network: Add function to return a reverse pointer for networks

[people/ms/libloc.git] / src / network.c

diff --git a/src/network.c b/src/network.c
index d658709f9dba3eae5be2ec38a0895327f2f45528..69306a91f4b18ed0be8f4280373b34bbb7496c81 100644 (file)
--- a/src/network.c
+++ b/src/network.c
@@ -700,3 +700,121 @@ int loc_network_new_from_database_v1(struct loc_ctx* ctx, struct loc_network** n
 
        return 0;
 }
+
+static char* loc_network_reverse_pointer6(struct loc_network* network, const char* suffix) {
+       char* buffer = NULL;
+       int r;
+
+       unsigned int prefix = loc_network_prefix(network);
+
+       // Must border on a nibble
+       if (prefix % 4) {
+               errno = ENOTSUP;
+               return NULL;
+       }
+
+       if (!suffix)
+               suffix = "ip6.arpa.";
+
+       // Initialize the buffer
+       r = asprintf(&buffer, "%s", suffix);
+       if (r < 0)
+               goto ERROR;
+
+       for (unsigned int i = 0; i < (prefix / 4); i++) {
+               r = asprintf(&buffer, "%x.%s", loc_address_get_nibble(&network->first_address, i), buffer);
+               if (r < 0)
+                       goto ERROR;
+       }
+
+       // Add the asterisk
+       if (prefix < 128) {
+               r = asprintf(&buffer, "*.%s", buffer);
+               if (r < 0)
+                       goto ERROR;
+       }
+
+       return buffer;
+
+ERROR:
+       if (buffer)
+               free(buffer);
+
+       return NULL;
+}
+
+static char* loc_network_reverse_pointer4(struct loc_network* network, const char* suffix) {
+       char* buffer = NULL;
+       int r;
+
+       unsigned int prefix = loc_network_prefix(network);
+
+       // Must border on an octet
+       if (prefix % 8) {
+               errno = ENOTSUP;
+               return NULL;
+       }
+
+       if (!suffix)
+               suffix = "in-addr.arpa.";
+
+       switch (prefix) {
+               case 32:
+                       r = asprintf(&buffer, "%d.%d.%d.%d.%s",
+                               loc_address_get_octet(&network->first_address, 3),
+                               loc_address_get_octet(&network->first_address, 2),
+                               loc_address_get_octet(&network->first_address, 1),
+                               loc_address_get_octet(&network->first_address, 0),
+                               suffix);
+                       break;
+
+               case 24:
+                       r = asprintf(&buffer, "*.%d.%d.%d.%s",
+                               loc_address_get_octet(&network->first_address, 2),
+                               loc_address_get_octet(&network->first_address, 1),
+                               loc_address_get_octet(&network->first_address, 0),
+                               suffix);
+                       break;
+
+               case 16:
+                       r = asprintf(&buffer, "*.%d.%d.%s",
+                               loc_address_get_octet(&network->first_address, 1),
+                               loc_address_get_octet(&network->first_address, 0),
+                               suffix);
+                       break;
+
+               case 8:
+                       r = asprintf(&buffer, "*.%d.%s",
+                               loc_address_get_octet(&network->first_address, 0),
+                               suffix);
+                       break;
+
+               case 0:
+                       r = asprintf(&buffer, "*.%s", suffix);
+                       break;
+
+               // To make the compiler happy
+               default:
+                       return NULL;
+       }
+
+       if (r < 0)
+               return NULL;
+
+       return buffer;
+}
+
+LOC_EXPORT char* loc_network_reverse_pointer(struct loc_network* network, const char* suffix) {
+       switch (network->family) {
+               case AF_INET6:
+                       return loc_network_reverse_pointer6(network, suffix);
+
+               case AF_INET:
+                       return loc_network_reverse_pointer4(network, suffix);
+
+               default:
+                       break;
+       }
+
+       return NULL;
+}