network: Refactor composing the reverse pointer

The previous versions had a lot of memory leaks because of the repeated
use of asprintf and appended a trailing dot if there was not suffix
given.

This version allocates the buffer only once and only appends a dot if
there is a suffix.

Signed-off-by: Michael Tremer <michael.tremer@ipfire.org>

diff --git a/src/network.c b/src/network.c
index 3cc2d3cdc92c11f94ab12700ba58aa93bcf2dd1b..f9438370d59d506e8323b751997bce0a3f7ca155 100644 (file)
--- a/src/network.c
+++ b/src/network.c
@@ -702,7 +702,7 @@ int loc_network_new_from_database_v1(struct loc_ctx* ctx, struct loc_network** n
 
 static char* loc_network_reverse_pointer6(struct loc_network* network, const char* suffix) {
        char* buffer = NULL;
-       int r;
+       size_t length = 1;
 
        unsigned int prefix = loc_network_prefix(network);
 
@@ -715,25 +715,60 @@ static char* loc_network_reverse_pointer6(struct loc_network* network, const cha
        if (!suffix)
                suffix = "ip6.arpa.";
 
-       // Initialize the buffer
-       r = asprintf(&buffer, "%s", suffix);
-       if (r < 0)
+       const int nibbles = prefix / 4;
+
+       // Make space for all nibbles
+       length += nibbles * 2;
+
+       // Make space for the star for wildcards
+       if (prefix < 128)
+               length += 2;
+
+       // Make space for the suffix
+       length += strlen(suffix);
+
+       // Allocate the buffer
+       buffer = malloc(length);
+       if (!buffer)
                goto ERROR;
 
-       for (unsigned int i = 0; i < (prefix / 4); i++) {
-               r = asprintf(&buffer, "%x.%s",
-                       (unsigned int)loc_address_get_nibble(&network->first_address, i), buffer);
-               if (r < 0)
-                       goto ERROR;
-       }
+       char* p = buffer;
 
        // Add the asterisk
        if (prefix < 128) {
-               r = asprintf(&buffer, "*.%s", buffer);
-               if (r < 0)
+               *p++ = '*';
+
+               if (nibbles || *suffix)
+                       *p++ = '.';
+       }
+
+       static const char hex[] = "0123456789abcdef";
+
+       // Add nibbles
+       for (int i = nibbles - 1; i >= 0; i--) {
+               int nibble = loc_address_get_nibble(&network->first_address, i);
+
+               // Check if the nibble is in range
+               if (nibble < 0 || nibble > 0x0f) {
+                       errno = ERANGE;
                        goto ERROR;
+               }
+
+               *p++ = hex[nibble];
+
+               if (i > 0 || *suffix)
+                       *p++ = '.';
+       }
+
+       // Add suffix (may be empty)
+       if (*suffix) {
+               memcpy(p, suffix, strlen(suffix));
+               p += strlen(suffix);
        }
 
+       // Terminate the buffer
+       *p = '\0';
+
        return buffer;
 
 ERROR:
@@ -745,7 +780,7 @@ ERROR:
 
 static char* loc_network_reverse_pointer4(struct loc_network* network, const char* suffix) {
        char* buffer = NULL;
-       int r;
+       size_t length = 1;
 
        unsigned int prefix = loc_network_prefix(network);
 
@@ -758,50 +793,65 @@ static char* loc_network_reverse_pointer4(struct loc_network* network, const cha
        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;
+       const int octets = prefix / 8;
 
-               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;
+       // Make space for all octets
+       length += octets * 4;
 
-               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;
+       // Make space for the star
+       if (prefix < 32)
+               length += 2;
 
-               case 8:
-                       r = asprintf(&buffer, "*.%d.%s",
-                               loc_address_get_octet(&network->first_address, 0),
-                               suffix);
-                       break;
+       // Make space for the suffix
+       length += strlen(suffix);
 
-               case 0:
-                       r = asprintf(&buffer, "*.%s", suffix);
-                       break;
+       // Allocate the buffer
+       buffer = malloc(length);
+       if (!buffer)
+               goto ERROR;
 
-               // To make the compiler happy
-               default:
-                       return NULL;
+       char* p = buffer;
+
+       // Add asterisk if needed (prefix < 32)
+       if (prefix < 32) {
+               *p++ = '*';
+
+               if (octets || *suffix)
+                       *p++ = '.';
        }
 
-       if (r < 0)
-               return NULL;
+       // Append octets in reverse order
+       for (int i = octets - 1; i >= 0; i--) {
+               int oct = loc_address_get_octet(&network->first_address, i);
+               if (oct < 0) {
+                       errno = ERANGE;
+                       goto ERROR;
+               }
+
+               // Convert octet to decimal string
+               p += sprintf(p, "%d", oct);
+
+               // Dot between octets or before suffix
+               if (i > 0 || *suffix)
+                       *p++ = '.';
+       }
+
+       // Add suffix (may be empty)
+       if (*suffix) {
+               memcpy(p, suffix, strlen(suffix));
+               p += strlen(suffix);
+       }
+
+       // Terminate the buffer
+       *p = '\0';
 
        return buffer;
+
+ERROR:
+       if (buffer)
+               free(buffer);
+
+       return NULL;
 }
 
 LOC_EXPORT char* loc_network_reverse_pointer(struct loc_network* network, const char* suffix) {