networking/udhcp/serverpacket.c

/* vi: set sw=4 ts=4: */
/* serverpacket.c
 *
 * Construct and send DHCP server packets
 *
 * Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

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


/* send a packet to gateway_nip using the kernel ip stack */
static int send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
{
	log1("Forwarding packet to relay");

	return udhcp_send_kernel_packet(dhcp_pkt,
			server_config.server_nip, SERVER_PORT,
			dhcp_pkt->gateway_nip, SERVER_PORT);
}


/* send a packet to a specific mac address and ip address by creating our own ip packet */
static int send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
{
	const uint8_t *chaddr;
	uint32_t ciaddr;

	// Was:
	//if (force_broadcast) { /* broadcast */ }
	//else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
	//else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
	//else { /* unicast to dhcp_pkt->yiaddr */ }
	// But this is wrong: yiaddr is _our_ idea what client's IP is
	// (for example, from lease file). Client may not know that,
	// and may not have UDP socket listening on that IP!
	// We should never unicast to dhcp_pkt->yiaddr!
	// dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
	// and can be used.

	if (force_broadcast
	 || (dhcp_pkt->flags & htons(BROADCAST_FLAG))
	 || !dhcp_pkt->ciaddr
	) {
		log1("Broadcasting packet to client");
		ciaddr = INADDR_BROADCAST;
		chaddr = MAC_BCAST_ADDR;
	} else {
		log1("Unicasting packet to client ciaddr");
		ciaddr = dhcp_pkt->ciaddr;
		chaddr = dhcp_pkt->chaddr;
	}

	return udhcp_send_raw_packet(dhcp_pkt,
		/*src*/ server_config.server_nip, SERVER_PORT,
		/*dst*/ ciaddr, CLIENT_PORT, chaddr,
		server_config.ifindex);
}


/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
static int send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
{
	if (dhcp_pkt->gateway_nip)
		return send_packet_to_relay(dhcp_pkt);
	return send_packet_to_client(dhcp_pkt, force_broadcast);
}


static void init_packet(struct dhcp_packet *packet, struct dhcp_packet *oldpacket, char type)
{
	udhcp_init_header(packet, type);
	packet->xid = oldpacket->xid;
	memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
	packet->flags = oldpacket->flags;
	packet->gateway_nip = oldpacket->gateway_nip;
	packet->ciaddr = oldpacket->ciaddr;
	add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server_nip);
}


/* add in the bootp options */
static void add_bootp_options(struct dhcp_packet *packet)
{
	packet->siaddr_nip = server_config.siaddr_nip;
	if (server_config.sname)
		strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
	if (server_config.boot_file)
		strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
}


static uint32_t select_lease_time(struct dhcp_packet *packet)
{
	uint32_t lease_time_sec = server_config.max_lease_sec;
	uint8_t *lease_time_opt = get_option(packet, DHCP_LEASE_TIME);
	if (lease_time_opt) {
		move_from_unaligned32(lease_time_sec, lease_time_opt);
		lease_time_sec = ntohl(lease_time_sec);
		if (lease_time_sec > server_config.max_lease_sec)
			lease_time_sec = server_config.max_lease_sec;
		if (lease_time_sec < server_config.min_lease_sec)
			lease_time_sec = server_config.min_lease_sec;
	}
	return lease_time_sec;
}


/* send a DHCP OFFER to a DHCP DISCOVER */
int FAST_FUNC send_offer(struct dhcp_packet *oldpacket)
{
	struct dhcp_packet packet;
	uint32_t req_nip;
	uint32_t lease_time_sec = server_config.max_lease_sec;
	uint32_t static_lease_ip;
	uint8_t *req_ip_opt;
	const char *p_host_name;
	struct option_set *curr;
	struct in_addr addr;

	init_packet(&packet, oldpacket, DHCPOFFER);

	static_lease_ip = get_static_nip_by_mac(server_config.static_leases, oldpacket->chaddr);

	/* ADDME: if static, short circuit */
	if (!static_lease_ip) {
		struct dyn_lease *lease;

		lease = find_lease_by_mac(oldpacket->chaddr);
		/* The client is in our lease/offered table */
		if (lease) {
			signed_leasetime_t tmp = lease->expires - time(NULL);
			if (tmp >= 0)
				lease_time_sec = tmp;
			packet.yiaddr = lease->lease_nip;
		}
		/* Or the client has requested an IP */
		else if ((req_ip_opt = get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
		 /* (read IP) */
		 && (move_from_unaligned32(req_nip, req_ip_opt), 1)
		 /* and the IP is in the lease range */
		 && ntohl(req_nip) >= server_config.start_ip
		 && ntohl(req_nip) <= server_config.end_ip
		 /* and is not already taken/offered */
		 && (!(lease = find_lease_by_nip(req_nip))
			/* or its taken, but expired */
			|| is_expired_lease(lease))
		) {
			packet.yiaddr = req_nip;
		}
		/* Otherwise, find a free IP */
		else {
			packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
		}

