package railo.runtime.net.ntp;
import java.text.DecimalFormat;
import java.util.Date;
import railo.commons.i18n.DateFormatPool;
public final class NtpMessage
{
/**
* This is a two-bit code warning of an impending leap second to be
* inserted/deleted in the last minute of the current day. It's values
* may be as follows:
*
* Value Meaning
* ----- -------
* 0 no warning
* 1 last minute has 61 seconds
* 2 last minute has 59 seconds)
* 3 alarm condition (clock not synchronized)
*/
public byte leapIndicator = 0;
/**
* This value indicates the NTP/SNTP version number. The version number
* is 3 for Version 3 (IPv4 only) and 4 for Version 4 (IPv4, IPv6 and OSI).
* If necessary to distinguish between IPv4, IPv6 and OSI, the
* encapsulating context must be inspected.
*/
public byte version = 3;
/**
* This value indicates the mode, with values defined as follows:
*
* Mode Meaning
* ---- -------
* 0 reserved
* 1 symmetric active
* 2 symmetric passive
* 3 client
* 4 server
* 5 broadcast
* 6 reserved for NTP control message
* 7 reserved for private use
*
* In unicast and anycast modes, the client sets this field to 3 (client)
* in the request and the server sets it to 4 (server) in the reply. In
* multicast mode, the server sets this field to 5 (broadcast).
*/
public byte mode = 0;
/**
* This value indicates the stratum level of the local clock, with values
* defined as follows:
*
* Stratum Meaning
* ----------------------------------------------
* 0 unspecified or unavailable
* 1 primary reference (e.g., radio clock)
* 2-15 secondary reference (via NTP or SNTP)
* 16-255 reserved
*/
public short stratum = 0;
/**
* This value indicates the maximum interval between successive messages,
* in seconds to the nearest power of two. The values that can appear in
* this field presently range from 4 (16 s) to 14 (16284 s); however, most
* applications use only the sub-range 6 (64 s) to 10 (1024 s).
*/
public byte pollInterval = 0;
/**
* This value indicates the precision of the local clock, in seconds to
* the nearest power of two. The values that normally appear in this field\
* range from -6 for mains-frequency clocks to -20 for microsecond clocks
* found in some workstations.
*/
public byte precision = 0;
/**
* This value indicates the total roundtrip delay to the primary reference
* source, in seconds. Note that this variable can take on both positive
* and negative values, depending on the relative time and frequency
* offsets. The values that normally appear in this field range from
* negative values of a few milliseconds to positive values of several
* hundred milliseconds.
*/
public double rootDelay = 0;
/**
* This value indicates the nominal error relative to the primary reference
* source, in seconds. The values that normally appear in this field
* range from 0 to several hundred milliseconds.
*/
public double rootDispersion = 0;
/**
* This is a 4-byte array identifying the particular reference source.
* In the case of NTP Version 3 or Version 4 stratum-0 (unspecified) or
* stratum-1 (primary) servers, this is a four-character ASCII string, left
* justified and zero padded to 32 bits. In NTP Version 3 secondary
* servers, this is the 32-bit IPv4 address of the reference source. In NTP
* Version 4 secondary servers, this is the low order 32 bits of the latest
* transmit timestamp of the reference source. NTP primary (stratum 1)
* servers should set this field to a code identifying the external
* reference source according to the following list. If the external
* reference is one of those listed, the associated code should be used.
* Codes for sources not listed can be contrived as appropriate.
*
* Code External Reference Source
* ---- -------------------------
* LOCL uncalibrated local clock used as a primary reference for
* a subnet without external means of synchronization
* PPS atomic clock or other pulse-per-second source
* individually calibrated to national standards
* ACTS NIST dialup modem service
* USNO USNO modem service
* PTB PTB (Germany) modem service
* TDF Allouis (France) Radio 164 kHz
* DCF Mainflingen (Germany) Radio 77.5 kHz
* MSF Rugby (UK) Radio 60 kHz
* WWV Ft. Collins (US) Radio 2.5, 5, 10, 15, 20 MHz
* WWVB Boulder (US) Radio 60 kHz
* WWVH Kaui Hawaii (US) Radio 2.5, 5, 10, 15 MHz
* CHU Ottawa (Canada) Radio 3330, 7335, 14670 kHz
* LORC LORAN-C radionavigation system
* OMEG OMEGA radionavigation system
* GPS Global Positioning Service
* GOES Geostationary Orbit Environment Satellite
*/
public byte[] referenceIdentifier = {0, 0, 0, 0};
/**
* This is the time at which the local clock was last set or corrected, in
* seconds since 00:00 1-Jan-1900.
*/
public double referenceTimestamp = 0;
/**
* This is the time at which the request departed the client for the
* server, in seconds since 00:00 1-Jan-1900.
