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/* llc_parser.c
*
* This file contains functions to parse llc 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"
/*
* This function parses the bytes in the received packet to extract LLC metadata.
*
* its parameters are:
* - a pointer on the list of bytes representing the packet
* the first byte must be the beginning of the LLC 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 LLC 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 *llc_parse(const uchar *packet, int pktSize, struct json_object *jparent) {
DBGPRINTF("entered llc_parse\n");
DBGPRINTF("packet size %d\n", pktSize);
if (pktSize < 3) { /* too short for llc header */
DBGPRINTF("LLC packet too small : %d\n", pktSize);
RETURN_DATA_AFTER(0)
}
uint8_t dsapField, dsap, ssapField, ssap;
uint16_t ctrl;
uint8_t headerLen;
dsapField = (uint8_t)packet[0];
ssapField = (uint8_t)packet[1];
DBGPRINTF("dsapField : %02X\n", dsapField);
DBGPRINTF("ssapField : %02X\n", ssapField);
if (dsapField == 0xff && ssapField == 0xff) {
/* this is an IPX packet, without LLC */
return ipx_parse(packet, pktSize, jparent);
}
if ((packet[2] & 0x03) == 3) {
/* U frame: LLC control is 8 bits */
ctrl = (uint8_t)packet[2];
headerLen = 3;
} else {
/* I and S data frames: LLC control is 16 bits */
ctrl = ntohs((uint16_t)packet[2]);
headerLen = 4;
}
/* don't take last bit into account */
dsap = dsapField & 0xfe;
ssap = ssapField & 0xfe;
json_object_object_add(jparent, "LLC_dsap", json_object_new_int(dsap));
json_object_object_add(jparent, "LLC_ssap", json_object_new_int(ssap));
json_object_object_add(jparent, "LLC_ctrl", json_object_new_int(ctrl));
if (dsap == 0xaa && ssap == 0xaa && ctrl == 0x03) {
/* SNAP header */
uint32_t orgCode = packet[headerLen] << 16 |
packet[headerLen + 1] << 8 |
packet[headerLen + 2];
uint16_t ethType = packet[headerLen + 3] << 8 |
packet[headerLen + 4];
json_object_object_add(jparent, "SNAP_oui", json_object_new_int(orgCode));
json_object_object_add(jparent, "SNAP_ethType", json_object_new_int(ethType));
return eth_proto_parse(ethType, packet + headerLen, pktSize - headerLen, jparent);
}
if (dsap == 0x06 && ssap == 0x06 && ctrl == 0x03) {
/* IPv4 header */
return ipv4_parse(packet + headerLen, pktSize - headerLen, jparent);
}
if (dsap == 0xe0 && ssap == 0xe0 && ctrl == 0x03) {
/* IPX packet with LLC */
return ipx_parse(packet + headerLen, pktSize - headerLen, jparent);
}
RETURN_DATA_AFTER(headerLen)
}
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