-const char* User::GetCIDRMask(int range)
-{
- static char buf[44];
-
- if (range < 0)
- throw "Negative range, sorry, no.";
-
- /*
- * Original code written by Oliver Lupton (Om).
- * Integrated by me. Thanks. :) -- w00t
- */
- switch (this->client_sa.sa.sa_family)
- {
- case AF_INET6:
- {
- /* unsigned char s6_addr[16]; */
- struct in6_addr v6;
- int i, bytestozero, extrabits;
- char buffer[40];
-
- if(range > 128)
- throw "CIDR mask width greater than address width (IPv6, 128 bit)";
-
- /* To create the CIDR mask we want to set all the bits after 'range' bits of the address
- * to zero. This means the last (128 - range) bits of the address must be set to zero.
- * Hence this number divided by 8 is the number of whole bytes from the end of the address
- * which must be set to zero.
- */
- bytestozero = (128 - range) / 8;
-
- /* Some of the least significant bits of the next most significant byte may also have to
- * be zeroed. The number of bits is the remainder of the above division.
- */
- extrabits = (128 - range) % 8;
-
- /* Populate our working struct with the parts of the user's IP which are required in the
- * final CIDR mask. Set all the subsequent bytes to zero.
- * (16 - bytestozero) is the number of bytes which must be populated with actual IP data.
- */
- for(i = 0; i < (16 - bytestozero); i++)
- {
- v6.s6_addr[i] = client_sa.in6.sin6_addr.s6_addr[i];
- }
-
- /* And zero all the remaining bytes in the IP. */
- for(; i < 16; i++)
- {
- v6.s6_addr[i] = 0;
- }
-
- /* And finally, zero the extra bits required. */
- v6.s6_addr[15 - bytestozero] = (v6.s6_addr[15 - bytestozero] >> extrabits) << extrabits;
-
- snprintf(buf, 44, "%s/%d", inet_ntop(AF_INET6, &v6, buffer, 40), range);
- return buf;
- }
- break;
- case AF_INET:
- {
- struct in_addr v4;
- char buffer[16];
-
- if (range > 32)
- throw "CIDR mask width greater than address width (IPv4, 32 bit)";
-
- /* Users already have a sockaddr* pointer (User::ip) which contains either a v4 or v6 structure */
- v4.s_addr = client_sa.in4.sin_addr.s_addr;
-
- /* To create the CIDR mask we want to set all the bits after 'range' bits of the address
- * to zero. This means the last (32 - range) bits of the address must be set to zero.
- * This is done by shifting the value right and then back left by (32 - range) bits.
- */
- if(range > 0)
- {
- v4.s_addr = ntohl(v4.s_addr);
- v4.s_addr = (v4.s_addr >> (32 - range)) << (32 - range);
- v4.s_addr = htonl(v4.s_addr);
- }
- else
- {
- /* a range of zero would cause a 32 bit value to be shifted by 32 bits.
- * this has undefined behaviour, but for CIDR purposes the resulting mask
- * from a.b.c.d/0 is 0.0.0.0/0
- */
- v4.s_addr = 0;
- }
-
- snprintf(buf, 44, "%s/%d", inet_ntop(AF_INET, &v4, buffer, 16), range);
- return buf;
- }
- break;
- }
-
- return ""; // unused, but oh well
-}
-