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 #include "NTPClient.h"
00021 
00022 #include "UDPSocket.h"
00023 
00024 #include "mbed.h" //time() and set_time()
00025 #include "def.h"
00026 
00027 #define NTP_PORT 123
00028 #define NTP_CLIENT_PORT 0 //Random port
00029 #define NTP_TIMESTAMP_DELTA 2208988800ull //Diff btw a UNIX timestamp (Starting Jan, 1st 1970) and a NTP timestamp (Starting Jan, 1st 1900)
00030 
00031 NTPClient::NTPClient(NetworkInterface *networkInterface)
00032     : m_sock(networkInterface), m_net(networkInterface)
00033 {
00034 }
00035 
00036 NTPResult NTPClient::setTime(const char* host, uint16_t port, uint32_t timeout)
00037 {
00038     //Create & bind socket
00039     m_sock.set_blocking(false);
00040     m_sock.set_timeout(timeout);
00041     
00042     struct NTPPacket pkt;
00043 
00044     //Now ping the server and wait for response
00045     //Prepare NTP Packet:
00046     pkt.li = 0; //Leap Indicator : No warning
00047     pkt.vn = 4; //Version Number : 4
00048     pkt.mode = 3; //Client mode
00049     pkt.stratum = 0; //Not relevant here
00050     pkt.poll = 0; //Not significant as well
00051     pkt.precision = 0; //Neither this one is
00052 
00053     pkt.rootDelay = 0; //Or this one
00054     pkt.rootDispersion = 0; //Or that one
00055     pkt.refId = 0; //...
00056 
00057     pkt.refTm_s = 0;
00058     pkt.origTm_s = 0;
00059     pkt.rxTm_s = 0;
00060     pkt.txTm_s = htonl( NTP_TIMESTAMP_DELTA + time(NULL) ); //WARN: We are in LE format, network byte order is BE
00061 
00062     pkt.refTm_f = pkt.origTm_f = pkt.rxTm_f = pkt.txTm_f = 0;
00063 
00064     SocketAddress outEndpoint(host, port);
00065 
00066     if(m_net->gethostbyname(host, &outEndpoint)!= 0)
00067     {
00068         m_sock.close();
00069         return NTP_DNS;    
00070     }
00071     
00072     const char *ip = outEndpoint.get_ip_address();
00073     //Set timeout, non-blocking and wait using select
00074     int ret = m_sock.sendto(outEndpoint, (char*)&pkt, sizeof(NTPPacket) );
00075     if (ret < 0 )
00076     {
00077         m_sock.close();
00078         return NTP_CONN;
00079     }
00080     
00081     SocketAddress recvAddress;
00082     recvAddress.set_ip_address(outEndpoint.get_ip_address());
00083     recvAddress.set_port(port);
00084     ret = m_sock.recvfrom(&recvAddress, (char*)&pkt, sizeof(NTPPacket) ); //FIXME need a DNS Resolver to actually compare the incoming address with the DNS name
00085     if (ret > 0)
00086     {
00087         if (strcmp(outEndpoint.get_ip_address(), recvAddress.get_ip_address()) != 0)
00088         {
00089           m_sock.close();
00090           return NTP_CONN;
00091         }
00092     }
00093     else
00094     {
00095         m_sock.close();
00096         return NTP_CONN;
00097     }
00098 
00099     if(ret < (int)sizeof(NTPPacket)) //TODO: Accept chunks
00100     {
00101         m_sock.close();
00102         return NTP_PRTCL;
00103     }
00104 
00105     if( pkt.stratum == 0)  //Kiss of death message : Not good !
00106     {
00107         m_sock.close();
00108         return NTP_PRTCL;
00109     }
00110 
00111     //Correct Endianness
00112     pkt.refTm_s = ntohl( pkt.refTm_s );
00113     pkt.refTm_f = ntohl( pkt.refTm_f );
00114     pkt.origTm_s = ntohl( pkt.origTm_s );
00115     pkt.origTm_f = ntohl( pkt.origTm_f );
00116     pkt.rxTm_s = ntohl( pkt.rxTm_s );
00117     pkt.rxTm_f = ntohl( pkt.rxTm_f );
00118     pkt.txTm_s = ntohl( pkt.txTm_s );
00119     pkt.txTm_f = ntohl( pkt.txTm_f );
00120 
00121     //Compute offset, see RFC 4330 p.13
00122     uint32_t destTm_s = (NTP_TIMESTAMP_DELTA + time(NULL));
00123     int64_t offset = ( (int64_t)( pkt.rxTm_s - pkt.origTm_s ) + (int64_t) ( pkt.txTm_s - destTm_s ) ) / 2; //Avoid overflow
00124     //Set time accordingly
00125     set_time( time(NULL) + offset );
00126     
00127     m_sock.close();
00128 
00129     return NTP_OK;
00130 }
00131