Table of Contents
htable (str)
db_url (str)
key_name_column (str)
key_type_column (str)
value_type_column (str)
key_value_column (str)
expires_column (str)
array_size_suffix (str)
fetch_rows (integer)
timer_interval (integer)
timer_mode (integer)
db_expires (integer)
enable_dmq (integer)
List of Examples
hash_size parameterdb_url parameterkey_name_column parameterkey_type_column parametervalue_type_column parameterkey_value_column parameterexpires_column parameterarray_size_suffix parameterfetch_rows parametertimer_interval parametertimer_mode parameterdb_expires parameterenable_dmq parametersht_print usagesht_rm_name_re usagesht_rm_value_re usagesht_reset usagesht_lock usagesht_unlock usagesht_iterator_start usagesht_iterator_end usagesht_iterator_next usageTable of Contents
htable (str)
db_url (str)
key_name_column (str)
key_type_column (str)
value_type_column (str)
key_value_column (str)
expires_column (str)
array_size_suffix (str)
fetch_rows (integer)
timer_interval (integer)
timer_mode (integer)
db_expires (integer)
enable_dmq (integer)
The module adds a hash table container to the configuration language. The hash table is stored in shared memory and the access to it can be done via pseudo-variables: $sht(htname=>name). The module supports definition of many hash tables and can load values at startup from a database table.
A typical use case for the SIP server is to implement a cache system in configuration file - if a value is not found in hash table, load it from database and store it in hash table so next time the access to it is very fast. In the definition of the table you can define the default expiration time of cached items. The expiration time can be adjusted per item via assignment operation at runtime.
Replication between multiple servers is performed automatically (if enabled) via the DMQ module.
You can read more about hash tables at: http://en.wikipedia.org/wiki/Hash_table.
The “name” can be a static string or can include pseudo- variables that will be replaced at runtime.
Example 1.1. Accessing $sht(htname=>key)
...
modparam("htable", "htable", "a=>size=8;")
...
$sht(a=>test) = 1;
$sht(a=>$ci::srcip) = $si;
...
Next example shows a way to protect against dictionary attacks. If someone fails to authenticate 3 times, it is forbidden for 15min. Authenticatiion against database is expensive as it does a select on the “subscriberthe” table. By disabling the DB auth for 15min, resources on the server are saved and time to discover the password is increased substantially. Additional alerting can be done by writing a message to syslog or sending email, etc.
To implement the logic, two hash table variables are used: one counting the failed authentications per user and one for storing the time of last authentication attempt. To ensure a unique name per user, the hash table uses a combination of authentication username and text “::auth_count” and “::last_auth”.
Example 1.2. Dictionary attack limitation
...
modparam("htable", "htable", "a=>size=8;")
...
if(is_present_hf("Authorization"))
{
if($sht(a=>$au::auth_count)==3)
{
$var(exp) = $Ts - 900;
if($sht(a=>$au::last_auth) > $var(exp))
{
sl_send_reply("403", "Try later");
exit;
} else {
$sht(a=>$au::auth_count) = 0;
}
}
if(!www_authenticate("$td", "subscriber"))
{
switch ($retcode) {
case -1:
sl_send_reply("403", "Forbidden");
exit;
case -2:
if($sht(a=>$au::auth_count) == $null)
$sht(a=>$au::auth_count) = 0;
$sht(a=>$au::auth_count) = $sht(a=>$au::auth_count) + 1;
if($sht(a=>$au::auth_count) == 3)
xlog("auth failed 3rd time - src ip: $si\n");
$sht(a=>$au::last_auth) = $Ts;
break;
}
www_challenge("$td"/*realm*/,"0"/*qop*/);
exit;
}
$sht(a=>$au::auth_count) = 0;
} else {
www_challenge("$td","0");
exit;
}
...
The module also provides a way to store multiple values for a single key. This is emulated by storing individual keys as 'key_name[n]', where n is incremented for each key. The total number of keys is stored in a dedicated key, by default: 'key_name::size'.
The array is built when the table is loaded in memory and afterwards all the keys are treated as individual keys. If a particular entry in the array is deleted, it is the administrator's responsibility to update the size of the array and any other elements (if required).
