dhcp.h

/*
Copyright (c) 2014, Pierre-Henri Symoneaux
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:

* Redistributions of source code must retain the above copyright notice, this
  list of conditions and the following disclaimer.

* Redistributions in binary form must reproduce the above copyright notice,
  this list of conditions and the following disclaimer in the documentation
  and/or other materials provided with the distribution.

* Neither the name of LightDhcpClient nor the names of its
  contributors may be used to endorse or promote products derived from
  this software without specific prior written permission.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */
 
#ifndef _DHCP_H
#define _DHCP_H

#define DHCP_MAGIC 			htonl(0x63825363)

#define DHCP_MIN_PACK_SIZE 	240

#define OP_BOOT_REQUEST 	0x01
#define OP_BOOT_REPLY 		0x02

#define HW_TYPE_ETHERNET 	0x01
#define HW_LENGTH_ETHERNET 	0x06

//DHCP options

#define DHCP_END 	0xff

#define OPTION_DHCP_MESSAGE_TYPE 	53
#define VALUE_MESSAGE_DISCOVER 		0x01
#define VALUE_MESSAGE_OFFER 		0x02
#define VALUE_MESSAGE_REQUEST 		0x01
#define VALUE_MESSAGE_ACK 			0x05
#define VALUE_MESSAGE_NAK 			0x06
#define VALUE_MESSAGE_INFORM 		0x08

#define OPTION_SERVER_IP 			54
#define OPTION_LEASE_TIME 			51
#define OPTION_REQUESTED_IP 		50

#define OPTION_PARAMETER_REQUEST_LIST 	55

#define OPTION_SUBNET_MASK 		1
#define OPTION_ROUTER 			3
#define OPTION_BROADCAST_ADDR 	28
#define OPTION_DNS 				6
#define OPTION_DOMAIN_NAME 		15
#define OPTION_HOST_NAME 		12

//These should not really be usefull for what we do
#define OPTION_TIME_OFFSET 		2
#define OPTION_STATIC_ROUTE 	121
#define OPTION_NIS_DOMAIN 		40
#define OPTION_NIS_SERVERS 		41
#define OPTION_NTP_SERVERS 		42
#define OPTION_MTU 				26
#define OPTION_DOMAIN_SEARCH 	119

//DHCP options
struct dhcp_opt {
    unsigned char id;       // Option ID
    unsigned char len;      // Option value length
    unsigned char values[]; // Option value(s)
};

//DHCP packet structure
struct dhcp_pkt
{
    unsigned char   op;     // Message type
    unsigned char   htype;  // HW type
    unsigned char   hlen;   // HW addr length
    unsigned char   hops;   // Hops

    unsigned int    xid;    // Transaction ID

    unsigned short  secs;   // seconds elapsed
    unsigned short  flags;  // Bootp flags

    unsigned int    ci_addr; // Client address
    unsigned int    yi_addr; // Your address
    unsigned int    si_addr; // Next Server IP address
    unsigned int    gi_addr; // Relay agent IP address
    unsigned char   cm_addr[6];   // Client MAC address
    unsigned char   ch_addr[10];  // Client hardware address padding

    unsigned char   unused[192];

    unsigned int    magic;      // DHCP magic number

    unsigned char   opt[128];   // Options padding
//    struct dhcp_opt opt [64];
};

//Build a discover DHCP packet, return packet size
int build_dhcp_discover(struct dhcp_pkt* pkt, unsigned char* src_mac, int mac_len);

//Check if the packet is a DHCP one
int is_dhcp(struct dhcp_pkt* pkt);

//Find an option in the DHCP packet. offset is the position of the option in the packet.
// After the call, offset is updated to the offset of the next option (if any)
struct dhcp_opt* get_dhcp_option(struct dhcp_pkt *pkt, int *offset);

//Read an IP in a 4 bytes data array
unsigned int char_to_ip(unsigned char* ip);

#endif