1 /* vi: set sw=4 ts=4: */
2 /* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
4 * Licensed under GPLv2, see file LICENSE in this source tree.
6 * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
7 * Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
8 * Zuercher Hochschule Winterthur,
10 * Upstream has GPL v2 or later
13 //usage:#define dhcprelay_trivial_usage
14 //usage: "CLIENT_IFACE[,CLIENT_IFACE2]... SERVER_IFACE [SERVER_IP]"
15 //usage:#define dhcprelay_full_usage "\n\n"
16 //usage: "Relay DHCP requests between clients and server"
20 #define SERVER_PORT 67
22 /* lifetime of an xid entry in sec. */
23 #define MAX_LIFETIME 2*60
24 /* select timeout in sec. */
25 #define SELECT_TIMEOUT (MAX_LIFETIME / 8)
27 /* This list holds information about clients. The xid_* functions manipulate this list. */
32 struct sockaddr_in ip;
33 struct xid_item *next;
36 #define dhcprelay_xid_list (*(struct xid_item*)bb_common_bufsiz1)
37 #define INIT_G() do { setup_common_bufsiz(); } while (0)
39 static struct xid_item *xid_add(uint32_t xid, struct sockaddr_in *ip, int client)
41 struct xid_item *item;
43 /* create new xid entry */
44 item = xmalloc(sizeof(struct xid_item));
49 item->client = client;
50 item->timestamp = monotonic_sec();
51 item->next = dhcprelay_xid_list.next;
52 dhcprelay_xid_list.next = item;
57 static void xid_expire(void)
59 struct xid_item *item = dhcprelay_xid_list.next;
60 struct xid_item *last = &dhcprelay_xid_list;
61 unsigned current_time = monotonic_sec();
63 while (item != NULL) {
64 if ((current_time - item->timestamp) > MAX_LIFETIME) {
65 last->next = item->next;
75 static struct xid_item *xid_find(uint32_t xid)
77 struct xid_item *item = dhcprelay_xid_list.next;
78 while (item != NULL) {
79 if (item->xid == xid) {
87 static void xid_del(uint32_t xid)
89 struct xid_item *item = dhcprelay_xid_list.next;
90 struct xid_item *last = &dhcprelay_xid_list;
91 while (item != NULL) {
92 if (item->xid == xid) {
93 last->next = item->next;
104 * get_dhcp_packet_type - gets the message type of a dhcp packet
105 * p - pointer to the dhcp packet
106 * returns the message type on success, -1 otherwise
108 static int get_dhcp_packet_type(struct dhcp_packet *p)
112 /* it must be either a BOOTREQUEST or a BOOTREPLY */
113 if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
115 /* get message type option */
116 op = udhcp_get_option(p, DHCP_MESSAGE_TYPE);
123 * make_iface_list - parses client/server interface names
126 static char **make_iface_list(char **client_and_server_ifaces, int *client_number)
128 char *s, **iface_list;
131 /* get number of items */
132 cn = 2; /* 1 server iface + at least 1 client one */
133 s = client_and_server_ifaces[0]; /* list of client ifaces */
141 /* create vector of pointers */
142 iface_list = xzalloc(cn * sizeof(iface_list[0]));
144 iface_list[0] = client_and_server_ifaces[1]; /* server iface */
147 s = xstrdup(client_and_server_ifaces[0]); /* list of client ifaces */
148 goto store_client_iface_name;
153 store_client_iface_name:
161 /* Creates listen sockets (in fds) bound to client and server ifaces,
162 * and returns numerically max fd.
164 static int init_sockets(char **iface_list, int num_clients, int *fds)
169 for (i = 0; i < num_clients; i++) {
170 fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, iface_list[i]);
177 static int sendto_ip4(int sock, const void *msg, int msg_len, struct sockaddr_in *to)
182 err = sendto(sock, msg, msg_len, 0, (struct sockaddr*) to, sizeof(*to));
185 bb_perror_msg("sendto");
190 * pass_to_server() - forwards dhcp packets from client to server
192 * client - number of the client
194 static void pass_to_server(struct dhcp_packet *p, int packet_len, int client, int *fds,
195 struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
199 /* check packet_type */
200 type = get_dhcp_packet_type(p);
201 if (type != DHCPDISCOVER && type != DHCPREQUEST
202 && type != DHCPDECLINE && type != DHCPRELEASE
203 && type != DHCPINFORM
208 /* create new xid entry */
209 xid_add(p->xid, client_addr, client);
211 /* forward request to server */
212 /* note that we send from fds[0] which is bound to SERVER_PORT (67).
213 * IOW: we send _from_ SERVER_PORT! Although this may look strange,
214 * RFC 1542 not only allows, but prescribes this for BOOTP relays.
