networking/udhcp/dhcprelay.c

/* vi: set sw=4 ts=4: */
/* Port to Busybox Copyright (C) 2006 Jesse Dutton <jessedutton@gmail.com>
 *
 * Licensed under GPL v2, see file LICENSE in this tarball for details.
 *
 * DHCP Relay for 'DHCPv4 Configuration of IPSec Tunnel Mode' support
 * Copyright (C) 2002 Mario Strasser <mast@gmx.net>,
 *                   Zuercher Hochschule Winterthur,
 *                   Netbeat AG
 * Upstream has GPL v2 or later
 */

#include "common.h"
#include "dhcpd.h"
#include "options.h"

/* constants */
#define SELECT_TIMEOUT 5 /* select timeout in sec. */
#define MAX_LIFETIME 2*60 /* lifetime of an xid entry in sec. */
#define MAX_INTERFACES 9


/* This list holds information about clients. The xid_* functions manipulate this list. */
static struct xid_item {
	u_int32_t xid;
	struct sockaddr_in ip;
	int client;
	time_t timestamp;
	struct xid_item *next;
} dhcprelay_xid_list = {0, {0}, 0, 0, NULL};


static struct xid_item * xid_add(u_int32_t xid, struct sockaddr_in *ip, int client)
{
	struct xid_item *item;

	/* create new xid entry */
	item = xmalloc(sizeof(struct xid_item));

	/* add xid entry */
	item->ip = *ip;
	item->xid = xid;
	item->client = client;
	item->timestamp = time(NULL);
	item->next = dhcprelay_xid_list.next;
	dhcprelay_xid_list.next = item;

	return item;
}


static void xid_expire(void)
{
	struct xid_item *item = dhcprelay_xid_list.next;
	struct xid_item *last = &dhcprelay_xid_list;
	time_t current_time = time(NULL);

	while (item != NULL) {
		if ((current_time-item->timestamp) > MAX_LIFETIME) {
			last->next = item->next;
			free(item);
			item = last->next;
		} else {
			last = item;
			item = item->next;
		}
	}
}

static struct xid_item * xid_find(u_int32_t xid)
{
	struct xid_item *item = dhcprelay_xid_list.next;
	while (item != NULL) {
		if (item->xid == xid) {
			return item;
		}
		item = item->next;
	}
	return NULL;
}

static void xid_del(u_int32_t xid)
{
	struct xid_item *item = dhcprelay_xid_list.next;
	struct xid_item *last = &dhcprelay_xid_list;
	while (item != NULL) {
		if (item->xid == xid) {
			last->next = item->next;
			free(item);
			item = last->next;
		} else {
			last = item;
			item = item->next;
		}
	}
}


/**
 * get_dhcp_packet_type - gets the message type of a dhcp packet
 * p - pointer to the dhcp packet
 * returns the message type on success, -1 otherwise
 */
static int get_dhcp_packet_type(struct dhcpMessage *p)
{
	uint8_t *op;

	/* it must be either a BOOTREQUEST or a BOOTREPLY */
	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
		return -1;
	/* get message type option */
	op = get_option(p, DHCP_MESSAGE_TYPE);
	if (op != NULL)
		return op[0];
	return -1;
}

/**
 * signal_handler - handles signals ;-)
 * sig - sent signal
 */
static int dhcprelay_stopflag;
static void dhcprelay_signal_handler(int sig)
{
	dhcprelay_stopflag = 1;
}

/**
 * get_client_devices - parses the devices list
 * dev_list - comma separated list of devices
 * returns array
 */
static char ** get_client_devices(char *dev_list, int *client_number)
{
	char *s, *list, **client_dev;
	int i, cn;

	/* copy list */
	list = xstrdup(dev_list);
	if (list == NULL) return NULL;

	/* get number of items */
	for (s = dev_list, cn = 1; *s; s++)
		if (*s == ',')
			cn++;

	client_dev = xzalloc(cn * sizeof(*client_dev));

	/* parse list */
	s = strtok(list, ",");
	i = 0;
	while (s != NULL) {
		client_dev[i++] = xstrdup(s);
		s = strtok(NULL, ",");
	}

	/* free copy and exit */
	free(list);
	*client_number = cn;
	return client_dev;
}


/* Creates listen sockets (in fds) and returns the number allocated. */
static int init_sockets(char **client, int num_clients,
			char *server, int *fds, int *max_socket)
{
	int i;

	/* talk to real server on bootps */
	fds[0] = listen_socket(htonl(INADDR_ANY), 67, server);
	*max_socket = fds[0];

