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1 | 58d82c77 | Tom Mullins | // 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 | |||
5 | #include "w5100.h" |
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6 | #include "EthernetUdp.h" |
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7 | #include "util.h" |
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8 | |||
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 | |||
14 | |||
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 | |||
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 | |||
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 | |||
57 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
172 | return ret;
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173 | } |
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174 | |||
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 | |||
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 | |||
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 | |||
205 | twoByteBuffer = htons(1); // One question record |
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206 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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207 | |||
208 | twoByteBuffer = 0; // Zero answer records |
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209 | iUdp.write((uint8_t*)&twoByteBuffer, sizeof(twoByteBuffer));
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210 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
254 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
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 | |||
417 | // Mark the entire packet as read
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418 | iUdp.flush(); |
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419 | |||
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 | } |