File content as of revision 2:049ce85163c5:

// DHCP Library v0.3 - April 25, 2009
// Author: Jordan Terrell - blog.jordanterrell.com
#include <string.h>
#include <stdlib.h>
#include "Dhcp.h"
#include  "utility/util.h"
#include  "utility/uip_clock.h"

/**
 * @brief
 * @note
 * @param
 * @retval
 */
int DhcpClass::beginWithDHCP(uint8_t* mac, unsigned long timeout, unsigned long responseTimeout) {
    _dhcpLeaseTime = 0;
    _dhcpT1 = 0;
    _dhcpT2 = 0;
    _lastCheck = 0;
    _timeout = timeout;
    _responseTimeout = responseTimeout;

    // zero out _dhcpMacAddr
    memset(_dhcpMacAddr, 0, 6);
    reset_DHCP_lease();

    memcpy((void*)_dhcpMacAddr, (void*)mac, 6);
    _dhcp_state = STATE_DHCP_START;
    return request_DHCP_lease();
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void DhcpClass::reset_DHCP_lease(void) {

    // zero out _dhcpSubnetMask, _dhcpGatewayIp, _dhcpLocalIp, _dhcpDhcpServerIp, _dhcpDnsServerIp

    memset(_dhcpLocalIp, 0, 20);
}

//return:0 on error, 1 if request is sent and response is received
int DhcpClass::request_DHCP_lease(void) {
    uint8_t messageType = 0;

    // Pick an initial transaction ID

    _dhcpTransactionId = (rand() * 2000UL) / RAND_MAX + 1;
    _dhcpInitialTransactionId = _dhcpTransactionId;

    _dhcpUdpSocket.stop();
    if(_dhcpUdpSocket.begin(DHCP_CLIENT_PORT) == 0) {

        // Couldn't get a socket
        return 0;
    }

    presend_DHCP();

    int             result = 0;

    unsigned long   startTime = clock_time();

    while(_dhcp_state != STATE_DHCP_LEASED) {
        if(_dhcp_state == STATE_DHCP_START) {
            _dhcpTransactionId++;

            send_DHCP_MESSAGE(DHCP_DISCOVER, ((clock_time() - startTime) / 1000));
            _dhcp_state = STATE_DHCP_DISCOVER;
        }
        else
        if(_dhcp_state == STATE_DHCP_REREQUEST) {
            _dhcpTransactionId++;
            send_DHCP_MESSAGE(DHCP_REQUEST, ((clock_time() - startTime) / 1000));
            _dhcp_state = STATE_DHCP_REQUEST;
        }
        else
        if(_dhcp_state == STATE_DHCP_DISCOVER) {
            uint32_t    respId;
            messageType = parseDHCPResponse(_responseTimeout, respId);
            if(messageType == DHCP_OFFER) {

                // We'll use the transaction ID that the offer came with,
                // rather than the one we were up to
                _dhcpTransactionId = respId;
                send_DHCP_MESSAGE(DHCP_REQUEST, ((clock_time() - startTime) / 1000));
                _dhcp_state = STATE_DHCP_REQUEST;
            }
        }
        else
        if(_dhcp_state == STATE_DHCP_REQUEST) {
            uint32_t    respId;
            messageType = parseDHCPResponse(_responseTimeout, respId);
            if(messageType == DHCP_ACK) {
                _dhcp_state = STATE_DHCP_LEASED;
                result = 1;

                //use default lease time if we didn't get it
                if(_dhcpLeaseTime == 0) {
                    _dhcpLeaseTime = DEFAULT_LEASE;
                }

                //calculate T1 & T2 if we didn't get it
                if(_dhcpT1 == 0) {

                    //T1 should be 50% of _dhcpLeaseTime
                    _dhcpT1 = _dhcpLeaseTime >> 1;
                }

                if(_dhcpT2 == 0) {

                    //T2 should be 87.5% (7/8ths) of _dhcpLeaseTime
                    _dhcpT2 = _dhcpT1 << 1;
                }

