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"

#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 dhcp_packet *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) bound to client and server ifaces,
 * and returns numerically max fd.
 */
static int init_sockets(char **client_ifaces, int num_clients,
			char *server_iface, int *fds)
{
	int i, n;

	/* talk to real server on bootps */
	fds[0] = udhcp_listen_socket(/*INADDR_ANY,*/ SERVER_PORT, server_iface);
	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_ifaces[i-1]);
		if (fds[i] > n)
			n = fds[i];
	}
	return n;
}


/**
 * pass_to_server() - forwards dhcp packets from client to server
 * p - packet to send
 * client - number of the client
 */
static void pass_to_server(struct dhcp_packet *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) */
	errno = 0;
	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
			sizeof(struct sockaddr_in));
	if (res != packet_len) {
		bb_perror_msg("sendto");
	}
}

/**
 * pass_to_client() - forwards dhcp packets from server to client
 * p - packet to send
 */
static void pass_to_client(struct dhcp_packet *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);
	errno = 0;
	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip),
			sizeof(item->ip));
	if (res != packet_len) {
		bb_perror_msg("sendto");
		return;
	}

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

int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int dhcprelay_main(int argc, char **argv)
{
	struct dhcp_packet dhcp_msg;
	struct sockaddr_in server_addr;
	struct sockaddr_in client_addr;
	fd_set rfds;
	char **client_ifaces;
	int *fds;
	int num_sockets, max_socket;
	uint32_t our_nip;

	server_addr.sin_family = AF_INET;
	server_addr.sin_port = htons(SERVER_PORT);

	/* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
	if (argc == 4) {
		if (!inet_aton(argv[3], &server_addr.sin_addr))
			bb_perror_msg_and_die("bad server IP");
	} else if (argc == 3) {
		server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
	} else {
		bb_show_usage();
	}

	/* Produce list of client ifaces */
	client_ifaces = get_client_devices(argv[1], &num_sockets);

	num_sockets++; /* for server socket at fds[0] */
	fds = xmalloc(num_sockets * sizeof(fds[0]));

	/* Create sockets and bind one to every iface */
	max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds);

	/* Get our IP on server_iface */
	if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
		return 1;

	/* Main loop */
	while (1) {
//reinit stuff from time to time? go back to get_client_devices
//every N minutes?
		struct timeval tv;
		size_t packlen;
		socklen_t addr_size;
		int i;

		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_to_client(&dhcp_msg, packlen, fds);
				}
			}
			/* clients */
			for (i = 1; i < num_sockets; i++) {
				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;

				/* Get our IP on corresponding client_iface */
//why? what if server can't route such IP?
				if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) {
					/* Fall back to our server_iface's IP */
//this makes more sense!
					dhcp_msg.gateway_nip = our_nip;
				}
//maybe set dhcp_msg.flags |= BROADCAST_FLAG too?
				pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
			}
		}
		xid_expire();
	} /* while (1) */

