File content as of revision 9:2f607bafc29e:

/* NTPClient.cpp */
/* Copyright (C) 2012 mbed.org, MIT License
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
 * and associated documentation files (the "Software"), to deal in the Software without restriction,
 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in all copies or
 * substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 */
#include "mbed.h" //time() and set_time()

//#define DEBUG "NTPc"

#if (defined(DEBUG))
#include <cstdio>
#define INFO(x, ...) std::printf("[INF %s %4d] "x"\r\n", DEBUG, __LINE__, ##__VA_ARGS__);
#define WARN(x, ...) std::printf("[WRN %s %4d] "x"\r\n", DEBUG, __LINE__, ##__VA_ARGS__);
#define ERR(x, ...)  std::printf("[ERR %s %4d] "x"\r\n", DEBUG, __LINE__, ##__VA_ARGS__);
static void HexDump(const char * title, const uint8_t * p, int count)
{
    int i;
    char buf[100] = "0000: ";

    if (*title)
        INFO("%s", title);
    for (i=0; i<count; ) {
        sprintf(buf + strlen(buf), "%02X ", *(p+i));
        if ((++i & 0x0F) == 0x00) {
            INFO("%s", buf);
            if (i < count)
                sprintf(buf, "%04X: ", i);
            else
                buf[0] = '\0';
        }
    }
    if (strlen(buf))
        INFO("%s", buf);
}
#else
//Disable debug
#define INFO(x, ...)
#define WARN(x, ...)
#define ERR(x, ...)
#define HexDump(a,b,c)
#endif

#include "NTPClient.h"

#include "UDPSocket.h"


#define NTP_PORT 123
#define NTP_CLIENT_PORT 0 //Random port
#define NTP_TIMESTAMP_DELTA 2208988800ull //Diff btw a UNIX timestamp (Starting Jan, 1st 1970) and a NTP timestamp (Starting Jan, 1st 1900)

NTPClient::NTPClient() : m_sock()
{

}

NTPResult NTPClient::setTime(const char* host, uint16_t port, uint32_t timeout)
{
#ifdef DEBUG
    time_t ctTime;
    ctTime = time(NULL);
    INFO("Time is currently (UTC): %s", ctime(&ctTime));
#endif

    //Create & bind socket
    INFO("Binding socket");
    m_sock.bind(0); //Bind to a random port

    m_sock.set_blocking(false, timeout); //Set not blocking

    struct NTPPacket pkt;

    //Now ping the server and wait for response
    INFO("Ping");
    //Prepare NTP Packet:
    pkt.li = 0; //Leap Indicator : No warning
    pkt.vn = 4; //Version Number : 4
    pkt.mode = 3; //Client mode
    pkt.stratum = 0; //Not relevant here
    pkt.poll = 0; //Not significant as well
    pkt.precision = 0; //Neither this one is

    pkt.rootDelay = 0; //Or this one
    pkt.rootDispersion = 0; //Or that one
    pkt.refId = 0; //...

    pkt.refTm_s = 0;
    pkt.origTm_s = 0;
    pkt.rxTm_s = 0;
    pkt.txTm_s = htonl( NTP_TIMESTAMP_DELTA + time(NULL) ); //WARN: We are in LE format, network byte order is BE
    INFO("pkt.txTm_s = %u", ntohl(pkt.txTm_s) );
    pkt.refTm_f = pkt.origTm_f = pkt.rxTm_f = pkt.txTm_f = 0;

    HexDump("NTP Post", (uint8_t *)&pkt, sizeof(NTPPacket));
    
    Endpoint outEndpoint;
    INFO("outEndpoint instantiated");
    
    if( outEndpoint.set_address(host, port) < 0) {
        m_sock.close();
        return NTP_DNS;
    }
    INFO("outEndpoint: %s:%d", outEndpoint.get_address(), outEndpoint.get_port());

    //Set timeout, non-blocking and wait using select
    int ret = m_sock.sendTo( outEndpoint, (char*)&pkt, sizeof(NTPPacket) );
    if (ret < 0 ) {
        ERR("Could not send packet");
        m_sock.close();
        return NTP_CONN;
    }

    //Read response
    Endpoint inEndpoint;
    INFO(" inEndpoint instantiated: %s.", inEndpoint.get_address());
    
    // Set the inEndpoint address property
    inEndpoint.set_address(outEndpoint.get_address(), 0);

    INFO(" inEndpoint: %s", inEndpoint.get_address());

    INFO("Pong");
    int loopLimit = 20;  // semi-randomly selected so it doesn't hang forever here...
    do {
        ret = m_sock.receiveFrom( inEndpoint, (char*)&pkt, sizeof(NTPPacket) );
        if(ret < 0) {
            ERR("Could not receive packet");
            m_sock.close();
            return NTP_CONN;
        }
        INFO(".");
        loopLimit--;
    } while( strcmp(outEndpoint.get_address(), inEndpoint.get_address()) != 0 && loopLimit > 0);

    if(ret < (int)sizeof(NTPPacket)) { //TODO: Accept chunks
        ERR("Receive packet size does not match");
        m_sock.close();
        return NTP_PRTCL;
    }

    if( pkt.stratum == 0) { //Kiss of death message : Not good !
        ERR("Kissed to death!");
        m_sock.close();
        return NTP_PRTCL;
    }

    HexDump("NTP Info", (uint8_t *)&pkt, sizeof(NTPPacket));

    //Correct Endianness
    pkt.refTm_s = ntohl( pkt.refTm_s );
    pkt.refTm_f = ntohl( pkt.refTm_f );
    pkt.origTm_s = ntohl( pkt.origTm_s );
    pkt.origTm_f = ntohl( pkt.origTm_f );
    pkt.rxTm_s = ntohl( pkt.rxTm_s );
    pkt.rxTm_f = ntohl( pkt.rxTm_f );
    pkt.txTm_s = ntohl( pkt.txTm_s );
    pkt.txTm_f = ntohl( pkt.txTm_f );

    //Compute offset, see RFC 4330 p.13
    uint32_t destTm_s = (NTP_TIMESTAMP_DELTA + time(NULL));
    INFO("destTm_s = %u", destTm_s);
    INFO("pkt.txTm_s = %u", pkt.txTm_s );
    
    // Modification by David Smart
    // The setTime function was computing the offset incorrectly as the value was promoted to 64-bit.
    // The side effect was that a negative offset ended up as a very large positive (e.g. jump from 
    // 2016 to 2084). This change revises that computation.
    int64_t offset = ( ((int64_t)pkt.rxTm_s - pkt.origTm_s ) + ((int64_t) pkt.txTm_s - destTm_s ) ) / 2; //Avoid overflow
    
    // delay is not needed, this was for diagnostic purposes only.
    //int64_t delay = ((int64_t) destTm_s - pkt.origTm_s) - ((int64_t) pkt.txTm_s - pkt.rxTm_s);
    INFO("txTm_s   @%u", pkt.txTm_s);
    INFO("origTm_s @%u", pkt.origTm_s);
    INFO("rxTm_s   @%u", pkt.rxTm_s);
    INFO("destTm_s @%u", destTm_s);
    INFO("Offset: %lld", offset);
    //INFO("Delay:  %lld", delay);
    
    INFO(" time:    %u", time(NULL));
    //Set time accordingly
    set_time( time(NULL) + offset );

#ifdef __DEBUG__
    ctTime = time(NULL);
    INFO("Time is now (UTC): %s", ctime(&ctTime));
#endif

    m_sock.close();

    return NTP_OK;
}