Andrew Boyson / net

A stack which works with or without an Mbed os library. Provides IPv4 or IPv6 with a full 1500 byte buffer.

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udp/dns/dnshdr.cpp@59:e0e556c8bd46, 2017-12-14 (annotated)

Committer:
andrewboyson
Date:
Thu Dec 14 20:55:40 2017 +0000
Revision:
59:e0e556c8bd46
Parent:
58:d48c899e482f 
Added buffer length to help avoid over runs

Who changed what in which revision?

UserRevisionLine numberNew contents of line
andrewboyson 13:9cd54f7db57a 1 #include "mbed.h"
andrewboyson 13:9cd54f7db57a 2 #include "dns.h"
andrewboyson 13:9cd54f7db57a 3 #include "net.h"
andrewboyson 13:9cd54f7db57a 4 #include "log.h"
andrewboyson 14:e75a59c1123d 5 #include "net.h"
andrewboyson 14:e75a59c1123d 6 #include "eth.h"
andrewboyson 49:1a6336f2b3f9 7 #include "ip4addr.h"
andrewboyson 49:1a6336f2b3f9 8 #include "ip6addr.h"
andrewboyson 14:e75a59c1123d 9 #include "udp.h"
andrewboyson 37:793b39683406 10 #include "dnsname.h"
andrewboyson 13:9cd54f7db57a 11
andrewboyson 13:9cd54f7db57a 12 #define HEADER_LENGTH 12
andrewboyson 13:9cd54f7db57a 13
andrewboyson 13:9cd54f7db57a 14 __packed struct header
andrewboyson 13:9cd54f7db57a 15 {
andrewboyson 13:9cd54f7db57a 16 uint16_t id;
andrewboyson 13:9cd54f7db57a 17 uint8_t uflags;
andrewboyson 13:9cd54f7db57a 18 uint8_t lflags;
andrewboyson 13:9cd54f7db57a 19
andrewboyson 13:9cd54f7db57a 20 uint16_t qdcount;
andrewboyson 13:9cd54f7db57a 21 uint16_t ancount;
andrewboyson 13:9cd54f7db57a 22 uint16_t nscount;
andrewboyson 13:9cd54f7db57a 23 uint16_t arcount;
andrewboyson 13:9cd54f7db57a 24 };
andrewboyson 13:9cd54f7db57a 25
andrewboyson 13:9cd54f7db57a 26 uint16_t DnsHdrId;
andrewboyson 13:9cd54f7db57a 27
andrewboyson 13:9cd54f7db57a 28 bool DnsHdrIsReply;
andrewboyson 13:9cd54f7db57a 29 bool DnsHdrIsAuthoritative;
andrewboyson 13:9cd54f7db57a 30 bool DnsHdrIsRecursiveQuery;
andrewboyson 13:9cd54f7db57a 31
andrewboyson 13:9cd54f7db57a 32 uint16_t DnsHdrQdcount;
andrewboyson 13:9cd54f7db57a 33 uint16_t DnsHdrAncount;
andrewboyson 13:9cd54f7db57a 34 uint16_t DnsHdrNscount;
andrewboyson 13:9cd54f7db57a 35 uint16_t DnsHdrArcount;
andrewboyson 13:9cd54f7db57a 36
andrewboyson 13:9cd54f7db57a 37 char* DnsHdrPacket;
andrewboyson 13:9cd54f7db57a 38 char* DnsHdrData;
andrewboyson 59:e0e556c8bd46 39 int DnsHdrDataLength;
andrewboyson 13:9cd54f7db57a 40
andrewboyson 59:e0e556c8bd46 41 void DnsHdrSetup(void* pPacket, int lenPacket)
andrewboyson 13:9cd54f7db57a 42 {
andrewboyson 13:9cd54f7db57a 43 DnsHdrPacket = (char*)pPacket;
andrewboyson 59:e0e556c8bd46 44 DnsHdrData = DnsHdrPacket + sizeof(header);
andrewboyson 59:e0e556c8bd46 45 DnsHdrDataLength = lenPacket - sizeof(header);
andrewboyson 13:9cd54f7db57a 46 }
andrewboyson 13:9cd54f7db57a 47
andrewboyson 13:9cd54f7db57a 48 void DnsHdrRead()
andrewboyson 13:9cd54f7db57a 49 {
andrewboyson 13:9cd54f7db57a 50 struct header* pHeader = (header*)DnsHdrPacket;
andrewboyson 13:9cd54f7db57a 51
andrewboyson 13:9cd54f7db57a 52 DnsHdrId = NetToHost16(pHeader->id);
andrewboyson 13:9cd54f7db57a 53
andrewboyson 13:9cd54f7db57a 54 uint8_t uflags = pHeader->uflags;
andrewboyson 13:9cd54f7db57a 55 DnsHdrIsReply = uflags & 0x80;
andrewboyson 13:9cd54f7db57a 56 DnsHdrIsAuthoritative = uflags & 0x04;