	/* 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	#define SERVER_PORT 67
17	#define SELECT_TIMEOUT 5 /* select timeout in sec. */
18	#define MAX_LIFETIME 260 / lifetime of an xid entry in sec. */
19
20	/* This list holds information about clients. The xid_* functions manipulate this list. */
21	struct xid_item {
22	unsigned timestamp;
23	int client;
24	uint32_t xid;
25	struct sockaddr_in ip;
26	struct xid_item *next;
27	};
28
29	#define dhcprelay_xid_list ((struct xid_item)&bb_common_bufsiz1)
30
31	static struct xid_item xid_add(uint32_t xid, struct sockaddr_in ip, int client)
32	{
33	struct xid_item *item;
34
35	/* create new xid entry */
36	item = xmalloc(sizeof(struct xid_item));
37
38	/* add xid entry */
39	item->ip = *ip;
40	item->xid = xid;
41	item->client = client;
42	item->timestamp = monotonic_sec();
43	item->next = dhcprelay_xid_list.next;
44	dhcprelay_xid_list.next = item;
45
46	return item;
47	}
48
49	static void xid_expire(void)
50	{
51	struct xid_item *item = dhcprelay_xid_list.next;
52	struct xid_item *last = &dhcprelay_xid_list;
53	unsigned current_time = monotonic_sec();
54
55	while (item != NULL) {
56	if ((current_time - item->timestamp) > MAX_LIFETIME) {
57	last->next = item->next;
58	free(item);
59	item = last->next;
60	} else {
61	last = item;
62	item = item->next;
63	}
64	}
65	}
66
67	static struct xid_item *xid_find(uint32_t xid)
68	{
69	struct xid_item *item = dhcprelay_xid_list.next;
70	while (item != NULL) {
71	if (item->xid == xid) {
72	return item;
73	}
74	item = item->next;
75	}
76	return NULL;
77	}
78
79	static void xid_del(uint32_t xid)
80	{
81	struct xid_item *item = dhcprelay_xid_list.next;
82	struct xid_item *last = &dhcprelay_xid_list;
83	while (item != NULL) {
84	if (item->xid == xid) {
85	last->next = item->next;
86	free(item);
87	item = last->next;
88	} else {
89	last = item;
90	item = item->next;
91	}
92	}
93	}
94
95	/**
96	* get_dhcp_packet_type - gets the message type of a dhcp packet
97	* p - pointer to the dhcp packet
98	* returns the message type on success, -1 otherwise
99	*/
100	static int get_dhcp_packet_type(struct dhcp_packet *p)
101	{
102	uint8_t *op;
103
104	/* it must be either a BOOTREQUEST or a BOOTREPLY */
105	if (p->op != BOOTREQUEST && p->op != BOOTREPLY)
106	return -1;
107	/* get message type option */
108	op = get_option(p, DHCP_MESSAGE_TYPE);
109	if (op != NULL)
110	return op[0];
111	return -1;
112	}
113
114	/**
115	* get_client_devices - parses the devices list
116	* dev_list - comma separated list of devices
117	* returns array
118	*/
119	static char *get_client_devices(char dev_list, int *client_number)
120	{
121	char s, *client_dev;
122	int i, cn;
123
124	/* copy list */
125	dev_list = xstrdup(dev_list);
126
127	/* get number of items, replace ',' with NULs */
128	s = dev_list;
129	cn = 1;
130	while (*s) {
131	if (*s == ',') {
132	*s = '\0';
133	cn++;
134	}
135	s++;
136	}
137	*client_number = cn;
138
139	/* create vector of pointers */
140	client_dev = xzalloc(cn * sizeof(*client_dev));
141	client_dev[0] = dev_list;
142	i = 1;
143	while (i != cn) {
144	client_dev[i] = client_dev[i - 1] + strlen(client_dev[i - 1]) + 1;
145	i++;
146	}
147	return client_dev;
148	}
149
150
151	/* Creates listen sockets (in fds) bound to client and server ifaces,
152	* and returns numerically max fd.
153	*/
154	static int init_sockets(char **client_ifaces, int num_clients,
155	char server_iface, int fds)
156	{
157	int i, n;
158
159	/* talk to real server on bootps */
160	fds[0] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, server_iface);
161	n = fds[0];
162
163	for (i = 1; i < num_clients; i++) {
164	/* listen for clients on bootps */
165	fds[i] = udhcp_listen_socket(/INADDR_ANY,/ SERVER_PORT, client_ifaces[i-1]);
166	if (fds[i] > n)
167	n = fds[i];
168	}
169	return n;
170	}
171
172
173	/**
174	* pass_to_server() - forwards dhcp packets from client to server
175	* p - packet to send
176	* client - number of the client
177	*/
178	static void pass_to_server(struct dhcp_packet p, int packet_len, int client, int fds,
179	struct sockaddr_in client_addr, struct sockaddr_in server_addr)