216 sendto_ip4(fds[0], p, packet_len, server_addr);
220 * pass_to_client() - forwards dhcp packets from server to client
223 static void pass_to_client(struct dhcp_packet *p, int packet_len, int *fds)
226 struct xid_item *item;
229 item = xid_find(p->xid);
234 /* check packet type */
235 type = get_dhcp_packet_type(p);
236 if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
240 //TODO: also do it if (p->flags & htons(BROADCAST_FLAG)) is set!
241 if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
242 item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
244 if (sendto_ip4(fds[item->client], p, packet_len, &item->ip) != 0) {
245 return; /* send error occurred */
248 /* remove xid entry */
252 int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
253 int dhcprelay_main(int argc, char **argv)
255 struct sockaddr_in server_addr;
258 int num_sockets, max_socket;
263 server_addr.sin_family = AF_INET;
264 server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
265 server_addr.sin_port = htons(SERVER_PORT);
267 /* dhcprelay CLIENT_IFACE1[,CLIENT_IFACE2...] SERVER_IFACE [SERVER_IP] */
269 if (!inet_aton(argv[3], &server_addr.sin_addr))
270 bb_perror_msg_and_die("bad server IP");
271 } else if (argc != 3) {
275 iface_list = make_iface_list(argv + 1, &num_sockets);
277 fds = xmalloc(num_sockets * sizeof(fds[0]));
279 /* Create sockets and bind one to every iface */
280 max_socket = init_sockets(iface_list, num_sockets, fds);
282 /* Get our IP on server_iface */
283 if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
288 // reinit stuff from time to time? go back to make_iface_list
295 for (i = 0; i < num_sockets; i++)
296 FD_SET(fds[i], &rfds);
297 tv.tv_sec = SELECT_TIMEOUT;
299 if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
301 struct dhcp_packet dhcp_msg;
304 if (FD_ISSET(fds[0], &rfds)) {
305 packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
307 pass_to_client(&dhcp_msg, packlen, fds);
312 for (i = 1; i < num_sockets; i++) {
313 struct sockaddr_in client_addr;
316 if (!FD_ISSET(fds[i], &rfds))
319 addr_size = sizeof(client_addr);
320 packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
321 (struct sockaddr *)(&client_addr), &addr_size);
325 /* Get our IP on corresponding client_iface */
327 // 4.1 General BOOTP Processing for Relay Agents
328 // 4.1.1 BOOTREQUEST Messages
329 // If the relay agent does decide to relay the request, it MUST examine
330 // the 'giaddr' ("gateway" IP address) field. If this field is zero,
331 // the relay agent MUST fill this field with the IP address of the
332 // interface on which the request was received. If the interface has
333 // more than one IP address logically associated with it, the relay
334 // agent SHOULD choose one IP address associated with that interface and
335 // use it consistently for all BOOTP messages it relays. If the
336 // 'giaddr' field contains some non-zero value, the 'giaddr' field MUST
337 // NOT be modified. The relay agent MUST NOT, under any circumstances,
338 // fill the 'giaddr' field with a broadcast address as is suggested in
339 // [1] (Section 8, sixth paragraph).
341 // but why? what if server can't route such IP? Client ifaces may be, say, NATed!
343 // 4.1.2 BOOTREPLY Messages
344 // BOOTP relay agents relay BOOTREPLY messages only to BOOTP clients.
345 // It is the responsibility of BOOTP servers to send BOOTREPLY messages
346 // directly to the relay agent identified in the 'giaddr' field.
347 // (yeah right, unless it is impossible... see comment above)
348 // Therefore, a relay agent may assume that all BOOTREPLY messages it
349 // receives are intended for BOOTP clients on its directly-connected
352 // When a relay agent receives a BOOTREPLY message, it should examine
353 // the BOOTP 'giaddr', 'yiaddr', 'chaddr', 'htype', and 'hlen' fields.
354 // These fields should provide adequate information for the relay agent
355 // to deliver the BOOTREPLY message to the client.
357 // The 'giaddr' field can be used to identify the logical interface from
358 // which the reply must be sent (i.e., the host or router interface
359 // connected to the same network as the BOOTP client). If the content
360 // of the 'giaddr' field does not match one of the relay agent's
361 // directly-connected logical interfaces, the BOOTREPLY messsage MUST be
362 // silently discarded.
363 if (udhcp_read_interface(iface_list[i], NULL, &dhcp_msg.gateway_nip, NULL)) {
364 /* Fall back to our IP on server iface */
365 // this makes more sense!
366 dhcp_msg.gateway_nip = our_nip;
368 // maybe dhcp_msg.hops++? drop packets with too many hops (RFC 1542 says 4 or 16)?
369 pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
375 /* return 0; - not reached */