1/* vi: set sw=4 ts=4: */ 2/* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com> 3 * 4 * Licensed under GPL v2, see file LICENSE in this tarball for details. 5 * 6 * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support 7 * Copyright (C) 2002 Mario Strasser <mast@gmx.net>, 8 * Zuercher Hochschule Winterthur, 9 * Netbeat AG 10 * Upstream has GPL v2 or later 11 */ 12 13#include "common.h" 14#include "dhcpd.h" 15#include "options.h" 16 17/* constants */ 18#define SELECT_TIMEOUT 5 /* select timeout in sec. */ 19#define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */ 20#define MAX_INTERFACES 9 21 22 23/* This list holds information about clients. The xid_* functions manipulate this list. */ 24static struct xid_item { 25 uint32_t xid; 26 struct sockaddr_in ip; 27 int client; 28 time_t timestamp; 29 struct xid_item *next; 30} dhcprelay_xid_list = {0, {0}, 0, 0, NULL}; 31 32 33static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client) 34{ 35 struct xid_item *item; 36 37 /* create new xid entry */ 38 item = xmalloc(sizeof(struct xid_item)); 39 40 /* add xid entry */ 41 item->ip = *ip; 42 item->xid = xid; 43 item->client = client; 44 item->timestamp = time(NULL); 45 item->next = dhcprelay_xid_list.next; 46 dhcprelay_xid_list.next = item; 47 48 return item; 49} 50 51static void xid_expire(void) 52{ 53 struct xid_item *item = dhcprelay_xid_list.next; 54 struct xid_item *last = &dhcprelay_xid_list; 55 time_t current_time = time(NULL); 56 57 while (item != NULL) { 58 if ((current_time - item->timestamp) > MAX_LIFETIME) { 59 last->next = item->next; 60 free(item); 61 item = last->next; 62 } else { 63 last = item; 64 item = item->next; 65 } 66 } 67} 68 69static struct xid_item *xid_find(uint32_t xid) 70{ 71 struct xid_item *item = dhcprelay_xid_list.next; 72 while (item != NULL) { 73 if (item->xid == xid) { 74 return item; 75 } 76 item = item->next; 77 } 78 return NULL; 79} 80 81static void xid_del(uint32_t xid) 82{ 83 struct xid_item *item = dhcprelay_xid_list.next; 84 struct xid_item *last = &dhcprelay_xid_list; 85 while (item != NULL) { 86 if (item->xid == xid) { 87 last->next = item->next; 88 free(item); 89 item = last->next; 90 } else { 91 last = item; 92 item = item->next; 93 } 94 } 95} 96 97/** 98 * get_dhcp_packet_type - gets the message type of a dhcp packet 99 * p - pointer to the dhcp packet 100 * returns the message type on success, -1 otherwise 101 */ 102static int get_dhcp_packet_type(struct dhcpMessage *p) 103{ 104 uint8_t *op; 105 106 /* it must be either a BOOTREQUEST or a BOOTREPLY */ 107 if (p->op != BOOTREQUEST && p->op != BOOTREPLY) 108 return -1; 109 /* get message type option */ 110 op = get_option(p, DHCP_MESSAGE_TYPE); 111 if (op != NULL) 112 return op[0]; 113 return -1; 114} 115 116/** 117 * signal_handler - handles signals ;-) 118 * sig - sent signal 119 */ 120static smallint dhcprelay_stopflag; 121 122static void dhcprelay_signal_handler(int sig) 123{ 124 dhcprelay_stopflag = 1; 125} 126 127/** 128 * get_client_devices - parses the devices list 129 * dev_list - comma separated list of devices 130 * returns array 131 */ 132static char **get_client_devices(char *dev_list, int *client_number) 133{ 134 char *s, *list, **client_dev; 135 int i, cn; 136 137 /* copy list */ 138 list = xstrdup(dev_list); 139 if (list == NULL) return NULL; 140 141 /* get number of items */ 142 for (s = dev_list, cn = 1; *s; s++) 143 if (*s == ',') 144 cn++; 145 146 client_dev = xzalloc(cn * sizeof(*client_dev)); 147 148 /* parse list */ 149 s = strtok(list, ","); 150 i = 0; 151 while (s != NULL) { 152 client_dev[i++] = xstrdup(s); 153 s = strtok(NULL, ","); 154 } 155 156 /* free copy and exit */ 157 free(list); 158 *client_number = cn; 159 return client_dev; 160} 161 162 163/* Creates listen sockets (in fds) and returns the number allocated. */ 164static int init_sockets(char **client, int num_clients, 165 char *server, int *fds, int *max_socket) 166{ 167 int i; 168 169 /* talk to real server on bootps */ 170 fds[0] = listen_socket(/*INADDR_ANY,*/ 67, server); 171 *max_socket = fds[0]; 172 173 /* array starts at 1 since server is 0 */ 174 num_clients++; 175 176 for (i = 1; i < num_clients; i++) { 177 /* listen for clients on bootps */ 178 fds[i] = listen_socket(/*NADDR_ANY,*/ 