Andrew Boyson
A stack which works with or without an Mbed os library. Provides IPv4 or IPv6 with a full 1500 byte buffer.
Dependents: oldheating gps motorhome heating
Diff: udp/dns/dnsname.cpp
- Revision:
- 13:9cd54f7db57a
- Child:
- 22:914b970356f0
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/udp/dns/dnsname.cpp Mon May 01 18:20:55 2017 +0000
@@ -0,0 +1,408 @@
+#include "mbed.h"
+#include "dnshdr.h"
+#include "ctype.h"
+#include "log.h"
+
+#define MAX_PACKET_SIZE 512
+#define MAX_DEPTH 10
+
+static bool isOffset(char c) { return (c & 0xC0) == 0xC0; }
+static char* derefOffset(char* p)
+{
+ int offset = (*p & 0x3F) << 8; //Any bits in the upper byte are added
+ p++; //Move to the lower byte
+ offset |= *p; //And add it
+ return DnsHdrPacket + offset; //Return a pointer
+}
+
+int DnsNameLength(char* pStart) //Returns 0 on error
+{
+ char* p = pStart;
+
+ while (true)
+ {
+ if (p > DnsHdrPacket + MAX_PACKET_SIZE)
+ {
+ LogTimeF("DnsNameLength strayed out of the packet\r\n");
+ return 0;
+ }
+
+ int length = *p++;
+ if (length == 0) //Its the last field so finish
+ {
+ return p - pStart;
+ }
+ else if (isOffset(length)) //it's a pointer so skip the length byte and return
+ {
+ p++;
+ return p - pStart;
+ }
+ else //it's a length plus a field eg 3www
+ {
+ p += length;
+ }
+ }
+}
+bool DnsNameCompare(char* pStart, char* pTarget)
+{
+ char* p = pStart;
+
+ bool isSame = true;
+
+ int depth = 0;
+
+ while (true)
+ {
+ if (p > DnsHdrPacket + MAX_PACKET_SIZE)
+ {
+ LogTimeF("DnsNameCompare strayed out of the packet\r\n");
+ return false;
+ }
+
+ int length = *p;
+ if (length == 0) //Its the last field so should be on the target's terminating NUL
+ {
+ if (*pTarget) isSame = false;
+ return isSame;
+ }
+ else if (isOffset(length)) //it's a pointer so go up one
+ {
+ depth++;
+ if (depth > MAX_DEPTH)
+ {
+ LogTimeF("DnsNameCompare exceeded depth limit\r\n");
+ return false;
+ }
+ p = derefOffset(p);
+ }
+ else //it's a length plus a field eg 3www
+ {
+ if (p > pStart) if (*pTarget++ != '.') isSame = false;
+ p++;
+ for (int i = 0; i < length; i++)
+ {
+ if (toupper(*pTarget++) != toupper(*p++)) isSame = false;
+ }
+ }
+ }
+}
+
+int DnsNameIndexFromPointer(char* p)
+{
+ int depth = 0;
+ while (isOffset(*p)) //it's a pointer so jump to the new offset eg ^C0 ^0C
+ {
+ depth++;
+ if (depth > MAX_DEPTH)
+ {
+ LogTimeF("DnsNameIndexFromPointer exceeded depth limit\r\n");
+ return -1;
+ }
+ p = derefOffset(p);
+ }
+ return p - DnsHdrPacket;
+}
+
+void DnsNameDecode(int offset, int lenName, char* pName)
+{
+ bool nameStarted = false;
+ int depth = 0;
+ char* p = DnsHdrPacket + offset;
+ while (true)
+ {
+ if (p > DnsHdrPacket + MAX_PACKET_SIZE)
+ {
+ *pName = 0;
+ LogTimeF("DnsNameDecode could not find name end\r\n");
+ return;
+ }
+
+ int length = *p;
+ if (length == 0) //Its the last field so terminate the string
+ {
+ *pName = 0;
+ return;
+ }
+ else if (isOffset(*p)) //it's a pointer so jump to the new offset eg ^C0 ^0C
+ {
+ depth++;
+ if (depth > MAX_DEPTH)
+ {
+ LogTimeF("DnsNameDecode exceeded depth limit\r\n");
+ *pName = 0;
+ return;
+ }
+ p = derefOffset(p);
+ }
+ else //it's a length plus a field eg 3www
+ {
+ if (pName)
+ {
+ if (length + 1 > lenName) //Leave room to terminate the string
+ {
+ *pName = 0;
+ LogTimeF("DnsNameDecode overran name buffer\r\n");
+ return;
+ }
+ lenName -= length + 1; //name chunk plus a '.'
