File content as of revision 2:a8df39b4f3aa:

// DHCPClient.cpp 2012/4/14
// DHCP Client for WIZ820io(W5200)
#include "mbed.h"
#include "w5100.h"
#include "UDPSocket.h"
#include "DHCPClient.h"

//#define DEBUG

#ifdef DEBUG
#include "Utils.h"
#define PRINT_FUNC() printf("%p %d:%s\n", this,__LINE__,__PRETTY_FUNCTION__)
#else //DEBUG
#define PRINT_FUNC()
#endif //DEBUG

int DHCPClient::discover(uint8_t buf[], int size) {
    memset(buf, 0x00, size);
    const uint8_t headers[] = {0x01,0x01,0x06,0x00,
                               0x12,0x34,0x56,0x78}; // xid
    memcpy(buf, headers, sizeof(headers));
    int t = clock();
    xid[0] = t<<24;
    xid[1] = t<<16;
    xid[2] = t<<8;
    xid[3] = t;
    memcpy(buf+DHCP_OFFSET_XID, xid, 4);
    W5100.getMACAddress(buf+DHCP_OFFSET_CHADDR);
    const uint8_t options[] = {0x63,0x82,0x53,0x63, // magic cookie
                               0x35,0x01,0x01, // DHCP DISCOVER
                               0xff};
    memcpy(buf+DHCP_OFFSET_MAGIC_COOKIE, options, sizeof(options));
    uint8_t ip[4] = {0,0,0,0};
    W5100.setIPAddress(ip);
    return DHCP_OFFSET_MAGIC_COOKIE + sizeof(options);
}

int DHCPClient::request(uint8_t buf[], int size) {
    memset(buf, 0x00, size);
    const uint8_t headers[] = {0x01,0x01,0x06,0x00,
                               0x12,0x34,0x56,0x78}; // xid
    memcpy(buf, headers, sizeof(headers));
    memcpy(buf+DHCP_OFFSET_XID, xid, 4);
    memcpy(buf+DHCP_OFFSET_YIADDR, yiaddr, 4);
    W5100.getMACAddress(buf+DHCP_OFFSET_CHADDR);
    const uint8_t options[] = {0x63,0x82,0x53,0x63, // magic cookie
                               0x35,0x01,0x03, // DHCP REQUEST
                               0x32,0x04,0x00,0x00,0x00,0x00, // request IP
                               0xff};
    memcpy(buf+DHCP_OFFSET_MAGIC_COOKIE, options, sizeof(options));
    memcpy(buf+DHCP_OFFSET_MAGIC_COOKIE+9, yiaddr, 4);
    return DHCP_OFFSET_MAGIC_COOKIE + sizeof(options);
}

int DHCPClient::offer_ack(uint8_t buf[], int size) {
    memcpy(yiaddr, &buf[DHCP_OFFSET_YIADDR], 4);   
    uint8_t *p;
    int msg_type = -1;
    p = buf + DHCP_OFFSET_OPTIONS;
    while(*p != 0xff && p < (uint8_t*)&buf[DHCP_MAX_PACKET_SIZE]) {
        int code = *p++;
        if (code == 0x00) {
            continue;
        }
        int len = *p++;
#ifdef DEBUG           
        char codeStr[24];
        snprintf(codeStr, sizeof(codeStr), "DHCP option: %d", code);
        printfBytes(codeStr, p, len);
#endif //DEBUG
        if (code == 53) {
           msg_type = *p;
        } else if (code == 1) {
            memcpy(netmask, p, 4); // Subnet mask address
        } else if (code == 3) {
            memcpy(gateway, p, 4); // Gateway IP address 
        } else if (code == 6) {// DNS
            memcpy(dnsaddr, p, 4);
        }
        p += len;
    }
    return msg_type;
}

bool DHCPClient::verify(uint8_t buf[], int len) {
    if (len < DHCP_OFFSET_OPTIONS) {
        return false;
    }
    if (buf[DHCP_OFFSET_OP] != 0x02) {
        return false;
    }
    if (memcmp(buf+DHCP_OFFSET_XID, xid, 4) != 0) {
        return false;
    }
    return true;
}

void DHCPClient::callback(UDPSocketEvent e)
{
    PRINT_FUNC();
    uint8_t buf[DHCP_MAX_PACKET_SIZE];
    Host host;
    int len = m_udp->recvfrom((char*)buf, sizeof(buf), &host);
    if (!verify(buf, len)) {
        return;
    }
    int r = offer_ack(buf, len);
    if (r == 2) { // OFFER
        request(buf, 300);
        Host server(IpAddr(255,255,255,255), 67); // DHCP broadcast
        m_udp->sendto((char*)buf, 300, &server);
    } else if (r == 5) { // ACK
        exit_flag = true;
    }
}

int DHCPClient::setup(int timeout_ms)
{
    PRINT_FUNC();   
    Timer t;
    t.start();
    m_udp = new UDPSocket;
    m_udp->setOnEvent(this, &DHCPClient::callback);
    Host local(IpAddr(0,0,0,0), 68);
    Host server(IpAddr(255,255,255,255), 67); // DHCP broadcast
    m_udp->bind(local);
    uint8_t buf[300];
    discover(buf, sizeof(buf));
    m_udp->sendto((char*)buf, sizeof(buf), &server);
    exit_flag = false;
    int err = 0;
    while(1) {
        Net::poll();
        if (exit_flag) {
            break;
        }
        if (t.read_ms() > timeout_ms) {
            err = -1;
            break;
        }
#ifdef DEBUG            
        wait_ms(500);
#endif //DEBUG
    }
    delete m_udp;
    return err;
}

DHCPClient::DHCPClient() {
    m_udp = NULL;
}