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/* SPDX-License-Identifier: LGPL-2.1-or-later */
/***
Copyright © 2013 Intel Corporation. All rights reserved.
***/
#include <errno.h>
#include <net/ethernet.h>
#include <net/if_arp.h>
#include <string.h>
#include "dhcp-option.h"
#include "dhcp-packet.h"
#include "memory-util.h"
#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
int dhcp_message_init(
DHCPMessage *message,
uint8_t op,
uint32_t xid,
uint8_t type,
uint16_t arp_type,
uint8_t hlen,
const uint8_t *chaddr,
size_t optlen,
size_t *optoffset) {
size_t offset = 0;
int r;
assert(IN_SET(op, BOOTREQUEST, BOOTREPLY));
assert(chaddr || hlen == 0);
message->op = op;
message->htype = arp_type;
/* RFC2131 section 4.1.1:
The client MUST include its hardware address in the ’chaddr’ field, if
necessary for delivery of DHCP reply messages.
RFC 4390 section 2.1:
A DHCP client, when working over an IPoIB interface, MUST follow the
following rules:
"htype" (hardware address type) MUST be 32 [ARPPARAM].
"hlen" (hardware address length) MUST be 0.
"chaddr" (client hardware address) field MUST be zeroed.
*/
message->hlen = arp_type == ARPHRD_INFINIBAND ? 0 : hlen;
memcpy_safe(message->chaddr, chaddr, message->hlen);
message->xid = htobe32(xid);
message->magic = htobe32(DHCP_MAGIC_COOKIE);
r = dhcp_option_append(message, optlen, &offset, 0,
SD_DHCP_OPTION_MESSAGE_TYPE, 1, &type);
if (r < 0)
return r;
*optoffset = offset;
return 0;
}
uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) {
uint64_t *buf_64 = (uint64_t*)buf;
uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t));
uint64_t sum = 0;
/* See RFC1071 */
while (buf_64 < end_64) {
sum += *buf_64;
if (sum < *buf_64)
/* wrap around in one's complement */
sum++;
buf_64++;
}
if (len % sizeof(uint64_t)) {
/* If the buffer is not aligned to 64-bit, we need
to zero-pad the last few bytes and add them in */
uint64_t buf_tail = 0;
memcpy(&buf_tail, buf_64, len % sizeof(uint64_t));
sum += buf_tail;
if (sum < buf_tail)
/* wrap around */
sum++;
}
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
uint16_t source_port, be32_t destination_addr,
uint16_t destination_port, uint16_t len, int ip_service_type) {
packet->ip.version = IPVERSION;
packet->ip.ihl = DHCP_IP_SIZE / 4;
packet->ip.tot_len = htobe16(len);
if (ip_service_type >= 0)
packet->ip.tos = ip_service_type;
else
packet->ip.tos = IPTOS_CLASS_CS6;
packet->ip.protocol = IPPROTO_UDP;
packet->ip.saddr = source_addr;
packet->ip.daddr = destination_addr;
packet->udp.source = htobe16(source_port);
packet->udp.dest = htobe16(destination_port);
packet->udp.len = htobe16(len - DHCP_IP_SIZE);
packet->ip.check = packet->udp.len;
packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8);
packet->ip.ttl = IPDEFTTL;
packet->ip.check = 0;
packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE);
}
int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum, uint16_t port) {
size_t hdrlen;
assert(packet);
if (len < sizeof(DHCPPacket))
return 0;
/* IP */
if (packet->ip.version != IPVERSION)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: not IPv4");
if (packet->ip.ihl < 5)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: IPv4 IHL (%i words) invalid",
packet->ip.ihl);
hdrlen = packet->ip.ihl * 4;
if (hdrlen < 20)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: IPv4 IHL (%zu bytes) smaller than minimum (20 bytes)",
hdrlen);
if (len < hdrlen)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: packet (%zu bytes) smaller than expected (%zu) by IP header",
len, hdrlen);
/* UDP */
if (packet->ip.protocol != IPPROTO_UDP)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: not UDP");
if (len < hdrlen + be16toh(packet->udp.len))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: packet (%zu bytes) smaller than expected (%zu) by UDP header",
len, hdrlen + be16toh(packet->udp.len));
if (be16toh(packet->udp.dest) != port)
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: to port %u, which is not the DHCP client port (%u)",
be16toh(packet->udp.dest), port);
/* checksums - computing these is relatively expensive, so only do it
if all the other checks have passed
*/
if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: invalid IP checksum");
if (checksum && packet->udp.check) {
packet->ip.check = packet->udp.len;
packet->ip.ttl = 0;
if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl,
be16toh(packet->udp.len) + 12))
return log_debug_errno(SYNTHETIC_ERRNO(EINVAL),
"ignoring packet: invalid UDP checksum");
}
return 0;
}
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