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udp/dns/dnsserver.c@190:c4415a7253f5, 2021-01-21 (annotated)

Committer:
andrewboyson
Date:
Thu Jan 21 14:56:55 2021 +0000
Revision:
190:c4415a7253f5
Parent:
189:e1c7990486c4 
Corrected a bug in DnsLabel whereby a ip4 encoded name was not recognised. This has been there a long time and came to light because MDNS was failing to return a name from an Ip4 address.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 61:aad055f1b0d1 1 #include <stdbool.h>
andrewboyson 61:aad055f1b0d1 2 #include <string.h>
andrewboyson 61:aad055f1b0d1 3
andrewboyson 128:79052cb4a41c 4 #include "dns.h"
andrewboyson 128:79052cb4a41c 5 #include "dnshdr.h"
andrewboyson 128:79052cb4a41c 6 #include "dnsname.h"
andrewboyson 128:79052cb4a41c 7 #include "dnslabel.h"
andrewboyson 128:79052cb4a41c 8 #include "net.h"
andrewboyson 178:52714fef5ca1 9 #include "net-this.h"
andrewboyson 128:79052cb4a41c 10 #include "action.h"
andrewboyson 128:79052cb4a41c 11 #include "log.h"
andrewboyson 128:79052cb4a41c 12 #include "dhcp.h"
andrewboyson 128:79052cb4a41c 13 #include "slaac.h"
andrewboyson 128:79052cb4a41c 14 #include "ip4.h"
andrewboyson 128:79052cb4a41c 15 #include "ip6.h"
andrewboyson 13:9cd54f7db57a 16
andrewboyson 37:793b39683406 17 bool DnsServerTrace = false;
andrewboyson 37:793b39683406 18
andrewboyson 172:9bc3c7b2cca1 19 #define RECORD_NONE 0
andrewboyson 172:9bc3c7b2cca1 20 #define RECORD_PTR4 1
andrewboyson 172:9bc3c7b2cca1 21 #define RECORD_PTR6_LINK_LOCAL 2
andrewboyson 172:9bc3c7b2cca1 22 #define RECORD_PTR6_UNIQUE_LOCAL 3
andrewboyson 172:9bc3c7b2cca1 23 #define RECORD_PTR6_GLOBAL 4
andrewboyson 172:9bc3c7b2cca1 24 #define RECORD_A 5
andrewboyson 172:9bc3c7b2cca1 25 #define RECORD_AAAA_LINK_LOCAL 6
andrewboyson 172:9bc3c7b2cca1 26 #define RECORD_AAAA_UNIQUE_LOCAL 7
andrewboyson 172:9bc3c7b2cca1 27 #define RECORD_AAAA_GLOBAL 8
andrewboyson 44:83ce5ace337b 28
andrewboyson 44:83ce5ace337b 29 #define MAX_ANSWERS 4
andrewboyson 13:9cd54f7db57a 30
andrewboyson 32:679654f2d023 31 //Set by 'initialise'
andrewboyson 36:900e24b27bfb 32 static char* p; //Position relative to DnsHdrData and is updated while both reading questions and writing answers
andrewboyson 178:52714fef5ca1 33 static char myFullName[100]; //The name, adjusted to include the domain if needed by the protocol, used when reading and when writing
andrewboyson 178:52714fef5ca1 34 static int myFullNameLength;
andrewboyson 32:679654f2d023 35
andrewboyson 32:679654f2d023 36 //Set by readQuestions and used by answerQuestions
andrewboyson 44:83ce5ace337b 37 static int answers[MAX_ANSWERS];
andrewboyson 44:83ce5ace337b 38 static int answerCount = 0;
andrewboyson 36:900e24b27bfb 39 static bool mdnsUnicastReply;
andrewboyson 32:679654f2d023 40
andrewboyson 32:679654f2d023 41 static int readQuestions()
andrewboyson 32:679654f2d023 42 {
andrewboyson 37:793b39683406 43 p = DnsHdrData;
andrewboyson 32:679654f2d023 44 mdnsUnicastReply = false;
andrewboyson 13:9cd54f7db57a 45
andrewboyson 13:9cd54f7db57a 46 //Get the questions
andrewboyson 44:83ce5ace337b 47 answerCount = 0;