*/
public double originateTimestamp = 0;
/**
* This is the time at which the request arrived at the server, in seconds
* since 00:00 1-Jan-1900.
*/
public double receiveTimestamp = 0;
/**
* This is the time at which the reply departed the server for the client,
* in seconds since 00:00 1-Jan-1900.
*/
public double transmitTimestamp = 0;
/**
* Constructs a new NtpMessage from an array of bytes.
* @param array
*/
public NtpMessage(byte[] array)
{
// See the packet format diagram in RFC 2030 for details
leapIndicator = (byte) ((array[0] >> 6) & 0x3);
version = (byte) ((array[0] >> 3) & 0x7);
mode = (byte) (array[0] & 0x7);
stratum = unsignedByteToShort(array[1]);
pollInterval = array[2];
precision = array[3];
rootDelay = (array[4] * 256.0) +
unsignedByteToShort(array[5]) +
(unsignedByteToShort(array[6]) / 256.0) +
(unsignedByteToShort(array[7]) / 65536.0);
rootDispersion = (unsignedByteToShort(array[8]) * 256.0) +
unsignedByteToShort(array[9]) +
(unsignedByteToShort(array[10]) / 256.0) +
(unsignedByteToShort(array[11]) / 65536.0);
referenceIdentifier[0] = array[12];
referenceIdentifier[1] = array[13];
referenceIdentifier[2] = array[14];
referenceIdentifier[3] = array[15];
referenceTimestamp = decodeTimestamp(array, 16);
originateTimestamp = decodeTimestamp(array, 24);
receiveTimestamp = decodeTimestamp(array, 32);
transmitTimestamp = decodeTimestamp(array, 40);
}
/**
* Constructs a new NtpMessage
* @param leapIndicator
* @param version
* @param mode
* @param stratum
* @param pollInterval
* @param precision
* @param rootDelay
* @param rootDispersion
* @param referenceIdentifier
* @param referenceTimestamp
* @param originateTimestamp
* @param receiveTimestamp
* @param transmitTimestamp
*/
public NtpMessage(byte leapIndicator,
byte version,
byte mode,
short stratum,
byte pollInterval,
byte precision,
double rootDelay,
double rootDispersion,
byte[] referenceIdentifier,
double referenceTimestamp,
double originateTimestamp,
double receiveTimestamp,
double transmitTimestamp)
{
// ToDo: Validity checking
this.leapIndicator = leapIndicator;
this.version = version;
this.mode = mode;
this.stratum = stratum;
this.pollInterval = pollInterval;
this.precision = precision;
this.rootDelay = rootDelay;
this.rootDispersion = rootDispersion;
this.referenceIdentifier = referenceIdentifier;
this.referenceTimestamp = referenceTimestamp;
this.originateTimestamp = originateTimestamp;
this.receiveTimestamp = receiveTimestamp;
this.transmitTimestamp = transmitTimestamp;
}
/**
* Constructs a new NtpMessage in client -> server mode, and sets the
* transmit timestamp to the current time.
*/
public NtpMessage()
{
// Note that all the other member variables are already set with
// appropriate default values.
this.mode = 3;
this.transmitTimestamp = (System.currentTimeMillis()/1000.0) + 2208988800.0;
}
/**
* This method constructs the data bytes of a raw NTP packet.
* @return
*/
public byte[] toByteArray()
{
// All bytes are automatically set to 0
byte[] p = new byte[48];
p[0] = (byte) (leapIndicator << 6 | version << 3 | mode);
p[1] = (byte) stratum;
p[2] = pollInterval;
p[3] = precision;
// root delay is a signed 16.16-bit FP, in Java an int is 32-bits
int l = (int) (rootDelay * 65536.0);
p[4] = (byte) ((l >> 24) & 0xFF);
p[5] = (byte) ((l >> 16) & 0xFF);
p[6] = (byte) ((l >> 8) & 0xFF);
p[7] = (byte) (l & 0xFF);
// root dispersion is an unsigned 16.16-bit FP, in Java there are no
// unsigned primitive types, so we use a long which is 64-bits
long ul = (long) (rootDispersion * 65536.0);
p[8] = (byte) ((ul >> 24) & 0xFF);
p[9] = (byte) ((ul >> 16) & 0xFF);
p[10] = (byte) ((ul >> 8) & 0xFF);
p[11] = (byte) (ul & 0xFF);
p[12] = referenceIdentifier[0];
p[13] = referenceIdentifier[1];
p[14] = referenceIdentifier[2];
p[15] = referenceIdentifier[3];
encodeTimestamp(p, 16, referenceTimestamp);
encodeTimestamp(p, 24, originateTimestamp);
encodeTimestamp(p, 32, receiveTimestamp);
encodeTimestamp(p, 40, transmitTimestamp);
return p;
}
/**
* Returns a string representation of a NtpMessage
* @return
*/
public String toString()
{
String precisionStr = new DecimalFormat("0.#E0").format(Math.pow(2, precision));
return "Leap indicator: " + leapIndicator + "\n" +
"Version: " + version + "\n" +
"Mode: " + mode + "\n" +
"Stratum: " + stratum + "\n" +
"Poll: " + pollInterval + "\n" +
"Precision: " + precision + " (" + precisionStr + " seconds)\n" +
"Root delay: " + new DecimalFormat("0.00").format(rootDelay*1000) + " ms\n" +
"Root dispersion: " + new DecimalFormat("0.00").format(rootDispersion*1000) + " ms\n" +
"Reference identifier: " + referenceIdentifierToString(referenceIdentifier, stratum, version) + "\n" +
"Reference timestamp: " + timestampToString(referenceTimestamp) + "\n" +
"Originate timestamp: " + timestampToString(originateTimestamp) + "\n" +
"Receive timestamp: " + timestampToString(receiveTimestamp) + "\n" +
"Transmit timestamp: " + timestampToString(transmitTimestamp);
}
/**
* Converts an unsigned byte to a short. By default, Java assumes that
* a byte is signed.
