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Dns.cpp
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Dns.cpp
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// Arduino DNS client for Enc28J60-based Ethernet shield
// (c) Copyright 2009-2010 MCQN Ltd.
// Released under Apache License, version 2.0
#include "utility/uipopt.h"
#if UIP_UDP
#include "Dns.h"
#include <string.h>
//#include <stdlib.h>
#if defined(ARDUINO)
#include "Arduino.h"
#if defined(__STM32F3__) || (!defined(ARDUINO_ARCH_STM32) && defined(STM32F3))
#include "mbed/Udp.h"
#else
#include "Udp.h"
#endif
#endif
#if defined(__MBED__)
#include <mbed.h>
#include "mbed/Udp.h"
#include "mbed/millis.h"
#define delay(x) wait_ms(x)
#endif
#include "utility/logging.h"
#include "utility/uip.h"
#define SOCKET_NONE 255
// Various flags and header field values for a DNS message
#define UDP_HEADER_SIZE 8
#define DNS_HEADER_SIZE 12
#define TTL_SIZE 4
#define QUERY_FLAG (0)
#define RESPONSE_FLAG (1<<15)
#define QUERY_RESPONSE_MASK (1<<15)
#define OPCODE_STANDARD_QUERY (0)
#define OPCODE_INVERSE_QUERY (1<<11)
#define OPCODE_STATUS_REQUEST (2<<11)
#define OPCODE_MASK (15<<11)
#define AUTHORITATIVE_FLAG (1<<10)
#define TRUNCATION_FLAG (1<<9)
#define RECURSION_DESIRED_FLAG (1<<8)
#define RECURSION_AVAILABLE_FLAG (1<<7)
#define RESP_NO_ERROR (0)
#define RESP_FORMAT_ERROR (1)
#define RESP_SERVER_FAILURE (2)
#define RESP_NAME_ERROR (3)
#define RESP_NOT_IMPLEMENTED (4)
#define RESP_REFUSED (5)
#define RESP_MASK (15)
#define TYPE_A (0x0001)
#define CLASS_IN (0x0001)
#define LABEL_COMPRESSION_MASK (0xC0)
// Port number that DNS servers listen on
#define DNS_PORT 53
// Possible return codes from ProcessResponse
#define SUCCESS 1
#define TIMED_OUT -1
#define INVALID_SERVER -2
#define TRUNCATED -3
#define INVALID_RESPONSE -4
void DNSClient::begin(const IPAddress& aDNSServer)
{
iDNSServer = aDNSServer;
iRequestId = 0;
}
int DNSClient::inet_aton(const char* aIPAddrString, IPAddress& aResult)
{
// See if we've been given a valid IP address
const char* p =aIPAddrString;
while (*p && ( (*p == '.') || ((*p >= '0') && (*p <= '9')) ))
{
p++;
}
if (*p == '\0')
{
// It's looking promising, we haven't found any invalid characters
p = aIPAddrString;
int segment =0;
int segmentValue =0;
while (*p && (segment < 4))
{
if (*p == '.')
{
// We've reached the end of a segment
if (segmentValue > 255)
{
// You can't have IP address segments that don't fit in a byte
return 0;
}
else
{
aResult[segment] = (uint8_t)segmentValue;
segment++;
segmentValue = 0;
}
}
else
{
// Next digit
segmentValue = (segmentValue*10)+(*p - '0');
}
p++;
}
// We've reached the end of address, but there'll still be the last
// segment to deal with
if ((segmentValue > 255) || (segment > 3))
{
// You can't have IP address segments that don't fit in a byte,
// or more than four segments
return 0;
}
else
{
aResult[segment] = (uint8_t)segmentValue;
return 1;
}
}
else
{
return 0;
}
}
int DNSClient::getHostByName(const char* aHostname, IPAddress& aResult)
{
int ret =0;
// See if it's a numeric IP address
if (inet_aton(aHostname, aResult))
{
// It is, our work here is done
return 1;
}
// Check we've got a valid DNS server to use
if (iDNSServer == INADDR_NONE)
{
return INVALID_SERVER;
}
// Find a socket to use
if (iUdp.begin(1024+(millis() & 0xF)) == 1)
{
// Try up to three times
int retries = 0;
// while ((retries < 3) && (ret <= 0))
{
// Send DNS request
ret = iUdp.beginPacket(iDNSServer, DNS_PORT);
if (ret != 0)
{
// Now output the request data
ret = BuildRequest(aHostname);
if (ret != 0)
{
// And finally send the request
ret = iUdp.endPacket();
if (ret != 0)
{
// Now wait for a response
int wait_retries = 0;
ret = TIMED_OUT;
while ((wait_retries < 3) && (ret == TIMED_OUT))
{
ret = ProcessResponse(5000, aResult);
wait_retries++;
}
}
}
}
retries++;
}
// We're done with the socket now
iUdp.stop();
}
return ret;
}
uint16_t DNSClient::BuildRequest(const char* aName)
{
// Build header
// 1 1 1 1 1 1
// 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ID |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// |QR| Opcode |AA|TC|RD|RA| Z | RCODE |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | QDCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ANCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | NSCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// | ARCOUNT |
// +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
// As we only support one request at a time at present, we can simplify
// some of this header
iRequestId = millis(); // generate a random ID
uint16_t twoByteBuffer;
// FIXME We should also check that there's enough space available to write to, rather
// FIXME than assume there's enough space (as the code does at present)
iUdp.write((uint8_t*)&iRequestId, sizeof(iRequestId));
twoByteBuffer = htons(QUERY_FLAG | OPCODE_STANDARD_QUERY | RECURSION_DESIRED_FLAG);
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
twoByteBuffer = htons(1); // One question record
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
twoByteBuffer = 0; // Zero answer records
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
// and zero additional records
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
// Build question
const char* start =aName;
const char* end =start;
uint8_t len;
// Run through the name being requested
while (*end)
{
// Find out how long this section of the name is
end = start;
while (*end && (*end != '.') )
{
end++;
}
if (end-start > 0)
{
// Write out the size of this section
len = end-start;
iUdp.write(&len, sizeof(len));
// And then write out the section
iUdp.write((uint8_t*)start, end-start);
}
start = end+1;
}
// We've got to the end of the question name, so
// terminate it with a zero-length section
len = 0;
iUdp.write(&len, sizeof(len));
// Finally the type and class of question
twoByteBuffer = htons(TYPE_A);
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
twoByteBuffer = htons(CLASS_IN); // Internet class of question
iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
// Success! Everything buffered okay
return 1;
}
int16_t DNSClient::ProcessResponse(uint16_t aTimeout, IPAddress& aAddress)
{
uint32_t startTime = millis();
// Wait for a response packet
while(iUdp.parsePacket() <= 0)
{
if((millis() - startTime) > aTimeout)
return TIMED_OUT;
delay(50);
}
// We've had a reply!