+ if (nameStarted) *pName++ = '.';
+ p++;
+ for (int i = 0; i < length; i++) *pName++ = *p++;
+ nameStarted = true;
+ }
+ else
+ {
+ p += length + 1;
+ }
+ }
+ }
+}
+void DnsNameDecodeIp4(int offset, uint32_t* pIp)
+{
+ int field = 0;
+ int depth = 0;
+ char* p = DnsHdrPacket + offset;
+ while (true)
+ {
+ if (p > DnsHdrPacket + MAX_PACKET_SIZE)
+ {
+ *pIp = 0;
+ LogTimeF("DnsNameDecodeIp4 could not find name end\r\n");
+ return;
+ }
+
+ int length = *p;
+ if (length == 0) //Its the last field so return the ip if it is the correct length
+ {
+ if (field != 6) *pIp = 0;
+ return;
+ }
+ else if (isOffset(*p)) //it's a pointer so jump to the new offset eg ^C0 ^0C
+ {
+ depth++;
+ if (depth > MAX_DEPTH)
+ {
+ LogTimeF("DnsNameDecodeIp4 exceeded depth limit\r\n");
+ *pIp = 0;
+ return;
+ }
+ p = derefOffset(p);
+ }
+ else //it's a length plus a field eg 3www
+ {
+ p++; // move past the length
+ if (field <= 3)
+ {
+ if (length > 3) {*pIp = 0; return; } // expect 90.1.168.192.in-addr.arpa
+ int byte = 0;
+ for (int i = 0; i < length; i++)
+ {
+ byte = byte * 10;
+ if (*p > '9' || *p < '0') {*pIp = 0; return; } // expect 90.1.168.192.in-addr.arpa
+ byte += *p - '0';
+ p++;
+ }
+ *pIp <<= 8;
+ *pIp |= byte;
+ }
+ else if (field == 4)
+ {
+ if (length != 7) {*pIp = 0; return; } // expect 90.1.168.192.in-addr.arpa
+ p+= length;
+ }
+ else if (field == 5)
+ {
+ if (length != 4) {*pIp = 0; return; } // expect 90.1.168.192.in-addr.arpa
+ p+= length;
+ }
+ else
+ {
+ *pIp = 0; return; // expect 90.1.168.192.in-addr.arpa
+ }
+ field++;
+ }
+ }
+}
+void DnsNameDecodeIp6(int offset, char* pIp)
+{
+ int field = 0;
+ int depth = 0;
+ char* p = DnsHdrPacket + offset;
+ while (true)
+ {
+ if (p > DnsHdrPacket + MAX_PACKET_SIZE)
+ {
+ pIp[0] = 0;
+ LogTimeF("DnsNameDecodeIp6 could not find name end\r\n");
+ return;
+ }
+
+ int length = *p;
+ if (length == 0) //Its the last field so return the ip if it is the correct length
+ {
+ if (field != 34) pIp[0] = 0;
+ return;
+ }
+ else if (isOffset(*p)) //it's a pointer so jump to the new offset eg ^C0 ^0C
+ {
+ depth++;
+ if (depth > MAX_DEPTH)
+ {
+ LogTimeF("DnsNameDecodeIp6 exceeded depth limit\r\n");
+ *pIp = 0;
+ return;
+ }
+ p = derefOffset(p);
+ }
+ else //it's a length plus a field eg 3www
+ {
+ p++; // move past the length
+ if (field <= 31)
+ {
+ if (length > 1) {pIp[0] = 0; return; } // expect 5.8.c.c.0.1.e.f.f.f.2.3.1.1.2.0.8.7.d.0.9.0.f.1.0.7.4.0.1.0.0.2.ip6.arpa
+ int nibble = 0;
+ if (*p >= '0' && *p <= '9') nibble = *p - '0';
+ else if (*p >= 'a' && *p <= 'f') nibble = *p - 'a' + 10;
+ else if (*p >= 'A' && *p <= 'F') nibble = *p - 'A' + 10;
