1 | /* clientpacket.c
|
---|
2 | *
|
---|
3 | * Packet generation and dispatching functions for the DHCP client.
|
---|
4 | *
|
---|
5 | * Russ Dill <Russ.Dill@asu.edu> July 2001
|
---|
6 | *
|
---|
7 | * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
|
---|
8 | */
|
---|
9 |
|
---|
10 | #include <string.h>
|
---|
11 | #include <sys/socket.h>
|
---|
12 | #include <features.h>
|
---|
13 | #if (__GLIBC__ >= 2 && __GLIBC_MINOR >= 1) || defined _NEWLIB_VERSION
|
---|
14 | #include <netpacket/packet.h>
|
---|
15 | #include <net/ethernet.h>
|
---|
16 | #else
|
---|
17 | #include <asm/types.h>
|
---|
18 | #include <linux/if_packet.h>
|
---|
19 | #include <linux/if_ether.h>
|
---|
20 | #endif
|
---|
21 | #include <stdlib.h>
|
---|
22 | #include <time.h>
|
---|
23 | #include <unistd.h>
|
---|
24 | #include <netinet/in.h>
|
---|
25 | #include <arpa/inet.h>
|
---|
26 | #include <fcntl.h>
|
---|
27 |
|
---|
28 |
|
---|
29 | #include "dhcpd.h"
|
---|
30 | #include "clientpacket.h"
|
---|
31 | #include "options.h"
|
---|
32 | #include "dhcpc.h"
|
---|
33 | #include "common.h"
|
---|
34 |
|
---|
35 |
|
---|
36 | /* Create a random xid */
|
---|
37 | unsigned long random_xid(void)
|
---|
38 | {
|
---|
39 | static int initialized;
|
---|
40 | if (!initialized) {
|
---|
41 | int fd;
|
---|
42 | unsigned long seed;
|
---|
43 |
|
---|
44 | fd = open("/dev/urandom", 0);
|
---|
45 | if (fd < 0 || read(fd, &seed, sizeof(seed)) < 0) {
|
---|
46 | LOG(LOG_WARNING, "Could not load seed from /dev/urandom: %m");
|
---|
47 | seed = time(0);
|
---|
48 | }
|
---|
49 | if (fd >= 0) close(fd);
|
---|
50 | srand(seed);
|
---|
51 | initialized++;
|
---|
52 | }
|
---|
53 | return rand();
|
---|
54 | }
|
---|
55 |
|
---|
56 |
|
---|
57 | /* initialize a packet with the proper defaults */
|
---|
58 | static void init_packet(struct dhcpMessage *packet, char type)
|
---|
59 | {
|
---|
60 | udhcp_init_header(packet, type);
|
---|
61 | memcpy(packet->chaddr, client_config.arp, 6);
|
---|
62 | if (client_config.clientid)
|
---|
63 | add_option_string(packet->options, client_config.clientid);
|
---|
64 | if (client_config.hostname) add_option_string(packet->options, client_config.hostname);
|
---|
65 | if (client_config.fqdn) add_option_string(packet->options, client_config.fqdn);
|
---|
66 | add_option_string(packet->options, client_config.vendorclass);
|
---|
67 | }
|
---|
68 |
|
---|
69 |
|
---|
70 | /* Add a parameter request list for stubborn DHCP servers. Pull the data
|
---|
71 | * from the struct in options.c. Don't do bounds checking here because it
|
---|
72 | * goes towards the head of the packet. */
|
---|
73 | static void add_requests(struct dhcpMessage *packet)
|
---|
74 | {
|
---|
75 | int end = end_option(packet->options);
|
---|
76 | int i, len = 0;
|
---|
77 |
|
---|
78 | packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
|
---|
79 | for (i = 0; dhcp_options[i].code; i++)
|
---|
80 | if (dhcp_options[i].flags & OPTION_REQ)
|
---|
81 | packet->options[end + OPT_DATA + len++] = dhcp_options[i].code;
|
---|
82 | packet->options[end + OPT_LEN] = len;
|
---|
83 | packet->options[end + OPT_DATA + len] = DHCP_END;
|
---|
84 |
|
---|
85 | }
|
---|
86 |
|
---|
87 |
|
---|
88 | /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
|
---|
89 | int send_discover(unsigned long xid, unsigned long requested)
|
---|
90 | {
|
---|
91 | struct dhcpMessage packet;
|
---|
92 |
|
---|
93 | init_packet(&packet, DHCPDISCOVER);
|
---|
94 | packet.xid = xid;
|
---|
95 | if (requested)
|
---|
96 | add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
|
---|
97 |
|
---|
98 | add_requests(&packet);
|
---|
99 | LOG(LOG_DEBUG, "Sending discover...");
|
---|
100 | return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
|
---|
101 | SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
|
---|
102 | }
|
---|
103 |
|
---|
104 |
|
---|
105 | /* Broadcasts a DHCP request message */
|
---|
106 | int send_selecting(unsigned long xid, unsigned long server, unsigned long requested)
|
---|
107 | {
|
---|
108 | struct dhcpMessage packet;
|
---|
109 | struct in_addr addr;
|
---|
110 |
|
---|
111 | init_packet(&packet, DHCPREQUEST);
|
---|
112 | packet.xid = xid;
|
---|
113 |
|
---|
114 | add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
|
---|
115 | add_simple_option(packet.options, DHCP_SERVER_ID, server);
|
---|
116 |
|
---|
117 | add_requests(&packet);
|
---|
118 | addr.s_addr = requested;
|
---|
119 | LOG(LOG_DEBUG, "Sending select for %s...", inet_ntoa(addr));
|
---|
120 | return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
|
---|
