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 add_option_string(packet->options, client_config.vendorclass);
55 /* Add a parameter request list for stubborn DHCP servers. Pull the data
56 * from the struct in options.c. Don't do bounds checking here because it
57 * goes towards the head of the packet. */
58 static void add_requests(struct dhcpMessage *packet)
61 int end = end_option(packet->options);
64 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
65 for (i = 0; (c = dhcp_options[i].code) != 0; i++) {
66 if (dhcp_options[i].flags & OPTION_REQ
67 || (client_config.opt_mask[c >> 3] & (1 << (c & 7)))
69 packet->options[end + OPT_DATA + len++] = c;
72 packet->options[end + OPT_LEN] = len;
73 packet->options[end + OPT_DATA + len] = DHCP_END;
77 #if ENABLE_FEATURE_UDHCPC_ARPING
78 /* Unicast a DHCP decline message */
79 int send_decline(uint32_t xid, uint32_t server)
81 struct dhcpMessage packet;
83 init_packet(&packet, DHCPDECLINE);
85 add_requests(&packet);
87 bb_info_msg("Sending decline...");
89 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
90 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
94 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
95 int send_discover(uint32_t xid, uint32_t requested)
97 struct dhcpMessage packet;
99 init_packet(&packet, DHCPDISCOVER);
102 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
104 /* Explicitly saying that we want RFC-compliant packets helps
105 * some buggy DHCP servers to NOT send bigger packets */
106 add_simple_option(packet.options, DHCP_MAX_SIZE, htons(576));
107 add_requests(&packet);
108 bb_info_msg("Sending discover...");
109 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
110 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
114 /* Broadcasts a DHCP request message */
115 int send_selecting(uint32_t xid, uint32_t server, uint32_t requested)
117 struct dhcpMessage packet;
120 init_packet(&packet, DHCPREQUEST);
123 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
124 add_simple_option(packet.options, DHCP_SERVER_ID, server);
126 add_requests(&packet);
127 addr.s_addr = requested;
128 bb_info_msg("Sending select for %s...", inet_ntoa(addr));
129 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
130 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
134 /* Unicasts or broadcasts a DHCP renew message */
135 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
137 struct dhcpMessage packet;
139 init_packet(&packet, DHCPREQUEST);
141 packet.ciaddr = ciaddr;
143 add_requests(&packet);
144 bb_info_msg("Sending renew...");
146 return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
148 return udhcp_send_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
149 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
153 /* Unicasts a DHCP release message */
154 int send_release(uint32_t server, uint32_t ciaddr)
156 struct dhcpMessage packet;
158 init_packet(&packet, DHCPRELEASE);
159 packet.xid = random_xid();
160 packet.ciaddr = ciaddr;
162 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
163 add_simple_option(packet.options, DHCP_SERVER_ID, server);
165 bb_info_msg("Sending release...");
166 return udhcp_send_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
170 /* Returns -1 on errors that are fatal for the socket, -2 for those that aren't */
171 int get_raw_packet(struct dhcpMessage *payload, int fd)
174 struct udp_dhcp_packet packet;
177 memset(&packet, 0, sizeof(packet));
178 bytes = safe_read(fd, &packet, sizeof(packet));
180 DEBUG("Cannot read on raw listening socket - ignoring");
181 sleep(1); /* possible down interface, looping condition */
182 return bytes; /* returns -1 */
185 if (bytes < (int) (sizeof(packet.ip) + sizeof(packet.udp))) {
186 DEBUG("Packet is too short, ignoring");
190 if (bytes < ntohs(packet.ip.tot_len)) {
191 /* packet is bigger than sizeof(packet), we did partial read */
192 DEBUG("Oversized packet, ignoring");
196 /* ignore any extra garbage bytes */
197 bytes = ntohs(packet.ip.tot_len);
199 /* make sure its the right packet for us, and that it passes sanity checks */
200 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
201 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
202 || packet.udp.dest != htons(CLIENT_PORT)
203 /* || bytes > (int) sizeof(packet) - can't happen */
204 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
206 DEBUG("Unrelated/bogus packet");
210 /* verify IP checksum */
211 check = packet.ip.check;
213 if (check != udhcp_checksum(&packet.ip, sizeof(packet.ip))) {
214 DEBUG("Bad IP header checksum, ignoring");
218 /* verify UDP checksum. IP header has to be modified for this */
219 memset(&packet.ip, 0, offsetof(struct iphdr, protocol));
220 /* ip.xx fields which are not memset: protocol, check, saddr, daddr */
221 packet.ip.tot_len = packet.udp.len; /* yes, this is needed */
222 check = packet.udp.check;
223 packet.udp.check = 0;
224 if (check && check != udhcp_checksum(&packet, bytes)) {
225 bb_error_msg("packet with bad UDP checksum received, ignoring");
229 memcpy(payload, &packet.data, bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
231 if (payload->cookie != htonl(DHCP_MAGIC)) {
232 bb_error_msg("received bogus message (bad magic), ignoring");
235 DEBUG("Got valid DHCP packet");
236 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));