andrewboyson 33:714a0345e59b 57 DnsHdrIsRecursiveQuery = uflags & 0x01;
andrewboyson 13:9cd54f7db57a 58
andrewboyson 13:9cd54f7db57a 59 DnsHdrQdcount = NetToHost16(pHeader->qdcount);
andrewboyson 13:9cd54f7db57a 60 DnsHdrAncount = NetToHost16(pHeader->ancount);
andrewboyson 13:9cd54f7db57a 61 DnsHdrNscount = NetToHost16(pHeader->nscount);
andrewboyson 13:9cd54f7db57a 62 DnsHdrArcount = NetToHost16(pHeader->arcount);
andrewboyson 13:9cd54f7db57a 63
andrewboyson 13:9cd54f7db57a 64 }
andrewboyson 13:9cd54f7db57a 65 void DnsHdrWrite()
andrewboyson 13:9cd54f7db57a 66 {
andrewboyson 13:9cd54f7db57a 67 struct header* pHeader = (header*)DnsHdrPacket;
andrewboyson 13:9cd54f7db57a 68
andrewboyson 13:9cd54f7db57a 69 pHeader->id = NetToHost16(DnsHdrId);
andrewboyson 13:9cd54f7db57a 70
andrewboyson 13:9cd54f7db57a 71 uint8_t uflags = 0;
andrewboyson 13:9cd54f7db57a 72 uint8_t lflags = 0;
andrewboyson 13:9cd54f7db57a 73 if (DnsHdrIsReply) uflags |= 0x80;
andrewboyson 13:9cd54f7db57a 74 if (DnsHdrIsAuthoritative) uflags |= 0x04;
andrewboyson 13:9cd54f7db57a 75 if (DnsHdrIsRecursiveQuery) uflags |= 0x01;
andrewboyson 13:9cd54f7db57a 76 pHeader->uflags = uflags;
andrewboyson 13:9cd54f7db57a 77 pHeader->lflags = lflags;
andrewboyson 13:9cd54f7db57a 78
andrewboyson 13:9cd54f7db57a 79 pHeader->qdcount = NetToHost16(DnsHdrQdcount);
andrewboyson 13:9cd54f7db57a 80 pHeader->ancount = NetToHost16(DnsHdrAncount);
andrewboyson 13:9cd54f7db57a 81 pHeader->nscount = NetToHost16(DnsHdrNscount);
andrewboyson 13:9cd54f7db57a 82 pHeader->arcount = NetToHost16(DnsHdrArcount);
andrewboyson 13:9cd54f7db57a 83 }
andrewboyson 58:d48c899e482f 84 static uint16_t decodeUint16(char* p)
andrewboyson 58:d48c899e482f 85 {
andrewboyson 58:d48c899e482f 86 uint16_t value = *p++;
andrewboyson 58:d48c899e482f 87 value <<= 8; value += *p++;
andrewboyson 58:d48c899e482f 88 return value;
andrewboyson 58:d48c899e482f 89 }
andrewboyson 58:d48c899e482f 90 static uint32_t decodeUint32(char* p)
andrewboyson 58:d48c899e482f 91 {
andrewboyson 58:d48c899e482f 92 uint32_t value = *p++;
andrewboyson 58:d48c899e482f 93 value <<= 8; value += *p++;
andrewboyson 58:d48c899e482f 94 value <<= 8; value += *p++;
andrewboyson 58:d48c899e482f 95 value <<= 8; value += *p++;
andrewboyson 58:d48c899e482f 96 return value;
andrewboyson 58:d48c899e482f 97 }
andrewboyson 58:d48c899e482f 98 static void logRecordA(int len, char* p)
andrewboyson 58:d48c899e482f 99 {
andrewboyson 58:d48c899e482f 100 if (len == 4) Ip4AddressLog(*(uint32_t*)p);
andrewboyson 58:d48c899e482f 101 else LogF("expected 4 bytes but had %d", len);
andrewboyson 58:d48c899e482f 102 }
andrewboyson 58:d48c899e482f 103 static void logRecordAAAA(int len, char* p)
andrewboyson 58:d48c899e482f 104 {
andrewboyson 58:d48c899e482f 105 if (len == 16) Ip6AddressLog(p);
andrewboyson 58:d48c899e482f 106 else LogF("expected 16 bytes but had %d", len);
andrewboyson 58:d48c899e482f 107 }
andrewboyson 58:d48c899e482f 108 static void logRecordPTR(int len, char* p)
andrewboyson 58:d48c899e482f 109 {
andrewboyson 58:d48c899e482f 110 if (len <= DNS_MAX_LABEL_LENGTH) DnsNameLogPtr(p);
andrewboyson 58:d48c899e482f 111 else LogF("length %d is greater than max DNS label length of %d\r\n", len, DNS_MAX_LABEL_LENGTH);
