1 | // Arduino DNS client for WizNet5100-based Ethernet shield
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2 | // (c) Copyright 2009-2010 MCQN Ltd.
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3 | // Released under Apache License, version 2.0
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4 |
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5 | #include "utility/w5500.h"
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6 | #include "EthernetUdp2.h"
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7 | #include "utility/util.h"
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8 |
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9 | #include "Dns.h"
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10 | #include <string.h>
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11 | //#include <stdlib.h>
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12 | #include "Arduino.h"
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13 |
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14 |
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15 | #define SOCKET_NONE 255
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16 | // Various flags and header field values for a DNS message
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17 | #define UDP_HEADER_SIZE 8
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18 | #define DNS_HEADER_SIZE 12
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19 | #define TTL_SIZE 4
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20 | #define QUERY_FLAG (0)
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21 | #define RESPONSE_FLAG (1<<15)
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22 | #define QUERY_RESPONSE_MASK (1<<15)
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23 | #define OPCODE_STANDARD_QUERY (0)
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24 | #define OPCODE_INVERSE_QUERY (1<<11)
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25 | #define OPCODE_STATUS_REQUEST (2<<11)
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26 | #define OPCODE_MASK (15<<11)
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27 | #define AUTHORITATIVE_FLAG (1<<10)
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28 | #define TRUNCATION_FLAG (1<<9)
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29 | #define RECURSION_DESIRED_FLAG (1<<8)
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30 | #define RECURSION_AVAILABLE_FLAG (1<<7)
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31 | #define RESP_NO_ERROR (0)
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32 | #define RESP_FORMAT_ERROR (1)
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33 | #define RESP_SERVER_FAILURE (2)
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34 | #define RESP_NAME_ERROR (3)
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35 | #define RESP_NOT_IMPLEMENTED (4)
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36 | #define RESP_REFUSED (5)
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37 | #define RESP_MASK (15)
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38 | #define TYPE_A (0x0001)
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39 | #define CLASS_IN (0x0001)
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40 | #define LABEL_COMPRESSION_MASK (0xC0)
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41 | // Port number that DNS servers listen on
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42 | #define DNS_PORT 53
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43 |
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44 | // Possible return codes from ProcessResponse
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45 | #define SUCCESS 1
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46 | #define TIMED_OUT -1
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47 | #define INVALID_SERVER -2
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48 | #define TRUNCATED -3
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49 | #define INVALID_RESPONSE -4
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50 |
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51 | void DNSClient::begin(const IPAddress& aDNSServer)
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52 | {
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53 | iDNSServer = aDNSServer;
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54 | iRequestId = 0;
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55 | }
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56 |
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57 |
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58 | int DNSClient::inet_aton(const char* aIPAddrString, IPAddress& aResult)
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59 | {
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60 | // See if we've been given a valid IP address
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61 | const char* p =aIPAddrString;
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62 | while (*p &&
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63 | ( (*p == '.') || (*p >= '0') || (*p <= '9') ))
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64 | {
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65 | p++;
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66 | }
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67 |
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68 | if (*p == '\0')
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69 | {
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70 | // It's looking promising, we haven't found any invalid characters
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71 | p = aIPAddrString;
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72 | int segment =0;
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73 | int segmentValue =0;
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74 | while (*p && (segment < 4))
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75 | {
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76 | if (*p == '.')
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77 | {
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78 | // We've reached the end of a segment
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79 | if (segmentValue > 255)
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80 | {
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81 | // You can't have IP address segments that don't fit in a byte
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82 | return 0;
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83 | }
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84 | else
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85 | {
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86 | aResult[segment] = (byte)segmentValue;
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87 | segment++;
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88 | segmentValue = 0;
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89 | }
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90 | }
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91 | else
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92 | {
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93 | // Next digit
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94 | segmentValue = (segmentValue*10)+(*p - '0');
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95 | }
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96 | p++;
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97 | }
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98 | // We've reached the end of address, but there'll still be the last
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99 | // segment to deal with
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100 | if ((segmentValue > 255) || (segment > 3))
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101 | {
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102 | // You can't have IP address segments that don't fit in a byte,
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103 | // or more than four segments
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104 | return 0;
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105 | }
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106 | else
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107 | {
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108 | aResult[segment] = (byte)segmentValue;
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109 | return 1;
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110 | }
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111 | }
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112 | else
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113 | {
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114 | return 0;
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115 | }
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116 | }
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117 |
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118 | int DNSClient::getHostByName(const char* aHostname, IPAddress& aResult)
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119 | {
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120 | int ret =0;
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121 |
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122 | // See if it's a numeric IP address
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123 | if (inet_aton(aHostname, aResult))
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124 | {
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125 | // It is, our work here is done
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126 | return 1;
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127 | }
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128 |
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129 | // Check we've got a valid DNS server to use
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130 | if (iDNSServer == INADDR_NONE)
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131 | {
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132 | return INVALID_SERVER;
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133 | }
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134 |
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135 | // Find a socket to use
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136 | if (iUdp.begin(1024+(millis() & 0xF)) == 1)
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137 | {