+ else {pIp[0] = 0; return; } // expect 5.8.c.c.0.1.e.f.f.f.2.3.1.1.2.0.8.7.d.0.9.0.f.1.0.7.4.0.1.0.0.2.ip6.arpa
+ if ((field & 1) == 0)
+ {
+ pIp[15 - (field >> 1)] = nibble;
+ }
+ else
+ {
+ nibble <<= 4;
+ pIp[15 - (field >> 1)] |= nibble;
+ }
+ p += length;
+ }
+ else if (field == 32)
+ {
+ if (length != 3) {pIp[0] = 0; return; } // expect 5.8.c.c.0.1.e.f.f.f.2.3.1.1.2.0.8.7.d.0.9.0.f.1.0.7.4.0.1.0.0.2.ip6.arpa
+ p+= length;
+ }
+ else if (field == 33)
+ {
+ if (length != 4) {pIp[0] = 0; return; } // expect 5.8.c.c.0.1.e.f.f.f.2.3.1.1.2.0.8.7.d.0.9.0.f.1.0.7.4.0.1.0.0.2.ip6.arpa
+ p+= length;
+ }
+ else
+ {
+ pIp[0] = 0; return; // expect 5.8.c.c.0.1.e.f.f.f.2.3.1.1.2.0.8.7.d.0.9.0.f.1.0.7.4.0.1.0.0.2.ip6.arpa
+ }
+ field++;
+ }
+ }
+}
+void DnsNameEncodeIp4(uint32_t ip, char** pp)
+{
+ char* p = *pp; //Get a convenient pointer to the next byte
+
+ char* pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "%d", (ip & 0xff000000) >> 24);
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "%d", (ip & 0x00ff0000) >> 16);
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "%d", (ip & 0x0000ff00) >> 8);
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "%d", (ip & 0x000000ff) >> 0);
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "in-addr");
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "arpa");
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = 0;
+
+ *pp = p; //Save the convenient pointer back into the pointer to pointer
+
+}
+
+void DnsNameEncodeIp6(char* ip, char** pp)
+{
+ char* p = *pp; //Get a convenient pointer to the next byte
+
+ ip += 16;
+ for (int i = 0; i < 16; i++)
+ {
+ ip--;
+
+ int v;
+
+ *p++ = 1;
+ v = *ip & 0x0F;
+ *p++ = v < 10 ? v + '0' : v - 10 + 'a';
+
+ *p++ = 1;
+ v = *ip >> 4;
+ *p++ = v < 10 ? v + '0' : v - 10 + 'a';
+ }
+ char* pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "ip6");
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = sprintf(p, "arpa");
+ p += *pLen;
+ pLen = p;
+ p++;
+
+ *pLen = 0;
+
+ *pp = p; //Save the convenient pointer back into the pointer to pointer
+
+}
+
+void DnsNameEncode(char* pName, char** pp)
+{
+ char* p = *pp; //Get a convenient pointer to the next byte
+
+ char* pLen = p; //Record the position of the first length byte
+ p++; //Move to the start of the first field
+
+ while (true)
+ {
+ char c = *pName;
+ switch (c)
+ {
+ case 0:
+ *pLen = p - pLen - 1;
+ *p = 0;
+ p++;
+ *pp = p; //Save the convenient pointer back into the pointer to pointer
+ return;
+ case '.':
+ *pLen = p - pLen - 1;
+ pLen = p;
+ p++;
+ break;
+ default:
+ *p = c;
+ p++;
+ break;
+ }
+ pName++;
+ }
+}