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udp/dns/dnsserver.c@169:336d499dc560, 2020-12-01 (annotated)

Committer:
andrewboyson
Date:
Tue Dec 01 12:56:34 2020 +0000
Revision:
169:336d499dc560
Parent:
160:6a1d1d368f80
Child:
172:9bc3c7b2cca1
Modified MDNS response authoritative server bit to be true as per rfc6762 18.4.

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 128:79052cb4a41c 9 #include "action.h"
andrewboyson 128:79052cb4a41c 10 #include "log.h"
andrewboyson 128:79052cb4a41c 11 #include "dhcp.h"
andrewboyson 128:79052cb4a41c 12 #include "slaac.h"
andrewboyson 128:79052cb4a41c 13 #include "ip4.h"
andrewboyson 128:79052cb4a41c 14 #include "ip6.h"
andrewboyson 13:9cd54f7db57a 15
andrewboyson 37:793b39683406 16 bool DnsServerTrace = false;
andrewboyson 37:793b39683406 17
andrewboyson 44:83ce5ace337b 18 #define RECORD_NONE 0
andrewboyson 44:83ce5ace337b 19 #define RECORD_PTR4 1
andrewboyson 44:83ce5ace337b 20 #define RECORD_PTR6_LOCAL 2
andrewboyson 44:83ce5ace337b 21 #define RECORD_PTR6_GLOBAL 3
andrewboyson 44:83ce5ace337b 22 #define RECORD_A 4
andrewboyson 44:83ce5ace337b 23 #define RECORD_AAAA_LOCAL 5
andrewboyson 44:83ce5ace337b 24 #define RECORD_AAAA_GLOBAL 6
andrewboyson 44:83ce5ace337b 25
andrewboyson 44:83ce5ace337b 26 #define MAX_ANSWERS 4
andrewboyson 13:9cd54f7db57a 27
andrewboyson 32:679654f2d023 28 //Set by 'initialise'
andrewboyson 36:900e24b27bfb 29 static char* p; //Position relative to DnsHdrData and is updated while both reading questions and writing answers
andrewboyson 44:83ce5ace337b 30 static char myFullName4[100]; //The name, adjusted to include the domain if needed by the protocol, used when reading and when writing
andrewboyson 44:83ce5ace337b 31 static int myFullName4Length;
andrewboyson 44:83ce5ace337b 32 static char myFullName6[100]; //The name, adjusted to include the domain if needed by the protocol, used when reading and when writing
andrewboyson 44:83ce5ace337b 33 static int myFullName6Length;
andrewboyson 32:679654f2d023 34
andrewboyson 32:679654f2d023 35 //Set by readQuestions and used by answerQuestions
andrewboyson 44:83ce5ace337b 36 static int answers[MAX_ANSWERS];
andrewboyson 44:83ce5ace337b 37 static int answerCount = 0;
andrewboyson 36:900e24b27bfb 38 static bool mdnsUnicastReply;
andrewboyson 32:679654f2d023 39
andrewboyson 32:679654f2d023 40 static int readQuestions()
andrewboyson 32:679654f2d023 41 {
andrewboyson 37:793b39683406 42 p = DnsHdrData;
andrewboyson 32:679654f2d023 43 mdnsUnicastReply = false;
andrewboyson 13:9cd54f7db57a 44
andrewboyson 13:9cd54f7db57a 45 //Get the questions
andrewboyson 44:83ce5ace337b 46 answerCount = 0;
andrewboyson 44:83ce5ace337b 47 for (int i = 0; i < DnsHdrQdcount; i++)
andrewboyson 13:9cd54f7db57a 48 {
andrewboyson 44:83ce5ace337b 49 //Bomb out if there are too many answers