		if (!packet.yiaddr) {
			bb_error_msg("no IP addresses to give - OFFER abandoned");
			return -1;
		}
		p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
		if (add_lease(packet.chaddr, packet.yiaddr,
				server_config.offer_time,
				p_host_name,
				p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
			) == 0
		) {
			bb_error_msg("lease pool is full - OFFER abandoned");
			return -1;
		}
		lease_time_sec = select_lease_time(oldpacket);
	} else {
		/* It is a static lease... use it */
		packet.yiaddr = static_lease_ip;
	}

	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	addr.s_addr = packet.yiaddr;
	bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
	return send_packet(&packet, 0);
}


int FAST_FUNC send_NAK(struct dhcp_packet *oldpacket)
{
	struct dhcp_packet packet;

	init_packet(&packet, oldpacket, DHCPNAK);

	log1("Sending NAK");
	return send_packet(&packet, 1);
}


int FAST_FUNC send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
{
	struct dhcp_packet packet;
	struct option_set *curr;
	uint32_t lease_time_sec;
	struct in_addr addr;
	const char *p_host_name;

	init_packet(&packet, oldpacket, DHCPACK);
	packet.yiaddr = yiaddr;

	lease_time_sec = select_lease_time(oldpacket);

	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	addr.s_addr = packet.yiaddr;
	bb_info_msg("Sending ACK to %s", inet_ntoa(addr));

	if (send_packet(&packet, 0) < 0)
		return -1;

	p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
	add_lease(packet.chaddr, packet.yiaddr,
		lease_time_sec,
		p_host_name,
		p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
	);
	if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
		/* rewrite the file with leases at every new acceptance */
		write_leases();
	}

	return 0;
}


int FAST_FUNC send_inform(struct dhcp_packet *oldpacket)
{
	struct dhcp_packet packet;
	struct option_set *curr;

	init_packet(&packet, oldpacket, DHCPACK);

	curr = server_config.options;
	while (curr) {
		if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
			add_option_string(packet.options, curr->data);
		curr = curr->next;
	}

	add_bootp_options(&packet);