andrewboyson 44:83ce5ace337b 48 for (int i = 0; i < DnsHdrQdcount; i++)
andrewboyson 13:9cd54f7db57a 49 {
andrewboyson 44:83ce5ace337b 50 //Bomb out if there are too many answers
andrewboyson 44:83ce5ace337b 51 if (answerCount >= MAX_ANSWERS)
andrewboyson 37:793b39683406 52 {
andrewboyson 44:83ce5ace337b 53 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions - exceeded %d answers\r\n", MAX_ANSWERS);
andrewboyson 37:793b39683406 54 break;
andrewboyson 37:793b39683406 55 }
andrewboyson 37:793b39683406 56
andrewboyson 37:793b39683406 57 //Bomb out if we are tending to overrun the buffer
andrewboyson 61:aad055f1b0d1 58 if (p - DnsHdrData > DnsHdrDataLength)
andrewboyson 37:793b39683406 59 {
andrewboyson 61:aad055f1b0d1 60 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions - overrunning the buffer of %d bytes\r\n", DnsHdrDataLength);
andrewboyson 37:793b39683406 61 return -1;
andrewboyson 37:793b39683406 62 }
andrewboyson 37:793b39683406 63
andrewboyson 37:793b39683406 64 //Node name
andrewboyson 13:9cd54f7db57a 65 int nameLength = DnsNameLength(p);
andrewboyson 37:793b39683406 66 if (!nameLength)
andrewboyson 37:793b39683406 67 {
andrewboyson 37:793b39683406 68 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions namelength is zero\r\n");
andrewboyson 37:793b39683406 69 return -1;
andrewboyson 37:793b39683406 70 }
andrewboyson 178:52714fef5ca1 71 bool nodeIsName = DnsNameComparePtr(p, myFullName);
andrewboyson 44:83ce5ace337b 72 bool nodeIsAddr4 = DnsNameCompareIp4(p, DhcpLocalIp);
andrewboyson 44:83ce5ace337b 73 bool nodeIsLocl6 = DnsNameCompareIp6(p, SlaacLinkLocalIp);
andrewboyson 172:9bc3c7b2cca1 74 bool nodeIsUniq6 = DnsNameCompareIp6(p, SlaacUniqueLocalIp);
andrewboyson 44:83ce5ace337b 75 bool nodeIsGlob6 = DnsNameCompareIp6(p, SlaacGlobalIp);
andrewboyson 44:83ce5ace337b 76 p += nameLength; //Skip past the name
andrewboyson 44:83ce5ace337b 77
andrewboyson 37:793b39683406 78 //Type
andrewboyson 44:83ce5ace337b 79 p++ ; //skip the first byte of the type
andrewboyson 44:83ce5ace337b 80 char recordType = *p++; //read the record type
andrewboyson 37:793b39683406 81
andrewboyson 37:793b39683406 82 //Class
andrewboyson 44:83ce5ace337b 83 if (*p++ & 0x80) mdnsUnicastReply = true; //check the class 15th bit (UNICAST-RESPONSE)
andrewboyson 44:83ce5ace337b 84 p++; //skip the class
andrewboyson 44:83ce5ace337b 85
andrewboyson 44:83ce5ace337b 86 //Handle the questions
andrewboyson 178:52714fef5ca1 87 if (nodeIsName && recordType == DNS_RECORD_A ) answers[answerCount++] = RECORD_A;
andrewboyson 178:52714fef5ca1 88 if (nodeIsName && recordType == DNS_RECORD_AAAA)
andrewboyson 177:2cd7fde8bfe5 89 {
andrewboyson 178:52714fef5ca1 90 answers[answerCount++] = RECORD_AAAA_LINK_LOCAL;
andrewboyson 178:52714fef5ca1 91 if (SlaacUniqueLocalIp[0]) answers[answerCount++] = RECORD_AAAA_UNIQUE_LOCAL;
andrewboyson 178:52714fef5ca1 92 if (SlaacGlobalIp [0]) answers[answerCount++] = RECORD_AAAA_GLOBAL;
andrewboyson 177:2cd7fde8bfe5 93 }
andrewboyson 178:52714fef5ca1 94 if (nodeIsAddr4 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR4;