67, client[i-1]); 179 if (fds[i] > *max_socket) 180 *max_socket = fds[i]; 181 } 182 183 return i; 184} 185 186 187/** 188 * pass_on() - forwards dhcp packets from client to server 189 * p - packet to send 190 * client - number of the client 191 */ 192static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds, 193 struct sockaddr_in *client_addr, struct sockaddr_in *server_addr) 194{ 195 int res, type; 196 struct xid_item *item; 197 198 /* check packet_type */ 199 type = get_dhcp_packet_type(p); 200 if (type != DHCPDISCOVER && type != DHCPREQUEST 201 && type != DHCPDECLINE && type != DHCPRELEASE 202 && type != DHCPINFORM 203 ) { 204 return; 205 } 206 207 /* create new xid entry */ 208 item = xid_add(p->xid, client_addr, client); 209 210 /* forward request to LAN (server) */ 211 res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr, 212 sizeof(struct sockaddr_in)); 213 if (res != packet_len) { 214 bb_perror_msg("pass_on"); 215 return; 216 } 217} 218 219/** 220 * pass_back() - forwards dhcp packets from server to client 221 * p - packet to send 222 */ 223static void pass_back(struct dhcpMessage *p, int packet_len, int *fds) 224{ 225 int res, type; 226 struct xid_item *item; 227 228 /* check xid */ 229 item = xid_find(p->xid); 230 if (!item) { 231 return; 232 } 233 234 /* check packet type */ 235 type = get_dhcp_packet_type(p); 236 if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) { 237 return; 238 } 239 240 if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY)) 241 item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST); 242 if (item->client > MAX_INTERFACES) 243 return; 244 res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip), 245 sizeof(item->ip)); 246 if (res != packet_len) { 247 bb_perror_msg("pass_back"); 248 return; 249 } 250 251 /* remove xid entry */ 252 xid_del(p->xid); 253} 254 255static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients, 256 struct sockaddr_in *server_addr, uint32_t gw_ip) 257{ 258 struct dhcpMessage dhcp_msg; 259 fd_set rfds; 260 size_t packlen; 261 socklen_t addr_size; 262 struct sockaddr_in client_addr; 263 struct timeval tv; 264 int i; 265 266 while (!dhcprelay_stopflag) { 267 FD_ZERO(&rfds); 268 for (i = 0; i < num_sockets; i++) 269 FD_SET(fds[i], &rfds); 270 tv.tv_sec = SELECT_TIMEOUT; 271 tv.tv_usec = 0; 272 if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) { 273 /* server */ 274 if (FD_ISSET(fds[0], &rfds)) { 275 packlen = udhcp_get_packet(&dhcp_msg, fds[0]); 276 if (packlen > 0) { 277 pass_back(&dhcp_msg, packlen, fds); 278 } 279 } 280 for (i = 1; i < num_sockets; i++) { 281 /* clients */ 282 if (!FD_ISSET(fds[i], &rfds)) 283 continue; 284 addr_size = sizeof(struct sockaddr_in); 285 packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0, 286 (struct sockaddr *)(&client_addr), &addr_size); 287 if (packlen <= 0) 288 continue; 289 if (read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL)) 290 dhcp_msg.giaddr = gw_ip; 291 pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr); 292 } 293 } 294 xid_expire(); 295 } 296} 297 298int dhcprelay_main(int argc, char **argv); 299int dhcprelay_main(int argc, char **argv) 300{ 301 int i, num_sockets, max_socket, fds[MAX_INTERFACES]; 302 uint32_t gw_ip; 303 char **clients; 304 struct sockaddr_in server_addr; 305 306 server_addr.sin_family = AF_INET; 307 server_addr.sin_port = htons(67); 308 if (argc == 4) { 309 if (!inet_aton(argv[3], &server_addr.sin_addr)) 310 bb_perror_msg_and_die("didn't grok server"); 311 } else if (argc == 3) { 312 server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST); 313 } else { 314 bb_show_usage(); 315 } 316 clients = get_client_devices(argv[1], &num_sockets); 317 if (!clients) return 0; 318 319 signal(SIGTERM, dhcprelay_signal_handler); 320 signal(SIGQUIT, dhcprelay_signal_handler); 321 signal(SIGINT, dhcprelay_signal_handler); 322 323 num_sockets = init_sockets(clients, num_sockets, argv[2], fds, &max_socket); 324 325 if (read_interface(argv[2], NULL, &gw_ip, NULL)) 326 return 1; 327 328 dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip); 329 330 if (ENABLE_FEATURE_CLEAN_UP) { 331 for (i = 0; i < num_sockets; i++) { 332 close(fds[i]); 333 free(clients[i]); 334 } 335 } 336 337 return 0; 338} 339