                _renewInSec = _dhcpT1;
                _rebindInSec = _dhcpT2;
            }
            else
            if(messageType == DHCP_NAK)
                _dhcp_state = STATE_DHCP_START;
        }

        if(messageType == 255) {
            messageType = 0;
            _dhcp_state = STATE_DHCP_START;
        }

        if(result != 1 && ((clock_time() - startTime) > _timeout))
            break;
    }

    // We're done with the socket now
    _dhcpUdpSocket.stop();
    _dhcpTransactionId++;

    return result;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void DhcpClass::presend_DHCP(void)
{ }

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void DhcpClass::send_DHCP_MESSAGE(uint8_t messageType, uint16_t secondsElapsed) {
    uint8_t buffer[32];
    memset(buffer, 0, 32);

    IPAddress   dest_addr(255, 255, 255, 255);  // Broadcast address

    if(-1 == _dhcpUdpSocket.beginPacket(dest_addr, DHCP_SERVER_PORT)) {

        // FIXME Need to return errors
        return;
    }

    buffer[0] = DHCP_BOOTREQUEST;       // op
    buffer[1] = DHCP_HTYPE10MB;         // htype
    buffer[2] = DHCP_HLENETHERNET;      // hlen
    buffer[3] = DHCP_HOPS;              // hops

    // xid
    unsigned long   xid = htonl(_dhcpTransactionId);
    memcpy(buffer + 4, &(xid), 4);

    // 8, 9 - seconds elapsed
    buffer[8] = ((secondsElapsed & 0xff00) >> 8);
    buffer[9] = (secondsElapsed & 0x00ff);

    // flags
    unsigned short  flags = htons(DHCP_FLAGSBROADCAST);
    memcpy(buffer + 10, &(flags), 2);

    // ciaddr: already zeroed
    // yiaddr: already zeroed
    // siaddr: already zeroed
    // giaddr: already zeroed
    //put data in W5100 transmit buffer
    _dhcpUdpSocket.write(buffer, 28);

    memset(buffer, 0, 32);              // clear local buffer
    memcpy(buffer, _dhcpMacAddr, 6);    // chaddr

    //put data in W5100 transmit buffer
    _dhcpUdpSocket.write(buffer, 16);

    memset(buffer, 0, 32);      // clear local buffer

    // leave zeroed out for sname && file
    // put in W5100 transmit buffer x 6 (192 bytes)
    for(int i = 0; i < 6; i++) {
        _dhcpUdpSocket.write(buffer, 32);
    }

    // OPT - Magic Cookie
    buffer[0] = (uint8_t) ((MAGIC_COOKIE >> 24) & 0xFF);
    buffer[1] = (uint8_t) ((MAGIC_COOKIE >> 16) & 0xFF);
    buffer[2] = (uint8_t) ((MAGIC_COOKIE >> 8) & 0xFF);
    buffer[3] = (uint8_t) (MAGIC_COOKIE & 0xFF);

    // OPT - message type
    buffer[4] = dhcpMessageType;
    buffer[5] = 0x01;
    buffer[6] = messageType;    //DHCP_REQUEST;

    // OPT - client identifier
    buffer[7] = dhcpClientIdentifier;
    buffer[8] = 0x07;
    buffer[9] = 0x01;
    memcpy(buffer + 10, _dhcpMacAddr, 6);

    // OPT - host name
    buffer[16] = hostName;
    buffer[17] = strlen(HOST_NAME) + 6; // length of hostname + last 3 bytes of mac address
    strcpy((char*) &(buffer[18]), HOST_NAME);

    printByte((char*) &(buffer[24]), _dhcpMacAddr[3]);
    printByte((char*) &(buffer[26]), _dhcpMacAddr[4]);
    printByte((char*) &(buffer[28]), _dhcpMacAddr[5]);