	/* array starts at 1 since server is 0 */
	num_clients++;

	for (i=1; i < num_clients; i++) {
		/* listen for clients on bootps */
		fds[i] = listen_socket(htonl(INADDR_ANY), 67, client[i-1]);
		if (fds[i] > *max_socket) *max_socket = fds[i];
	}

	return i;
}


/**
 * pass_on() - forwards dhcp packets from client to server
 * p - packet to send
 * client - number of the client
 */
static void pass_on(struct dhcpMessage *p, int packet_len, int client, int *fds,
			struct sockaddr_in *client_addr, struct sockaddr_in *server_addr)
{
	int res, type;
	struct xid_item *item;

	/* check packet_type */
	type = get_dhcp_packet_type(p);
	if (type != DHCPDISCOVER && type != DHCPREQUEST
	 && type != DHCPDECLINE && type != DHCPRELEASE
	 && type != DHCPINFORM
	) {
		return;
	}

	/* create new xid entry */
	item = xid_add(p->xid, client_addr, client);

	/* forward request to LAN (server) */
	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
			sizeof(struct sockaddr_in));
	if (res != packet_len) {
		bb_perror_msg("pass_on");
		return;
	}
}

/**
 * pass_back() - forwards dhcp packets from server to client
 * p - packet to send
 */
static void pass_back(struct dhcpMessage *p, int packet_len, int *fds)
{
	int res, type;
	struct xid_item *item;

	/* check xid */
	item = xid_find(p->xid);
	if (!item) {
		return;
	}

	/* check packet type */
	type = get_dhcp_packet_type(p);
	if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
		return;
	}

	if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
		item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	if (item->client > MAX_INTERFACES)
		return;
	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip),
				sizeof(item->ip));
	if (res != packet_len) {
		bb_perror_msg("pass_back");
		return;
	}

	/* remove xid entry */
	xid_del(p->xid);
}

static void dhcprelay_loop(int *fds, int num_sockets, int max_socket, char **clients,
		struct sockaddr_in *server_addr, uint32_t gw_ip)
{
	struct dhcpMessage dhcp_msg;
	fd_set rfds;
	size_t packlen;
	socklen_t addr_size;
	struct sockaddr_in client_addr;
	struct timeval tv;
	int i;

	while (!dhcprelay_stopflag) {
		FD_ZERO(&rfds);
		for (i = 0; i < num_sockets; i++)
			FD_SET(fds[i], &rfds);
		tv.tv_sec = SELECT_TIMEOUT;
		tv.tv_usec = 0;
		if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
			/* server */
			if (FD_ISSET(fds[0], &rfds)) {
				packlen = udhcp_get_packet(&dhcp_msg, fds[0]);
				if (packlen > 0) {
					pass_back(&dhcp_msg, packlen, fds);
				}
			}
			for (i = 1; i < num_sockets; i++) {
				/* clients */
				if (!FD_ISSET(fds[i], &rfds))
					continue;
				addr_size = sizeof(struct sockaddr_in);
				packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
							(struct sockaddr *)(&client_addr), &addr_size);
				if (packlen <= 0)
					continue;
				if (read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL) < 0)
					dhcp_msg.giaddr = gw_ip;
				pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr);
			}
		}
		xid_expire();
	}
}

int dhcprelay_main(int argc, char **argv)
{
	int i, num_sockets, max_socket, fds[MAX_INTERFACES];
	uint32_t gw_ip;
	char **clients;
	struct sockaddr_in server_addr;

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(67);
	if (argc == 4) {
		if (!inet_aton(argv[3], &server_addr.sin_addr))
			bb_perror_msg_and_die("didn't grok server");
	} else if (argc == 3) {
		server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	} else {
		bb_show_usage();
	}
	clients = get_client_devices(argv[1], &num_sockets);
	if (!clients) return 0;

	signal(SIGTERM, dhcprelay_signal_handler);
	signal(SIGQUIT, dhcprelay_signal_handler);
	signal(SIGINT, dhcprelay_signal_handler);

	num_sockets = init_sockets(clients, num_sockets, argv[2], fds, &max_socket);

	if (read_interface(argv[2], NULL, &gw_ip, NULL) == -1)
		return 1;

	dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);

	if (ENABLE_FEATURE_CLEAN_UP) {
		for (i = 0; i < num_sockets; i++) {
			close(fds[i]);
			free(clients[i]);
		}
	}