andrewboyson 58:d48c899e482f 112 }
andrewboyson 58:d48c899e482f 113 static void logRecordSRV(int len, char* p)
andrewboyson 58:d48c899e482f 114 {
andrewboyson 58:d48c899e482f 115 LogF("pri=%d " , decodeUint16(p)); p += 2;
andrewboyson 58:d48c899e482f 116 LogF("wei=%d " , decodeUint16(p)); p += 2;
andrewboyson 58:d48c899e482f 117 LogF("port=%d ", decodeUint16(p)); p += 2;
andrewboyson 58:d48c899e482f 118 DnsNameLogPtr(p);
andrewboyson 58:d48c899e482f 119 }
andrewboyson 58:d48c899e482f 120 static void logRecordTXT(int len, char* p)
andrewboyson 58:d48c899e482f 121 {
andrewboyson 58:d48c899e482f 122 char* pEnd = p + len;
andrewboyson 58:d48c899e482f 123 while (p < pEnd)
andrewboyson 58:d48c899e482f 124 {
andrewboyson 58:d48c899e482f 125 Log("\r\n ");
andrewboyson 58:d48c899e482f 126 int fieldLen = *p++;
andrewboyson 58:d48c899e482f 127 for (int i = 0; i < fieldLen; i++) LogPush(*p++);
andrewboyson 58:d48c899e482f 128 }
andrewboyson 58:d48c899e482f 129 }
andrewboyson 37:793b39683406 130 static void logContent()
andrewboyson 37:793b39683406 131 {
andrewboyson 58:d48c899e482f 132 char* p = DnsHdrData;
andrewboyson 37:793b39683406 133
andrewboyson 37:793b39683406 134 //Get the questions
andrewboyson 37:793b39683406 135 for (int q = 0; q < DnsHdrQdcount; q++)
andrewboyson 37:793b39683406 136 {
andrewboyson 59:e0e556c8bd46 137 if (p >= DnsHdrData + DnsHdrDataLength)
andrewboyson 37:793b39683406 138 {
andrewboyson 58:d48c899e482f 139 Log(" Questions have overrun the buffer\r\n");
andrewboyson 37:793b39683406 140 return;
andrewboyson 37:793b39683406 141 }
andrewboyson 58:d48c899e482f 142 char* pEncodedName = p;
andrewboyson 37:793b39683406 143 int nameLength = DnsNameLength(p);
andrewboyson 58:d48c899e482f 144 if (!nameLength) { LogTimeF(" Questions namelength is zero\r\n"); return; }
andrewboyson 37:793b39683406 145 p += nameLength; //Skip past the name
andrewboyson 37:793b39683406 146 p++ ; //skip the first byte of the type
andrewboyson 37:793b39683406 147 char recordType = *p++; //read the record type
andrewboyson 37:793b39683406 148 p += 2; //skip the class
andrewboyson 37:793b39683406 149
andrewboyson 47:73af5c0b0dc2 150 LogF(" Query ");
andrewboyson 47:73af5c0b0dc2 151 DnsRecordTypeLog(recordType);
andrewboyson 47:73af5c0b0dc2 152 Log(" type record of ");
andrewboyson 58:d48c899e482f 153 DnsNameLogPtr(pEncodedName);
andrewboyson 47:73af5c0b0dc2 154 Log("\r\n");
andrewboyson 37:793b39683406 155 }
andrewboyson 37:793b39683406 156
andrewboyson 37:793b39683406 157 //Get the answers
andrewboyson 37:793b39683406 158 for (int a = 0; a < DnsHdrAncount; a++)
andrewboyson 37:793b39683406 159 {
andrewboyson 59:e0e556c8bd46 160 if (p >= DnsHdrData + DnsHdrDataLength) { Log(" Answers have overrun the buffer\r\n"); return; }
andrewboyson 37:793b39683406 161
andrewboyson 58:d48c899e482f 162 char* pEncodedName = p;
andrewboyson 37:793b39683406 163 int nameLength = DnsNameLength(p);
andrewboyson 43:bc028d5a6424 164 if (!nameLength) { Log(" Answer name length is zero\r\n"); return; }
andrewboyson 37:793b39683406 165 p += nameLength; //Skip past the name
andrewboyson 37:793b39683406 166
andrewboyson 37:793b39683406 167 p++; //Skip the high byte of the record type
