ipv6 sqlite extension

ipv6_sql.c

#include "sqlite3ext.h"
#include <stdlib.h>
#include <string.h>
#include <arpa/inet.h>
// gcc -fPIC -shared ipv6_sql.c -g -o libipv6.so

SQLITE_EXTENSION_INIT1

static void andIPv6(struct in6_addr* ipv6, const struct in6_addr* mask)
{
    for (unsigned i = 0; i < sizeof(struct in6_addr); i++)
        ipv6->s6_addr[i] &= mask->s6_addr[i];
}

static int insideIPv6CIDR(const char* ipv6_cidr, const char* ipv6_in)
{
    const char* mask_location = strchr(ipv6_cidr, '/');
    if (mask_location == NULL)
        return 0;
    struct in6_addr v6_in;
    if (inet_pton(AF_INET6, ipv6_in, &v6_in) != 1)
        return 0;

    char ipv6[INET6_ADDRSTRLEN] = {};
    memcpy(ipv6, ipv6_cidr, mask_location - ipv6_cidr);
    struct in6_addr cidr;
    if (inet_pton(AF_INET6, ipv6, &cidr) != 1)
        return 0;

    int mask_length = atoi(mask_location + 1);    
    if (mask_length > 128 || mask_length <= 0)
        return 0;

    struct in6_addr mask = {};
    for (int i = mask_length, j = 0; i > 0; i -= 8, j++)
    {
        if (i >= 8)
            mask.s6_addr[j] = 0xff;
        else
            mask.s6_addr[j] = (unsigned long)(0xffU << (8 - i));
    }

    andIPv6(&cidr, &mask);
    andIPv6(&v6_in, &mask);
    for (unsigned i = 0; i < sizeof(struct in6_addr); i++)
    {
        if (cidr.s6_addr[i] != v6_in.s6_addr[i])
            return 0;
    }
    return 1;
}

static void insideIPv6CIDRSQL(sqlite3_context* context, int argc, sqlite3_value** argv)
{
    if (argc != 2)
    {
        sqlite3_result_int(context, 0);
        return;
    }

    char* ipv6_cidr = (char*)sqlite3_value_text(argv[0]);
    char* ipv6_in = (char*)sqlite3_value_text(argv[1]);
    if (ipv6_cidr == NULL || ipv6_in == NULL)
    {
        sqlite3_result_int(context, 0);
        return;
    }
    sqlite3_result_int(context, insideIPv6CIDR(ipv6_cidr, ipv6_in));
}

int sqlite3_extension_init(sqlite3* db, char** pzErrMsg, const sqlite3_api_routines* pApi)
{
    SQLITE_EXTENSION_INIT2(pApi)
    sqlite3_create_function(db, "insideIPv6CIDR", 2, SQLITE_UTF8,  0, insideIPv6CIDRSQL, 0, 0);
    return 0;
}