#include <unistd.h>#include <string.h>#include <netinet/in.h>#include <sys/types.h>#include <sys/socket.h>#include <features.h>#if (__GLIBC__ >= 2 && __GLIBC_MINOR >= 1) || defined _NEWLIB_VERSION#include <netpacket/packet.h>#include <net/ethernet.h>#else#include <asm/types.h>#include <linux/if_packet.h>#include <linux/if_ether.h>#endif#include <errno.h>#include "common.h"#include "packet.h"#include "dhcpd.h"#include "options.h"void udhcp_init_header(struct dhcpMessage *packet, char type){	memset(packet, 0, sizeof(struct dhcpMessage));	switch (type) {	case DHCPDISCOVER:	case DHCPREQUEST:	case DHCPRELEASE:	case DHCPINFORM:		packet->op = BOOTREQUEST;		break;	case DHCPOFFER:	case DHCPACK:	case DHCPNAK:		packet->op = BOOTREPLY;	}	packet->htype = ETH_10MB;	packet->hlen = ETH_10MB_LEN;	packet->cookie = htonl(DHCP_MAGIC);	packet->options[0] = DHCP_END;	add_simple_option(packet->options, DHCP_MESSAGE_TYPE, type);}/* read a packet from socket fd, return -1 on read error, -2 on packet error */int udhcp_get_packet(struct dhcpMessage *packet, int fd){	static const char broken_vendors[][8] = {		"MSFT 98",		""	};	int bytes;	int i;	char unsigned *vendor;	memset(packet, 0, sizeof(struct dhcpMessage));	bytes = read(fd, packet, sizeof(struct dhcpMessage));	if (bytes < 0) {		DEBUG(LOG_INFO, "couldn't read on listening socket, ignoring");		return -1;	}	if (ntohl(packet->cookie) != DHCP_MAGIC) {		LOG(LOG_ERR, "received bogus message, ignoring");		return -2;	}	DEBUG(LOG_INFO, "Received a packet");	if (packet->op == BOOTREQUEST && (vendor = get_option(packet, DHCP_VENDOR))) {		for (i = 0; broken_vendors[i][0]; i++) {			if (vendor[OPT_LEN - 2] == (uint8_t) strlen(broken_vendors[i]) &&			    !strncmp((char*)vendor, broken_vendors[i], vendor[OPT_LEN - 2])) {				DEBUG(LOG_INFO, "broken client (%s), forcing broadcast",					broken_vendors[i]);				packet->flags |= htons(BROADCAST_FLAG);			}		}	}	return bytes;}uint16_t udhcp_checksum(void *addr, int count){	/* Compute Internet Checksum for "count" bytes	 *         beginning at location "addr".	 */	register int32_t sum = 0;	uint16_t *source = (uint16_t *) addr;	while (count > 1)  {		/*  This is the inner loop */		sum += *source++;		count -= 2;	}	/*  Add left-over byte, if any */	if (count > 0) {		/* Make sure that the left-over byte is added correctly both		 * with little and big endian hosts */		uint16_t tmp = 0;		*(uint8_t *) (&tmp) = * (uint8_t *) source;		sum += tmp;	}	/*  Fold 32-bit sum to 16 bits */	while (sum >> 16)		sum = (sum & 0xffff) + (sum >> 16);	return ~sum;}/* Construct a ip/udp header for a packet, and specify the source and dest hardware address */int udhcp_raw_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,		   uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex){	int fd;	int result;	struct sockaddr_ll dest;	struct udp_dhcp_packet packet;	if ((fd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))) < 0) {		DEBUG(LOG_ERR, "socket call failed: %m");		return -1;	}	memset(&dest, 0, sizeof(dest));	memset(&packet, 0, sizeof(packet));	dest.sll_family = AF_PACKET;	dest.sll_protocol = htons(ETH_P_IP);	dest.sll_ifindex = ifindex;	dest.sll_halen = 6;	memcpy(dest.sll_addr, dest_arp, 6);	if (bind(fd, (struct sockaddr *)&dest, sizeof(struct sockaddr_ll)) < 0) {		DEBUG(LOG_ERR, "bind call failed: %m");		close(fd);		return -1;	}	packet.ip.protocol = IPPROTO_UDP;	packet.ip.saddr = source_ip;	packet.ip.daddr = dest_ip;	packet.udp.source = htons(source_port);	packet.udp.dest = htons(dest_port);	packet.udp.len = htons(sizeof(packet.udp) + sizeof(struct dhcpMessage)); /* cheat on the psuedo-header */	packet.ip.tot_len = packet.udp.len;	memcpy(&(packet.data), payload, sizeof(struct dhcpMessage));	packet.udp.check = udhcp_checksum(&packet, sizeof(struct udp_dhcp_packet));	packet.ip.tot_len = htons(sizeof(struct udp_dhcp_packet));	packet.ip.ihl = sizeof(packet.ip) >> 2;	packet.ip.version = IPVERSION;	packet.ip.ttl = IPDEFTTL;	packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));	result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0, (struct sockaddr *) &dest, sizeof(dest));	if (result <= 0) {		DEBUG(LOG_ERR, "write on socket failed: %m");	}	close(fd);	return result;}/* Let the kernel do all the work for packet generation */int udhcp_kernel_packet(struct dhcpMessage *payload, uint32_t source_ip, int source_port,		   uint32_t dest_ip, int dest_port){	int n = 1;	int fd, result;	struct sockaddr_in client;	if ((fd = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0)		return -1;	if (setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &n, sizeof(n)) == -1) {		close(fd);		return -1;	}	memset(&client, 0, sizeof(client));	client.sin_family = AF_INET;	client.sin_port = htons(source_port);	client.sin_addr.s_addr = source_ip;	if (bind(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {		close(fd);		return -1;	}	memset(&client, 0, sizeof(client));	client.sin_family = AF_INET;	client.sin_port = htons(dest_port);	client.sin_addr.s_addr = dest_ip;	if (connect(fd, (struct sockaddr *)&client, sizeof(struct sockaddr)) == -1) {		close(fd);		return -1;	}	result = write(fd, payload, sizeof(struct dhcpMessage));	close(fd);	return result;}