    //put data in W5100 transmit buffer
    _dhcpUdpSocket.write(buffer, 30);

    if(messageType == DHCP_REQUEST) {
        buffer[0] = dhcpRequestedIPaddr;
        buffer[1] = 0x04;
        buffer[2] = _dhcpLocalIp[0];
        buffer[3] = _dhcpLocalIp[1];
        buffer[4] = _dhcpLocalIp[2];
        buffer[5] = _dhcpLocalIp[3];

        buffer[6] = dhcpServerIdentifier;
        buffer[7] = 0x04;
        buffer[8] = _dhcpDhcpServerIp[0];
        buffer[9] = _dhcpDhcpServerIp[1];
        buffer[10] = _dhcpDhcpServerIp[2];
        buffer[11] = _dhcpDhcpServerIp[3];

        //put data in W5100 transmit buffer
        _dhcpUdpSocket.write(buffer, 12);
    }

    buffer[0] = dhcpParamRequest;
    buffer[1] = 0x06;
    buffer[2] = subnetMask;
    buffer[3] = routersOnSubnet;
    buffer[4] = dns;
    buffer[5] = domainName;
    buffer[6] = dhcpT1value;
    buffer[7] = dhcpT2value;
    buffer[8] = endOption;

    //put data in W5100 transmit buffer
    _dhcpUdpSocket.write(buffer, 9);

    _dhcpUdpSocket.endPacket();
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
uint8_t DhcpClass::parseDHCPResponse(unsigned long responseTimeout, uint32_t& transactionId) {
    uint8_t         type = 0;
    uint8_t         opt_len = 0;

    unsigned long   startTime = clock_time();

    while(_dhcpUdpSocket.parsePacket() <= 0) {
        if((clock_time() - startTime) > responseTimeout) {
            return 255;
        }

        wait(0.050);
    }

    // start reading in the packet
    RIP_MSG_FIXED   fixedMsg;
    _dhcpUdpSocket.read((uint8_t*) &fixedMsg, sizeof(RIP_MSG_FIXED));

    if(fixedMsg.op == DHCP_BOOTREPLY && _dhcpUdpSocket.remotePort() == DHCP_SERVER_PORT) {
        transactionId = ntohl(fixedMsg.xid);
        if
        (
            memcmp(fixedMsg.chaddr, _dhcpMacAddr, 6) != 0
        ||  (transactionId < _dhcpInitialTransactionId)
        ||  (transactionId > _dhcpTransactionId)
        ) {

            // Need to read the rest of the packet here regardless
            _dhcpUdpSocket.flush();
            return 0;
        }

        memcpy(_dhcpLocalIp, fixedMsg.yiaddr, 4);

        // Skip to the option part
        // Doing this a byte at a time so we don't have to put a big buffer
        // on the stack (as we don't have lots of memory lying around)
        for(int i = 0; i < (240 - (int)sizeof(RIP_MSG_FIXED)); i++) {
            _dhcpUdpSocket.read();  // we don't care about the returned byte
        }

        while(_dhcpUdpSocket.available() > 0) {
            switch(_dhcpUdpSocket.read()) {
            case endOption:
                break;

            case padOption:
                break;

            case dhcpMessageType:
                opt_len = _dhcpUdpSocket.read();
                type = _dhcpUdpSocket.read();
                break;

            case subnetMask:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read(_dhcpSubnetMask, 4);
                break;

            case routersOnSubnet:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read(_dhcpGatewayIp, 4);
                for(int i = 0; i < opt_len - 4; i++) {
                    _dhcpUdpSocket.read();
                }
                break;

            case dns:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read(_dhcpDnsServerIp, 4);
                for(int i = 0; i < opt_len - 4; i++) {
                    _dhcpUdpSocket.read();
                }
                break;

            case dhcpServerIdentifier:
                opt_len = _dhcpUdpSocket.read();
                if(*((uint32_t*)_dhcpDhcpServerIp) == 0 || IPAddress(_dhcpDhcpServerIp) == _dhcpUdpSocket.remoteIP()) {
                    _dhcpUdpSocket.read(_dhcpDhcpServerIp, sizeof(_dhcpDhcpServerIp));
                }
                else {

