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