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;
73 /* Broadcast a DHCP discover packet to the network, with an optionally requested IP */
74 int send_discover(uint32_t xid, uint32_t requested)
76 struct dhcpMessage packet;
78 init_packet(&packet, DHCPDISCOVER);
81 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
83 add_requests(&packet);
84 bb_info_msg("Sending discover...");
85 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
86 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
90 /* Broadcasts a DHCP request message */
91 int send_selecting(uint32_t xid, uint32_t server, uint32_t requested)
93 struct dhcpMessage packet;
96 init_packet(&packet, DHCPREQUEST);
99 add_simple_option(packet.options, DHCP_REQUESTED_IP, requested);
100 add_simple_option(packet.options, DHCP_SERVER_ID, server);
102 add_requests(&packet);
103 addr.s_addr = requested;
104 bb_info_msg("Sending select for %s...", inet_ntoa(addr));
105 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
106 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
110 /* Unicasts or broadcasts a DHCP renew message */
111 int send_renew(uint32_t xid, uint32_t server, uint32_t ciaddr)
113 struct dhcpMessage packet;
115 init_packet(&packet, DHCPREQUEST);
117 packet.ciaddr = ciaddr;
119 add_requests(&packet);
120 bb_info_msg("Sending renew...");
122 return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
124 return udhcp_raw_packet(&packet, INADDR_ANY, CLIENT_PORT, INADDR_BROADCAST,
125 SERVER_PORT, MAC_BCAST_ADDR, client_config.ifindex);
129 /* Unicasts a DHCP release message */
130 int send_release(uint32_t server, uint32_t ciaddr)
132 struct dhcpMessage packet;
134 init_packet(&packet, DHCPRELEASE);
135 packet.xid = random_xid();
136 packet.ciaddr = ciaddr;
138 add_simple_option(packet.options, DHCP_REQUESTED_IP, ciaddr);
139 add_simple_option(packet.options, DHCP_SERVER_ID, server);
141 bb_info_msg("Sending release...");
142 return udhcp_kernel_packet(&packet, ciaddr, CLIENT_PORT, server, SERVER_PORT);
146 /* return -1 on errors that are fatal for the socket, -2 for those that aren't */
147 int get_raw_packet(struct dhcpMessage *payload, int fd)
150 struct udp_dhcp_packet packet;
151 uint32_t source, dest;
154 memset(&packet, 0, sizeof(struct udp_dhcp_packet));
155 bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
157 DEBUG("Cannot read on raw listening socket - ignoring");
158 usleep(500000); /* possible down interface, looping condition */
162 if (bytes < (int) (sizeof(struct iphdr) + sizeof(struct udphdr))) {
163 DEBUG("Message too short, ignoring");
167 if (bytes < ntohs(packet.ip.tot_len)) {
168 DEBUG("Truncated packet");
172 /* ignore any extra garbage bytes */
173 bytes = ntohs(packet.ip.tot_len);
175 /* Make sure its the right packet for us, and that it passes sanity checks */
176 if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
177 || packet.ip.ihl != sizeof(packet.ip) >> 2
178 || packet.udp.dest != htons(CLIENT_PORT)
179 || bytes > (int) sizeof(struct udp_dhcp_packet)
180 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
182 DEBUG("Unrelated/bogus packet");
186 /* check IP checksum */
187 check = packet.ip.check;
189 if (check != udhcp_checksum(&(packet.ip), sizeof(packet.ip))) {
190 DEBUG("bad IP header checksum, ignoring");
194 /* verify the UDP checksum by replacing the header with a psuedo header */
195 source = packet.ip.saddr;
196 dest = packet.ip.daddr;
197 check = packet.udp.check;
198 packet.udp.check = 0;
199 memset(&packet.ip, 0, sizeof(packet.ip));
201 packet.ip.protocol = IPPROTO_UDP;
202 packet.ip.saddr = source;
203 packet.ip.daddr = dest;
204 packet.ip.tot_len = packet.udp.len; /* cheat on the psuedo-header */
205 if (check && check != udhcp_checksum(&packet, bytes)) {
206 bb_error_msg("packet with bad UDP checksum received, ignoring");
210 memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
212 if (ntohl(payload->cookie) != DHCP_MAGIC) {
213 bb_error_msg("received bogus message (bad magic) - ignoring");
216 DEBUG("oooooh!!! got some!");
217 return bytes - (sizeof(packet.ip) + sizeof(packet.udp));