]>
git.ipfire.org Git - thirdparty/systemd.git/blob - src/libsystemd-network/dhcp-packet.c
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/>.
22 #include <net/ethernet.h>
23 #include <net/if_arp.h>
26 #include "dhcp-internal.h"
27 #include "dhcp-protocol.h"
29 #define DHCP_CLIENT_MIN_OPTIONS_SIZE 312
31 int dhcp_message_init(DHCPMessage
*message
, uint8_t op
, uint32_t xid
,
32 uint8_t type
, uint16_t arp_type
, size_t optlen
,
37 assert(op
== BOOTREQUEST
|| op
== BOOTREPLY
);
38 assert(arp_type
== ARPHRD_ETHER
|| arp_type
== ARPHRD_INFINIBAND
);
41 message
->htype
= arp_type
;
42 message
->hlen
= (arp_type
== ARPHRD_ETHER
) ? ETHER_ADDR_LEN
: 0;
43 message
->xid
= htobe32(xid
);
44 message
->magic
= htobe32(DHCP_MAGIC_COOKIE
);
46 r
= dhcp_option_append(message
, optlen
, &offset
, 0,
47 DHCP_OPTION_MESSAGE_TYPE
, 1, &type
);
56 uint16_t dhcp_packet_checksum(uint8_t *buf
, size_t len
) {
57 uint64_t *buf_64
= (uint64_t*)buf
;
58 uint64_t *end_64
= buf_64
+ (len
/ sizeof(uint64_t));
63 while (buf_64
< end_64
) {
66 /* wrap around in one's complement */
72 if (len
% sizeof(uint64_t)) {
73 /* If the buffer is not aligned to 64-bit, we need
74 to zero-pad the last few bytes and add them in */
75 uint64_t buf_tail
= 0;
77 memcpy(&buf_tail
, buf_64
, len
% sizeof(uint64_t));
86 sum
= (sum
& 0xffff) + (sum
>> 16);
91 void dhcp_packet_append_ip_headers(DHCPPacket
*packet
, be32_t source_addr
,
92 uint16_t source_port
, be32_t destination_addr
,
93 uint16_t destination_port
, uint16_t len
) {
94 packet
->ip
.version
= IPVERSION
;
95 packet
->ip
.ihl
= DHCP_IP_SIZE
/ 4;
96 packet
->ip
.tot_len
= htobe16(len
);
98 packet
->ip
.tos
= IPTOS_CLASS_CS6
;
100 packet
->ip
.protocol
= IPPROTO_UDP
;
101 packet
->ip
.saddr
= source_addr
;
102 packet
->ip
.daddr
= destination_addr
;
104 packet
->udp
.source
= htobe16(source_port
);
105 packet
->udp
.dest
= htobe16(destination_port
);
107 packet
->udp
.len
= htobe16(len
- DHCP_IP_SIZE
);
109 packet
->ip
.check
= packet
->udp
.len
;
110 packet
->udp
.check
= dhcp_packet_checksum((uint8_t*)&packet
->ip
.ttl
, len
- 8);
112 packet
->ip
.ttl
= IPDEFTTL
;
113 packet
->ip
.check
= 0;
114 packet
->ip
.check
= dhcp_packet_checksum((uint8_t*)&packet
->ip
, DHCP_IP_SIZE
);
117 int dhcp_packet_verify_headers(DHCPPacket
*packet
, size_t len
, bool checksum
) {
124 if (packet
->ip
.version
!= IPVERSION
) {
125 log_debug("ignoring packet: not IPv4");
129 if (packet
->ip
.ihl
< 5) {
130 log_debug("ignoring packet: IPv4 IHL (%u words) invalid",
135 hdrlen
= packet
->ip
.ihl
* 4;
137 log_debug("ignoring packet: IPv4 IHL (%zu bytes) "
138 "smaller than minimum (20 bytes)", hdrlen
);
143 log_debug("ignoring packet: packet (%zu bytes) "
144 "smaller than expected (%zu) by IP header", len
,
151 if (packet
->ip
.protocol
!= IPPROTO_UDP
) {
152 log_debug("ignoring packet: not UDP");
156 if (len
< hdrlen
+ be16toh(packet
->udp
.len
)) {
157 log_debug("ignoring packet: packet (%zu bytes) "
158 "smaller than expected (%zu) by UDP header", len
,
159 hdrlen
+ be16toh(packet
->udp
.len
));
163 if (be16toh(packet
->udp
.dest
) != DHCP_PORT_CLIENT
) {
164 log_debug("ignoring packet: to port %u, which "
165 "is not the DHCP client port (%u)",
166 be16toh(packet
->udp
.dest
), DHCP_PORT_CLIENT
);
170 /* checksums - computing these is relatively expensive, so only do it
171 if all the other checks have passed
174 if (dhcp_packet_checksum((uint8_t*)&packet
->ip
, hdrlen
)) {
175 log_debug("ignoring packet: invalid IP checksum");
179 if (checksum
&& packet
->udp
.check
) {
180 packet
->ip
.check
= packet
->udp
.len
;
183 if (dhcp_packet_checksum((uint8_t*)&packet
->ip
.ttl
,
184 be16toh(packet
->udp
.len
) + 12)) {
185 log_debug("ignoring packet: invalid UDP checksum");