1#include <unistd.h>
2#include <string.h>
3#include <netinet/in.h>
4#include <sys/types.h>
5#include <sys/socket.h>
6#include <features.h>
7#if __GLIBC__ >=2 && __GLIBC_MINOR >= 1
8#include <netpacket/packet.h>
9#include <net/ethernet.h>
10#else
11#include <asm/types.h>
12#include <linux/if_packet.h>
13#include <linux/if_ether.h>
14#endif
15#include <errno.h>
16
17#include "packet.h"
18#include "debug.h"
19#include "dhcpd.h"
20#include "options.h"
21
22
23void init_header(struct dhcpMessage *packet, char type)
24{
25	memset(packet, 0, sizeof(struct dhcpMessage));
26	switch (type) {
27	case DHCPDISCOVER:
28	case DHCPREQUEST:
29	case DHCPRELEASE:
30	case DHCPINFORM:
31	case DHCPDECLINE: /* foxconn wklin added, 08/10/2007 */
32		packet->op = BOOTREQUEST;
33		break;
34	case DHCPOFFER:
35	case DHCPACK:
36	case DHCPNAK:
37		packet->op = BOOTREPLY;
38	}
39	packet->htype = ETH_10MB;
40	packet->hlen = ETH_10MB_LEN;
41	packet->cookie = htonl(DHCP_MAGIC);
42	packet->options[0] = DHCP_END;
43	add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
44}
45
46
47/* read a packet from socket fd, return -1 on read error, -2 on packet error */
48int get_packet(struct dhcpMessage *packet, int fd)
49{
50	int bytes;
51	int i;
52	const char broken_vendors[][8] = {
53		"MSFT 98",
54		""
55	};
56	char unsigned *vendor;
57
58	memset(packet, 0, sizeof(struct dhcpMessage));
59	bytes = read(fd, packet, sizeof(struct dhcpMessage));
60	if (bytes < 0) {
61		DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");
62		return -1;
63	}
64
65	if (ntohl(packet->cookie) != DHCP_MAGIC) {
66		LOG(LOG_ERR, "received bogus message, ignoring");
67		return -2;
68	}
69	DEBUG(LOG_INFO, "Received a packet");
70
71	if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
72		for (i = 0; broken_vendors[i][0]; i++) {
73			if (vendor[OPT_LEN - 2] == (unsigned char) strlen(broken_vendors[i]) &&
74			    !strncmp(vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {
75			    	DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",
76			    		broken_vendors[i]);
77			    	packet->flags |= htons(BROADCAST_FLAG);
78			}
79		}
80	}
81
82
83	return bytes;
84}
85
86
87u_int16_t checksum(void *addr, int count)
88{
89	/* Compute Internet Checksum for "count" bytes
90	 *         beginning at location "addr".
91	 */
92	register int32_t sum = 0;
93	u_int16_t *source = (u_int16_t *) addr;
94
95	while (count > 1)  {
96		/*  This is the inner loop */
97		sum += *source++;
98		count -= 2;
99	}
100
101	/*  Add left-over byte, if any */
102	if (count > 0) {
103		/* Make sure that the left-over byte is added correctly both
104		 * with little and big endian hosts */
105		u_int16_t tmp = 0;
106		*(unsigned char *) (&tmp) = * (unsigned char *) source;
107		sum += tmp;
108	}
109	/*  Fold 32-bit sum to 16 bits */
110	while (sum >> 16)
111		sum = (sum & 0xffff) + (sum >> 16);
112
113	return ~sum;
114}
115
116
117/* Constuct a ip/udp header for a packet, and specify the source and dest hardware address */
118int raw_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
119		   u_int32_t dest_ip, int dest_port, unsigned char *dest_arp, int ifindex)
120{
121	int fd;
122	int result;
123	struct sockaddr_ll dest;
124	struct udp_dhcp_packet packet;
125
126	if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
127		DEBUG(LOG_ERR, "socket call failed: %s", strerror(errno));
128		return -1;
129	}
130
131	memset(&dest, 0, sizeof(dest));
132	memset(&packet, 0, sizeof(packet));
133
134	dest.sll_family = AF_PACKET;
135	dest.sll_protocol = htons(ETH_P_IP);
136	dest.sll_ifindex = ifindex;
137	dest.sll_halen = 6;
138	memcpy(dest.sll_addr, dest_arp, 6);
139	if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
140		DEBUG(LOG_ERR, "bind call failed: %s", strerror(errno));
141		close(fd);
142		return -1;
143	}
144
145	packet.ip.protocol = IPPROTO_UDP;
146	packet.ip.saddr = source_ip;
147	packet.ip.daddr = dest_ip;
148	packet.udp.source = htons(source_port);
149	packet.udp.dest = htons(dest_port);
150	packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
151	packet.ip.tot_len = packet.udp.len;
152	memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
153	packet.udp.check = checksum(&packet, sizeof(struct udp_dhcp_packet));
154
155	packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
156	packet.ip.ihl = sizeof(packet.ip) >> 2;
157	packet.ip.version = IPVERSION;
158	packet.ip.ttl = IPDEFTTL;
159	packet.ip.check = checksum(&(packet.ip), sizeof(packet.ip));
160
161	result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));
162	if (result <= 0) {
163		DEBUG(LOG_ERR, "write on socket failed: %s", strerror(errno));
164	}
165	close(fd);
166	return result;
167}
168
169
170/* Let the kernel do all the work for packet generation */
171int kernel_packet(struct dhcpMessage *payload, u_int32_t source_ip, int source_port,
172		   u_int32_t dest_ip, int dest_port)
173{
174	int n = 1;
175	int fd, result;
176	struct sockaddr_in client;
177
178	if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
179		return -1;
180
181	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1)
182		return -1;
183
184	memset(&client, 0, sizeof(client));
185	client.sin_family = AF_INET;
186	client.sin_port = htons(source_port);
187	client.sin_addr.s_addr = source_ip;
188
189	if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
190		return -1;
191
192	memset(&client, 0, sizeof(client));
193	client.sin_family = AF_INET;
194	client.sin_port = htons(dest_port);
195	client.sin_addr.s_addr = dest_ip;
196
197	if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1)
198		return -1;
199
200	result = write(fd, payload, sizeof(struct dhcpMessage));
201	close(fd);
202	return result;
203}
204
205