NTPClient.cpp

00001 /* NTPClient.cpp */
00002 /* Copyright (C) 2012 mbed.org, MIT License
00003  *
00004  * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
00005  * and associated documentation files (the "Software"), to deal in the Software without restriction,
00006  * including without limitation the rights to use, copy, modify, merge, publish, distribute,
00007  * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
00008  * furnished to do so, subject to the following conditions:
00009  *
00010  * The above copyright notice and this permission notice shall be included in all copies or
00011  * substantial portions of the Software.
00012  *
00013  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
00014  * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
00015  * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
00016  * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
00017  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
00018  */
00019 
00020 //Debug is disabled by default
00021 #if 0
00022 //Enable debug
00023 #define __DEBUG__
00024 #include <cstdio>
00025 #define DBG(x, ...) std::printf("[NTPClient : DBG]"x"\r\n", ##__VA_ARGS__); 
00026 #define WARN(x, ...) std::printf("[NTPClient : WARN]"x"\r\n", ##__VA_ARGS__); 
00027 #define ERR(x, ...) std::printf("[NTPClient : ERR]"x"\r\n", ##__VA_ARGS__); 
00028 
00029 #else
00030 //Disable debug
00031 #define DBG(x, ...) 
00032 #define WARN(x, ...)
00033 #define ERR(x, ...) 
00034 
00035 #endif
00036 
00037 #include "NTPClient.h"
00038 
00039 #include "UDPSocket.h"
00040 
00041 #include "mbed.h" //time() and set_time()
00042 
00043 #define NTP_PORT 123
00044 #define NTP_CLIENT_PORT 0 //Random port
00045 #define NTP_TIMESTAMP_DELTA 2208988800ull //Diff btw a UNIX timestamp (Starting Jan, 1st 1970) and a NTP timestamp (Starting Jan, 1st 1900)
00046 
00047 NTPClient::NTPClient() : m_sock()
00048 {
00049 
00050 
00051 }
00052 
00053 NTPResult NTPClient::setTime(const char* host, uint16_t port, uint32_t timeout)
00054 {
00055 #ifdef __DEBUG__
00056   time_t ctTime;
00057   ctTime = time(NULL);
00058   DBG("Time is set to (UTC): %s", ctime(&ctTime));
00059 #endif
00060 
00061   //Create & bind socket
00062   DBG("Binding socket");
00063   m_sock.bind(0); //Bind to a random port
00064   
00065   m_sock.set_blocking(false, timeout); //Set not blocking
00066 
00067   struct NTPPacket pkt;
00068 
00069   //Now ping the server and wait for response
00070   DBG("Ping");
00071   //Prepare NTP Packet:
00072   pkt.li = 0; //Leap Indicator : No warning
00073   pkt.vn = 4; //Version Number : 4
00074   pkt.mode = 3; //Client mode
00075   pkt.stratum = 0; //Not relevant here
00076   pkt.poll = 0; //Not significant as well
00077   pkt.precision = 0; //Neither this one is
00078 
00079   pkt.rootDelay = 0; //Or this one
00080   pkt.rootDispersion = 0; //Or that one
00081   pkt.refId = 0; //...
00082 
00083   pkt.refTm_s = 0;
00084   pkt.origTm_s = 0;
00085   pkt.rxTm_s = 0;
00086   pkt.txTm_s = htonl( NTP_TIMESTAMP_DELTA + time(NULL) ); //WARN: We are in LE format, network byte order is BE
00087 
00088   pkt.refTm_f = pkt.origTm_f = pkt.rxTm_f = pkt.txTm_f = 0;
00089 
00090   Endpoint outEndpoint;
00091   
00092   if( outEndpoint.set_address(host, port) < 0)
00093   {
00094     m_sock.close();
00095     return NTP_DNS;
00096   }
00097   
00098   //Set timeout, non-blocking and wait using select
00099   int ret = m_sock.sendTo( outEndpoint, (char*)&pkt, sizeof(NTPPacket) );
00100   if (ret < 0 )
00101   {
00102     ERR("Could not send packet");
00103     m_sock.close();
00104     return NTP_CONN;
00105   }
00106 
00107   //Read response
00108   Endpoint inEndpoint;
00109 
00110   DBG("Pong");
00111   do
00112   {
00113     ret = m_sock.receiveFrom( inEndpoint, (char*)&pkt, sizeof(NTPPacket) ); //FIXME need a DNS Resolver to actually compare the incoming address with the DNS name
00114     if(ret < 0)
00115     {
00116       ERR("Could not receive packet");
00117       m_sock.close();
00118       return NTP_CONN;
00119     }
00120   } while( strcmp(outEndpoint.get_address(), inEndpoint.get_address()) != 0 );
00121 
00122   if(ret < sizeof(NTPPacket)) //TODO: Accept chunks
00123   {
00124     ERR("Receive packet size does not match");
00125     m_sock.close();
00126     return NTP_PRTCL;
00127   }
00128 
00129   if( pkt.stratum == 0)  //Kiss of death message : Not good !
00130   {
00131     ERR("Kissed to death!");
00132     m_sock.close();
00133     return NTP_PRTCL;
00134   }
00135 
00136   //Correct Endianness
00137   pkt.refTm_s = ntohl( pkt.refTm_s );
00138   pkt.refTm_f = ntohl( pkt.refTm_f );
00139   pkt.origTm_s = ntohl( pkt.origTm_s );
00140   pkt.origTm_f = ntohl( pkt.origTm_f );
00141   pkt.rxTm_s = ntohl( pkt.rxTm_s );
00142   pkt.rxTm_f = ntohl( pkt.rxTm_f );
00143   pkt.txTm_s = ntohl( pkt.txTm_s );
00144   pkt.txTm_f = ntohl( pkt.txTm_f );
00145 
00146   //Compute offset, see RFC 4330 p.13
00147   uint32_t destTm_s = (NTP_TIMESTAMP_DELTA + time(NULL));
00148   int64_t offset = ( (int64_t)( pkt.rxTm_s - pkt.origTm_s ) + (int64_t) ( pkt.txTm_s - destTm_s ) ) / 2; //Avoid overflow
00149   DBG("Sent @%ul", pkt.txTm_s);
00150   DBG("Offset: %lld", offset);
00151   //Set time accordingly
00152   set_time( time(NULL) + offset );
00153 
00154 #ifdef __DEBUG__
00155   ctTime = time(NULL);
00156   DBG("Time is now (UTC): %s", ctime(&ctTime));
00157 #endif
00158 
00159   m_sock.close();
00160 
00161   return NTP_OK;
00162 }
00163