#include <stdlib.h>

#include <errno.h>

#include <string.h>

#include <stdio.h>

#include <net/ethernet.h>

#include <net/if_arp.h>

#include <sys/param.h>

#include "util.h"

#include "list.h"

#include "dhcp-protocol.h"

#include "dhcp-lease-internal.h"

#include "dhcp-internal.h"

#include "sd-dhcp-lease.h"

#include "sd-dhcp-client.h"

#define DHCP_CLIENT_MIN_OPTIONS_SIZE 312

int dhcp_message_init(DHCPMessage *message, uint8_t op, uint32_t xid,

uint8_t type, uint8_t **opt, size_t *optlen) {

int err;

assert(op == BOOTREQUEST || op == BOOTREPLY);

*opt = (uint8_t *)(message + 1);

if (*optlen < 4)

return -ENOBUFS;

*optlen -= 4;

message->op = op;

message->htype = ARPHRD_ETHER;

message->hlen = ETHER_ADDR_LEN;

message->xid = htobe32(xid);

(*opt)[0] = 0x63;

(*opt)[1] = 0x82;

(*opt)[2] = 0x53;

(*opt)[3] = 0x63;

*opt += 4;

err = dhcp_option_append(opt, optlen, DHCP_OPTION_MESSAGE_TYPE, 1,

&type);

if (err < 0)

return err;

return 0;

}

static uint16_t dhcp_checksum(void *buf, int len) {

uint32_t sum;

uint16_t *check;

int i;

uint8_t *odd;

sum = 0;

check = buf;

for (i = 0; i < len / 2 ; i++)

sum += check[i];

if (len & 0x01) {

odd = buf;

sum += odd[len - 1];

}

while (sum >> 16)

sum = (sum & 0xffff) + (sum >> 16);

return ~sum;

}

void dhcp_packet_append_ip_headers(DHCPPacket *packet, uint16_t len) {

packet->ip.version = IPVERSION;

packet->ip.ihl = DHCP_IP_SIZE / 4;

packet->ip.tot_len = htobe16(len);

packet->ip.protocol = IPPROTO_UDP;

packet->ip.saddr = INADDR_ANY;

packet->ip.daddr = INADDR_BROADCAST;

packet->udp.source = htobe16(DHCP_PORT_CLIENT);

packet->udp.dest = htobe16(DHCP_PORT_SERVER);

packet->udp.len = htobe16(len - DHCP_IP_SIZE);

packet->ip.check = packet->udp.len;

packet->udp.check = dhcp_checksum(&packet->ip.ttl, len - 8);

packet->ip.ttl = IPDEFTTL;

packet->ip.check = 0;

packet->ip.check = dhcp_checksum(&packet->ip, DHCP_IP_SIZE);

}

int dhcp_packet_verify_headers(DHCPPacket *packet, size_t len, bool checksum) {

size_t hdrlen;

assert(packet);

/* IP */

if (len < DHCP_IP_SIZE) {

log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "

" smaller than IP header (%u bytes)", len,

DHCP_IP_SIZE);

return -EINVAL;

}

if (packet->ip.ihl < 5) {

log_dhcp_client(client, "ignoring packet: IPv4 IHL (%u words) invalid",

packet->ip.ihl);

return -EINVAL;

}

hdrlen = packet->ip.ihl * 4;

if (hdrlen < 20) {

log_dhcp_client(client, "ignoring packet: IPv4 IHL (%zu bytes) "

"smaller than minimum (20 bytes)", hdrlen);

return -EINVAL;

}

if (len < hdrlen) {

log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "

"smaller than expected (%zu) by IP header", len,

hdrlen);

return -EINVAL;

}

if (dhcp_checksum(&packet->ip, hdrlen)) {

log_dhcp_client(client, "ignoring packet: invalid IP checksum");

return -EINVAL;

}

/* UDP */

if (len < DHCP_IP_UDP_SIZE) {

log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "

" smaller than IP+UDP header (%u bytes)", len,

DHCP_IP_UDP_SIZE);

return -EINVAL;

}

if (len < hdrlen + be16toh(packet->udp.len)) {

log_dhcp_client(client, "ignoring packet: packet (%zu bytes) "

"smaller than expected (%zu) by UDP header", len,

hdrlen + be16toh(packet->udp.len));

return -EINVAL;

}

if (checksum && packet->udp.check) {

packet->ip.check = packet->udp.len;

packet->ip.ttl = 0;

if (dhcp_checksum(&packet->ip.ttl,

be16toh(packet->udp.len) + 12)) {

log_dhcp_client(client, "ignoring packet: invalid UDP checksum");

return -EINVAL;

}

}

if (be16toh(packet->udp.dest) != DHCP_PORT_CLIENT) {

log_dhcp_client(client, "ignoring packet: to port %u, which "

"is not the DHCP client port (%u)",

be16toh(packet->udp.dest), DHCP_PORT_CLIENT);

return -EINVAL;

}

return 0;

}