badvpn/misc/ipv4_proto.h
2012-12-30 03:20:36 +00:00

146 lines
4.3 KiB
C

/**
* @file ipv4_proto.h
* @author Ambroz Bizjak <ambrop7@gmail.com>
*
* @section LICENSE
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. Neither the name of the author nor the
* names of its contributors may be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY
* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
* @section DESCRIPTION
*
* Definitions for the IPv4 protocol.
*/
#ifndef BADVPN_MISC_IPV4_PROTO_H
#define BADVPN_MISC_IPV4_PROTO_H
#include <stdint.h>
#include <string.h>
#include <misc/debug.h>
#include <misc/byteorder.h>
#include <misc/packed.h>
#include <misc/read_write_int.h>
#define IPV4_PROTOCOL_IGMP 2
#define IPV4_PROTOCOL_UDP 17
B_START_PACKED
struct ipv4_header {
uint8_t version4_ihl4;
uint8_t ds;
uint16_t total_length;
//
uint16_t identification;
uint16_t flags3_fragmentoffset13;
//
uint8_t ttl;
uint8_t protocol;
uint16_t checksum;
//
uint32_t source_address;
//
uint32_t destination_address;
} B_PACKED;
B_END_PACKED
#define IPV4_GET_VERSION(_header) (((_header).version4_ihl4&0xF0)>>4)
#define IPV4_GET_IHL(_header) (((_header).version4_ihl4&0x0F)>>0)
#define IPV4_MAKE_VERSION_IHL(size) (((size)/4) + (4 << 4))
static uint16_t ipv4_checksum (const struct ipv4_header *header, const char *extra, uint16_t extra_len)
{
ASSERT(extra_len % 2 == 0)
ASSERT(extra_len == 0 || extra)
uint32_t t = 0;
for (uint16_t i = 0; i < sizeof(*header) / 2; i++) {
t += badvpn_read_be16((const char *)header + 2 * i);
}
for (uint16_t i = 0; i < extra_len / 2; i++) {
t += badvpn_read_be16((const char *)extra + 2 * i);
}
while (t >> 16) {
t = (t & 0xFFFF) + (t >> 16);
}
return hton16(~t);
}
static int ipv4_check (uint8_t *data, int data_len, struct ipv4_header *out_header, uint8_t **out_payload, int *out_payload_len)
{
ASSERT(data_len >= 0)
ASSERT(out_header)
ASSERT(out_payload)
ASSERT(out_payload_len)
// check base header
if (data_len < sizeof(struct ipv4_header)) {
return 0;
}
memcpy(out_header, data, sizeof(*out_header));
// check version
if (IPV4_GET_VERSION(*out_header) != 4) {
return 0;
}
// check options
uint16_t header_len = IPV4_GET_IHL(*out_header) * 4;
if (header_len < sizeof(struct ipv4_header)) {
return 0;
}
if (header_len > data_len) {
return 0;
}
// check total length
uint16_t total_length = ntoh16(out_header->total_length);
if (total_length < header_len) {
return 0;
}
if (total_length > data_len) {
return 0;
}
// check checksum
uint16_t checksum_in_packet = out_header->checksum;
out_header->checksum = hton16(0);
uint16_t checksum_computed = ipv4_checksum(out_header, (char *)data + sizeof(*out_header), header_len - sizeof(*out_header));
out_header->checksum = checksum_in_packet;
if (checksum_in_packet != checksum_computed) {
return 0;
}
*out_payload = data + header_len;
*out_payload_len = total_length - header_len;
return 1;
}
#endif