Skip to content
This repository has been archived by the owner on Jan 25, 2019. It is now read-only.

Commit

Permalink
Refactor query logic to reduce program size.
Browse files Browse the repository at this point in the history 
Simplified the query logic to reduce the program size and take up less flash memory.

Tested by querying MDNS names from Linux and Mac OSX machines.
  • Loading branch information
@tdicola
tdicola committed Dec 13, 2013
1 parent 3d9fcb6 commit fb13d0f
Show file tree
Hide file tree
Showing 3 changed files with 46 additions and 96 deletions.
128 changes: 42 additions & 86 deletions CC3000_MDNS.cpp
View file
@@ -1,7 +1,7 @@
/*
CC3000 Multicast DNS
Version 1.0
Version 1.1
Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
License (MIT license):
Expand Down Expand Up @@ -31,39 +31,27 @@ License (MIT license):

#include "CC3000_MDNS.h"

#define READ_BUFFER_SIZE 20
#define HEADER_SIZE 12
#define QDCOUNT_OFFSET 4
#define A_RECORD_SIZE 14
#define NSEC_RECORD_SIZE 20
#define TTL_OFFSET 4
#define IP_OFFSET 10

// TODO: Put these in flash, or refactor away into better state handling.
uint8_t MDNSResponder::_queryHeader[] = {
0x00, 0x00, // ID = 0
0x00, 0x00, // Flags = query
0x00, 0x00, // Question count = ignored
0x00, 0x00, // Answer count = ignored
0x00, 0x00, // Name server records = ignored
0x00, 0x00 // Additional records = ignored
};

int MDNSResponder::_mdnsSocket = -1;

MDNSResponder::MDNSResponder()
: _queryFQDN(NULL)
, _queryFQDNLen(0)
, _current(NULL)
, _currentLen(0)
, _index(0)
, _FQDNcount(0)
: _expected(NULL)
, _expectedLen(0)
, _response(NULL)
, _responseLen(0)
, _index(0)
{ }

MDNSResponder::~MDNSResponder() {
if (_queryFQDN != NULL) {
free(_queryFQDN);
if (_expected != NULL) {
free(_expected);
}
if (_response != NULL) {
free(_response);
Expand All @@ -79,23 +67,27 @@ bool MDNSResponder::begin(const char* domain, Adafruit_CC3000& cc3000, uint32_t
// Can only handle domains that are 255 chars in length.
return false;
}
_queryFQDNLen = 8 + n;
if (_queryFQDN != NULL) {
free(_queryFQDN);
_expectedLen = 12 + n;
if (_expected != NULL) {
free(_expected);
}
_queryFQDN = (uint8_t*) malloc(_queryFQDNLen);
if (_queryFQDN == NULL) {
_expected = (uint8_t*) malloc(_expectedLen);
if (_expected == NULL) {
return false;
}
_queryFQDN[0] = (uint8_t)n;
_expected[0] = (uint8_t)n;
// Copy in domain characters as lowercase
for (int i = 0; i < n; ++i) {
_queryFQDN[1+i] = tolower(domain[i]);
_expected[1+i] = tolower(domain[i]);
}
// Values for 5 (length), "local":
uint8_t local[] = { 0x05, 0x6C, 0x6F, 0x63, 0x61, 0x6C };
memcpy(&_queryFQDN[1+n], local, 6);
_queryFQDN[7+n] = 0;
// Values for:
// - 5 (length)
// - "local"
// - 0x00 (end of domain)
// - 0x00 0x01 (A record query)
// - 0x00 0x01 (Class IN)
uint8_t local[] = { 0x05, 0x6C, 0x6F, 0x63, 0x61, 0x6C, 0x00, 0x00, 0x01, 0x00, 0x01 };
memcpy(&_expected[1+n], local, 11);

// Construct DNS query response
// TODO: Move these to flash or just construct in code.
Expand Down Expand Up @@ -125,7 +117,8 @@ bool MDNSResponder::begin(const char* domain, Adafruit_CC3000& cc3000, uint32_t
0x40, 0x00, 0x00, 0x00 // Bitmap value = Only first bit (A record/IPV4) is set
};
// Allocate memory for response.
_responseLen = HEADER_SIZE + _queryFQDNLen + A_RECORD_SIZE + NSEC_RECORD_SIZE;
int queryFQDNLen = _expectedLen - 4;
_responseLen = HEADER_SIZE + queryFQDNLen + A_RECORD_SIZE + NSEC_RECORD_SIZE;
if (_response != NULL) {
free(_response);
}
Expand All @@ -135,8 +128,8 @@ bool MDNSResponder::begin(const char* domain, Adafruit_CC3000& cc3000, uint32_t
}
// Copy data into response.
memcpy(_response, respHeader, HEADER_SIZE);
memcpy(_response + HEADER_SIZE, _queryFQDN, _queryFQDNLen);
uint8_t* records = _response + HEADER_SIZE + _queryFQDNLen;
memcpy(_response + HEADER_SIZE, _expected, queryFQDNLen);
uint8_t* records = _response + HEADER_SIZE + queryFQDNLen;
memcpy(records, aRecord, A_RECORD_SIZE);
memcpy(records + A_RECORD_SIZE, nsecRecord, NSEC_RECORD_SIZE);
// Add TTL to records.
Expand Down Expand Up @@ -174,9 +167,6 @@ bool MDNSResponder::begin(const char* domain, Adafruit_CC3000& cc3000, uint32_t
_mdnsSocket = soc;
}

