networking/udhcp/packet.c

/* vi: set sw=4 ts=4: */
/*
 * packet.c -- packet ops
 * Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
 *
 * Licensed under GPLv2, see file LICENSE in this tarball for details.
 */
#include <netinet/in.h>
#if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
#include <netpacket/packet.h>
#include <net/ethernet.h>
#else
#include <asm/types.h>
#include <linux/if_packet.h>
#include <linux/if_ether.h>
#endif

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

void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
{
	memset(packet, 0, sizeof(struct dhcp_packet));
	packet->op = BOOTREQUEST; /* if client to a server */
	switch (type) {
	case DHCPOFFER:
	case DHCPACK:
	case DHCPNAK:
		packet->op = BOOTREPLY; /* if server to client */
	}
	packet->htype = ETH_10MB;
	packet->hlen = ETH_10MB_LEN;
	packet->cookie = htonl(DHCP_MAGIC);
	packet->options[0] = DHCP_END;
	add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
}

#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
{
	char buf[sizeof(packet->chaddr)*2 + 1];

	if (dhcp_verbose < 2)
		return;

	bb_info_msg(
		//" op %x"
		//" htype %x"
		" hlen %x"
		//" hops %x"
		" xid %x"
		//" secs %x"
		//" flags %x"
		" ciaddr %x"
		" yiaddr %x"
		" siaddr %x"
		" giaddr %x"
		//" chaddr %s"
		//" sname %s"
		//" file %s"
		//" cookie %x"
		//" options %s"
		//, packet->op
		//, packet->htype
		, packet->hlen
		//, packet->hops
		, packet->xid
		//, packet->secs
		//, packet->flags
		, packet->ciaddr
		, packet->yiaddr
		, packet->siaddr_nip
		, packet->gateway_nip
		//, packet->chaddr[16]
		//, packet->sname[64]
		//, packet->file[128]
		//, packet->cookie
		//, packet->options[]
	);
	*bin2hex(buf, (void *) packet->chaddr, sizeof(packet->chaddr)) = '\0';
	bb_info_msg(" chaddr %s", buf);
}
#endif

/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
{
	int bytes;
	unsigned char *vendor;

	memset(packet, 0, sizeof(*packet));
	bytes = safe_read(fd, packet, sizeof(*packet));
	if (bytes < 0) {
		log1("Packet read error, ignoring");
		return bytes; /* returns -1 */
	}

	if (packet->cookie != htonl(DHCP_MAGIC)) {
		bb_info_msg("Packet with bad magic, ignoring");
		return -2;
	}
	log1("Received a packet");
	udhcp_dump_packet(packet);

	if (packet->op == BOOTREQUEST) {
		vendor = get_option(packet, DHCP_VENDOR);
		if (vendor) {
#if 0
			static const char broken_vendors[][8] = {
				"MSFT 98",
				""
			};
			int i;
			for (i = 0; broken_vendors[i][0]; i++) {
				if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
				 && !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
				) {
					log1("Broken client (%s), forcing broadcast replies",
						broken_vendors[i]);
					packet->flags |= htons(BROADCAST_FLAG);
				}
			}
#else
			if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
			 && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
			) {
				log1("Broken client (%s), forcing broadcast replies", "MSFT 98");
				packet->flags |= htons(BROADCAST_FLAG);
			}
#endif
		}
	}

	return bytes;
}

uint16_t FAST_FUNC udhcp_checksum(void *addr, int count)
{
	/* Compute Internet Checksum for "count" bytes
	 * beginning at location "addr".
	 */
	int32_t sum = 0;
	uint16_t *source = (uint16_t *) addr;

	while (count > 1)  {
		/*  This is the inner loop */
		sum += *source++;
		count -= 2;
	}

	/*  Add left-over byte, if any */
	if (count > 0) {
		/* Make sure that the left-over byte is added correctly both
		 * with little and big endian hosts */
		uint16_t tmp = 0;
		*(uint8_t*)&tmp = *(uint8_t*)source;
		sum += tmp;
	}
	/*  Fold 32-bit sum to 16 bits */
	while (sum >> 16)
		sum = (sum & 0xffff) + (sum >> 16);

	return ~sum;
}

/* Construct a ip/udp header for a packet, send packet */
int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
		uint32_t source_ip, int source_port,
		uint32_t dest_ip, int dest_port, const uint8_t *dest_arp,
		int ifindex)
{
	struct sockaddr_ll dest;
	struct ip_udp_dhcp_packet packet;
	int fd;
	int result = -1;
	const char *msg;

	enum {
		IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
		UPD_DHCP_SIZE    = IP_UPD_DHCP_SIZE - offsetof(struct ip_udp_dhcp_packet, udp),
	};

