1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
|
/* vi: set sw=4 ts=4: */
#include <netinet/in.h>
#if (__GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
#include <netpacket/packet.h>
#include <net/ethernet.h>
#else
#include <asm/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#endif
#include "common.h"
#include "dhcpd.h"
#include "options.h"
void udhcp_init_header(struct dhcpMessage *packet, char type)
{
memset(packet, 0, sizeof(struct dhcpMessage));
switch (type) {
case DHCPDISCOVER:
case DHCPREQUEST:
case DHCPRELEASE:
case DHCPINFORM:
packet->op = BOOTREQUEST;
break;
case DHCPOFFER:
case DHCPACK:
case DHCPNAK:
packet->op = BOOTREPLY;
}
packet->htype = ETH_10MB;
packet->hlen = ETH_10MB_LEN;
packet->cookie = htonl(DHCP_MAGIC);
packet->options[0] = DHCP_END;
add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
}
/* read a packet from socket fd, return -1 on read error, -2 on packet error */
int udhcp_get_packet(struct dhcpMessage *packet, int fd)
{
static const char broken_vendors[][8] = {
"MSFT 98",
""
};
int bytes;
int i;
char unsigned *vendor;
memset(packet, 0, sizeof(struct dhcpMessage));
bytes = read(fd, packet, sizeof(struct dhcpMessage));
if (bytes < 0) {
DEBUG("cannot read on listening socket, ignoring");
return -1;
}
if (ntohl(packet->cookie) != DHCP_MAGIC) {
bb_error_msg("received bogus message, ignoring");
return -2;
}
DEBUG("Received a packet");
if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
for (i = 0; broken_vendors[i][0]; i++) {
if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
&& !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
) {
DEBUG("broken client (%s), forcing broadcast",
broken_vendors[i]);
packet->flags |= htons(BROADCAST_FLAG);
}
}
}
return bytes;
}
uint16_t udhcp_checksum(void *addr, int count)
{
/* Compute Internet Checksum for "count" bytes
* beginning at location "addr".
*/
int32_t sum = 0;
uint16_t *source = (uint16_t *) addr;
while (count > 1) {
/* This is the inner loop */
sum += *source++;
count -= 2;
}
/* Add left-over byte, if any */
if (count > 0) {
/* Make sure that the left-over byte is added correctly both
* with little and big endian hosts */
uint16_t tmp = 0;
*(uint8_t *) (&tmp) = * (uint8_t *) source;
sum += tmp;
}
/* Fold 32-bit sum to 16 bits */
while (sum >> 16)
sum = (sum & 0xffff) + (sum >> 16);
return ~sum;
}
/* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
int udhcp_raw_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex)
{
int fd;
int result;
struct sockaddr_ll dest;
struct udp_dhcp_packet packet;
fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
if (fd < 0) {
bb_perror_msg("socket");
return -1;
}
memset(&dest, 0, sizeof(dest));
memset(&packet, 0, sizeof(packet));
dest.sll_family = AF_PACKET;
dest.sll_protocol = htons(ETH_P_IP);
dest.sll_ifindex = ifindex;
dest.sll_halen = 6;
memcpy(dest.sll_addr, dest_arp, 6);
if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
bb_perror_msg("bind");
close(fd);
return -1;
}
packet.ip.protocol = IPPROTO_UDP;
packet.ip.saddr = source_ip;
packet.ip.daddr = dest_ip;
packet.udp.source = htons(source_port);
packet.udp.dest = htons(dest_port);
packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
packet.ip.tot_len = packet.udp.len;
memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));
packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
packet.ip.ihl = sizeof(packet.ip) >> 2;
packet.ip.version = IPVERSION;
packet.ip.ttl = IPDEFTTL;
packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
(struct sockaddr *) &dest, sizeof(dest));
if (result <= 0) {
bb_perror_msg("sendto");
}
close(fd);
return result;
}
/* Let the kernel do all the work for packet generation */
int udhcp_kernel_packet(struct dhcpMessage *payload,
uint32_t source_ip, int source_port,
uint32_t dest_ip, int dest_port)
{
int n = 1;
int fd, result;
struct sockaddr_in client;
fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (fd < 0)
return -1;
if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1) {
close(fd);
return -1;
}
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(source_port);
client.sin_addr.s_addr = source_ip;
if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
close(fd);
return -1;
}
memset(&client, 0, sizeof(client));
client.sin_family = AF_INET;
client.sin_port = htons(dest_port);
client.sin_addr.s_addr = dest_ip;
if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
close(fd);
return -1;
}
result = write(fd, payload, sizeof(struct dhcpMessage));
close(fd);
return result;
}
|
