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