	return 0;
}
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 260 / 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. */
24	static struct xid_item {
25	u_int32_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
33	static struct xid_item * xid_add(u_int32_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
51
52	static void xid_expire(void)
53	{
54	struct xid_item *item = dhcprelay_xid_list.next;
55	struct xid_item *last = &dhcprelay_xid_list;
56	time_t current_time = time(NULL);
57
58	while (item != NULL) {
59	if ((current_time-item->timestamp) > MAX_LIFETIME) {
60	last->next = item->next;
61	free(item);
62	item = last->next;
63	} else {
64	last = item;
65	item = item->next;
66	}
67	}
68	}
69
70	static struct xid_item * xid_find(u_int32_t xid)
71	{
72	struct xid_item *item = dhcprelay_xid_list.next;
73	while (item != NULL) {
74	if (item->xid == xid) {
75	return item;
76	}
77	item = item->next;
78	}
79	return NULL;
80	}
81
82	static void xid_del(u_int32_t xid)
83	{
84	struct xid_item *item = dhcprelay_xid_list.next;
85	struct xid_item *last = &dhcprelay_xid_list;
86	while (item != NULL) {
87	if (item->xid == xid) {
88	last->next = item->next;
89	free(item);
90	item = last->next;
91	} else {
92	last = item;
93	item = item->next;
94	}
95	}
96	}
97
98
99	/**
100	* get_dhcp_packet_type - gets the message type of a dhcp packet
101	* p - pointer to the dhcp packet
102	* returns the message type on success, -1 otherwise
103	*/
104	static int get_dhcp_packet_type(struct dhcpMessage *p)
105	{
106	uint8_t *op;
107
108	/* it must be either a BOOTREQUEST or a BOOTREPLY */
109	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
110	return -1;
111	/* get message type option */
112	op = get_option(p, DHCP_MESSAGE_TYPE);
113	if (op != NULL)
114	return op[0];
115	return -1;
116	}
117
118	/**
119	* signal_handler - handles signals ;-)
120	* sig - sent signal
121	*/
122	static int dhcprelay_stopflag;
123	static void dhcprelay_signal_handler(int sig)
124	{
125	dhcprelay_stopflag = 1;
126	}
127
128	/**
129	* get_client_devices - parses the devices list
130	* dev_list - comma separated list of devices
131	* returns array
132	*/
133	static char ** get_client_devices(char dev_list, int client_number)
134	{
135	char s, list, **client_dev;
136	int i, cn;
137
138	/* copy list */
139	list = xstrdup(dev_list);
140	if (list == NULL) return NULL;
141
142	/* get number of items */
143	for (s = dev_list, cn = 1; *s; s++)
144	if (*s == ',')
145	cn++;
146
147	client_dev = xzalloc(cn * sizeof(*client_dev));
148
149	/* parse list */
150	s = strtok(list, ",");
151	i = 0;
152	while (s != NULL) {
153	client_dev[i++] = xstrdup(s);
154	s = strtok(NULL, ",");
155	}
156
157	/* free copy and exit */
158	free(list);
159	*client_number = cn;
160	return client_dev;
161	}
162
163
164	/* Creates listen sockets (in fds) and returns the number allocated. */
165	static int init_sockets(char **client, int num_clients,
166	char server, int fds, int *max_socket)
167	{
168	int i;
169
170	/* talk to real server on bootps */
171	fds[0] = listen_socket(htonl(INADDR_ANY), 67, server);
172	*max_socket = fds[0];
173
174	/* array starts at 1 since server is 0 */
175	num_clients++;
176
177	for (i=1; i < num_clients; i++) {
178	/* listen for clients on bootps */
179	fds[i] = listen_socket(htonl(INADDR_ANY), 67, client[i-1]);
180	if (fds[i] > max_socket) 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	*/
192	static 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	*/
223	static 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
255	static 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) < 0)
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
298	int dhcprelay_main(int argc, char **argv)
299	{
300	int i, num_sockets, max_socket, fds[MAX_INTERFACES];
301	uint32_t gw_ip;
302	char **clients;
303	struct sockaddr_in server_addr;
304
305	server_addr.sin_family = AF_INET;
306	server_addr.sin_port = htons(67);
307	if (argc == 4) {
308	if (!inet_aton(argv[3], &server_addr.sin_addr))
309	bb_perror_msg_and_die("didn't grok server");
310	} else if (argc == 3) {
311	server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
312	} else {
313	bb_show_usage();
314	}
315	clients = get_client_devices(argv[1], &num_sockets);
316	if (!clients) return 0;
317
318	signal(SIGTERM, dhcprelay_signal_handler);
319	signal(SIGQUIT, dhcprelay_signal_handler);
320	signal(SIGINT, dhcprelay_signal_handler);
321
322	num_sockets = init_sockets(clients, num_sockets, argv[2], fds, &max_socket);
323
324	if (read_interface(argv[2], NULL, &gw_ip, NULL) == -1)
325	return 1;
326
327	dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
328
329	if (ENABLE_FEATURE_CLEAN_UP) {
330	for (i = 0; i < num_sockets; i++) {
331	close(fds[i]);
332	free(clients[i]);
333	}
334	}
335
336	return 0;
337	}