andrewboyson 178:52714fef5ca1 95 if (nodeIsLocl6 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR6_LINK_LOCAL;
andrewboyson 178:52714fef5ca1 96 if (nodeIsUniq6 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR6_UNIQUE_LOCAL;
andrewboyson 178:52714fef5ca1 97 if (nodeIsGlob6 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR6_GLOBAL;
andrewboyson 13:9cd54f7db57a 98 }
andrewboyson 32:679654f2d023 99 return 0;
andrewboyson 32:679654f2d023 100 }
andrewboyson 32:679654f2d023 101 static int addAnswers(int dnsProtocol)
andrewboyson 59:e0e556c8bd46 102 {
andrewboyson 44:83ce5ace337b 103 //Go through each answer
andrewboyson 33:714a0345e59b 104 DnsHdrAncount = 0;
andrewboyson 44:83ce5ace337b 105 for (int i = 0; i < answerCount; i++)
andrewboyson 44:83ce5ace337b 106 {
andrewboyson 37:793b39683406 107 //Bomb out if we are tending to overrun the buffer
andrewboyson 61:aad055f1b0d1 108 if (p - DnsHdrData > DnsHdrDataLength)
andrewboyson 32:679654f2d023 109 {
andrewboyson 37:793b39683406 110 if (DnsServerTrace) LogTimeF("DnsServer-addAnswers - reply is getting too big\r\n");
andrewboyson 32:679654f2d023 111 return -1;
andrewboyson 32:679654f2d023 112 }
andrewboyson 43:bc028d5a6424 113
andrewboyson 37:793b39683406 114 //Encode the node name
andrewboyson 44:83ce5ace337b 115 switch (answers[i])
andrewboyson 32:679654f2d023 116 {
andrewboyson 178:52714fef5ca1 117 case RECORD_A: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 118 case RECORD_AAAA_LINK_LOCAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 119 case RECORD_AAAA_UNIQUE_LOCAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 120 case RECORD_AAAA_GLOBAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 172:9bc3c7b2cca1 121 case RECORD_PTR4: DnsNameEncodeIp4(DhcpLocalIp, &p); break;
andrewboyson 172:9bc3c7b2cca1 122 case RECORD_PTR6_LINK_LOCAL: DnsNameEncodeIp6(SlaacLinkLocalIp, &p); break;
andrewboyson 172:9bc3c7b2cca1 123 case RECORD_PTR6_UNIQUE_LOCAL: DnsNameEncodeIp6(SlaacUniqueLocalIp, &p); break;
andrewboyson 172:9bc3c7b2cca1 124 case RECORD_PTR6_GLOBAL: DnsNameEncodeIp6(SlaacGlobalIp, &p); break;
andrewboyson 13:9cd54f7db57a 125 }
andrewboyson 37:793b39683406 126
andrewboyson 44:83ce5ace337b 127 //Add the 16 bit type
andrewboyson 44:83ce5ace337b 128 *p++ = 0;
andrewboyson 44:83ce5ace337b 129 switch (answers[i])
andrewboyson 44:83ce5ace337b 130 {
andrewboyson 172:9bc3c7b2cca1 131 case RECORD_A: *p++ = DNS_RECORD_A; break;
andrewboyson 172:9bc3c7b2cca1 132 case RECORD_AAAA_LINK_LOCAL: *p++ = DNS_RECORD_AAAA; break;
andrewboyson 172:9bc3c7b2cca1 133 case RECORD_AAAA_UNIQUE_LOCAL: *p++ = DNS_RECORD_AAAA; break;
andrewboyson 172:9bc3c7b2cca1 134 case RECORD_AAAA_GLOBAL: *p++ = DNS_RECORD_AAAA; break;
andrewboyson 172:9bc3c7b2cca1 135 case RECORD_PTR4: *p++ = DNS_RECORD_PTR; break;
andrewboyson 172:9bc3c7b2cca1 136 case RECORD_PTR6_LINK_LOCAL: *p++ = DNS_RECORD_PTR; break;
andrewboyson 172:9bc3c7b2cca1 137 case RECORD_PTR6_UNIQUE_LOCAL: *p++ = DNS_RECORD_PTR; break;
andrewboyson 172:9bc3c7b2cca1 138 case RECORD_PTR6_GLOBAL: *p++ = DNS_RECORD_PTR; break;
andrewboyson 44:83ce5ace337b 139 }
andrewboyson 37:793b39683406 140
andrewboyson 37:793b39683406 141 //Add the class