andrewboyson 37:793b39683406 168 int recordType = *p++; //Record type
andrewboyson 37:793b39683406 169
andrewboyson 37:793b39683406 170 p++; //Skip the high byte of the class type
andrewboyson 37:793b39683406 171 int classType = *p++; //Class type
andrewboyson 37:793b39683406 172
andrewboyson 58:d48c899e482f 173 int ttl = decodeUint32(p); p += 4; //32bit TTL
andrewboyson 37:793b39683406 174
andrewboyson 58:d48c899e482f 175 int len = decodeUint16(p); p += 2; //16bit length
andrewboyson 37:793b39683406 176
andrewboyson 43:bc028d5a6424 177 Log(" Answer ");
andrewboyson 47:73af5c0b0dc2 178 DnsRecordTypeLog(recordType);
andrewboyson 43:bc028d5a6424 179 Log(" type record of ");
andrewboyson 58:d48c899e482f 180 DnsNameLogPtr(pEncodedName);
andrewboyson 43:bc028d5a6424 181 Log(" ==> ");
andrewboyson 37:793b39683406 182
andrewboyson 37:793b39683406 183 switch (recordType) //Log the payload if its type is known
andrewboyson 37:793b39683406 184 {
andrewboyson 58:d48c899e482f 185 case DNS_RECORD_A: logRecordA (len, p); break;
andrewboyson 58:d48c899e482f 186 case DNS_RECORD_AAAA: logRecordAAAA(len, p); break;
andrewboyson 58:d48c899e482f 187 case DNS_RECORD_PTR: logRecordPTR (len, p); break;
andrewboyson 58:d48c899e482f 188 case DNS_RECORD_SRV: logRecordSRV (len, p); break;
andrewboyson 58:d48c899e482f 189 case DNS_RECORD_TXT: logRecordTXT (len, p); break;
andrewboyson 58:d48c899e482f 190 default: LogF("%d characters", len); break;
andrewboyson 37:793b39683406 191 }
andrewboyson 43:bc028d5a6424 192 Log("\r\n");
andrewboyson 37:793b39683406 193 p += len; //Adjust the pointer to the next character after the payload
andrewboyson 37:793b39683406 194 }
andrewboyson 37:793b39683406 195 }
andrewboyson 37:793b39683406 196
andrewboyson 37:793b39683406 197 void DnsHdrLog(int protocol)
andrewboyson 13:9cd54f7db57a 198 {
andrewboyson 43:bc028d5a6424 199 if (NetTraceVerbose)
andrewboyson 15:6ca6778168b1 200 {
andrewboyson 47:73af5c0b0dc2 201 DnsProtocolLog(protocol);
andrewboyson 47:73af5c0b0dc2 202 Log(" header\r\n");
andrewboyson 43:bc028d5a6424 203 LogF(" Ident %hd\r\n", DnsHdrId);
andrewboyson 43:bc028d5a6424 204 if (DnsHdrIsReply)
andrewboyson 43:bc028d5a6424 205 {
andrewboyson 43:bc028d5a6424 206 if (DnsHdrIsAuthoritative) LogF(" Authoritative reply\r\n");
andrewboyson 43:bc028d5a6424 207 else LogF(" Non authoritative reply\r\n");
andrewboyson 43:bc028d5a6424 208 }
andrewboyson 43:bc028d5a6424 209 else
andrewboyson 43:bc028d5a6424 210 {
andrewboyson 43:bc028d5a6424 211 if (DnsHdrIsRecursiveQuery) LogF(" Recursive query\r\n");
andrewboyson 43:bc028d5a6424 212 else LogF(" Non recursive query\r\n");
andrewboyson 43:bc028d5a6424 213 }
andrewboyson 43:bc028d5a6424 214 LogF(" qd, an, ns, ar %hu, %hu, %hu, %hu\r\n", DnsHdrQdcount, DnsHdrAncount, DnsHdrNscount, DnsHdrArcount);
andrewboyson 15:6ca6778168b1 215 }
andrewboyson 15:6ca6778168b1 216 else
andrewboyson 15:6ca6778168b1 217 {
andrewboyson 47:73af5c0b0dc2 218 DnsProtocolLog(protocol);
andrewboyson 47:73af5c0b0dc2 219 LogF(" header qd, an, ns, ar %hu, %hu, %hu, %hu\r\n", DnsHdrQdcount, DnsHdrAncount, DnsHdrNscount, DnsHdrArcount);
andrewboyson 15:6ca6778168b1 220 }
andrewboyson 37:793b39683406 221 logContent();
andrewboyson 13:9cd54f7db57a 222 }
andrewboyson 13:9cd54f7db57a 223