andrewboyson 44:83ce5ace337b 50 if (answerCount >= MAX_ANSWERS)
andrewboyson 37:793b39683406 51 {
andrewboyson 44:83ce5ace337b 52 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions - exceeded %d answers\r\n", MAX_ANSWERS);
andrewboyson 37:793b39683406 53 break;
andrewboyson 37:793b39683406 54 }
andrewboyson 37:793b39683406 55
andrewboyson 37:793b39683406 56 //Bomb out if we are tending to overrun the buffer
andrewboyson 61:aad055f1b0d1 57 if (p - DnsHdrData > DnsHdrDataLength)
andrewboyson 37:793b39683406 58 {
andrewboyson 61:aad055f1b0d1 59 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions - overrunning the buffer of %d bytes\r\n", DnsHdrDataLength);
andrewboyson 37:793b39683406 60 return -1;
andrewboyson 37:793b39683406 61 }
andrewboyson 37:793b39683406 62
andrewboyson 37:793b39683406 63 //Node name
andrewboyson 13:9cd54f7db57a 64 int nameLength = DnsNameLength(p);
andrewboyson 37:793b39683406 65 if (!nameLength)
andrewboyson 37:793b39683406 66 {
andrewboyson 37:793b39683406 67 if (DnsServerTrace) LogTimeF("DnsServer-readQuestions namelength is zero\r\n");
andrewboyson 37:793b39683406 68 return -1;
andrewboyson 37:793b39683406 69 }
andrewboyson 44:83ce5ace337b 70 bool nodeIsName4 = DnsNameComparePtr(p, myFullName4);
andrewboyson 44:83ce5ace337b 71 bool nodeIsName6 = DnsNameComparePtr(p, myFullName6);
andrewboyson 44:83ce5ace337b 72 bool nodeIsAddr4 = DnsNameCompareIp4(p, DhcpLocalIp);
andrewboyson 44:83ce5ace337b 73 bool nodeIsLocl6 = DnsNameCompareIp6(p, SlaacLinkLocalIp);
andrewboyson 44:83ce5ace337b 74 bool nodeIsGlob6 = DnsNameCompareIp6(p, SlaacGlobalIp);
andrewboyson 44:83ce5ace337b 75 p += nameLength; //Skip past the name
andrewboyson 44:83ce5ace337b 76
andrewboyson 37:793b39683406 77 //Type
andrewboyson 44:83ce5ace337b 78 p++ ; //skip the first byte of the type
andrewboyson 44:83ce5ace337b 79 char recordType = *p++; //read the record type
andrewboyson 37:793b39683406 80
andrewboyson 37:793b39683406 81 //Class
andrewboyson 44:83ce5ace337b 82 if (*p++ & 0x80) mdnsUnicastReply = true; //check the class 15th bit (UNICAST-RESPONSE)
andrewboyson 44:83ce5ace337b 83 p++; //skip the class
andrewboyson 44:83ce5ace337b 84
andrewboyson 44:83ce5ace337b 85 //Handle the questions
andrewboyson 44:83ce5ace337b 86 if (nodeIsName4 && recordType == DNS_RECORD_A ) answers[answerCount++] = RECORD_A;
andrewboyson 44:83ce5ace337b 87 if (nodeIsName6 && recordType == DNS_RECORD_AAAA) { answers[answerCount++] = RECORD_AAAA_LOCAL; answers[answerCount++] = RECORD_AAAA_GLOBAL; }
andrewboyson 44:83ce5ace337b 88 if (nodeIsAddr4 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR4;
andrewboyson 44:83ce5ace337b 89 if (nodeIsLocl6 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR6_LOCAL;