Example 1.3. Storing array values
# Example of dbtext with multiple keys
$ cat /usr/local/etc/kamailio/dbtext/htable
1:key:1:0:value3:0
2:key:1:0:value2:0
3:key:1:0:value1:0
# The array key will be loaded in memory in the following format:
$ kamcmd htable.dump htable
{
entry: 35
size: 1
slot: {
item: {
name: key[0]
value: value1
}
}
}
{
entry: 50
size: 1
slot: {
item: {
name: key::size
value: 3
}
}
}
{
entry: 67
size: 1
slot: {
item: {
name: key[1]
value: value2
}
}
}
{
entry: 227
size: 1
slot: {
item: {
name: key[2]
value: value3
}
}
}
# Now let's delete a particular entry in the array: key[0].
$ kamcmd htable.delete htable key[0]
# The array key will look like this after a key was deleted:
$ kamcmd htable.dump htable
{
entry: 50
size: 1
slot: {
item: {
name: key::size
value: 3
}
}
}
{
entry: 67
size: 1
slot: {
item: {
name: key[1]
value: value2
}
}
}
{
entry: 227
size: 1
slot: {
item: {
name: key[2]
value: value3
}
}
}
The following modules must be loaded before this module:
If DMQ replication is enabled, the DMQ module must be loaded first..
The following libraries or applications must be installed before running Kamailio with this module loaded:
None.
The module is able to load values in a hash table at startup upon providing a DB URL and table name.
The structure of the table must contain:
key name - string containing the name of the key.
key type - the type of the key
0 - simple key - the key is added as 'key_name'.
1 - array key - the key is added as 'key_name[n]' - n is incremented for each key with this name to build an array in hash table. In addition, an additional key is built to hold the total number of key in the array, by default key_name::size (see array_size_suffix parameter).
value type - the type of the key value
0 - value is string.
1 - value is integer.
key value - string containing the value of the key.
The definition of a hash table. The value of the parameter must have the following format:
"htname=>size=_number_;autoexpire=_number_;dbtable=_string_"
The parameter can be set multiple times to get more hash tables in same configuration file.
htname - string specifying the name of the hash table. This string is used by $sht(...) to refer to the hash table.
size - number specifying the size of hash table. Larger value means less collisions. The number of entries (aka slots or buckets) in the table is 2^size. The possible range for this value is from 2 to 31, smaller or larger values will be increased to 3 (8 slots) or decreased to 14 (16384 slots).
autoexpire -time in seconds to delete an item from hash table if no update was done to it. If is missing or set to 0, the items won't expire.
dbtable - name of database to be loaded at startup in hash table. If empty or missing, no data will be loaded.
dbmode - if set to 1, the content of hash table is written to database table when the SIP server is stopped (i.e., ensure persistency over restarts). Default value is 0 (no write back to db table).
initval - the integer value to be returned instead of $null when a requested key is not set.
updateexpire - if set to 1 (default), the time until expiration of an item is reset when that item is updated. Certain uses of htable may dictate that updates should not reset the expiration timeout, however, in which case this attribute can be set to 0.
dmqreplicate - if set to 1, any actions (set, update, delete etc.) performed upon entries in this table will be replicated to other nodes (htable peers). Please note, module parameter “enable_dmq” must also be set in order for this to apply (see below). Default is 0 (no replication).
Default value is NULL.
Example 1.4. Set hash_size parameter
...
modparam("htable", "htable", "a=>size=4;autoexpire=7200;dbtable=htable_a;")
modparam("htable", "htable", "b=>size=5;")
modparam("htable", "htable", "c=>size=4;autoexpire=7200;initval=1;dmqreplicate=1;")
...
The URL to connect to database for loading values in hash table at start up.
Default value is NULL (do not connect).
Example 1.5. Set db_url parameter
...
modparam("htable", "db_url", "mysql://kamailio:kamailiorw@localhost/kamailio")
...
The name of the column containing the hash table key name.
Default value is 'key_name'.
The name of the column containing the hash table key type.
Default value is 'key_type'.
The name of the column containing the hash table value type.
Default value is 'value_type'.
Example 1.8. Set value_type_column parameter
...
modparam("htable", "value_type_column", "vtype")
...
The name of the column containing hash table key value.
Default value is 'key_value'.
Example 1.9. Set key_value_column parameter
...
modparam("htable", "key_value_column", "kvalue")
...
The name of the column containing the expires value.