// Start in a state of parsing the DNS query header.
changeState(_queryHeader);

return true;
}

Expand All @@ -194,67 +184,33 @@ void MDNSResponder::update() {
return;
}
// Read available data.
uint8_t buffer[20];
uint8_t buffer[READ_BUFFER_SIZE];
int n = recv(_mdnsSocket, &buffer, sizeof(buffer), 0);
if (n < 1) {
// Error getting data.
return;
}
// Compare incoming data to expected data from current state.
// Look for domain name in request and respond with canned response if found.
for (int i = 0; i < n; ++i) {
uint8_t ch = buffer[i];
// If we're processing an FQDN character, make the comparison case insensitive.
if (_current == _queryFQDN && _FQDNcount > 0) {
ch = tolower(ch);
}
// Check character matches expected, or in the case of parsing the question counts
// ignore it completely (this is done because MDNS queries on different platforms
// sometimes ask for different record types).
if (ch == _current[_index] ||
(_current == _queryHeader && _index >= QDCOUNT_OFFSET))
uint8_t ch = tolower(buffer[i]);
// Check character matches expected.
if (ch == _expected[_index])
{
// Update FQDN char count when processing FQDN characters.
if (_current == _queryFQDN) {
if (_FQDNcount == 0) {
// Handle the next characters as case insensitive FQDN characters.
_FQDNcount = ch;
}
else {
_FQDNcount--;
}
}
// Update state when the end of the current one has been reached.
_index++;
if (_index >= _currentLen) {
// Switch to next state
if (_current == _queryHeader) {
changeState(_queryFQDN);
}
else if (_current == _queryFQDN) {
sendResponse();
changeState(_queryHeader);
}
// Check if domain name was found and send a response.
if (_index >= _expectedLen) {
// Send response to multicast address.
send(_mdnsSocket, _response, _responseLen, 0);
_index = 0;
}
}
else if (ch == _expected[0]) {
// Found a character that doesn't match, but does match the start of the domain.
_index = 1;
}
else {
// Reset to start looking from the start again
changeState(_queryHeader);
// Found a character that doesn't match the expected character or start of domain.
_index = 0;
}
}
}

void MDNSResponder::changeState(uint8_t* state) {
_current = state;
if (state == _queryFQDN) {
_currentLen = _queryFQDNLen;
}
else if (state == _queryHeader) {
_currentLen = HEADER_SIZE;
}
_index = 0;
_FQDNcount = 0;
}

void MDNSResponder::sendResponse() {
send(_mdnsSocket, _response, _responseLen, 0);
}
12 changes: 3 additions & 9 deletions CC3000_MDNS.h
View file
@@ -1,7 +1,7 @@
/*
CC3000 Multicast DNS
Version 1.0
Version 1.1
Copyright (c) 2013 Tony DiCola (tony@tonydicola.com)
This is a simple implementation of multicast DNS query support for an Arduino
Expand Down Expand Up @@ -56,21 +56,15 @@ class MDNSResponder {
private:
// Expected query values
static uint8_t _queryHeader[];
uint8_t* _queryFQDN;
int _queryFQDNLen;
uint8_t* _expected;
int _expectedLen;
// Current parsing state
uint8_t* _current;
int _currentLen;
int _index;
uint8_t _FQDNcount;
// Response data
uint8_t* _response;
int _responseLen;
// Socket for MDNS communication
static int _mdnsSocket;

void changeState(uint8_t* state);
void sendResponse();
};

#endif
2 changes: 1 addition & 1 deletion README.md
View file
@@ -1,7 +1,7 @@
CC3000 Multicast DNS
====================

Version 1.0
Version 1.1

This is a simple implementation of multicast DNS query support for an Arduino
and CC3000 WiFI chip. Only support for resolving address queries is currently
Expand Down

0 comments on commit fb13d0f

Please sign in to comment.