andrewboyson 37:793b39683406 142 char mdns = dnsProtocol == DNS_PROTOCOL_MDNS ? 0x80 : 0; //Set the 15th bit (CACHE_FLUSH) of the class to 1 if MDNS
andrewboyson 32:679654f2d023 143 *p++ = mdns; *p++ = 1; //16 bit Class LSB QCLASS_IN = 1 - internet
andrewboyson 37:793b39683406 144
andrewboyson 37:793b39683406 145 //Add the TTL
andrewboyson 32:679654f2d023 146 *p++ = 0; *p++ = 0; *p++ = 4; *p++ = 0; //32 bit TTL seconds - 1024
andrewboyson 37:793b39683406 147
andrewboyson 37:793b39683406 148
andrewboyson 37:793b39683406 149 //Add the 16 bit payload length
andrewboyson 44:83ce5ace337b 150 *p++ = 0;
andrewboyson 44:83ce5ace337b 151 switch (answers[i])
andrewboyson 37:793b39683406 152 {
andrewboyson 178:52714fef5ca1 153 case RECORD_A: *p++ = 4; break;
andrewboyson 178:52714fef5ca1 154 case RECORD_AAAA_LINK_LOCAL: *p++ = 16; break;
andrewboyson 178:52714fef5ca1 155 case RECORD_AAAA_UNIQUE_LOCAL: *p++ = 16; break;
andrewboyson 178:52714fef5ca1 156 case RECORD_AAAA_GLOBAL: *p++ = 16; break;
andrewboyson 178:52714fef5ca1 157 case RECORD_PTR4: *p++ = myFullNameLength + 2; break; //add a byte for the initial length and another for the terminating zero length
andrewboyson 178:52714fef5ca1 158 case RECORD_PTR6_LINK_LOCAL: *p++ = myFullNameLength + 2; break;
andrewboyson 178:52714fef5ca1 159 case RECORD_PTR6_UNIQUE_LOCAL: *p++ = myFullNameLength + 2; break;
andrewboyson 178:52714fef5ca1 160 case RECORD_PTR6_GLOBAL: *p++ = myFullNameLength + 2; break;
andrewboyson 37:793b39683406 161 }
andrewboyson 37:793b39683406 162
andrewboyson 37:793b39683406 163 //Add the payload
andrewboyson 44:83ce5ace337b 164 switch (answers[i])
andrewboyson 37:793b39683406 165 {
andrewboyson 172:9bc3c7b2cca1 166 case RECORD_A: memcpy(p, &DhcpLocalIp, 4); p += 4; break;
andrewboyson 172:9bc3c7b2cca1 167 case RECORD_AAAA_LINK_LOCAL: memcpy(p, SlaacLinkLocalIp, 16); p += 16; break;
andrewboyson 172:9bc3c7b2cca1 168 case RECORD_AAAA_UNIQUE_LOCAL: memcpy(p, SlaacUniqueLocalIp, 16); p += 16; break;
andrewboyson 172:9bc3c7b2cca1 169 case RECORD_AAAA_GLOBAL: memcpy(p, SlaacGlobalIp, 16); p += 16; break;
andrewboyson 178:52714fef5ca1 170 case RECORD_PTR4: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 171 case RECORD_PTR6_LINK_LOCAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 172 case RECORD_PTR6_UNIQUE_LOCAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 178:52714fef5ca1 173 case RECORD_PTR6_GLOBAL: DnsNameEncodePtr(myFullName, &p); break;
andrewboyson 37:793b39683406 174 }
andrewboyson 44:83ce5ace337b 175 //Increment the number of good answers to send
andrewboyson 44:83ce5ace337b 176 DnsHdrAncount++;
andrewboyson 13:9cd54f7db57a 177 }
andrewboyson 32:679654f2d023 178 return 0;
andrewboyson 32:679654f2d023 179 }
andrewboyson 32:679654f2d023 180
andrewboyson 59:e0e556c8bd46 181 int DnsServerHandleQuery(void (*traceback)(void), int dnsProtocol, void* pPacketTx, int *pSizeTx) //Received an mdns or llmnr query on port 5353 or 5355
andrewboyson 59:e0e556c8bd46 182 {
andrewboyson 178:52714fef5ca1 183 myFullNameLength = DnsLabelMakeFullNameFromName(dnsProtocol, NET_NAME, sizeof(myFullName), myFullName);