                    // Skip over the rest of this option
                    while(opt_len--) {
                        _dhcpUdpSocket.read();
                    }
                }
                break;

            case dhcpT1value:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read((uint8_t*) &_dhcpT1, sizeof(_dhcpT1));
                _dhcpT1 = ntohl(_dhcpT1);
                break;

            case dhcpT2value:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read((uint8_t*) &_dhcpT2, sizeof(_dhcpT2));
                _dhcpT2 = ntohl(_dhcpT2);
                break;

            case dhcpIPaddrLeaseTime:
                opt_len = _dhcpUdpSocket.read();
                _dhcpUdpSocket.read((uint8_t*) &_dhcpLeaseTime, sizeof(_dhcpLeaseTime));
                _dhcpLeaseTime = ntohl(_dhcpLeaseTime);
                _renewInSec = _dhcpLeaseTime;
                break;

            default:
                opt_len = _dhcpUdpSocket.read();

                // Skip over the rest of this option
                while(opt_len--) {
                    _dhcpUdpSocket.read();
                }
                break;
            }
        }
    }

    // Need to skip to end of the packet regardless here
    _dhcpUdpSocket.flush();

    return type;
}

/*
    returns:
    0/DHCP_CHECK_NONE: nothing happened
    1/DHCP_CHECK_RENEW_FAIL: renew failed
    2/DHCP_CHECK_RENEW_OK: renew success
    3/DHCP_CHECK_REBIND_FAIL: rebind fail
    4/DHCP_CHECK_REBIND_OK: rebind success
*/
int DhcpClass::checkLease(void) {

    //this uses a signed / unsigned trick to deal with millis overflow
    unsigned long   now = clock_time();
    signed long     snow = (long)now;
    int             rc = DHCP_CHECK_NONE;
    if(_lastCheck != 0) {
        signed long factor;
        //calc how many ms past the timeout we are

        factor = snow - (long)_secTimeout;

        //if on or passed the timeout, reduce the counters
        if(factor >= 0) {

            //next timeout should be now plus 1000 ms minus parts of second in factor
            _secTimeout = snow + 1000 - factor % 1000;

            //how many seconds late are we, minimum 1
            factor = factor / 1000 + 1;

            //reduce the counters by that mouch
            //if we can assume that the cycle time (factor) is fairly constant
            //and if the remainder is less than cycle time * 2
            //do it early instead of late
            if(_renewInSec < factor * 2)
                _renewInSec = 0;
            else
                _renewInSec -= factor;

            if(_rebindInSec < factor * 2)
                _rebindInSec = 0;
            else
                _rebindInSec -= factor;
        }

        //if we have a lease but should renew, do it
        if(_dhcp_state == STATE_DHCP_LEASED && _renewInSec <= 0) {
            _dhcp_state = STATE_DHCP_REREQUEST;
            rc = 1 + request_DHCP_lease();
        }

        //if we have a lease or is renewing but should bind, do it
        if((_dhcp_state == STATE_DHCP_LEASED || _dhcp_state == STATE_DHCP_START) && _rebindInSec <= 0) {

            //this should basically restart completely
            _dhcp_state = STATE_DHCP_START;
            reset_DHCP_lease();
            rc = 3 + request_DHCP_lease();
        }
    }
    else {
        _secTimeout = snow + 1000;
    }

    _lastCheck = now;
    return rc;
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
IPAddress DhcpClass::getLocalIp(void) {
    return IPAddress(_dhcpLocalIp);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
IPAddress DhcpClass::getSubnetMask(void) {
    return IPAddress(_dhcpSubnetMask);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
IPAddress DhcpClass::getGatewayIp(void) {
    return IPAddress(_dhcpGatewayIp);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
IPAddress DhcpClass::getDhcpServerIp(void) {
    return IPAddress(_dhcpDhcpServerIp);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
IPAddress DhcpClass::getDnsServerIp(void) {
    return IPAddress(_dhcpDnsServerIp);
}

/**
 * @brief
 * @note
 * @param
 * @retval
 */
void DhcpClass::printByte(char* buf, uint8_t n) {
    char*   str = &buf[1];
    buf[0] = '0';
    do
    {
        unsigned long   m = n;
        n /= 16;

        char    c = m - 16 * n;
        *str-- = c < 10 ? c + '0' : c + 'A' - 10;
    } while(n);
}