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138 | // Try up to three times
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139 | int retries = 0;
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140 | // while ((retries < 3) && (ret <= 0))
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141 | {
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142 | // Send DNS request
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143 | ret = iUdp.beginPacket(iDNSServer, DNS_PORT);
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144 | if (ret != 0)
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145 | {
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146 | // Now output the request data
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147 | ret = BuildRequest(aHostname);
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148 | if (ret != 0)
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149 | {
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150 | // And finally send the request
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151 | ret = iUdp.endPacket();
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152 | if (ret != 0)
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153 | {
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154 | // Now wait for a response
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155 | int wait_retries = 0;
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156 | ret = TIMED_OUT;
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157 | while ((wait_retries < 3) && (ret == TIMED_OUT))
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158 | {
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159 | ret = ProcessResponse(5000, aResult);
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160 | wait_retries++;
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161 | }
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162 | }
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163 | }
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164 | }
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165 | retries++;
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166 | }
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167 |
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168 | // We're done with the socket now
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169 | iUdp.stop();
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170 | }
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171 |
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172 | return ret;
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173 | }
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174 |
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175 | uint16_t DNSClient::BuildRequest(const char* aName)
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176 | {
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177 | // Build header
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178 | // 1 1 1 1 1 1
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179 | // 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
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180 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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181 | // | ID |
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182 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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183 | // |QR| Opcode |AA|TC|RD|RA| Z | RCODE |
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184 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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185 | // | QDCOUNT |
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186 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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187 | // | ANCOUNT |
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188 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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189 | // | NSCOUNT |
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190 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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191 | // | ARCOUNT |
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192 | // +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
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193 | // As we only support one request at a time at present, we can simplify
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194 | // some of this header
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195 | iRequestId = millis(); // generate a random ID
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196 | uint16_t twoByteBuffer;
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197 |
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198 | // FIXME We should also check that there's enough space available to write to, rather
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199 | // FIXME than assume there's enough space (as the code does at present)
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200 | iUdp.write((uint8_t*)&iRequestId, sizeof(iRequestId));
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201 |
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202 | twoByteBuffer = htons(QUERY_FLAG | OPCODE_STANDARD_QUERY | RECURSION_DESIRED_FLAG);
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203 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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204 |
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205 | twoByteBuffer = htons(1); // One question record
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206 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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207 |
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208 | twoByteBuffer = 0; // Zero answer records
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209 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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210 |
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211 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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212 | // and zero additional records
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213 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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214 |
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215 | // Build question
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216 | const char* start =aName;
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217 | const char* end =start;
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218 | uint8_t len;
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219 | // Run through the name being requested
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220 | while (*end)
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221 | {
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222 | // Find out how long this section of the name is
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223 | end = start;
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224 | while (*end && (*end != '.') )
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225 | {
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226 | end++;
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227 | }
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228 |
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229 | if (end-start > 0)
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230 | {
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231 | // Write out the size of this section
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232 | len = end-start;
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233 | iUdp.write(&len, sizeof(len));
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234 | // And then write out the section
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235 | iUdp.write((uint8_t*)start, end-start);
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236 | }
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237 | start = end+1;
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238 | }
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239 |
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240 | // We've got to the end of the question name, so
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241 | // terminate it with a zero-length section
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242 | len = 0;
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243 | iUdp.write(&len, sizeof(len));
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244 | // Finally the type and class of question
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245 | twoByteBuffer = htons(TYPE_A);
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246 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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247 |
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248 | twoByteBuffer = htons(CLASS_IN); // Internet class of question
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249 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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250 | // Success! Everything buffered okay
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251 | return 1;
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252 | }
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253 |
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254 |
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255 | uint16_t DNSClient::ProcessResponse(uint16_t aTimeout, IPAddress& aAddress)
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256 | {
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257 | uint32_t startTime = millis();
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258 |
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259 | // Wait for a response packet
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260 | while(iUdp.parsePacket() <= 0)
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261 | {
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262 | if((millis() - startTime) > aTimeout)
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263 | return TIMED_OUT;
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264 | delay(50);
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265 | }
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266 |
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267 | // We've had a reply!
