[1765] | 1 | /* vi: set sw=4 ts=4: */
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| 2 |
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[821] | 3 | #include <netinet/in.h>
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[1765] | 4 | #if (defined(__GLIBC__) && __GLIBC__ >= 2 && __GLIBC_MINOR__ >= 1) || defined _NEWLIB_VERSION
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[821] | 5 | #include <netpacket/packet.h>
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| 6 | #include <net/ethernet.h>
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| 7 | #else
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| 8 | #include <asm/types.h>
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| 9 | #include <linux/if_packet.h>
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| 10 | #include <linux/if_ether.h>
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| 11 | #endif
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| 12 |
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| 13 | #include "common.h"
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| 14 | #include "dhcpd.h"
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| 15 | #include "options.h"
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| 16 |
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| 17 |
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| 18 | void udhcp_init_header(struct dhcpMessage *packet, char type)
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| 19 | {
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| 20 | memset(packet, 0, sizeof(struct dhcpMessage));
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| 21 | switch (type) {
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| 22 | case DHCPDISCOVER:
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| 23 | case DHCPREQUEST:
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| 24 | case DHCPRELEASE:
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| 25 | case DHCPINFORM:
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| 26 | packet->op = BOOTREQUEST;
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| 27 | break;
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| 28 | case DHCPOFFER:
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| 29 | case DHCPACK:
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| 30 | case DHCPNAK:
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| 31 | packet->op = BOOTREPLY;
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| 32 | }
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| 33 | packet->htype = ETH_10MB;
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| 34 | packet->hlen = ETH_10MB_LEN;
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| 35 | packet->cookie = htonl(DHCP_MAGIC);
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| 36 | packet->options[0] = DHCP_END;
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| 37 | add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);
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| 38 | }
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| 39 |
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| 40 |
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| 41 | /* read a packet from socket fd, return -1 on read error, -2 on packet error */
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| 42 | int udhcp_get_packet(struct dhcpMessage *packet, int fd)
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| 43 | {
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[1765] | 44 | #if 0
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[821] | 45 | static const char broken_vendors[][8] = {
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| 46 | "MSFT 98",
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| 47 | ""
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| 48 | };
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[1765] | 49 | #endif
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[821] | 50 | int bytes;
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[1765] | 51 | unsigned char *vendor;
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[821] | 52 |
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[1765] | 53 | memset(packet, 0, sizeof(*packet));
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| 54 | bytes = read(fd, packet, sizeof(*packet));
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[821] | 55 | if (bytes < 0) {
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[1765] | 56 | DEBUG("cannot read on listening socket, ignoring");
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[821] | 57 | return -1;
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| 58 | }
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| 59 |
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| 60 | if (ntohl(packet->cookie) != DHCP_MAGIC) {
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[1765] | 61 | bb_error_msg("received bogus message, ignoring");
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[821] | 62 | return -2;
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| 63 | }
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[1765] | 64 | DEBUG("Received a packet");
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[821] | 65 |
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[1765] | 66 | if (packet->op == BOOTREQUEST) {
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| 67 | vendor = get_option(packet, DHCP_VENDOR);
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| 68 | if (vendor) {
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| 69 | #if 0
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| 70 | int i;
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| 71 | for (i = 0; broken_vendors[i][0]; i++) {
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| 72 | if (vendor[OPT_LEN - 2] == (uint8_t)strlen(broken_vendors[i])
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| 73 | && !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])
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| 74 | ) {
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| 75 | DEBUG("broken client (%s), forcing broadcast",
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| 76 | broken_vendors[i]);
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| 77 | packet->flags |= htons(BROADCAST_FLAG);
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| 78 | }
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| 79 | }
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| 80 | #else
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| 81 | if (vendor[OPT_LEN - 2] == (uint8_t)(sizeof("MSFT 98")-1)
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| 82 | && memcmp(vendor, "MSFT 98", sizeof("MSFT 98")-1) == 0
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| 83 | ) {
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| 84 | DEBUG("broken client (%s), forcing broadcast", "MSFT 98");
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[821] | 85 | packet->flags |= htons(BROADCAST_FLAG);
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| 86 | }
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[1765] | 87 | #endif
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[821] | 88 | }
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| 89 | }
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| 90 |
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| 91 | return bytes;
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| 92 | }
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| 93 |
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| 94 |
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| 95 | uint16_t udhcp_checksum(void *addr, int count)
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| 96 | {
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| 97 | /* Compute Internet Checksum for "count" bytes
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| 98 | * beginning at location "addr".
