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
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
|
--
-- 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:
--
-- BEGIN TRAN; "SELECT FOR UPDATE"; UPDATE; COMMIT TRAN; -> EXEC 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 = "\
-- EXEC fr_allocate_previous_or_new_framedipaddress \
-- @v_pool_name = '%{control:${pool_name}}', \
-- @v_username = '%{User-Name}', \
-- @v_callingstationid = '%{Calling-Station-Id}', \
-- @v_nasipaddress = '%{NAS-IP-Address}', \
-- @v_pool_key = '${pool_key}', \
-- @v_lease_duration = ${lease_duration} \
-- "
-- allocate_update = ""
-- allocate_commit = ""
--
CREATE INDEX UserName_CallingStationId ON radippool(pool_name,UserName,CallingStationId)
GO
CREATE OR ALTER PROCEDURE fr_allocate_previous_or_new_framedipaddress
@v_pool_name VARCHAR(64),
@v_username VARCHAR(64),
@v_callingstationid VARCHAR(64),
@v_nasipaddress VARCHAR(15),
@v_pool_key VARCHAR(64),
@v_lease_duration INT
AS
BEGIN
-- MS SQL lacks a "SELECT FOR UPDATE" statement, and its table
-- hints do not provide a direct means to implement the row-level
-- read lock needed to guarentee that concurrent queries do not
-- select the same Framed-IP-Address for allocation to distinct
-- users.
--
-- The "WITH cte AS ( SELECT ... ) UPDATE cte ... OUTPUT INTO"
-- patterns in this procedure body compensate by wrapping
-- the SELECT in a synthetic UPDATE which locks the row.
DECLARE @r_address_tab TABLE(id VARCHAR(15));
DECLARE @r_address VARCHAR(15);
BEGIN TRAN;
-- Reissue an existing IP address lease when re-authenticating a session
--
WITH cte AS (
SELECT TOP(1) FramedIPAddress
FROM radippool WITH (xlock rowlock readpast)
WHERE pool_name = @v_pool_name
AND expiry_time > CURRENT_TIMESTAMP
AND NASIPAddress = @v_nasipaddress AND pool_key = @v_pool_key
)
UPDATE cte
SET FramedIPAddress = FramedIPAddress
OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
SELECT @r_address = id FROM @r_address_tab;
-- 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.
--
-- WITH cte AS (
-- SELECT TOP(1) FramedIPAddress
-- FROM radippool WITH (xlock rowlock readpast)
-- WHERE pool_name = @v_pool_name
-- AND NASIPAddress = @v_nasipaddress AND pool_key = @v_pool_key
-- )
-- UPDATE cte
-- SET FramedIPAddress = FramedIPAddress
-- OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
-- SELECT @r_address = id FROM @r_address_tab;
-- 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
BEGIN
WITH cte AS (
SELECT TOP(1) FramedIPAddress
FROM radippool WITH (xlock rowlock readpast)
WHERE pool_name = @v_pool_name
AND expiry_time < CURRENT_TIMESTAMP
ORDER BY
expiry_time
)
UPDATE cte
SET FramedIPAddress = FramedIPAddress
OUTPUT INSERTED.FramedIPAddress INTO @r_address_tab;
SELECT @r_address = id FROM @r_address_tab;
END
-- Return nothing if we failed to allocated an address
--
IF @r_address IS NULL
BEGIN
COMMIT TRAN;
RETURN;
END
-- 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 = DATEADD(SECOND,@v_lease_duration,CURRENT_TIMESTAMP)
WHERE framedipaddress = @r_address;
COMMIT TRAN;
-- Return the address that we allocated
SELECT @r_address;
END
GO
|
