[136] | 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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