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