180	{
181	int res, type;
182	struct xid_item *item;
183
184	/* check packet_type */
185	type = get_dhcp_packet_type(p);
186	if (type != DHCPDISCOVER && type != DHCPREQUEST
187	&& type != DHCPDECLINE && type != DHCPRELEASE
188	&& type != DHCPINFORM
189	) {
190	return;
191	}
192
193	/* create new xid entry */
194	item = xid_add(p->xid, client_addr, client);
195
196	/* forward request to LAN (server) */
197	errno = 0;
198	res = sendto(fds[0], p, packet_len, 0, (struct sockaddr*)server_addr,
199	sizeof(struct sockaddr_in));
200	if (res != packet_len) {
201	bb_perror_msg("sendto");
202	}
203	}
204
205	/**
206	* pass_to_client() - forwards dhcp packets from server to client
207	* p - packet to send
208	*/
209	static void pass_to_client(struct dhcp_packet p, int packet_len, int fds)
210	{
211	int res, type;
212	struct xid_item *item;
213
214	/* check xid */
215	item = xid_find(p->xid);
216	if (!item) {
217	return;
218	}
219
220	/* check packet type */
221	type = get_dhcp_packet_type(p);
222	if (type != DHCPOFFER && type != DHCPACK && type != DHCPNAK) {
223	return;
224	}
225
226	if (item->ip.sin_addr.s_addr == htonl(INADDR_ANY))
227	item->ip.sin_addr.s_addr = htonl(INADDR_BROADCAST);
228	errno = 0;
229	res = sendto(fds[item->client], p, packet_len, 0, (struct sockaddr*) &(item->ip),
230	sizeof(item->ip));
231	if (res != packet_len) {
232	bb_perror_msg("sendto");
233	return;
234	}
235
236	/* remove xid entry */
237	xid_del(p->xid);
238	}
239
240	int dhcprelay_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
241	int dhcprelay_main(int argc, char **argv)
242	{
243	struct dhcp_packet dhcp_msg;
244	struct sockaddr_in server_addr;
245	struct sockaddr_in client_addr;
246	fd_set rfds;
247	char **client_ifaces;
248	int *fds;
249	int num_sockets, max_socket;
250	uint32_t our_nip;
251
252	server_addr.sin_family = AF_INET;
253	server_addr.sin_port = htons(SERVER_PORT);
254
255	/* dhcprelay client_iface1,client_iface2,... server_iface [server_IP] */
256	if (argc == 4) {
257	if (!inet_aton(argv[3], &server_addr.sin_addr))
258	bb_perror_msg_and_die("bad server IP");
259	} else if (argc == 3) {
260	server_addr.sin_addr.s_addr = htonl(INADDR_BROADCAST);
261	} else {
262	bb_show_usage();
263	}
264
265	/* Produce list of client ifaces */
266	client_ifaces = get_client_devices(argv[1], &num_sockets);
267
268	num_sockets++; /* for server socket at fds[0] */
269	fds = xmalloc(num_sockets * sizeof(fds[0]));
270
271	/* Create sockets and bind one to every iface */
272	max_socket = init_sockets(client_ifaces, num_sockets, argv[2], fds);
273
274	/* Get our IP on server_iface */
275	if (udhcp_read_interface(argv[2], NULL, &our_nip, NULL))
276	return 1;
277
278	/* Main loop */
279	while (1) {
280	//reinit stuff from time to time? go back to get_client_devices
281	//every N minutes?
282	struct timeval tv;
283	size_t packlen;
284	socklen_t addr_size;
285	int i;
286
287	FD_ZERO(&rfds);
288	for (i = 0; i < num_sockets; i++)
289	FD_SET(fds[i], &rfds);
290	tv.tv_sec = SELECT_TIMEOUT;
291	tv.tv_usec = 0;
292	if (select(max_socket + 1, &rfds, NULL, NULL, &tv) > 0) {
293	/* server */
294	if (FD_ISSET(fds[0], &rfds)) {
295	packlen = udhcp_recv_kernel_packet(&dhcp_msg, fds[0]);
296	if (packlen > 0) {
297	pass_to_client(&dhcp_msg, packlen, fds);
298	}
299	}
300	/* clients */
301	for (i = 1; i < num_sockets; i++) {
302	if (!FD_ISSET(fds[i], &rfds))
303	continue;
304	addr_size = sizeof(struct sockaddr_in);
305	packlen = recvfrom(fds[i], &dhcp_msg, sizeof(dhcp_msg), 0,
306	(struct sockaddr *)(&client_addr), &addr_size);
307	if (packlen <= 0)
308	continue;
309
310	/* Get our IP on corresponding client_iface */
311	//why? what if server can't route such IP?
312	if (udhcp_read_interface(client_ifaces[i-1], NULL, &dhcp_msg.gateway_nip, NULL)) {
313	/* Fall back to our server_iface's IP */
314	//this makes more sense!
315	dhcp_msg.gateway_nip = our_nip;
316	}
317	//maybe set dhcp_msg.flags \|= BROADCAST_FLAG too?
318	pass_to_server(&dhcp_msg, packlen, i, fds, &client_addr, &server_addr);
319	}
320	}
321	xid_expire();
322	} /* while (1) */
323
324	/* return 0; - not reached */
325	}