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 "options.h"

/* constants */
#define SERVER_PORT      67
#define SELECT_TIMEOUT    5 /* select timeout in sec. */
#define MAX_LIFETIME   2*60 /* lifetime of an xid entry in sec. */

/* This list holds information about clients. The xid_* functions manipulate this list. */
struct xid_item {
	unsigned timestamp;
	int client;
	uint32_t xid;
	struct sockaddr_in ip;
	struct xid_item *next;
};

#define dhcprelay_xid_list (*(struct xid_item*)&bb_common_bufsiz1)

static struct xid_item *xid_add(uint32_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 = monotonic_sec();
	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;
	unsigned current_time = monotonic_sec();

	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(uint32_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(uint32_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;
}

/**
 * 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, **client_dev;
	int i, cn;

	/* copy list */
	dev_list = xstrdup(dev_list);

	/* get number of items, replace ',' with NULs */
	s = dev_list;
	cn = 1;
	while (*s) {
		if (*s == ',') {
			*s = '\0';
			cn++;
		}
		s++;
	}
	*client_number = cn;

	/* create vector of pointers */
	client_dev = xzalloc(cn * sizeof(*client_dev));
	client_dev[0] = dev_list;
	i = 1;
	while (i != cn) {
		client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
		i++;
	}
	return client_dev;
}


/* Creates listen sockets (in fds) and returns numerically max fd. */
static int init_sockets(char **client, int num_clients,
			char *server, int *fds)
{
	int i, n;

	/* talk to real server on bootps */
	fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server);
	n = fds[0];

	for (i = 1; i < num_clients; i++) {
		/* listen for clients on bootps */
		fds[i] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, client[i-1]);
		if (fds[i] > n)
			n = fds[i];
	}
	return n;
}


/**
 * 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);
	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) NORETURN;
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 (1) {
		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_recv_kernel_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 (udhcp_read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL))
					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) MAIN_EXTERNALLY_VISIBLE;
int dhcprelay_main(int argc, char **argv)
{
	int num_sockets, max_socket;
	int *fds;
	uint32_t gw_ip;
	char **clients;
	struct sockaddr_in server_addr;

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(SERVER_PORT);
	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);
	num_sockets++; /* for server socket at fds[0] */
	fds = xmalloc(num_sockets * sizeof(fds[0]));
	max_socket = init_sockets(clients, num_sockets, argv[2], fds);

	if (udhcp_read_interface(argv[2], NULL, &gw_ip, NULL))
		return 1;