* @param b
* @return
*/
public static short unsignedByteToShort(byte b)
{
if((b & 0x80)==0x80) return (short) (128 + (b & 0x7f));
return b;
}
/**
* Will read 8 bytes of a message beginning at <code>pointer</code>
* and return it as a double, according to the NTP 64-bit timestamp
* format.
* @param array
* @param pointer
* @return
*/
public static double decodeTimestamp(byte[] array, int pointer)
{
double r = 0.0;
for(int i=0; i<8; i++)
{
r += unsignedByteToShort(array[pointer+i]) * Math.pow(2, (3-i)*8);
}
return r;
}
/**
* Encodes a timestamp in the specified position in the message
* @param array
* @param pointer
* @param timestamp
*/
public static void encodeTimestamp(byte[] array, int pointer, double timestamp)
{
// Converts a double into a 64-bit fixed point
for(int i=0; i<8; i++)
{
// 2^24, 2^16, 2^8, .. 2^-32
double base = Math.pow(2, (3-i)*8);
// Capture byte value
array[pointer+i] = (byte) (timestamp / base);
// Subtract captured value from remaining total
timestamp = timestamp - (unsignedByteToShort(array[pointer+i]) * base);
}
// From RFC 2030: It is advisable to fill the non-significan't
// low order bits of the timestamp with a random, unbiased
// bitstring, both to avoid systematic roundoff errors and as
// a means of loop detection and replay detection.
array[7] = (byte) (Math.random()*255.0);
}
/**
* Returns a timestamp (number of seconds since 00:00 1-Jan-1900) as a
* formatted date/time string.
* @param timestamp
* @return
*/
public static String timestampToString(double timestamp)
{
if(timestamp==0) return "0";
// timestamp is relative to 1900, utc is used by Java and is relative
// to 1970
double utc = timestamp - (2208988800.0);
// milliseconds
long ms = (long) (utc * 1000.0);
// date/time
String date = DateFormatPool.format("dd-MMM-yyyy HH:mm:ss",new Date(ms));
// fraction
double fraction = timestamp - ((long) timestamp);
String fractionSting = new DecimalFormat(".000000").format(fraction);
return date + fractionSting;
}
/**
* Returns a string representation of a reference identifier according
* to the rules set out in RFC 2030.
* @param ref
* @param stratum
* @param version
* @return
*/
public static String referenceIdentifierToString(byte[] ref, short stratum, byte version)
{
// From the RFC 2030:
// In the case of NTP Version 3 or Version 4 stratum-0 (unspecified)
// or stratum-1 (primary) servers, this is a four-character ASCII
// string, left justified and zero padded to 32 bits.
if(stratum==0 || stratum==1)
{
return new String(ref);
}
// In NTP Version 3 secondary servers, this is the 32-bit IPv4
// address of the reference source.
else if(version==3)
{
return unsignedByteToShort(ref[0]) + "." +
unsignedByteToShort(ref[1]) + "." +
unsignedByteToShort(ref[2]) + "." +
unsignedByteToShort(ref[3]);
}
// In NTP Version 4 secondary servers, this is the low order 32 bits
// of the latest transmit timestamp of the reference source.
else if(version==4)
{
return "" + ((unsignedByteToShort(ref[0]) / 256.0) +
(unsignedByteToShort(ref[1]) / 65536.0) +
(unsignedByteToShort(ref[2]) / 16777216.0) +
(unsignedByteToShort(ref[3]) / 4294967296.0));
}
return "";
}
}