--
-- A stored procedure to reallocate a user's previous address, otherwise
-- provide a free address.
--
-- Using this SP reduces the usual set dialogue of queries to a single
-- query:
--
--   START TRANSACTION; SELECT FOR UPDATE; UPDATE; COMMIT;  ->  CALL sp()
--
-- The stored procedure is executed on an database instance within a single
-- round trip which often leads to reduced deadlocking and significant
-- performance improvements especially on multi-master clusters, perhaps even
-- by an order of magnitude or more.
--
-- To use this stored procedure the corresponding queries.conf statements must
-- be configured as follows:
--
-- allocate_begin = ""
-- allocate_find = "\
-- 	CALL fr_allocate_previous_or_new_framedipaddress( \
-- 		'%{control:${pool_name}}', \
-- 		'%{User-Name}', \
-- 		'%{Calling-Station-Id}', \
-- 		'%{NAS-IP-Address}', \
-- 		'${pool_key}', \
-- 		${lease_duration} \
-- 	)"
-- allocate_update = ""
-- allocate_commit = ""
--

CREATE INDEX poolname_username_callingstationid ON radippool(pool_name,username,callingstationid);

DELIMITER $$

DROP PROCEDURE IF EXISTS fr_allocate_previous_or_new_framedipaddress;
CREATE PROCEDURE fr_allocate_previous_or_new_framedipaddress (
        IN v_pool_name VARCHAR(64),
        IN v_username VARCHAR(64),
        IN v_callingstationid VARCHAR(64),
        IN v_nasipaddress VARCHAR(15),
        IN v_pool_key VARCHAR(64),
        IN v_lease_duration INT
)
proc:BEGIN
        DECLARE r_address VARCHAR(15);

        SET TRANSACTION ISOLATION LEVEL READ COMMITTED;

        START TRANSACTION;

        -- Reissue an existing IP address lease when re-authenticating a session
        --
        SELECT framedipaddress INTO r_address
        FROM radippool
        WHERE pool_name = v_pool_name
                AND expiry_time > NOW()
                AND username = v_username
                AND callingstationid = v_callingstationid
        LIMIT 1
        FOR UPDATE;
--      FOR UPDATE SKIP LOCKED;  -- Better performance, but limited support

        -- Reissue an user's previous IP address, provided that the lease is
        -- available (i.e. enable sticky IPs)
        --
        -- When using this SELECT you should delete the one above. You must also
        -- set allocate_clear = "" in queries.conf to persist the associations
        -- for expired leases.
        --
        -- SELECT framedipaddress INTO r_address
        -- FROM radippool
        -- WHERE pool_name = v_pool_name
        --         AND username = v_username
        --         AND callingstationid = v_callingstationid
        -- LIMIT 1
        -- FOR UPDATE;
        -- -- FOR UPDATE SKIP LOCKED;  -- Better performance, but limited support

        -- If we didn't reallocate a previous address then pick the least
        -- recently used address from the pool which maximises the likelihood
        -- of re-assigning the other addresses to their recent user
        --
        IF r_address IS NULL THEN
                SELECT framedipaddress INTO r_address
                FROM radippool
                WHERE pool_name = v_pool_name
                        AND ( expiry_time < NOW() OR expiry_time IS NULL )
                ORDER BY
                        expiry_time
                LIMIT 1
                FOR UPDATE;
--              FOR UPDATE SKIP LOCKED;  -- Better performance, but limited support
        END IF;

        -- Return nothing if we failed to allocated an address
        --
        IF r_address IS NULL THEN
                COMMIT;
                LEAVE proc;
        END IF;

        -- Update the pool having allocated an IP address
        --
        UPDATE radippool
        SET
                nasipaddress = v_nasipaddress,
                pool_key = v_pool_key,
                callingstationid = v_callingstationid,
                username = v_username,
                expiry_time = NOW() + INTERVAL v_lease_duration SECOND
        WHERE framedipaddress = r_address;

        COMMIT;

        -- Return the address that we allocated
        SELECT r_address;

END$$

DELIMITER ;
