2 This file is part of systemd.
4 Copyright (C) 2013 Intel Corporation. All rights reserved.
5 Copyright (C) 2014 Tom Gundersen
7 systemd is free software; you can redistribute it and/or modify it
8 under the terms of the GNU Lesser General Public License as published by
9 the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version.
12 systemd is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public License
18 along with systemd; If not, see <http://www.gnu.org/licenses/>.
23 #include <net/ethernet.h>
24 #include <net/if_arp.h>
27 #include "dhcp-protocol.h"
28 #include "dhcp-internal.h"
30 #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
32 int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,
33 uint8_t type, uint16_t arp_type, size_t optlen,
38 assert(op == BOOTREQUEST || op == BOOTREPLY);
39 assert(arp_type == ARPHRD_ETHER || arp_type == ARPHRD_INFINIBAND);
42 message->htype = arp_type;
43 message->hlen = (arp_type == ARPHRD_ETHER) ? ETHER_ADDR_LEN : 0;
44 message->xid = htobe32(xid);
45 message->magic = htobe32(DHCP_MAGIC_COOKIE);
47 r = dhcp_option_append(message, optlen, &offset, 0,
48 DHCP_OPTION_MESSAGE_TYPE, 1, &type);
57 uint16_t dhcp_packet_checksum(uint8_t *buf, size_t len) {
58 uint64_t *buf_64 = (uint64_t*)buf;
59 uint64_t *end_64 = buf_64 + (len / sizeof(uint64_t));
64 while (buf_64 < end_64) {
67 /* wrap around in one's complement */
73 if (len % sizeof(uint64_t)) {
74 /* If the buffer is not aligned to 64-bit, we need
75 to zero-pad the last few bytes and add them in */
76 uint64_t buf_tail = 0;
78 memcpy(&buf_tail, buf_64, len % sizeof(uint64_t));
87 sum = (sum & 0xffff) + (sum >> 16);
92 void dhcp_packet_append_ip_headers(DHCPPacket *packet, be32_t source_addr,
93 uint16_t source_port, be32_t destination_addr,
94 uint16_t destination_port, uint16_t len) {
95 packet->ip.version = IPVERSION;
96 packet->ip.ihl = DHCP_IP_SIZE / 4;
97 packet->ip.tot_len = htobe16(len);
99 packet->ip.tos = IPTOS_CLASS_CS6;
101 packet->ip.protocol = IPPROTO_UDP;
102 packet->ip.saddr = source_addr;
103 packet->ip.daddr = destination_addr;
105 packet->udp.source = htobe16(source_port);
106 packet->udp.dest = htobe16(destination_port);
108 packet->udp.len = htobe16(len - DHCP_IP_SIZE);
110 packet->ip.check = packet->udp.len;
111 packet->udp.check = dhcp_packet_checksum((uint8_t*)&packet->ip.ttl, len - 8);
113 packet->ip.ttl = IPDEFTTL;
114 packet->ip.check = 0;
115 packet->ip.check = dhcp_packet_checksum((uint8_t*)&packet->ip, DHCP_IP_SIZE);
118 int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {
125 if (packet->ip.version != IPVERSION) {
126 log_debug("ignoring packet: not IPv4");
130 if (packet->ip.ihl < 5) {
131 log_debug("ignoring packet: IPv4 IHL (%u words) invalid",
136 hdrlen = packet->ip.ihl * 4;
138 log_debug("ignoring packet: IPv4 IHL (%zu bytes) "
139 "smaller than minimum (20 bytes)", hdrlen);
144 log_debug("ignoring packet: packet (%zu bytes) "
145 "smaller than expected (%zu) by IP header", len,
152 if (packet->ip.protocol != IPPROTO_UDP) {
153 log_debug("ignoring packet: not UDP");
157 if (len < hdrlen + be16toh(packet->udp.len)) {
158 log_debug("ignoring packet: packet (%zu bytes) "
159 "smaller than expected (%zu) by UDP header", len,
160 hdrlen + be16toh(packet->udp.len));
164 if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {
165 log_debug("ignoring packet: to port %u, which "
166 "is not the DHCP client port (%u)",
167 be16toh(packet->udp.dest), DHCP_PORT_CLIENT);
171 /* checksums - computing these is relatively expensive, so only do it
172 if all the other checks have passed
175 if (dhcp_packet_checksum((uint8_t*)&packet->ip, hdrlen)) {
176 log_debug("ignoring packet: invalid IP checksum");
180 if (checksum && packet->udp.check) {
181 packet->ip.check = packet->udp.len;
184 if (dhcp_packet_checksum((uint8_t*)&packet->ip.ttl,
185 be16toh(packet->udp.len) + 12)) {
186 log_debug("ignoring packet: invalid UDP checksum");