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Arduino-Development / libraries /Ethernet /src /Dns.cpp
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Archive original Arduino development files (part 8)
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// Arduino DNS client for WizNet5100-based Ethernet shield
// (c) Copyright 2009-2010 MCQN Ltd.
// Released under Apache License, version 2.0
#include <Arduino.h>
#include "Ethernet.h"
#include "Dns.h"
#include "utility/w5100.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* address, IPAddress& result)
{
uint16_t acc = 0; // Accumulator
uint8_t dots = 0;
while (*address) {
char c = *address++;
if (c >= '0' && c <= '9') {
acc = acc * 10 + (c - '0');
if (acc > 255) {
// Value out of [0..255] range
return 0;
}
} else if (c == '.') {
if (dots == 3) {
// Too much dots (there must be 3 dots)
return 0;
}
result[dots++] = acc;
acc = 0;
} else {
// Invalid char
return 0;
}
}
if (dots != 3) {
// Too few dots (there must be 3 dots)
return 0;
}
result[3] = acc;
return 1;
}
int DNSClient::getHostByName(const char* aHostname, IPAddress& aResult, uint16_t timeout)
{
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(timeout, 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;
}
uint16_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
union {
uint8_t byte[DNS_HEADER_SIZE]; // Enough space to reuse for the DNS header
uint16_t word[DNS_HEADER_SIZE/2];
} 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(header.byte, DNS_HEADER_SIZE);
uint16_t header_flags = htons(header.word[1]);
// Check that it's a response to this request
if ((iRequestId != (header.word[0])) ||
((header_flags & QUERY_RESPONSE_MASK) != (uint16_t)RESPONSE_FLAG) ) {
// Mark the entire packet as read
iUdp.flush(); // FIXME
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(); // FIXME
return -5; //INVALID_RESPONSE;
}
// And make sure we've got (at least) one answer
uint16_t answerCount = htons(header.word[3]);
if (answerCount == 0) {
// Mark the entire packet as read
iUdp.flush(); // FIXME
return -6; //INVALID_RESPONSE;
}
// Skip over any questions
for (uint16_t i=0; i < htons(header.word[2]); i++) {
// Skip over the name
uint8_t len;
do {
iUdp.read(&len, sizeof(len));
if (len > 0) {
// Don't need to actually read the data out for the string, just
// advance ptr to beyond it
iUdp.read((uint8_t *)NULL, (size_t)len);
}
} while (len != 0);
// Now jump over the type and class
iUdp.read((uint8_t *)NULL, 4);
}
// 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(&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
iUdp.read((uint8_t *)NULL, len);
}
} 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((uint8_t *)NULL, 1); // we don't care about the 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((uint8_t*)&answerType, sizeof(answerType));
iUdp.read((uint8_t*)&answerClass, sizeof(answerClass));
// Ignore the Time-To-Live as we don't do any caching
iUdp.read((uint8_t *)NULL, TTL_SIZE); // don't care about the returned bytes
// And read out the length of this answer
// Don't need header_flags anymore, so we can reuse it here
iUdp.read((uint8_t*)&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(); // FIXME
return -9;//INVALID_RESPONSE;
}
// FIXME: seeems to lock up here on ESP8266, but why??
iUdp.read(aAddress.raw_address(), 4);
return SUCCESS;
} else {
// This isn't an answer type we're after, move onto the next one
iUdp.read((uint8_t *)NULL, htons(header_flags));
}
}
// Mark the entire packet as read
iUdp.flush(); // FIXME
// If we get here then we haven't found an answer
return -10; //INVALID_RESPONSE;
}