	return send_packet(&packet, 0);
}
1	niro	532	/* vi: set sw=4 ts=4: */
2			/* serverpacket.c
3			*
4			* Construct and send DHCP server packets
5			*
6			* Russ Dill <Russ.Dill@asu.edu> July 2001
7			*
8			* This program is free software; you can redistribute it and/or modify
9			* it under the terms of the GNU General Public License as published by
10			* the Free Software Foundation; either version 2 of the License, or
11			* (at your option) any later version.
12			*
13			* This program is distributed in the hope that it will be useful,
14			* but WITHOUT ANY WARRANTY; without even the implied warranty of
15			* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
16			* GNU General Public License for more details.
17			*
18			* You should have received a copy of the GNU General Public License
19			* along with this program; if not, write to the Free Software
20			* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
21			*/
22
23			#include "common.h"
24	niro	816	#include "dhcpc.h"
25	niro	532	#include "dhcpd.h"
26			#include "options.h"
27
28
29	niro	984	/* send a packet to gateway_nip using the kernel ip stack */
30			static int send_packet_to_relay(struct dhcp_packet *dhcp_pkt)
31	niro	532	{
32	niro	984	log1("Forwarding packet to relay");
33	niro	532
34	niro	984	return udhcp_send_kernel_packet(dhcp_pkt,
35			server_config.server_nip, SERVER_PORT,
36			dhcp_pkt->gateway_nip, SERVER_PORT);
37	niro	532	}
38
39
40	niro	984	/* send a packet to a specific mac address and ip address by creating our own ip packet */
41			static int send_packet_to_client(struct dhcp_packet *dhcp_pkt, int force_broadcast)
42	niro	532	{
43	niro	816	const uint8_t *chaddr;
44	niro	532	uint32_t ciaddr;
45
46	niro	984	// Was:
47			//if (force_broadcast) { /* broadcast */ }
48			//else if (dhcp_pkt->ciaddr) { /* unicast to dhcp_pkt->ciaddr */ }
49			//else if (dhcp_pkt->flags & htons(BROADCAST_FLAG)) { /* broadcast */ }
50			//else { /* unicast to dhcp_pkt->yiaddr */ }
51			// But this is wrong: yiaddr is _our_ idea what client's IP is
52			// (for example, from lease file). Client may not know that,
53			// and may not have UDP socket listening on that IP!
54			// We should never unicast to dhcp_pkt->yiaddr!
55			// dhcp_pkt->ciaddr, OTOH, comes from client's request packet,
56			// and can be used.
57
58			if (force_broadcast
59			\|\| (dhcp_pkt->flags & htons(BROADCAST_FLAG))
60			\|\| !dhcp_pkt->ciaddr
61			) {
62			log1("Broadcasting packet to client");
63	niro	532	ciaddr = INADDR_BROADCAST;
64			chaddr = MAC_BCAST_ADDR;
65			} else {
66	niro	984	log1("Unicasting packet to client ciaddr");
67			ciaddr = dhcp_pkt->ciaddr;
68			chaddr = dhcp_pkt->chaddr;
69	niro	532	}
70	niro	984
71			return udhcp_send_raw_packet(dhcp_pkt,
72			/src/ server_config.server_nip, SERVER_PORT,
73	niro	816	/dst/ ciaddr, CLIENT_PORT, chaddr,
74			server_config.ifindex);
75	niro	532	}
76
77
78			/* send a dhcp packet, if force broadcast is set, the packet will be broadcast to the client */
79	niro	984	static int send_packet(struct dhcp_packet *dhcp_pkt, int force_broadcast)
80	niro	532	{
81	niro	984	if (dhcp_pkt->gateway_nip)
82			return send_packet_to_relay(dhcp_pkt);
83			return send_packet_to_client(dhcp_pkt, force_broadcast);
84	niro	532	}
85
86
87	niro	984	static void init_packet(struct dhcp_packet packet, struct dhcp_packet oldpacket, char type)
88	niro	532	{
89			udhcp_init_header(packet, type);
90			packet->xid = oldpacket->xid;
91	niro	984	memcpy(packet->chaddr, oldpacket->chaddr, sizeof(oldpacket->chaddr));
92	niro	532	packet->flags = oldpacket->flags;
93	niro	984	packet->gateway_nip = oldpacket->gateway_nip;
94	niro	532	packet->ciaddr = oldpacket->ciaddr;
95	niro	984	add_simple_option(packet->options, DHCP_SERVER_ID, server_config.server_nip);
96	niro	532	}
97
98
99			/* add in the bootp options */
100	niro	984	static void add_bootp_options(struct dhcp_packet *packet)
101	niro	532	{
102	niro	984	packet->siaddr_nip = server_config.siaddr_nip;
103	niro	532	if (server_config.sname)
104			strncpy((char*)packet->sname, server_config.sname, sizeof(packet->sname) - 1);
105			if (server_config.boot_file)
106			strncpy((char*)packet->file, server_config.boot_file, sizeof(packet->file) - 1);
107			}
108
109
110	niro	984	static uint32_t select_lease_time(struct dhcp_packet *packet)
111			{
112			uint32_t lease_time_sec = server_config.max_lease_sec;
113			uint8_t *lease_time_opt = get_option(packet, DHCP_LEASE_TIME);
114			if (lease_time_opt) {
115			move_from_unaligned32(lease_time_sec, lease_time_opt);
116			lease_time_sec = ntohl(lease_time_sec);
117			if (lease_time_sec > server_config.max_lease_sec)
118			lease_time_sec = server_config.max_lease_sec;
119			if (lease_time_sec < server_config.min_lease_sec)
120			lease_time_sec = server_config.min_lease_sec;
121			}
122			return lease_time_sec;
123			}
124
125
126	niro	532	/* send a DHCP OFFER to a DHCP DISCOVER */
127	niro	984	int FAST_FUNC send_offer(struct dhcp_packet *oldpacket)