121 | SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
|
---|
122 | }
|
---|
123 |
|
---|
124 |
|
---|
125 | /* Unicasts or broadcasts a DHCP renew message */
|
---|
126 | int send_renew(unsigned long xid, unsigned long server, unsigned long ciaddr)
|
---|
127 | {
|
---|
128 | struct dhcpMessage packet;
|
---|
129 | int ret = 0;
|
---|
130 |
|
---|
131 | init_packet(&packet, DHCPREQUEST);
|
---|
132 | packet.xid = xid;
|
---|
133 | packet.ciaddr = ciaddr;
|
---|
134 |
|
---|
135 | add_requests(&packet);
|
---|
136 | LOG(LOG_DEBUG, "Sending renew...");
|
---|
137 | if (server)
|
---|
138 | ret = udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
|
---|
139 | else ret = udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
|
---|
140 | SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
|
---|
141 | return ret;
|
---|
142 | }
|
---|
143 |
|
---|
144 |
|
---|
145 | /* Unicasts a DHCP release message */
|
---|
146 | int send_release(unsigned long server, unsigned long ciaddr)
|
---|
147 | {
|
---|
148 | struct dhcpMessage packet;
|
---|
149 |
|
---|
150 | init_packet(&packet, DHCPRELEASE);
|
---|
151 | packet.xid = random_xid();
|
---|
152 | packet.ciaddr = ciaddr;
|
---|
153 |
|
---|
154 | add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
|
---|
155 | add_simple_option(packet.options, DHCP_SERVER_ID, server);
|
---|
156 |
|
---|
157 | LOG(LOG_DEBUG, "Sending release...");
|
---|
158 | return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
|
---|
159 | }
|
---|
160 |
|
---|
161 |
|
---|
162 | /* return -1 on errors that are fatal for the socket, -2 for those that aren't */
|
---|
163 | int get_raw_packet(struct dhcpMessage *payload, int fd)
|
---|
164 | {
|
---|
165 | int bytes;
|
---|
166 | struct udp_dhcp_packet packet;
|
---|
167 | uint32_t source, dest;
|
---|
168 | uint16_t check;
|
---|
169 |
|
---|
170 | memset(&packet, 0, sizeof(struct udp_dhcp_packet));
|
---|
171 | bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
|
---|
172 | if (bytes < 0) {
|
---|
173 | DEBUG(LOG_INFO, "couldn't read on raw listening socket -- ignoring");
|
---|
174 | usleep(500000); /* possible down interface, looping condition */
|
---|
175 | return -1;
|
---|
176 | }
|
---|
177 |
|
---|
178 | if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
|
---|
179 | DEBUG(LOG_INFO, "message too short, ignoring");
|
---|
180 | return -2;
|
---|
181 | }
|
---|
182 |
|
---|
183 | if (bytes < ntohs(packet.ip.tot_len)) {
|
---|
184 | DEBUG(LOG_INFO, "Truncated packet");
|
---|
185 | return -2;
|
---|
186 | }
|
---|
187 |
|
---|
188 | /* ignore any extra garbage bytes */
|
---|
189 | bytes = ntohs(packet.ip.tot_len);
|
---|
190 |
|
---|
191 | /* Make sure its the right packet for us, and that it passes sanity checks */
|
---|
192 | if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION ||
|
---|
193 | packet.ip.ihl != sizeof(packet.ip) >> 2 || packet.udp.dest != htons(CLIENT_PORT) ||
|
---|
194 | bytes > (int) sizeof(struct udp_dhcp_packet) ||
|
---|
195 | ntohs(packet.udp.len) != (uint16_t) (bytes - sizeof(packet.ip))) {
|
---|
196 | DEBUG(LOG_INFO, "unrelated/bogus packet");
|
---|
197 | return -2;
|
---|
198 | }
|
---|
199 |
|
---|
200 | /* check IP checksum */
|
---|
201 | check = packet.ip.check;
|
---|
202 | packet.ip.check = 0;
|
---|
203 | if (check != udhcp_checksum(&(packet.ip), sizeof(packet.ip))) {
|
---|
204 | DEBUG(LOG_INFO, "bad IP header checksum, ignoring");
|
---|
205 | return -1;
|
---|
206 | }
|
---|
207 |
|
---|
208 | /* verify the UDP checksum by replacing the header with a psuedo header */
|
---|
209 | source = packet.ip.saddr;
|
---|
210 | dest = packet.ip.daddr;
|
---|
211 | check = packet.udp.check;
|
---|
212 | packet.udp.check = 0;
|
---|
213 | memset(&packet.ip, 0, sizeof(packet.ip));
|
---|
214 |
|
---|
215 | packet.ip.protocol = IPPROTO_UDP;
|
---|
216 | packet.ip.saddr = source;
|
---|
217 | packet.ip.daddr = dest;
|
---|
218 | packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
|
---|
219 | if (check && check != udhcp_checksum(&packet, bytes)) {
|
---|
220 | DEBUG(LOG_ERR, "packet with bad UDP checksum received, ignoring");
|
---|
221 | return -2;
|
---|
222 | }
|
---|
223 |
|
---|
224 | memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
|
---|
225 |
|
---|
226 | if (ntohl(payload->cookie) != DHCP_MAGIC) {
|
---|
227 | LOG(LOG_ERR, "received bogus message (bad magic) -- ignoring");
|
---|
228 | return -2;
|
---|
229 | }
|
---|
230 | DEBUG(LOG_INFO, "oooooh!!! got some!");
|
---|
231 | return bytes - (sizeof(packet.ip) + sizeof(packet.udp));
|
---|
232 |
|
---|
233 | }
|
---|