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| 99 | */
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[1765] | 100 | int32_t sum = 0;
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[821] | 101 | uint16_t *source = (uint16_t *) addr;
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| 102 |
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| 103 | while (count > 1) {
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| 104 | /* This is the inner loop */
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| 105 | sum += *source++;
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| 106 | count -= 2;
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| 107 | }
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| 108 |
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| 109 | /* Add left-over byte, if any */
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| 110 | if (count > 0) {
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| 111 | /* Make sure that the left-over byte is added correctly both
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| 112 | * with little and big endian hosts */
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| 113 | uint16_t tmp = 0;
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| 114 | *(uint8_t *) (&tmp) = * (uint8_t *) source;
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| 115 | sum += tmp;
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| 116 | }
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| 117 | /* Fold 32-bit sum to 16 bits */
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| 118 | while (sum >> 16)
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| 119 | sum = (sum & 0xffff) + (sum >> 16);
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| 120 |
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| 121 | return ~sum;
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| 122 | }
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| 123 |
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| 124 |
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| 125 | /* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
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[1765] | 126 | void BUG_sizeof_struct_udp_dhcp_packet_must_be_576(void);
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| 127 | int udhcp_raw_packet(struct dhcpMessage *payload,
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| 128 | uint32_t source_ip, int source_port,
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| 129 | uint32_t dest_ip, int dest_port, const uint8_t *dest_arp, int ifindex)
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[821] | 130 | {
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| 131 | int fd;
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| 132 | int result;
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| 133 | struct sockaddr_ll dest;
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| 134 | struct udp_dhcp_packet packet;
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| 135 |
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[1765] | 136 | fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP));
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| 137 | if (fd < 0) {
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| 138 | bb_perror_msg("socket");
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[821] | 139 | return -1;
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| 140 | }
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| 141 |
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| 142 | memset(&dest, 0, sizeof(dest));
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| 143 | memset(&packet, 0, sizeof(packet));
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| 144 |
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| 145 | dest.sll_family = AF_PACKET;
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| 146 | dest.sll_protocol = htons(ETH_P_IP);
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| 147 | dest.sll_ifindex = ifindex;
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| 148 | dest.sll_halen = 6;
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| 149 | memcpy(dest.sll_addr, dest_arp, 6);
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| 150 | if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {
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[1765] | 151 | bb_perror_msg("bind");
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[821] | 152 | close(fd);
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| 153 | return -1;
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| 154 | }
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| 155 |
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| 156 | packet.ip.protocol = IPPROTO_UDP;
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| 157 | packet.ip.saddr = source_ip;
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| 158 | packet.ip.daddr = dest_ip;
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| 159 | packet.udp.source = htons(source_port);
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| 160 | packet.udp.dest = htons(dest_port);
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| 161 | packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */
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| 162 | packet.ip.tot_len = packet.udp.len;
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| 163 | memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));
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| 164 | packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));
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| 165 |
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| 166 | packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));
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| 167 | packet.ip.ihl = sizeof(packet.ip) >> 2;
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| 168 | packet.ip.version = IPVERSION;
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| 169 | packet.ip.ttl = IPDEFTTL;
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| 170 | packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
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| 171 |
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[1765] | 172 | if (sizeof(struct udp_dhcp_packet) != 576)
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| 173 | BUG_sizeof_struct_udp_dhcp_packet_must_be_576();
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| 174 |
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| 175 | result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
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| 176 | (struct sockaddr *) &dest, sizeof(dest));
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[821] | 177 | if (result <= 0) {
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[1765] | 178 | bb_perror_msg("sendto");
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[821] | 179 | }
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| 180 | close(fd);
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| 181 | return result;
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| 182 | }
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| 183 |
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| 184 |
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| 185 | /* Let the kernel do all the work for packet generation */
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[1765] | 186 | int udhcp_kernel_packet(struct dhcpMessage *payload,
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| 187 | uint32_t source_ip, int source_port,
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| 188 | uint32_t dest_ip, int dest_port)
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[821] | 189 | {
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| 190 | int fd, result;
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| 191 | struct sockaddr_in client;
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| 192 |
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[1765] | 193 | fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
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| 194 | if (fd < 0)
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[821] | 195 | return -1;
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| 196 |
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[1765] | 197 | setsockopt_reuseaddr(fd);
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[821] | 198 |
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| 199 | memset(&client, 0, sizeof(client));
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| 200 | client.sin_family = AF_INET;
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| 201 | client.sin_port = htons(source_port);
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| 202 | client.sin_addr.s_addr = source_ip;
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| 203 |
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[1765] | 204 | if (bind(fd, (struct sockaddr *)&client, sizeof(client)) == -1) {
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[821] | 205 | close(fd);
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| 206 | return -1;
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| 207 | }
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| 208 |
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| 209 | memset(&client, 0, sizeof(client));
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| 210 | client.sin_family = AF_INET;
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| 211 | client.sin_port = htons(dest_port);
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| 212 | client.sin_addr.s_addr = dest_ip;
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| 213 |
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| 214 | if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {
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| 215 | close(fd);
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| 216 | return -1;
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| 217 | }
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| 218 |
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| 219 | result = write(fd, payload, sizeof(struct dhcpMessage));
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| 220 | close(fd);
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| 221 | return result;
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| 222 | }
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