	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
	if (fd < 0) {
		msg = "socket(%s)";
		goto ret_msg;
	}

	memset(&dest, 0, sizeof(dest));
	memset(&packet, 0, sizeof(packet));
	packet.data = *dhcp_pkt; /* struct copy */

	dest.sll_family = AF_PACKET;
	dest.sll_protocol = htons(ETH_P_IP);
	dest.sll_ifindex = ifindex;
	dest.sll_halen = 6;
	memcpy(dest.sll_addr, dest_arp, 6);
	if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
		msg = "bind(%s)";
		goto ret_close;
	}

	packet.ip.protocol = IPPROTO_UDP;
	packet.ip.saddr = source_ip;
	packet.ip.daddr = dest_ip;
	packet.udp.source = htons(source_port);
	packet.udp.dest = htons(dest_port);
	/* size, excluding IP header: */
	packet.udp.len = htons(UPD_DHCP_SIZE);
	/* for UDP checksumming, ip.len is set to UDP packet len */
	packet.ip.tot_len = packet.udp.len;
	packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
	/* but for sending, it is set to IP packet len */
	packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
	packet.ip.ihl = sizeof(packet.ip) >> 2;
	packet.ip.version = IPVERSION;
	packet.ip.ttl = IPDEFTTL;
	packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));

	/* Currently we send full-sized DHCP packets (zero padded).
	 * If you need to change this: last byte of the packet is
	 * packet.data.options[end_option(packet.data.options)]
	 */
	udhcp_dump_packet(dhcp_pkt);
	result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
				(struct sockaddr *) &dest, sizeof(dest));
	msg = "sendto";
 ret_close:
	close(fd);
	if (result < 0) {
 ret_msg:
		bb_perror_msg(msg, "PACKET");
	}
	return result;
}

/* Let the kernel do all the work for packet generation */
int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
		uint32_t source_ip, int source_port,
		uint32_t dest_ip, int dest_port)
{
	struct sockaddr_in client;
	int fd;
	int result = -1;
	const char *msg;

	enum {
		DHCP_SIZE = sizeof(struct dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
	};

	fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
	if (fd < 0) {
		msg = "socket(%s)";
		goto ret_msg;
	}
	setsockopt_reuseaddr(fd);

	memset(&client, 0, sizeof(client));
	client.sin_family = AF_INET;
	client.sin_port = htons(source_port);
	client.sin_addr.s_addr = source_ip;
	if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
		msg = "bind(%s)";
		goto ret_close;
	}

	memset(&client, 0, sizeof(client));
	client.sin_family = AF_INET;
	client.sin_port = htons(dest_port);
	client.sin_addr.s_addr = dest_ip;
	if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
		msg = "connect";
		goto ret_close;
	}

