- case SUBNET_IPV6:
- snprintf(netstr, len, "%hx:%hx:%hx:%hx:%hx:%hx:%hx:%hx/%d#%d",
- ntohs(subnet->net.ipv6.address.x[0]),
- ntohs(subnet->net.ipv6.address.x[1]),
- ntohs(subnet->net.ipv6.address.x[2]),
- ntohs(subnet->net.ipv6.address.x[3]),
- ntohs(subnet->net.ipv6.address.x[4]),
- ntohs(subnet->net.ipv6.address.x[5]),
- ntohs(subnet->net.ipv6.address.x[6]),
- ntohs(subnet->net.ipv6.address.x[7]),
- subnet->net.ipv6.prefixlength,
- subnet->weight);
+ case SUBNET_IPV6: {
+ /* Find the longest sequence of consecutive zeroes */
+ int max_zero_length = 0;
+ int max_zero_length_index = 0;
+ int current_zero_length = 0;
+ int current_zero_length_index = 0;
+ for (int i = 0; i < 8; i++) {
+ if (subnet->net.ipv6.address.x[i] != 0)
+ current_zero_length = 0;
+ else {
+ if (current_zero_length == 0)
+ current_zero_length_index = i;
+ current_zero_length++;
+ if (current_zero_length > max_zero_length) {
+ max_zero_length = current_zero_length;
+ max_zero_length_index = current_zero_length_index;
+ }
+ }
+ }
+
+ /* Print the address */
+ for (int i = 0; i < 8;) {
+ if (max_zero_length > 1 && max_zero_length_index == i) {
+ /* Shorten the representation as per RFC 5952 */
+ const char* const FORMATS[] = { "%.1s", "%.2s", "%.3s" };
+ const char* const* format = &FORMATS[0];
+ if (i == 0)
+ format++;
+ if (i + max_zero_length == 8)
+ format++;
+ result = snprintf(netstr, len, *format, ":::");
+ i += max_zero_length;
+ } else {
+ result = snprintf(netstr, len, "%hx:", ntohs(subnet->net.ipv6.address.x[i]));
+ i++;
+ }
+ netstr += result;
+ len -= result;
+ }
+
+ /* Remove the trailing colon */
+ netstr--;
+ len++;
+ *netstr = 0;
+
+ prefixlength = subnet->net.ipv6.prefixlength;
+ if (prefixlength == 128)
+ prefixlength = -1;