andrewboyson 44:83ce5ace337b 90 if (nodeIsGlob6 && recordType == DNS_RECORD_PTR ) answers[answerCount++] = RECORD_PTR6_GLOBAL;
andrewboyson 13:9cd54f7db57a 91 }
andrewboyson 32:679654f2d023 92 return 0;
andrewboyson 32:679654f2d023 93 }
andrewboyson 32:679654f2d023 94 static int addAnswers(int dnsProtocol)
andrewboyson 59:e0e556c8bd46 95 {
andrewboyson 44:83ce5ace337b 96 //Go through each answer
andrewboyson 33:714a0345e59b 97 DnsHdrAncount = 0;
andrewboyson 44:83ce5ace337b 98 for (int i = 0; i < answerCount; i++)
andrewboyson 44:83ce5ace337b 99 {
andrewboyson 37:793b39683406 100 //Bomb out if we are tending to overrun the buffer
andrewboyson 61:aad055f1b0d1 101 if (p - DnsHdrData > DnsHdrDataLength)
andrewboyson 32:679654f2d023 102 {
andrewboyson 37:793b39683406 103 if (DnsServerTrace) LogTimeF("DnsServer-addAnswers - reply is getting too big\r\n");
andrewboyson 32:679654f2d023 104 return -1;
andrewboyson 32:679654f2d023 105 }
andrewboyson 43:bc028d5a6424 106
andrewboyson 37:793b39683406 107 //Encode the node name
andrewboyson 44:83ce5ace337b 108 switch (answers[i])
andrewboyson 32:679654f2d023 109 {
andrewboyson 44:83ce5ace337b 110 case RECORD_A: DnsNameEncodePtr(myFullName4, &p); break;
andrewboyson 44:83ce5ace337b 111 case RECORD_AAAA_LOCAL: DnsNameEncodePtr(myFullName6, &p); break;
andrewboyson 44:83ce5ace337b 112 case RECORD_AAAA_GLOBAL: DnsNameEncodePtr(myFullName6, &p); break;
andrewboyson 44:83ce5ace337b 113 case RECORD_PTR4: DnsNameEncodeIp4(DhcpLocalIp, &p); break;
andrewboyson 44:83ce5ace337b 114 case RECORD_PTR6_LOCAL: DnsNameEncodeIp6(SlaacLinkLocalIp, &p); break;
andrewboyson 44:83ce5ace337b 115 case RECORD_PTR6_GLOBAL: DnsNameEncodeIp6(SlaacGlobalIp, &p); break;
andrewboyson 13:9cd54f7db57a 116 }
andrewboyson 37:793b39683406 117
andrewboyson 44:83ce5ace337b 118 //Add the 16 bit type
andrewboyson 44:83ce5ace337b 119 *p++ = 0;
andrewboyson 44:83ce5ace337b 120 switch (answers[i])
andrewboyson 44:83ce5ace337b 121 {
andrewboyson 44:83ce5ace337b 122 case RECORD_A: *p++ = DNS_RECORD_A; break;
andrewboyson 44:83ce5ace337b 123 case RECORD_AAAA_LOCAL: *p++ = DNS_RECORD_AAAA; break;
andrewboyson 44:83ce5ace337b 124 case RECORD_AAAA_GLOBAL: *p++ = DNS_RECORD_AAAA; break;
andrewboyson 44:83ce5ace337b 125 case RECORD_PTR4: *p++ = DNS_RECORD_PTR; break;
andrewboyson 44:83ce5ace337b 126 case RECORD_PTR6_LOCAL: *p++ = DNS_RECORD_PTR; break;
andrewboyson 44:83ce5ace337b 127 case RECORD_PTR6_GLOBAL: *p++ = DNS_RECORD_PTR; break;
andrewboyson 44:83ce5ace337b 128 }
andrewboyson 37:793b39683406 129
andrewboyson 37:793b39683406 130 //Add the class
andrewboyson 37:793b39683406 131 char mdns = dnsProtocol == DNS_PROTOCOL_MDNS ? 0x80 : 0; //Set the 15th bit (CACHE_FLUSH) of the class to 1 if MDNS
andrewboyson 32:679654f2d023 132 *p++ = mdns; *p++ = 1; //16 bit Class LSB QCLASS_IN = 1 - internet