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268 | // Read the UDP header
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269 | uint8_t header[DNS_HEADER_SIZE]; // Enough space to reuse for the DNS header
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270 | // Check that it's a response from the right server and the right port
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271 | if ( (iDNSServer != iUdp.remoteIP()) ||
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272 | (iUdp.remotePort() != DNS_PORT) )
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273 | {
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274 | // It's not from who we expected
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275 | return INVALID_SERVER;
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276 | }
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277 |
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278 | // Read through the rest of the response
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279 | if (iUdp.available() < DNS_HEADER_SIZE)
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280 | {
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281 | return TRUNCATED;
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282 | }
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283 | iUdp.read(header, DNS_HEADER_SIZE);
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284 |
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285 | uint16_t header_flags = htons(*((uint16_t*)&header[2]));
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286 | // Check that it's a response to this request
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287 | if ( ( iRequestId != (*((uint16_t*)&header[0])) ) ||
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288 | ((header_flags & QUERY_RESPONSE_MASK) != (uint16_t)RESPONSE_FLAG) )
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289 | {
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290 | // Mark the entire packet as read
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291 | iUdp.flush();
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292 | return INVALID_RESPONSE;
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293 | }
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294 | // Check for any errors in the response (or in our request)
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295 | // although we don't do anything to get round these
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296 | if ( (header_flags & TRUNCATION_FLAG) || (header_flags & RESP_MASK) )
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297 | {
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298 | // Mark the entire packet as read
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299 | iUdp.flush();
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300 | return -5; //INVALID_RESPONSE;
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301 | }
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302 |
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303 | // And make sure we've got (at least) one answer
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304 | uint16_t answerCount = htons(*((uint16_t*)&header[6]));
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305 | if (answerCount == 0 )
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306 | {
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307 | // Mark the entire packet as read
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308 | iUdp.flush();
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309 | return -6; //INVALID_RESPONSE;
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310 | }
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311 |
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312 | // Skip over any questions
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313 | for (uint16_t i =0; i < htons(*((uint16_t*)&header[4])); i++)
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314 | {
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315 | // Skip over the name
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316 | uint8_t len;
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317 | do
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318 | {
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319 | iUdp.read(&len, sizeof(len));
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320 | if (len > 0)
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321 | {
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322 | // Don't need to actually read the data out for the string, just
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323 | // advance ptr to beyond it
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324 | while(len--)
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325 | {
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326 | iUdp.read(); // we don't care about the returned byte
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327 | }
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328 | }
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329 | } while (len != 0);
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330 |
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331 | // Now jump over the type and class
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332 | for (int i =0; i < 4; i++)
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333 | {
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334 | iUdp.read(); // we don't care about the returned byte
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335 | }
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336 | }
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337 |
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338 | // Now we're up to the bit we're interested in, the answer
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339 | // There might be more than one answer (although we'll just use the first
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340 | // type A answer) and some authority and additional resource records but
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341 | // we're going to ignore all of them.
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342 |
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343 | for (uint16_t i =0; i < answerCount; i++)
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344 | {
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345 | // Skip the name
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346 | uint8_t len;
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347 | do
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348 | {
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349 | iUdp.read(&len, sizeof(len));
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350 | if ((len & LABEL_COMPRESSION_MASK) == 0)
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351 | {
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352 | // It's just a normal label
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353 | if (len > 0)
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354 | {
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355 | // And it's got a length
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356 | // Don't need to actually read the data out for the string,
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357 | // just advance ptr to beyond it
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358 | while(len--)
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359 | {
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360 | iUdp.read(); // we don't care about the returned byte
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361 | }
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362 | }
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363 | }
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364 | else
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365 | {
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366 | // This is a pointer to a somewhere else in the message for the
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367 | // rest of the name. We don't care about the name, and RFC1035
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368 | // says that a name is either a sequence of labels ended with a
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369 | // 0 length octet or a pointer or a sequence of labels ending in
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370 | // a pointer. Either way, when we get here we're at the end of
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371 | // the name
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372 | // Skip over the pointer
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373 | iUdp.read(); // we don't care about the returned byte
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374 | // And set len so that we drop out of the name loop
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375 | len = 0;
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376 | }
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377 | } while (len != 0);
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378 |
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379 | // Check the type and class
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380 | uint16_t answerType;
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381 | uint16_t answerClass;
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382 | iUdp.read((uint8_t*)&answerType, sizeof(answerType));
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383 | iUdp.read((uint8_t*)&answerClass, sizeof(answerClass));
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384 |
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385 | // Ignore the Time-To-Live as we don't do any caching
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386 | for (int i =0; i < TTL_SIZE; i++)
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387 | {
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388 | iUdp.read(); // we don't care about the returned byte
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389 | }
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390 |
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391 | // And read out the length of this answer
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392 | // Don't need header_flags anymore, so we can reuse it here
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393 | iUdp.read((uint8_t*)&header_flags, sizeof(header_flags));
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394 |
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395 | if ( (htons(answerType) == TYPE_A) && (htons(answerClass) == CLASS_IN) )
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396 | {
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397 | if (htons(header_flags) != 4)
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398 | {
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399 | // It's a weird size
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400 | // Mark the entire packet as read
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401 | iUdp.flush();
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402 | return -9;//INVALID_RESPONSE;
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403 | }
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404 | iUdp.read(aAddress.raw_address(), 4);
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405 | return SUCCESS;
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406 | }
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407 | else
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408 | {
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409 | // This isn't an answer type we're after, move onto the next one
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410 | for (uint16_t i =0; i < htons(header_flags); i++)
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411 | {
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412 | iUdp.read(); // we don't care about the returned byte
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413 | }
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414 | }
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415 | }
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416 |
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417 | // Mark the entire packet as read
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418 | iUdp.flush();
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419 |
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420 | // If we get here then we haven't found an answer
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421 | return -10;//INVALID_RESPONSE;
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422 | }
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423 |
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