128	niro	532	{
129	niro	984	struct dhcp_packet packet;
130			uint32_t req_nip;
131			uint32_t lease_time_sec = server_config.max_lease_sec;
132			uint32_t static_lease_ip;
133			uint8_t *req_ip_opt;
134			const char *p_host_name;
135	niro	532	struct option_set *curr;
136			struct in_addr addr;
137
138			init_packet(&packet, oldpacket, DHCPOFFER);
139
140	niro	984	static_lease_ip = get_static_nip_by_mac(server_config.static_leases, oldpacket->chaddr);
141	niro	532
142			/* ADDME: if static, short circuit */
143			if (!static_lease_ip) {
144	niro	984	struct dyn_lease *lease;
145
146			lease = find_lease_by_mac(oldpacket->chaddr);
147			/* The client is in our lease/offered table */
148	niro	532	if (lease) {
149	niro	984	signed_leasetime_t tmp = lease->expires - time(NULL);
150			if (tmp >= 0)
151			lease_time_sec = tmp;
152			packet.yiaddr = lease->lease_nip;
153			}
154			/* Or the client has requested an IP */
155			else if ((req_ip_opt = get_option(oldpacket, DHCP_REQUESTED_IP)) != NULL
156			/* (read IP) */
157			&& (move_from_unaligned32(req_nip, req_ip_opt), 1)
158			/* and the IP is in the lease range */
159			&& ntohl(req_nip) >= server_config.start_ip
160			&& ntohl(req_nip) <= server_config.end_ip
161	niro	816	/* and is not already taken/offered */
162	niro	984	&& (!(lease = find_lease_by_nip(req_nip))
163			/* or its taken, but expired */
164			\|\| is_expired_lease(lease))
165	niro	532	) {
166	niro	984	packet.yiaddr = req_nip;
167	niro	532	}
168	niro	984	/* Otherwise, find a free IP */
169			else {
170			packet.yiaddr = find_free_or_expired_nip(oldpacket->chaddr);
171			}
172	niro	532
173			if (!packet.yiaddr) {
174			bb_error_msg("no IP addresses to give - OFFER abandoned");
175			return -1;
176			}
177	niro	984	p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
178			if (add_lease(packet.chaddr, packet.yiaddr,
179			server_config.offer_time,
180			p_host_name,
181			p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
182			) == 0
183			) {
184	niro	532	bb_error_msg("lease pool is full - OFFER abandoned");
185			return -1;
186			}
187	niro	984	lease_time_sec = select_lease_time(oldpacket);
188	niro	532	} else {
189			/* It is a static lease... use it */
190			packet.yiaddr = static_lease_ip;
191			}
192
193	niro	984	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
194	niro	532
195			curr = server_config.options;
196			while (curr) {
197			if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
198			add_option_string(packet.options, curr->data);
199			curr = curr->next;
200			}
201
202			add_bootp_options(&packet);
203
204			addr.s_addr = packet.yiaddr;
205			bb_info_msg("Sending OFFER of %s", inet_ntoa(addr));
206			return send_packet(&packet, 0);
207			}
208
209
210	niro	984	int FAST_FUNC send_NAK(struct dhcp_packet *oldpacket)
211	niro	532	{
212	niro	984	struct dhcp_packet packet;
213	niro	532
214			init_packet(&packet, oldpacket, DHCPNAK);
215
216	niro	984	log1("Sending NAK");
217	niro	532	return send_packet(&packet, 1);
218			}
219
220
221	niro	984	int FAST_FUNC send_ACK(struct dhcp_packet *oldpacket, uint32_t yiaddr)
222	niro	532	{
223	niro	984	struct dhcp_packet packet;
224	niro	532	struct option_set *curr;
225	niro	984	uint32_t lease_time_sec;
226	niro	532	struct in_addr addr;
227	niro	984	const char *p_host_name;
228	niro	532
229			init_packet(&packet, oldpacket, DHCPACK);
230			packet.yiaddr = yiaddr;
231
232	niro	984	lease_time_sec = select_lease_time(oldpacket);
233	niro	532
234	niro	984	add_simple_option(packet.options, DHCP_LEASE_TIME, htonl(lease_time_sec));
235	niro	532
236			curr = server_config.options;
237			while (curr) {
238			if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
239			add_option_string(packet.options, curr->data);
240			curr = curr->next;
241			}
242
243			add_bootp_options(&packet);
244
245			addr.s_addr = packet.yiaddr;
246			bb_info_msg("Sending ACK to %s", inet_ntoa(addr));
247
248			if (send_packet(&packet, 0) < 0)
249			return -1;
250
251	niro	984	p_host_name = (const char*) get_option(oldpacket, DHCP_HOST_NAME);
252			add_lease(packet.chaddr, packet.yiaddr,
253			lease_time_sec,
254			p_host_name,
255			p_host_name ? (unsigned char)p_host_name[OPT_LEN - OPT_DATA] : 0
256			);
257	niro	816	if (ENABLE_FEATURE_UDHCPD_WRITE_LEASES_EARLY) {
258			/* rewrite the file with leases at every new acceptance */
259			write_leases();
260			}
261	niro	532
262			return 0;
263			}
264
265
266	niro	984	int FAST_FUNC send_inform(struct dhcp_packet *oldpacket)
267	niro	532	{
268	niro	984	struct dhcp_packet packet;
269	niro	532	struct option_set *curr;
270
271			init_packet(&packet, oldpacket, DHCPACK);
272
273			curr = server_config.options;
274			while (curr) {
275			if (curr->data[OPT_CODE] != DHCP_LEASE_TIME)
276			add_option_string(packet.options, curr->data);
277			curr = curr->next;
278			}
279
280			add_bootp_options(&packet);
281
282			return send_packet(&packet, 0);
283			}