andrewboyson 32:679654f2d023 184
andrewboyson 37:793b39683406 185 if (readQuestions()) return DO_NOTHING;
andrewboyson 44:83ce5ace337b 186 if (!answerCount) return DO_NOTHING;
andrewboyson 37:793b39683406 187
andrewboyson 57:e0fb648acf48 188 if (DnsServerTrace || NetTraceHostGetMatched())
andrewboyson 37:793b39683406 189 {
andrewboyson 43:bc028d5a6424 190 if (NetTraceNewLine) Log("\r\n");
andrewboyson 37:793b39683406 191 LogTimeF("DnsServer received query\r\n");
andrewboyson 43:bc028d5a6424 192 if (NetTraceStack) traceback();
andrewboyson 37:793b39683406 193 DnsHdrLog(dnsProtocol);
andrewboyson 37:793b39683406 194 }
andrewboyson 37:793b39683406 195
andrewboyson 59:e0e556c8bd46 196 char* pRx = DnsHdrData;
andrewboyson 59:e0e556c8bd46 197 char* pEndRx = p;
andrewboyson 59:e0e556c8bd46 198 int qdcount = DnsHdrQdcount;
andrewboyson 59:e0e556c8bd46 199 int nscount = DnsHdrNscount;
andrewboyson 59:e0e556c8bd46 200 int arcount = DnsHdrArcount;
andrewboyson 59:e0e556c8bd46 201
andrewboyson 59:e0e556c8bd46 202 DnsHdrSetup(pPacketTx, *pSizeTx);
andrewboyson 59:e0e556c8bd46 203 p = DnsHdrData;
andrewboyson 59:e0e556c8bd46 204
andrewboyson 59:e0e556c8bd46 205 //Add the questions if this is not MDNS
andrewboyson 59:e0e556c8bd46 206 if (dnsProtocol == DNS_PROTOCOL_MDNS)
andrewboyson 59:e0e556c8bd46 207 {
andrewboyson 59:e0e556c8bd46 208 DnsHdrQdcount = 0;
andrewboyson 59:e0e556c8bd46 209 DnsHdrNscount = 0;
andrewboyson 59:e0e556c8bd46 210 DnsHdrArcount = 0;
andrewboyson 59:e0e556c8bd46 211 }
andrewboyson 59:e0e556c8bd46 212 else
andrewboyson 59:e0e556c8bd46 213 {
andrewboyson 59:e0e556c8bd46 214 DnsHdrQdcount = qdcount;
andrewboyson 59:e0e556c8bd46 215 DnsHdrNscount = nscount;
andrewboyson 59:e0e556c8bd46 216 DnsHdrArcount = arcount;
andrewboyson 59:e0e556c8bd46 217 while (pRx < pEndRx) *p++ = *pRx++;
andrewboyson 59:e0e556c8bd46 218 }
andrewboyson 59:e0e556c8bd46 219
andrewboyson 59:e0e556c8bd46 220
andrewboyson 37:793b39683406 221 if (addAnswers(dnsProtocol)) return DO_NOTHING;
andrewboyson 13:9cd54f7db57a 222
andrewboyson 59:e0e556c8bd46 223 DnsHdrIsReply = true;
andrewboyson 59:e0e556c8bd46 224 DnsHdrIsAuthoritative = false;
andrewboyson 169:336d499dc560 225 if (dnsProtocol == DNS_PROTOCOL_MDNS) DnsHdrIsAuthoritative = true; //See rfc6762 18.4
andrewboyson 59:e0e556c8bd46 226 DnsHdrIsRecursiveQuery = false;
andrewboyson 59:e0e556c8bd46 227
andrewboyson 13:9cd54f7db57a 228 DnsHdrWrite();
andrewboyson 13:9cd54f7db57a 229
andrewboyson 59:e0e556c8bd46 230 *pSizeTx = p - DnsHdrPacket;
andrewboyson 13:9cd54f7db57a 231
andrewboyson 57:e0fb648acf48 232 if (DnsServerTrace || NetTraceHostGetMatched()) DnsHdrLog(dnsProtocol);
andrewboyson 13:9cd54f7db57a 233
andrewboyson 37:793b39683406 234 int dest;
andrewboyson 37:793b39683406 235 if (dnsProtocol == DNS_PROTOCOL_MDNS && !mdnsUnicastReply) dest = MULTICAST_MDNS;
andrewboyson 37:793b39683406 236 else dest = UNICAST;
andrewboyson 37:793b39683406 237
andrewboyson 160:6a1d1d368f80 238 return ActionMakeFromDestAndTrace(dest, (NetTraceStack && DnsServerTrace) || NetTraceHostGetMatched());
andrewboyson 13:9cd54f7db57a 239 }