Using SQL to determine cidr value of a subnet mask

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故里飘歌
故里飘歌 2021-02-05 21:56

I\'d like to find a way to do a SQL query that will calculate the cidr (bit representation) of a subnet mask stored in the database. So for example, I\'ve got either 255.255.25

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  • 2021-02-05 22:35

    e.g. you need to convert 255.255.255.252 netmask into bit mask.

    I always use this simple query (PostgreSQL) :

    SELECT 32-length(trim(((split_part('255.255.255.252','.',1)::bigint*(256^3)::bigint +
                            split_part('255.255.255.252','.',2)::bigint*(256^2)::bigint +
                            split_part('255.255.255.252','.',3)::bigint*256 +
                            split_part('255.255.255.252','.',4)::bigint)::bit(32))::text,'1'));
    

    not as nice as could be, but it's short and working like a charm..

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  • 2021-02-05 22:39
    --
    -- Dumping routines for database
    --
    /*!50003 DROP FUNCTION IF EXISTS `INET_ATOC` */;
    /*!50003 SET @saved_cs_client      = @@character_set_client */ ;
    /*!50003 SET @saved_cs_results     = @@character_set_results */ ;
    /*!50003 SET @saved_col_connection = @@collation_connection */ ;
    /*!50003 SET character_set_client  = utf8 */ ;
    /*!50003 SET character_set_results = utf8 */ ;
    /*!50003 SET collation_connection  = utf8_general_ci */ ;
    /*!50003 SET @saved_sql_mode       = @@sql_mode */ ;
    /*!50003 SET sql_mode              = 'ALLOW_INVALID_DATES' */ ;
    DELIMITER ;;
    CREATE DEFINER=`root`@`localhost` FUNCTION `INET_ATOC`(`paramNETMASK` varchar(15)) RETURNS int(2) unsigned
        DETERMINISTIC
        COMMENT 'Converts an IPv4 netmask in dotted decimal notation to a CIDR integer between 0 and 32'
    BEGIN
        DECLARE `netmask` int unsigned;
        DECLARE `cidr` int unsigned;
        SET `netmask` = INET_ATON(`paramNETMASK`);
        IF (`netmask` IS NULL)
        THEN
            RETURN NULL;
        ELSE
            SET `cidr` = 0;
            countNetBits: WHILE (`cidr` < 32)
            DO
                IF ( (0x80000000 & `netmask`) = 0x80000000 )
                THEN
                    SET `netmask` = 0xFFFFFFFF & (`netmask` << 1);
                    SET `cidr` = `cidr` + 1;
                ELSE
                    LEAVE countNetBits;
                END IF;
            END WHILE;
            IF (`netmask` != 0)
            THEN
                RETURN NULL;
            END IF;
            RETURN `cidr`;
        END IF;
    END ;;
    DELIMITER ;
    /*!50003 SET sql_mode              = @saved_sql_mode */ ;
    /*!50003 SET character_set_client  = @saved_cs_client */ ;
    /*!50003 SET character_set_results = @saved_cs_results */ ;
    /*!50003 SET collation_connection  = @saved_col_connection */ ;
    /*!50003 DROP FUNCTION IF EXISTS `INET_CTOA` */;
    /*!50003 SET @saved_cs_client      = @@character_set_client */ ;
    /*!50003 SET @saved_cs_results     = @@character_set_results */ ;
    /*!50003 SET @saved_col_connection = @@collation_connection */ ;
    /*!50003 SET character_set_client  = utf8 */ ;
    /*!50003 SET character_set_results = utf8 */ ;
    /*!50003 SET collation_connection  = utf8_general_ci */ ;
    /*!50003 SET @saved_sql_mode       = @@sql_mode */ ;
    /*!50003 SET sql_mode              = 'ALLOW_INVALID_DATES' */ ;
    DELIMITER ;;
    CREATE DEFINER=`root`@`localhost` FUNCTION `INET_CTOA`(`paramCIDR` int) RETURNS varchar(15) CHARSET utf8
        DETERMINISTIC
        COMMENT 'Converts a CIDR suffix (integer between 0 and 32) to an IPv4 netmask in dotted decimal notation'
    BEGIN
        DECLARE `netmask` int unsigned;
        IF  ( (`paramCIDR` < 0) OR (`paramCIDR` > 32) )
        THEN
            RETURN NULL;
        ELSE
            SET `netmask` = 0xFFFFFFFF - (pow( 2, (32-`paramCIDR`) ) - 1);
            RETURN INET_NTOA(`netmask`);
        END IF;
    END ;;
    DELIMITER ;
    /*!50003 SET sql_mode              = @saved_sql_mode */ ;
    /*!50003 SET character_set_client  = @saved_cs_client */ ;
    /*!50003 SET character_set_results = @saved_cs_results */ ;
    /*!50003 SET collation_connection  = @saved_col_connection */ ;
    /*!50003 DROP PROCEDURE IF EXISTS `getSubnet` */;
    /*!50003 SET @saved_cs_client      = @@character_set_client */ ;
    /*!50003 SET @saved_cs_results     = @@character_set_results */ ;
    /*!50003 SET @saved_col_connection = @@collation_connection */ ;
    /*!50003 SET character_set_client  = utf8 */ ;
    /*!50003 SET character_set_results = utf8 */ ;
    /*!50003 SET collation_connection  = utf8_general_ci */ ;
    /*!50003 SET @saved_sql_mode       = @@sql_mode */ ;
    /*!50003 SET sql_mode              = '' */ ;
    DELIMITER ;;
    CREATE DEFINER=`root`@`localhost` PROCEDURE `getSubnet`(INOUT `paramADDR` VARCHAR(15), INOUT `paramCIDR` INT, OUT `paramMASK` VARCHAR(15), OUT `paramNETWORK` VARCHAR(15), OUT `paramBROADCAST` VARCHAR(15), OUT `paramNUMHOSTS` INT) CHARSET utf8
        DETERMINISTIC
    BEGIN
        DECLARE `numaddrs`  int unsigned;
        DECLARE `ipaddr`    int unsigned;
        DECLARE `netmask`   int unsigned;
        DECLARE `wildcard`  int unsigned;
        DECLARE `network`   int unsigned;
        DECLARE `broadcast` int unsigned;
        DECLARE `numhosts`  int unsigned;
    
