1 /* vi: set sw=4 ts=4: */
4 * Packet generation and dispatching functions for the DHCP client.
6 * Russ Dill <Russ.Dill@asu.edu> July 2001
8 * Licensed under GPLv2 or later, see file LICENSE in this tarball for details.
12 #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
13 #include <netpacket/packet.h>
14 #include <net/ethernet.h>
16 #include <asm/types.h>
17 #include <linux/if_packet.h>
18 #include <linux/if_ether.h>
27 /* Create a random xid */
28 uint32_t random_xid(void)
30 static smallint initialized;
33 srand(monotonic_us());
40 /* initialize a packet with the proper defaults */
41 static void init_packet(struct dhcpMessage *packet, char type)
43 udhcp_init_header(packet, type);
44 memcpy(packet->chaddr, client_config.arp, 6);
45 if (client_config.clientid)
46 add_option_string(packet->options, client_config.clientid);
47 if (client_config.hostname)
48 add_option_string(packet->options, client_config.hostname);
49 if (client_config.fqdn)
50 add_option_string(packet->options, client_config.fqdn);
51 if ((type != DHCPDECLINE) && (type != DHCPRELEASE))
52 add_option_string(packet->options, client_config.vendorclass);
56 /* Add a parameter request list for stubborn DHCP servers. Pull the data
57 * from the struct in options.c. Don't do bounds checking here because it
58 * goes towards the head of the packet. */
59 static void add_param_req_option(struct dhcpMessage *packet)
62 int end = end_option(packet->options);
65 for (i = 0; (c = dhcp_options[i].code) != 0; i++) {
66 if (((dhcp_options[i].flags & OPTION_REQ)
67 && !client_config.no_default_options)
68 || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
70 packet->options[end + OPT_DATA + len] = c;
75 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
76 packet->options[end + OPT_LEN] = len;
77 packet->options[end + OPT_DATA + len] = DHCP_END;
82 #if ENABLE_FEATURE_UDHCPC_ARPING
83 /* Unicast a DHCP decline message */
84 int send_decline(uint32_t xid, uint32_t server, uint32_t requested)
86 struct dhcpMessage packet;
88 init_packet(&packet, DHCPDECLINE);
90 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
91 add_simple_option(packet.options, DHCP_SERVER_ID, server);
93 bb_info_msg("Sending decline...");
95 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
96 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
100 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
101 int send_discover(uint32_t xid, uint32_t requested)
103 struct dhcpMessage packet;
105 init_packet(&packet, DHCPDISCOVER);
108 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
110 /* Explicitly saying that we want RFC-compliant packets helps
111 * some buggy DHCP servers to NOT send bigger packets */
112 add_simple_option(packet.options, DHCP_MAX_SIZE, htons(576));
114 add_param_req_option(&packet);
116 bb_info_msg("Sending discover...");
117 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
118 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
122 /* Broadcasts a DHCP request message */
123 int send_selecting(uint32_t xid, uint32_t server, uint32_t requested)
125 struct dhcpMessage packet;
128 init_packet(&packet, DHCPREQUEST);
131 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
132 add_simple_option(packet.options, DHCP_SERVER_ID, server);
133 add_param_req_option(&packet);
135 addr.s_addr = requested;
136 bb_info_msg("Sending select for %s...", inet_ntoa(addr));
137 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
138 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
142 /* Unicasts or broadcasts a DHCP renew message */
143 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
145 struct dhcpMessage packet;
147 init_packet(&packet, DHCPREQUEST);
149 packet.ciaddr = ciaddr;
151 add_param_req_option(&packet);
152 bb_info_msg("Sending renew...");
154 return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
156 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
157 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
161 /* Unicasts a DHCP release message */
162 int send_release(uint32_t server, uint32_t ciaddr)
164 struct dhcpMessage packet;
166 init_packet(&packet, DHCPRELEASE);
167 packet.xid = random_xid();
168 packet.ciaddr = ciaddr;
170 add_simple_option(packet.options, DHCP_SERVER_ID, server);
172 bb_info_msg("Sending release...");
173 return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
177 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
178 int get_raw_packet(struct dhcpMessage *payload, int fd)
181 struct udp_dhcp_packet packet;
184 memset(&packet, 0, sizeof(packet));
185 bytes = safe_read(fd, &packet, sizeof(packet));
187 DEBUG("Cannot read on raw listening socket - ignoring");
188 sleep(1); /* possible down interface, looping condition */
189 return bytes; /* returns -1 */
192 if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
193 DEBUG("Packet is too short, ignoring");
197 if (bytes < ntohs(packet.ip.tot_len)) {
198 /* packet is bigger than sizeof(packet), we did partial read */
199 DEBUG("Oversized packet, ignoring");
203 /* ignore any extra garbage bytes */
204 bytes = ntohs(packet.ip.tot_len);
206 /* make sure its the right packet for us, and that it passes sanity checks */
207 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
208 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
209 || packet.udp.dest != htons(CLIENT_PORT)
210 /* || bytes > (int) sizeof(packet) - can't happen */
211 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
213 DEBUG("Unrelated/bogus packet");
217 /* verify IP checksum */
218 check = packet.ip.check;
220 if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
221 DEBUG("Bad IP header checksum, ignoring");
225 /* verify UDP checksum. IP header has to be modified for this */
226 memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
227 /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
228 packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
229 check = packet.udp.check;
230 packet.udp.check = 0;
231 if (check && check != udhcp_checksum(&packet, bytes)) {
232 bb_error_msg("packet with bad UDP checksum received, ignoring");
236 memcpy(payload, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
238 if (payload->cookie != htonl(DHCP_MAGIC)) {
239 bb_error_msg("received bogus message (bad magic), ignoring");
242 DEBUG("Got valid DHCP packet");
243 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));