andrewboyson 37:793b39683406 133
andrewboyson 37:793b39683406 134 //Add the TTL
andrewboyson 32:679654f2d023 135 *p++ = 0; *p++ = 0; *p++ = 4; *p++ = 0; //32 bit TTL seconds - 1024
andrewboyson 37:793b39683406 136
andrewboyson 37:793b39683406 137
andrewboyson 37:793b39683406 138 //Add the 16 bit payload length
andrewboyson 44:83ce5ace337b 139 *p++ = 0;
andrewboyson 44:83ce5ace337b 140 switch (answers[i])
andrewboyson 37:793b39683406 141 {
andrewboyson 44:83ce5ace337b 142 case RECORD_A: *p++ = 4; break;
andrewboyson 44:83ce5ace337b 143 case RECORD_AAAA_LOCAL: *p++ = 16; break;
andrewboyson 44:83ce5ace337b 144 case RECORD_AAAA_GLOBAL: *p++ = 16; break;
andrewboyson 44:83ce5ace337b 145 case RECORD_PTR4: *p++ = myFullName4Length + 2; break; //add a byte for the initial length and another for the terminating zero length
andrewboyson 44:83ce5ace337b 146 case RECORD_PTR6_LOCAL: *p++ = myFullName6Length + 2; break;
andrewboyson 44:83ce5ace337b 147 case RECORD_PTR6_GLOBAL: *p++ = myFullName6Length + 2; break;
andrewboyson 37:793b39683406 148 }
andrewboyson 37:793b39683406 149
andrewboyson 37:793b39683406 150 //Add the payload
andrewboyson 44:83ce5ace337b 151 switch (answers[i])
andrewboyson 37:793b39683406 152 {
andrewboyson 44:83ce5ace337b 153 case RECORD_A: memcpy(p, &DhcpLocalIp, 4); p += 4; break;
andrewboyson 44:83ce5ace337b 154 case RECORD_AAAA_LOCAL: memcpy(p, SlaacLinkLocalIp, 16); p += 16; break;
andrewboyson 44:83ce5ace337b 155 case RECORD_AAAA_GLOBAL: memcpy(p, SlaacGlobalIp, 16); p += 16; break;
andrewboyson 44:83ce5ace337b 156 case RECORD_PTR4: DnsNameEncodePtr(myFullName4, &p); break;
andrewboyson 44:83ce5ace337b 157 case RECORD_PTR6_LOCAL: DnsNameEncodePtr(myFullName6, &p); break;
andrewboyson 44:83ce5ace337b 158 case RECORD_PTR6_GLOBAL: DnsNameEncodePtr(myFullName6, &p); break;
andrewboyson 37:793b39683406 159 }
andrewboyson 44:83ce5ace337b 160 //Increment the number of good answers to send
andrewboyson 44:83ce5ace337b 161 DnsHdrAncount++;
andrewboyson 13:9cd54f7db57a 162 }
andrewboyson 32:679654f2d023 163 return 0;
andrewboyson 32:679654f2d023 164 }
andrewboyson 32:679654f2d023 165
andrewboyson 59:e0e556c8bd46 166 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 167 {
andrewboyson 128:79052cb4a41c 168 myFullName4Length = DnsLabelMakeFullNameFromName(dnsProtocol, NetName4, sizeof(myFullName4), myFullName4);
andrewboyson 128:79052cb4a41c 169 myFullName6Length = DnsLabelMakeFullNameFromName(dnsProtocol, NetName6, sizeof(myFullName6), myFullName6);
andrewboyson 32:679654f2d023 170
andrewboyson 37:793b39683406 171 if (readQuestions()) return DO_NOTHING;
andrewboyson 44:83ce5ace337b 172 if (!answerCount) return DO_NOTHING;
andrewboyson 37:793b39683406 173
andrewboyson 57:e0fb648acf48 174 if (DnsServerTrace || NetTraceHostGetMatched())
