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/* udp_parser.c
*
* This file contains functions to parse UDP headers.
*
* File begun on 2018-11-13
*
* Created by:
* - Théo Bertin (theo.bertin@advens.fr)
*
* With:
* - François Bernard (francois.bernard@isen.yncrea.fr)
* - Tianyu Geng (tianyu.geng@isen.yncrea.fr)
*
* This file is part of rsyslog.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
* -or-
* see COPYING.ASL20 in the source distribution
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include "config.h"
#include "parsers.h"
#define DNS_PORT 53
struct udp_header_s {
uint16_t srcPort;
uint16_t dstPort;
uint16_t totalLength;
uint16_t checksum;
};
typedef struct udp_header_s udp_header_t;
/*
* This function parses the bytes in the received packet to extract UDP metadata.
*
* its parameters are:
* - a pointer on the list of bytes representing the packet
* the first byte must be the beginning of the UDP header
* - the size of the list passed as first parameter
* - a pointer on a json_object, containing all the metadata recovered so far
* this is also where UDP metadata will be added
*
* This function returns a structure containing the data unprocessed by this parser
* or the ones after (as a list of bytes), and the length of this data.
*/
data_ret_t *udp_parse(const uchar *packet, int pktSize, struct json_object *jparent) {
DBGPRINTF("udp_parse\n");
DBGPRINTF("packet size %d\n", pktSize);
if (pktSize < 8) {
DBGPRINTF("UDP packet too small : %d\n", pktSize);
RETURN_DATA_AFTER(0)
}
/* Union to prevent cast from uchar to udp_header_t */
union {
const uchar *pck;
udp_header_t *hdr;
} udp_header_to_char;
udp_header_to_char.pck = packet;
udp_header_t *udp_header = udp_header_to_char.hdr;
// Prevent endianness issue
unsigned short int src_port = ntohs(udp_header->srcPort);
unsigned short int dst_port = ntohs(udp_header->dstPort);
json_object_object_add(jparent, "net_src_port", json_object_new_int(src_port));
json_object_object_add(jparent, "net_dst_port", json_object_new_int(dst_port));
json_object_object_add(jparent, "UDP_Length", json_object_new_int(ntohs(udp_header->totalLength)));
json_object_object_add(jparent, "UDP_Checksum", json_object_new_int(ntohs(udp_header->checksum)));
if (src_port == DNS_PORT || dst_port == DNS_PORT) {
return dns_parse(packet + sizeof(udp_header_t), pktSize - sizeof(udp_header_t), jparent);
}
RETURN_DATA_AFTER(8)
}
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