dnslabel.c

00001 #include <stdbool.h>
00002 #include <string.h>
00003 
00004 #include "dns.h"
00005 #include "dnslabel.h"
00006 #include "dhcp.h"
00007 
00008 bool DnsLabelIsExternal(char* p)
00009 {
00010     while (true)
00011     {
00012         if (*p == '\0') return false;
00013         if (*p == '.') return true;
00014         p++;
00015     }
00016 }
00017 
00018 void DnsLabelCopy(char* dst, char* src)
00019 {
00020     strncpy(dst, src, DNS_MAX_LABEL_LENGTH); //Copies up to 63 bytes
00021     dst[DNS_MAX_LABEL_LENGTH] = 0; //dst[63] is the 64th position from 0..63 is set to null. All labels must be declared as a size of 64
00022 }
00023 
00024 bool DnsLabelIsSame(char* pA, char* pB)
00025 {
00026     while(true)
00027     {
00028         char a = *pA++;
00029         char b = *pB++;
00030         if (a >= 'A' && a <= 'Z') a |= 0x20; //Make lower case
00031         if (b >= 'A' && b <= 'Z') b |= 0x20; //Make lower case
00032         if (a != b) return false;            //If different then stop and return the fact
00033         if (!a) break;                       //No need to check 'b' too as it will necessarily be equal to 'a' at this point.
00034     }
00035     return true;                             //If we get here the strings must equate.
00036 }
00037 
00038 int DnsLabelMakeFullNameFromName(int protocol, const char* p, int size, char* result)
00039 {
00040     int i = 0;
00041     char c;
00042     bool isExternal = false;
00043     
00044     while (i < size - 1)
00045     {
00046         c = *p++;
00047         if (c == '.') isExternal = true;
00048         if (!c) break;
00049         *result++ = c;
00050         i++;
00051     }
00052     if (protocol == DNS_PROTOCOL_MDNS)
00053     {
00054         p = ".local";
00055         while (i < size - 1)
00056         {
00057             c = *p++;
00058             if (!c) break;
00059             *result++ = c;
00060             i++;
00061         }
00062     }
00063     if (protocol == DNS_PROTOCOL_UDNS && !isExternal && DhcpDomainName[0]) //Shouldn't do this in IPv6 as DHCP is IPv4 only
00064     {
00065         if (i < size - 1)
00066         {
00067             *result++ = '.';
00068             i++;
00069         }
00070         p = DhcpDomainName;
00071         while (i < size - 1)
00072         {
00073             c = *p++;
00074             if (!c) break;
00075             *result++ = c;
00076             i++;
00077         }
00078     }
00079     *result = 0; //Terminate the resulting string
00080     return i;
00081 }
00082 int DnsLabelStripNameFromFullName(int protocol, char* p, int size, char* result)
00083 {
00084     int i = 0;
00085     char c;
00086     
00087     while (i < size - 1)
00088     {
00089         c = *p++;
00090         if (c == 0)   break;                               //End of the fqdn so stop
00091         if (c == '.')
00092         {
00093             if (protocol == DNS_PROTOCOL_UDNS)
00094             {
00095                 if (strcmp(p, DhcpDomainName) == 0) break; //Strip the domain from a UDNS fqdn if, and only if, it matches the domain given in DHCP. IPv4 only.
00096             }
00097             else
00098             {
00099                 break;                                     //Strip the domain from an LLMNR (there shouldn't be one) or MDNS (it should always be '.local') fqdn
00100             }
00101         }
00102         *result++ = c;
00103         i++;
00104     }
00105     *result = 0;           //Terminate the copied string
00106     return i;
00107 }