// Read the UDP header
uint8_t header[DNS_HEADER_SIZE]; // Enough space to reuse for the DNS header
// Check that it's a response from the right server and the right port
if ( (iDNSServer != iUdp.remoteIP()) ||
(iUdp.remotePort() != DNS_PORT) )
{
// It's not from who we expected
return INVALID_SERVER;
}
// Read through the rest of the response
if (iUdp.available() < DNS_HEADER_SIZE)
{
return TRUNCATED;
}
iUdp.read((char*)header, DNS_HEADER_SIZE);
uint16_t header_flags = htons(*((uint16_t*)&header[2]));
// Check that it's a response to this request
if ( ( iRequestId != (*((uint16_t*)&header[0])) ) ||
((header_flags & QUERY_RESPONSE_MASK) != (uint16_t)RESPONSE_FLAG) )
{
// Mark the entire packet as read
iUdp.flush();
return INVALID_RESPONSE;
}
// Check for any errors in the response (or in our request)
// although we don't do anything to get round these
if ( (header_flags & TRUNCATION_FLAG) || (header_flags & RESP_MASK) )
{
// Mark the entire packet as read
iUdp.flush();
return -5; //INVALID_RESPONSE;
}
// And make sure we've got (at least) one answer
uint16_t answerCount = htons(*((uint16_t*)&header[6]));
if (answerCount == 0 )
{
// Mark the entire packet as read
iUdp.flush();
return -6; //INVALID_RESPONSE;
}
// Skip over any questions
for (uint16_t i =0; i < htons(*((uint16_t*)&header[4])); i++)
{
// Skip over the name
uint8_t len;
do
{
iUdp.read((char*)&len, sizeof(len));
if (len > 0)
{
// Don't need to actually read the data out for the string, just
// advance ptr to beyond it
while(len--)
{
iUdp.read(); // we don't care about the returned byte
}
}
} while (len != 0);
// Now jump over the type and class
for (int i =0; i < 4; i++)
{
iUdp.read(); // we don't care about the returned byte
}
}
// Now we're up to the bit we're interested in, the answer
// There might be more than one answer (although we'll just use the first
// type A answer) and some authority and additional resource records but
// we're going to ignore all of them.
for (uint16_t i =0; i < answerCount; i++)
{
// Skip the name
uint8_t len;
do
{
iUdp.read((char*)&len, sizeof(len));
if ((len & LABEL_COMPRESSION_MASK) == 0)
{
// It's just a normal label
if (len > 0)
{
// And it's got a length
// Don't need to actually read the data out for the string,
// just advance ptr to beyond it
while(len--)
{
iUdp.read(); // we don't care about the returned byte
}
}
}
else
{
// This is a pointer to a somewhere else in the message for the
// rest of the name. We don't care about the name, and RFC1035
// says that a name is either a sequence of labels ended with a
// 0 length octet or a pointer or a sequence of labels ending in
// a pointer. Either way, when we get here we're at the end of
// the name
// Skip over the pointer
iUdp.read(); // we don't care about the returned byte
// And set len so that we drop out of the name loop
len = 0;
}
} while (len != 0);
// Check the type and class
uint16_t answerType;
uint16_t answerClass;
iUdp.read((char*)&answerType, sizeof(answerType));
iUdp.read((char*)&answerClass, sizeof(answerClass));
// Ignore the Time-To-Live as we don't do any caching
for (int i =0; i < TTL_SIZE; i++)
{
iUdp.read(); // we don't care about the returned byte
}
// And read out the length of this answer
// Don't need header_flags anymore, so we can reuse it here
iUdp.read((char*)&header_flags, sizeof(header_flags));
if ( (htons(answerType) == TYPE_A) && (htons(answerClass) == CLASS_IN) )
{
if (htons(header_flags) != 4)
{
// It's a weird size
// Mark the entire packet as read
iUdp.flush();
return -9;//INVALID_RESPONSE;
}
iUdp.read((char*)aAddress.raw_address(), 4);
return SUCCESS;
}
else
{
// This isn't an answer type we're after, move onto the next one
for (uint16_t i =0; i < htons(header_flags); i++)
{
iUdp.read(); // we don't care about the returned byte
}
}
}
// Mark the entire packet as read
iUdp.flush();
// If we get here then we haven't found an answer
return -10;//INVALID_RESPONSE;
}
#endif