	/* Currently we send full-sized DHCP packets (see above) */
	udhcp_dump_packet(dhcp_pkt);
	result = safe_write(fd, dhcp_pkt, DHCP_SIZE);
	msg = "write";
 ret_close:
	close(fd);
	if (result < 0) {
 ret_msg:
		bb_perror_msg(msg, "UDP");
	}
	return result;
}
1	/* vi: set sw=4 ts=4: */
2	/*
3	* packet.c -- packet ops
4	* Rewrite by Russ Dill <Russ.Dill@asu.edu> July 2001
5	*
6	* Licensed under GPLv2, see file LICENSE in this tarball for details.
7	*/
8	#include <netinet/in.h>
9	#if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) \|\| defined _NEWLIB_VERSION
10	#include <netpacket/packet.h>
11	#include <net/ethernet.h>
12	#else
13	#include <asm/types.h>
14	#include <linux/if_packet.h>
15	#include <linux/if_ether.h>
16	#endif
17
18	#include "common.h"
19	#include "dhcpd.h"
20	#include "options.h"
21
22	void FAST_FUNC udhcp_init_header(struct dhcp_packet *packet, char type)
23	{
24	memset(packet, 0, sizeof(struct dhcp_packet));
25	packet->op = BOOTREQUEST; /* if client to a server */
26	switch (type) {
27	case DHCPOFFER:
28	case DHCPACK:
29	case DHCPNAK:
30	packet->op = BOOTREPLY; /* if server to client */
31	}
32	packet->htype = ETH_10MB;
33	packet->hlen = ETH_10MB_LEN;
34	packet->cookie = htonl(DHCP_MAGIC);
35	packet->options[0] = DHCP_END;
36	add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
37	}
38
39	#if defined CONFIG_UDHCP_DEBUG && CONFIG_UDHCP_DEBUG >= 2
40	void FAST_FUNC udhcp_dump_packet(struct dhcp_packet *packet)
41	{
42	char buf[sizeof(packet->chaddr)*2 + 1];
43
44	if (dhcp_verbose < 2)
45	return;
46
47	bb_info_msg(
48	//" op %x"
49	//" htype %x"
50	" hlen %x"
51	//" hops %x"
52	" xid %x"
53	//" secs %x"
54	//" flags %x"
55	" ciaddr %x"
56	" yiaddr %x"
57	" siaddr %x"
58	" giaddr %x"
59	//" chaddr %s"
60	//" sname %s"
61	//" file %s"
62	//" cookie %x"
63	//" options %s"
64	//, packet->op
65	//, packet->htype
66	, packet->hlen
67	//, packet->hops
68	, packet->xid
69	//, packet->secs
70	//, packet->flags
71	, packet->ciaddr
72	, packet->yiaddr
73	, packet->siaddr_nip
74	, packet->gateway_nip
75	//, packet->chaddr[16]
76	//, packet->sname[64]
77	//, packet->file[128]
78	//, packet->cookie
79	//, packet->options[]
80	);
81	bin2hex(buf, (void ) packet->chaddr, sizeof(packet->chaddr)) = '\0';
82	bb_info_msg(" chaddr %s", buf);
83	}
84	#endif
85
86	/* Read a packet from socket fd, return -1 on read error, -2 on packet error */
87	int FAST_FUNC udhcp_recv_kernel_packet(struct dhcp_packet *packet, int fd)
88	{
89	int bytes;
90	unsigned char *vendor;
91
92	memset(packet, 0, sizeof(*packet));
93	bytes = safe_read(fd, packet, sizeof(*packet));
94	if (bytes < 0) {
95	log1("Packet read error, ignoring");
96	return bytes; /* returns -1 */
97	}
98
99	if (packet->cookie != htonl(DHCP_MAGIC)) {
100	bb_info_msg("Packet with bad magic, ignoring");
101	return -2;
102	}
103	log1("Received a packet");
104	udhcp_dump_packet(packet);
105
106	if (packet->op == BOOTREQUEST) {
107	vendor = get_option(packet, DHCP_VENDOR);
108	if (vendor) {
109	#if 0
110	static const char broken_vendors[][8] = {
111	"MSFT 98",
112	""
113	};
114	int i;
115	for (i = 0; broken_vendors[i][0]; i++) {
116	if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
117	&& !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
118	) {
119	log1("Broken client (%s), forcing broadcast replies",
120	broken_vendors[i]);
121	packet->flags \|= htons(BROADCAST_FLAG);
122	}
123	}
124	#else
125	if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
126	&& memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
127	) {
128	log1("Broken client (%s), forcing broadcast replies", "MSFT 98");
129	packet->flags \|= htons(BROADCAST_FLAG);
130	}
131	#endif
132	}
133	}
134
135	return bytes;
136	}
137
138	uint16_t FAST_FUNC udhcp_checksum(void *addr, int count)
139	{
140	/* Compute Internet Checksum for "count" bytes
141	* beginning at location "addr".
142	*/
143	int32_t sum = 0;
144	uint16_t source = (uint16_t ) addr;
145
146	while (count > 1) {
147	/* This is the inner loop */
148	sum += *source++;
149	count -= 2;
150	}
151
