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)
60 int end = end_option(packet->options);
63 packet->options[end + OPT_CODE] = DHCP_PARAM_REQ;
64 for (i = 0; dhcp_options[i].code; i++)
65 if (dhcp_options[i].flags & OPTION_REQ)
66 packet->options[end + OPT_DATA + len++] = dhcp_options[i].code;
67 packet->options[end + OPT_LEN] = len;
68 packet->options[end + OPT_DATA + len] = DHCP_END;
72 #if ENABLE_FEATURE_UDHCPC_ARPING
73 /* Unicast a DHCP decline message */
74 int send_decline(uint32_t xid, uint32_t server)
76 struct dhcpMessage packet;
78 init_packet(&packet, DHCPDECLINE);
80 add_requests(&packet);
82 bb_info_msg("Sending decline...");
84 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
85 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
89 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
90 int send_discover(uint32_t xid, uint32_t requested)
92 struct dhcpMessage packet;
94 init_packet(&packet, DHCPDISCOVER);
97 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
99 add_requests(&packet);
100 bb_info_msg("Sending discover...");
101 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
102 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
106 /* Broadcasts a DHCP request message */
107 int send_selecting(uint32_t xid, uint32_t server, uint32_t requested)
109 struct dhcpMessage packet;
112 init_packet(&packet, DHCPREQUEST);
115 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
116 add_simple_option(packet.options, DHCP_SERVER_ID, server);
118 add_requests(&packet);
119 addr.s_addr = requested;
120 bb_info_msg("Sending select for %s...", inet_ntoa(addr));
121 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
122 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
126 /* Unicasts or broadcasts a DHCP renew message */
127 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
129 struct dhcpMessage packet;
131 init_packet(&packet, DHCPREQUEST);
133 packet.ciaddr = ciaddr;
135 add_requests(&packet);
136 bb_info_msg("Sending renew...");
138 return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
140 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
141 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
145 /* Unicasts a DHCP release message */
146 int send_release(uint32_t server, uint32_t ciaddr)
148 struct dhcpMessage packet;
150 init_packet(&packet, DHCPRELEASE);
151 packet.xid = random_xid();
152 packet.ciaddr = ciaddr;
154 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
155 add_simple_option(packet.options, DHCP_SERVER_ID, server);
157 bb_info_msg("Sending release...");
158 return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
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)
166 struct udp_dhcp_packet packet;
167 uint32_t source, dest;
170 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
171 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
173 DEBUG("Cannot read on raw listening socket - ignoring");
174 sleep(1); /* possible down interface, looping condition */
178 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
179 DEBUG("Message too short, ignoring");
183 if (bytes < ntohs(packet.ip.tot_len)) {
184 DEBUG("Truncated packet");
188 /* ignore any extra garbage bytes */
189 bytes = ntohs(packet.ip.tot_len);
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)
194 || packet.udp.dest != htons(CLIENT_PORT)
195 || bytes > (int) sizeof(struct udp_dhcp_packet)
196 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
198 DEBUG("Unrelated/bogus packet");
202 /* check IP checksum */
203 check = packet.ip.check;
205 if (check != udhcp_checksum(&(packet.ip), sizeof(packet.ip))) {
206 DEBUG("bad IP header checksum, ignoring");
210 /* verify the UDP checksum by replacing the header with a pseudo header */
211 source = packet.ip.saddr;
212 dest = packet.ip.daddr;
213 check = packet.udp.check;
214 packet.udp.check = 0;
215 memset(&packet.ip, 0, sizeof(packet.ip));
217 packet.ip.protocol = IPPROTO_UDP;
218 packet.ip.saddr = source;
219 packet.ip.daddr = dest;
220 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
221 if (check && check != udhcp_checksum(&packet, bytes)) {
222 bb_error_msg("packet with bad UDP checksum received, ignoring");
226 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
228 if (payload->cookie != htonl(DHCP_MAGIC)) {
229 bb_error_msg("received bogus message (bad magic) - ignoring");
232 DEBUG("oooooh!!! got some!");
233 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));