	/* doesn't return */
	dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
	/* return 0; - not reached */
}
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 "options.h"
15
16	/* constants */
17	#define SERVER_PORT 67
18	#define SELECT_TIMEOUT 5 /* select timeout in sec. */
19	#define MAX_LIFETIME 260 / lifetime of an xid entry in sec. */
20
21	/* This list holds information about clients. The xid_* functions manipulate this list. */
22	struct xid_item {
23	unsigned timestamp;
24	int client;
25	uint32_t xid;
26	struct sockaddr_in ip;
27	struct xid_item *next;
28	};
29
30	#define dhcprelay_xid_list ((struct xid_item)&bb_common_bufsiz1)
31
32	static struct xid_item xid_add(uint32_t xid, struct sockaddr_in ip, int client)
33	{
34	struct xid_item *item;
35
36	/* create new xid entry */
37	item = xmalloc(sizeof(struct xid_item));
38
39	/* add xid entry */
40	item->ip = *ip;
41	item->xid = xid;
42	item->client = client;
43	item->timestamp = monotonic_sec();
44	item->next = dhcprelay_xid_list.next;
45	dhcprelay_xid_list.next = item;
46
47	return item;
48	}
49
50	static void xid_expire(void)
51	{
52	struct xid_item *item = dhcprelay_xid_list.next;
53	struct xid_item *last = &dhcprelay_xid_list;
54	unsigned current_time = monotonic_sec();
55
56	while (item != NULL) {
57	if ((current_time - item->timestamp) > MAX_LIFETIME) {
58	last->next = item->next;
59	free(item);
60	item = last->next;
61	} else {
62	last = item;
63	item = item->next;
64	}
65	}
66	}
67
68	static struct xid_item *xid_find(uint32_t xid)
69	{
70	struct xid_item *item = dhcprelay_xid_list.next;
71	while (item != NULL) {
72	if (item->xid == xid) {
73	return item;
74	}
75	item = item->next;
76	}
77	return NULL;
78	}
79
80	static void xid_del(uint32_t xid)
81	{
82	struct xid_item *item = dhcprelay_xid_list.next;
83	struct xid_item *last = &dhcprelay_xid_list;
84	while (item != NULL) {
85	if (item->xid == xid) {
86	last->next = item->next;
87	free(item);
88	item = last->next;
89	} else {
90	last = item;
91	item = item->next;
92	}
93	}
94	}
95
96	/**
97	* get_dhcp_packet_type - gets the message type of a dhcp packet
98	* p - pointer to the dhcp packet
99	* returns the message type on success, -1 otherwise
100	*/
101	static int get_dhcp_packet_type(struct dhcpMessage *p)
102	{
103	uint8_t *op;
104
105	/* it must be either a BOOTREQUEST or a BOOTREPLY */
106	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
107	return -1;
108	/* get message type option */
109	op = get_option(p, DHCP_MESSAGE_TYPE);
110	if (op != NULL)
111	return op[0];
112	return -1;
113	}
114
115	/**
116	* get_client_devices - parses the devices list
117	* dev_list - comma separated list of devices
118	* returns array
119	*/
120	static char *get_client_devices(char dev_list, int *client_number)
121	{
122	char s, *client_dev;
123	int i, cn;
124
125	/* copy list */
126	dev_list = xstrdup(dev_list);
127
128	/* get number of items, replace ',' with NULs */
129	s = dev_list;
130	cn = 1;
131	while (*s) {
132	if (*s == ',') {
133	*s = '\0';
134	cn++;
135	}
136	s++;
137	}
138	*client_number = cn;
139
140	/* create vector of pointers */
141	client_dev = xzalloc(cn * sizeof(*client_dev));
142	client_dev[0] = dev_list;
143	i = 1;
144	while (i != cn) {
145	client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
146	i++;
147	}
148	return client_dev;
149	}
150
151
152	/* Creates listen sockets (in fds) and returns numerically max fd. */
153	static int init_sockets(char **client, int num_clients,
154	char server, int fds)
155	{
156	int i, n;
157
158	/* talk to real server on bootps */
159	fds[0] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, server);
160	n = fds[0];
161
162	for (i = 1; i < num_clients; i++) {
163	/* listen for clients on bootps */
164	fds[i] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, client[i-1]);
165	if (fds[i] > n)
166	n = fds[i];
167	}
168	return n;
169	}
170
171
172	/**
173	* pass_on() - forwards dhcp packets from client to server
174	* p - packet to send
175	* client - number of the client
176	*/
177	static void pass_on(struct dhcpMessage p, int packet_len, int client, int fds,
178	struct sockaddr_in client_addr, struct sockaddr_in server_addr)
179	{
180	int res, type;
181	struct xid_item *item;
182
183	/* check packet_type */
184	type = get_dhcp_packet_type(p);
185	if (type != DHCPDISCOVER && type != DHCPREQUEST
186	&& type != DHCPDECLINE && type != DHCPRELEASE
187	&& type != DHCPINFORM
188	) {
189	return;
190	}
191
192	/* create new xid entry */
193	item = xid_add(p->xid, client_addr, client);
194
195	/* forward request to LAN (server) */
196	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
197	sizeof(struct sockaddr_in));
198	if (res != packet_len) {
199	bb_perror_msg("pass_on");
200	return;
201	}
202	}
203
204	/**
205	* pass_back() - forwards dhcp packets from server to client
206	* p - packet to send
207	*/
208	static void pass_back(struct dhcpMessage p, int packet_len, int fds)
209	{
210	int res, type;
211	struct xid_item *item;
212
213	/* check xid */
214	item = xid_find(p->xid);
215	if (!item) {
216	return;
217	}
218
219	/* check packet type */
220	type = get_dhcp_packet_type(p);
221	if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
222	return;
223	}
224
225	if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
226	item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
227	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*)(&item->ip),
228	sizeof(item->ip));
229	if (res != packet_len) {
230	bb_perror_msg("pass_back");
231	return;
232	}
233
234	/* remove xid entry */
235	xid_del(p->xid);
236	}
237
238	static void dhcprelay_loop(int fds, int num_sockets, int max_socket, char *clients,
239	struct sockaddr_in *server_addr, uint32_t gw_ip) NORETURN;
240	static void dhcprelay_loop(int fds, int num_sockets, int max_socket, char *clients,
241	struct sockaddr_in *server_addr, uint32_t gw_ip)
242	{
243	struct dhcpMessage dhcp_msg;
244	fd_set rfds;
245	size_t packlen;
246	socklen_t addr_size;
247	struct sockaddr_in client_addr;
248	struct timeval tv;
249	int i;
250
251	while (1) {
252	FD_ZERO(&rfds);
253	for (i = 0; i < num_sockets; i++)
254	FD_SET(fds[i], &rfds);
255	tv.tv_sec = SELECT_TIMEOUT;
256	tv.tv_usec = 0;
257	if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
258	/* server */
259	if (FD_ISSET(fds[0], &rfds)) {
260	packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
261	if (packlen > 0) {
262	pass_back(&dhcp_msg, packlen, fds);
263	}
264	}
265	for (i = 1; i < num_sockets; i++) {
266	/* clients */
267	if (!FD_ISSET(fds[i], &rfds))
268	continue;
269	addr_size = sizeof(struct sockaddr_in);
270	packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
271	(struct sockaddr *)(&client_addr), &addr_size);
272	if (packlen <= 0)
273	continue;
274	if (udhcp_read_interface(clients[i-1], NULL, &dhcp_msg.giaddr, NULL))
275	dhcp_msg.giaddr = gw_ip;
276	pass_on(&dhcp_msg, packlen, i, fds, &client_addr, server_addr);
277	}
278	}
279	xid_expire();
280	}
281	}
282
283	int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
284	int dhcprelay_main(int argc, char **argv)
285	{
286	int num_sockets, max_socket;
287	int *fds;
288	uint32_t gw_ip;
289	char **clients;
290	struct sockaddr_in server_addr;
291
292	server_addr.sin_family = AF_INET;
293	server_addr.sin_port = htons(SERVER_PORT);
294	if (argc == 4) {
295	if (!inet_aton(argv[3], &server_addr.sin_addr))
296	bb_perror_msg_and_die("didn't grok server");
297	} else if (argc == 3) {
298	server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
299	} else {
300	bb_show_usage();
301	}
302
303	clients = get_client_devices(argv[1], &num_sockets);
304	num_sockets++; /* for server socket at fds[0] */
305	fds = xmalloc(num_sockets * sizeof(fds[0]));
306	max_socket = init_sockets(clients, num_sockets, argv[2], fds);
307
308	if (udhcp_read_interface(argv[2], NULL, &gw_ip, NULL))
309	return 1;
310
311	/* doesn't return */
312	dhcprelay_loop(fds, num_sockets, max_socket, clients, &server_addr, gw_ip);
313	/* return 0; - not reached */
314	}