152	/* Add left-over byte, if any */
153	if (count > 0) {
154	/* Make sure that the left-over byte is added correctly both
155	* with little and big endian hosts */
156	uint16_t tmp = 0;
157	(uint8_t)&tmp = (uint8_t)source;
158	sum += tmp;
159	}
160	/* Fold 32-bit sum to 16 bits */
161	while (sum >> 16)
162	sum = (sum & 0xffff) + (sum >> 16);
163
164	return ~sum;
165	}
166
167	/* Construct a ip/udp header for a packet, send packet */
168	int FAST_FUNC udhcp_send_raw_packet(struct dhcp_packet *dhcp_pkt,
169	uint32_t source_ip, int source_port,
170	uint32_t dest_ip, int dest_port, const uint8_t *dest_arp,
171	int ifindex)
172	{
173	struct sockaddr_ll dest;
174	struct ip_udp_dhcp_packet packet;
175	int fd;
176	int result = -1;
177	const char *msg;
178
179	enum {
180	IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
181	UPD_DHCP_SIZE = IP_UPD_DHCP_SIZE - offsetof(struct ip_udp_dhcp_packet, udp),
182	};
183
184	fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
185	if (fd < 0) {
186	msg = "socket(%s)";
187	goto ret_msg;
188	}
189
190	memset(&dest, 0, sizeof(dest));
191	memset(&packet, 0, sizeof(packet));
192	packet.data = dhcp_pkt; / struct copy */
193
194	dest.sll_family = AF_PACKET;
195	dest.sll_protocol = htons(ETH_P_IP);
196	dest.sll_ifindex = ifindex;
197	dest.sll_halen = 6;
198	memcpy(dest.sll_addr, dest_arp, 6);
199	if (bind(fd, (struct sockaddr *)&dest, sizeof(dest)) < 0) {
200	msg = "bind(%s)";
201	goto ret_close;
202	}
203
204	packet.ip.protocol = IPPROTO_UDP;
205	packet.ip.saddr = source_ip;
206	packet.ip.daddr = dest_ip;
207	packet.udp.source = htons(source_port);
208	packet.udp.dest = htons(dest_port);
209	/* size, excluding IP header: */
210	packet.udp.len = htons(UPD_DHCP_SIZE);
211	/* for UDP checksumming, ip.len is set to UDP packet len */
212	packet.ip.tot_len = packet.udp.len;
213	packet.udp.check = udhcp_checksum(&packet, IP_UPD_DHCP_SIZE);
214	/* but for sending, it is set to IP packet len */
215	packet.ip.tot_len = htons(IP_UPD_DHCP_SIZE);
216	packet.ip.ihl = sizeof(packet.ip) >> 2;
217	packet.ip.version = IPVERSION;
218	packet.ip.ttl = IPDEFTTL;
219	packet.ip.check = udhcp_checksum(&packet.ip, sizeof(packet.ip));
220
221	/* Currently we send full-sized DHCP packets (zero padded).
222	* If you need to change this: last byte of the packet is
223	* packet.data.options[end_option(packet.data.options)]
224	*/
225	udhcp_dump_packet(dhcp_pkt);
226	result = sendto(fd, &packet, IP_UPD_DHCP_SIZE, 0,
227	(struct sockaddr *) &dest, sizeof(dest));
228	msg = "sendto";
229	ret_close:
230	close(fd);
231	if (result < 0) {
232	ret_msg:
233	bb_perror_msg(msg, "PACKET");
234	}
235	return result;
236	}
237
238	/* Let the kernel do all the work for packet generation */
239	int FAST_FUNC udhcp_send_kernel_packet(struct dhcp_packet *dhcp_pkt,
240	uint32_t source_ip, int source_port,
241	uint32_t dest_ip, int dest_port)
242	{
243	struct sockaddr_in client;
244	int fd;
245	int result = -1;
246	const char *msg;
247
248	enum {
249	DHCP_SIZE = sizeof(struct dhcp_packet) - CONFIG_UDHCPC_SLACK_FOR_BUGGY_SERVERS,
250	};
251
252	fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
253	if (fd < 0) {
254	msg = "socket(%s)";
255	goto ret_msg;
256	}
257	setsockopt_reuseaddr(fd);
258
259	memset(&client, 0, sizeof(client));
260	client.sin_family = AF_INET;
261	client.sin_port = htons(source_port);
262	client.sin_addr.s_addr = source_ip;
263	if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
264	msg = "bind(%s)";
265	goto ret_close;
266	}
267
268	memset(&client, 0, sizeof(client));
269	client.sin_family = AF_INET;
270	client.sin_port = htons(dest_port);
271	client.sin_addr.s_addr = dest_ip;
272	if (connect(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
273	msg = "connect";
274	goto ret_close;
275	}
276
277	/* Currently we send full-sized DHCP packets (see above) */
278	udhcp_dump_packet(dhcp_pkt);
279	result = safe_write(fd, dhcp_pkt, DHCP_SIZE);
280	msg = "write";
281	ret_close:
282	close(fd);
283	if (result < 0) {
284	ret_msg:
285	bb_perror_msg(msg, "UDP");
286	}
287	return result;
288	}