        SET `ipaddr` = INET_ATON(`paramADDR`);
    
        IF (`ipaddr` IS NULL) OR (`paramCIDR` < 1) OR (`paramCIDR` > 30)
        THEN
            SELECT
                NULL, NULL, NULL, NULL, NULL, NULL
            INTO
                `paramADDR`, `paramCIDR`, `paramMASK`, `paramNETWORK`, `paramBROADCAST`, `paramNUMHOSTS`;
        ELSE
            SET `numaddrs`  = pow( 2, (32-`paramCIDR`) );
            SET `numhosts`  = `numaddrs` - 2;
            SET `netmask`   = 0xFFFFFFFF - (`numaddrs` - 1);
            SET `wildcard`  = 0xFFFFFFFF & (~`netmask`);
            SET `network`   = `ipaddr` & `netmask`;
            SET `broadcast` = `ipaddr` | `wildcard`;
    
            SELECT
                INET_NTOA(`ipaddr`), `paramCIDR`, INET_NTOA(`netmask`), INET_NTOA(`network`), INET_NTOA(`broadcast`), `numhosts`
            INTO
                `paramADDR`, `paramCIDR`, `paramMASK`, `paramNETWORK`, `paramBROADCAST`, `paramNUMHOSTS`;
        END IF;
    END ;;
    DELIMITER ;
    /*!50003 SET sql_mode              = @saved_sql_mode */ ;
    /*!50003 SET character_set_client  = @saved_cs_client */ ;
    /*!50003 SET character_set_results = @saved_cs_results */ ;
    /*!50003 SET collation_connection  = @saved_col_connection */ ;
    /*!40103 SET TIME_ZONE=@OLD_TIME_ZONE */;
    
    /*!40101 SET SQL_MODE=@OLD_SQL_MODE */;
    /*!40014 SET FOREIGN_KEY_CHECKS=@OLD_FOREIGN_KEY_CHECKS */;
    /*!40014 SET UNIQUE_CHECKS=@OLD_UNIQUE_CHECKS */;
    /*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
    /*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
    /*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;
    /*!40111 SET SQL_NOTES=@OLD_SQL_NOTES */;
    
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  • 2021-02-05 22:47

    SQL queries don't have a procedural looping construct (notwithstanding procedural language), but you can compare one set of rows to another set of rows, which is kind of like a loop.

    You only have 32 possible subnet masks. In cases like this, it makes sense to create a small table that stores these 32 masks and the associated CIDR number.

    CREATE TABLE cidr (
      bits INT UNSIGNED PRIMARY KEY,
      mask INT UNSIGNED NOT NULL
    );
    
    INSERT INTO cidr (bits) VALUES
      ( 1), ( 2), ( 3), ( 4), ( 5), ( 6), ( 7), ( 8), ( 9), (10),
      (11), (12), (13), (14), (15), (16), (17), (18), (19), (20),
      (21), (22), (23), (24), (25), (26), (27), (28), (29), (30),
      (31), (32);
    
    UPDATE cidr SET mask = ((POWER(2,32)-1)<<(32-bits)) & (POWER(2,32)-1);
    
    SELECT CONCAT(s.ip_addr, '/', c.bits)
    FROM cidr c JOIN subnets s ON (c.mask = inet_aton(s.ip_mask));
    
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  • 2021-02-05 22:58

    I think I have found the solution to my issue. Here is what I have done:

    select CONCAT(INET_NTOA(ip_addr),'/',32-log2((4294967296-ip_mask))) net 
    from subnets 
    order by ip_addr
    

    Basically I take my decmial mask and subtract it from the maximum decimal value. I then to a log2 on that value to get the logarithm value. Then simply subtract that from 32 (the maximum bit available).

    Hope that helps others.

    Thanks

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