andrewboyson 37:793b39683406 175 {
andrewboyson 43:bc028d5a6424 176 if (NetTraceNewLine) Log("\r\n");
andrewboyson 37:793b39683406 177 LogTimeF("DnsServer received query\r\n");
andrewboyson 43:bc028d5a6424 178 if (NetTraceStack) traceback();
andrewboyson 37:793b39683406 179 DnsHdrLog(dnsProtocol);
andrewboyson 37:793b39683406 180 }
andrewboyson 37:793b39683406 181
andrewboyson 59:e0e556c8bd46 182 char* pRx = DnsHdrData;
andrewboyson 59:e0e556c8bd46 183 char* pEndRx = p;
andrewboyson 59:e0e556c8bd46 184 int qdcount = DnsHdrQdcount;
andrewboyson 59:e0e556c8bd46 185 int nscount = DnsHdrNscount;
andrewboyson 59:e0e556c8bd46 186 int arcount = DnsHdrArcount;
andrewboyson 59:e0e556c8bd46 187
andrewboyson 59:e0e556c8bd46 188 DnsHdrSetup(pPacketTx, *pSizeTx);
andrewboyson 59:e0e556c8bd46 189 p = DnsHdrData;
andrewboyson 59:e0e556c8bd46 190
andrewboyson 59:e0e556c8bd46 191 //Add the questions if this is not MDNS
andrewboyson 59:e0e556c8bd46 192 if (dnsProtocol == DNS_PROTOCOL_MDNS)
andrewboyson 59:e0e556c8bd46 193 {
andrewboyson 59:e0e556c8bd46 194 DnsHdrQdcount = 0;
andrewboyson 59:e0e556c8bd46 195 DnsHdrNscount = 0;
andrewboyson 59:e0e556c8bd46 196 DnsHdrArcount = 0;
andrewboyson 59:e0e556c8bd46 197 }
andrewboyson 59:e0e556c8bd46 198 else
andrewboyson 59:e0e556c8bd46 199 {
andrewboyson 59:e0e556c8bd46 200 DnsHdrQdcount = qdcount;
andrewboyson 59:e0e556c8bd46 201 DnsHdrNscount = nscount;
andrewboyson 59:e0e556c8bd46 202 DnsHdrArcount = arcount;
andrewboyson 59:e0e556c8bd46 203 while (pRx < pEndRx) *p++ = *pRx++;
andrewboyson 59:e0e556c8bd46 204 }
andrewboyson 59:e0e556c8bd46 205
andrewboyson 59:e0e556c8bd46 206
andrewboyson 37:793b39683406 207 if (addAnswers(dnsProtocol)) return DO_NOTHING;
andrewboyson 13:9cd54f7db57a 208
andrewboyson 59:e0e556c8bd46 209 DnsHdrIsReply = true;
andrewboyson 59:e0e556c8bd46 210 DnsHdrIsAuthoritative = false;
andrewboyson 169:336d499dc560 211 if (dnsProtocol == DNS_PROTOCOL_MDNS) DnsHdrIsAuthoritative = true; //See rfc6762 18.4
andrewboyson 59:e0e556c8bd46 212 DnsHdrIsRecursiveQuery = false;
andrewboyson 59:e0e556c8bd46 213
andrewboyson 13:9cd54f7db57a 214 DnsHdrWrite();
andrewboyson 13:9cd54f7db57a 215
andrewboyson 59:e0e556c8bd46 216 *pSizeTx = p - DnsHdrPacket;
andrewboyson 13:9cd54f7db57a 217
andrewboyson 57:e0fb648acf48 218 if (DnsServerTrace || NetTraceHostGetMatched()) DnsHdrLog(dnsProtocol);
andrewboyson 13:9cd54f7db57a 219
andrewboyson 37:793b39683406 220 int dest;
andrewboyson 37:793b39683406 221 if (dnsProtocol == DNS_PROTOCOL_MDNS && !mdnsUnicastReply) dest = MULTICAST_MDNS;
andrewboyson 37:793b39683406 222 else dest = UNICAST;
andrewboyson 37:793b39683406 223
andrewboyson 160:6a1d1d368f80 224 return ActionMakeFromDestAndTrace(dest, (NetTraceStack && DnsServerTrace) || NetTraceHostGetMatched());
andrewboyson 13:9cd54f7db57a 225 }