECTION_BITMASK_AS_UNKNOWN,
ADD_TO_DETECTION_BITMASK);
*id += 1;
}
#endif
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