source: MondoRescue/branches/stable/mindi-busybox/networking/udhcp/packet.c @ 821

Last change on this file since 821 was 821, checked in by Bruno Cornec, 14 years ago

Addition of busybox 1.2.1 as a mindi-busybox new package
This should avoid delivering binary files in mindi not built there (Fedora and Debian are quite serious about that)

File size: 5.3 KB
Line 
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) || defined _NEWLIB_VERSION
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 "common.h"
18#include "packet.h"
19#include "dhcpd.h"
20#include "options.h"
21
22
23void udhcp_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        packet->op = BOOTREQUEST;
32        break;
33    case DHCPOFFER:
34    case DHCPACK:
35    case DHCPNAK:
36        packet->op = BOOTREPLY;
37    }
38    packet->htype = ETH_10MB;
39    packet->hlen = ETH_10MB_LEN;
40    packet->cookie = htonl(DHCP_MAGIC);
41    packet->options[0] = DHCP_END;
42    add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
43}
44
45
46/* read a packet from socket fd, return -1 on read error, -2 on packet error */
47int udhcp_get_packet(struct dhcpMessage *packet, int fd)
48{
49    static const char broken_vendors[][8] = {
50        "MSFT 98",
51        ""
52    };
53    int bytes;
54    int i;
55    char unsigned *vendor;
56
57    memset(packet, 0, sizeof(struct dhcpMessage));
58    bytes = read(fd, packet, sizeof(struct dhcpMessage));
59    if (bytes < 0) {
60        DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");
61        return -1;
62    }
63
64    if (ntohl(packet->cookie) != DHCP_MAGIC) {
65        LOG(LOG_ERR, "received bogus message, ignoring");
66        return -2;
67    }
68    DEBUG(LOG_INFO, "Received a packet");
69
70    if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {
71        for (i = 0; broken_vendors[i][0]; i++) {
72            if (vendor[OPT_LEN - 2] == (uint8_t) strlen(broken_vendors[i]) &&
73                !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {
74                DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",
75                    broken_vendors[i]);
76                packet->flags |= htons(BROADCAST_FLAG);
77            }
78        }
79    }
80
81    return bytes;
82}
83
84
85uint16_t udhcp_checksum(void *addr, int count)
86{
87    /* Compute Internet Checksum for "count" bytes
88     *         beginning at location "addr".
89     */
90    register int32_t sum = 0;
91    uint16_t *source = (uint16_t *) addr;
92
93    while (count > 1)  {
94        /*  This is the inner loop */
95        sum += *source++;
96        count -= 2;
97    }
98
99    /*  Add left-over byte, if any */
100    if (count > 0) {
101        /* Make sure that the left-over byte is added correctly both
102         * with little and big endian hosts */
103        uint16_t tmp = 0;
104        *(uint8_t *) (&tmp) = * (uint8_t *) source;
105        sum += tmp;
106    }
107    /*  Fold 32-bit sum to 16 bits */
108    while (sum >> 16)
109        sum = (sum & 0xffff) + (sum >> 16);
110
111    return ~sum;
112}
113
114
115/* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
116int udhcp_raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
117           uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex)
118{
119    int fd;
120    int result;
121    struct sockaddr_ll dest;
122    struct udp_dhcp_packet packet;
123
124    if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {
125        DEBUG(LOG_ERR, "socket call failed: %m");
126        return -1;
127    }
128
129    memset(&dest, 0, sizeof(dest));
130    memset(&packet, 0, sizeof(packet));
131
132    dest.sll_family = AF_PACKET;
133    dest.sll_protocol = htons(ETH_P_IP);
134    dest.sll_ifindex = ifindex;
135    dest.sll_halen = 6;
136    memcpy(dest.sll_addr, dest_arp, 6);
137    if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
138        DEBUG(LOG_ERR, "bind call failed: %m");
139        close(fd);
140        return -1;
141    }
142
143    packet.ip.protocol = IPPROTO_UDP;
144    packet.ip.saddr = source_ip;
145    packet.ip.daddr = dest_ip;
146    packet.udp.source = htons(source_port);
147    packet.udp.dest = htons(dest_port);
148    packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
149    packet.ip.tot_len = packet.udp.len;
150    memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
151    packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));
152
153    packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
154    packet.ip.ihl = sizeof(packet.ip) >> 2;
155    packet.ip.version = IPVERSION;
156    packet.ip.ttl = IPDEFTTL;
157    packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
158
159    result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));
160    if (result <= 0) {
161        DEBUG(LOG_ERR, "write on socket failed: %m");
162    }
163    close(fd);
164    return result;
165}
166
167
168/* Let the kernel do all the work for packet generation */
169int udhcp_kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,
170           uint32_t dest_ip, int dest_port)
171{
172    int n = 1;
173    int fd, result;
174    struct sockaddr_in client;
175
176    if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)
177        return -1;
178
179    if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1) {
180        close(fd);
181        return -1;
182    }
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        close(fd);
191        return -1;
192    }
193
194    memset(&client, 0, sizeof(client));
195    client.sin_family = AF_INET;
196    client.sin_port = htons(dest_port);
197    client.sin_addr.s_addr = dest_ip;
198
199    if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
200        close(fd);
201        return -1;
202    }
203
204    result = write(fd, payload, sizeof(struct dhcpMessage));
205    close(fd);
206    return result;
207}
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