Default value is 'expires'.
The suffix to be added to store the number of items in an array (see key type).
Default value is '::size'.
Example 1.11. Set array_size_suffix parameter
...
modparam("htable", "array_size_suffix", "-count")
...
How many rows to fetch at once from database.
Default value is 100.
Interval in seconds to check for expired htable values.
Default value is 20.
If set to 1, the module will start a new timer process. If set to 0 will use the default timer process to check for expired htable values.
Default value is 0.
If set to 1, the module will load/save the expires values of the items in hash table from/to database. It applies only to hash tables that have the auto-expires attribute defined.
Default value is 0.
If set to 1, will enable DMQ replication of actions performed upon entries in all tables having "dmqreplicate" parameter set. Any update action performed via pseudo-variables, MI and RPC commands will be repeated on all other nodes. Therefore, it is important to ensure the table definition (size, autoexpire etc.) is identical across all instances.
Important: If this parameter is enabled, the DMQ module must be loaded first - otherwise, startup will fail.
Currently, values are not replicated on load from DB as it is expected that in these cases, all servers will load their values from the same DB.
Default value is 0.
Dump content of hash table to L_ERR log level. Intended for debug purposes.
This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.
Delete all entries in the htable that match the name against regular expression.
This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.
Delete all entries in the htable that match the value against regular expression.
This function can be used from REQUEST_ROUTE, FAILURE_ROUTE, ONREPLY_ROUTE, BRANCH_ROUTE.
Delete all entries in the htable. The name of the hash table can be a dynamic string with variables.
This function can be used from ANY_ROUTE.
Lock the slot in htable corespoding to the key item. Note that the locking is re-entrant for the process, therefore the lock and unlock should be done by the same process.
This function can be used from ANY_ROUTE.
Unlock the slot in htable corespoding to the key item. Note that the locking is re-entrant for the process, therefore the lock and unlock should be done by the same process.
This function can be used from ANY_ROUTE.
Example 1.22. sht_unlock usage
...
sht_lock("ha=>test");
$sht(ha=>test) = $sht(ha=>test) + 10;
sht_unlock("ha=>test");
...
Start an iterator for hash table named by the value of parameter hname. The parameter iname is used to identify the iterator. There can be up to 4 iterators at the same time, with different name.
Both parameters can be dynamic strings with variables.
IMPORTANT: the slot of the hash table is left locked when retrieving in item. Therefore be sure you do not update the content of the hash table in between sht_iterator_start() and sht_iterator_end(), because it may end up in dead lock.
This function can be used from ANY_ROUTE.
Close the iterator identified by iname parameter and release the hash table slot aquired by the iterator. The iname value must be the same used for sht_iterator_start().
The parameter can be dynamic string with variables.
This function can be used from ANY_ROUTE.
Move the iterator to the next item in hash table. It must be called also after sht_iterator_start() to get the first item in the hash table. Items are returned as they are found in the hash table slot, starting with the first slot.
The return code is false when there is no (more) item in the hash table.
The item name and value are accessible via variables: $shtitkey(iname) and $shtitval(iname).
The parameter can be dynamic string with variables.
This function can be used from ANY_ROUTE.
Example 1.25. sht_iterator_next usage
...
sht_iterator_start("i1", "h1");
while(sht_iterator_next("i1")) {
xlog("h1[$shtitkey(i1)] is: $shtitval(i1)\n");
}
sht_iterator_end("i1");
...
$sht(htable=>key)
$shtex(htable=>key)
$shtcn(htable=>key)
$shtcv(htable=>key)
$shtinc(htable=>key)
$shtval(htable=>key)
$shtrecord(attribute)
Exported pseudo-variables are documented at http://www.kamailio.org/wiki/.
Reload a hash table from database.
Name: sht_reload
Parameters: _hash_table_name_ - the name of hash table to reload.
MI FIFO Command Format:
:sht_reload:_reply_fifo_file_ _hash_table_name_ _empty_line_
Dump content of a hash table via MI.
Name: sht_dump
Parameters: _hash_table_name_ - the name of hash table to dump.
MI FIFO Command Format:
:sht_dump:_reply_fifo_file_ _hash_table_name_ _empty_line_
Delete a key from a hash table via MI.
Name: sht_delete
Parameters:
_hash_table_name: The table name to delete the key from
_key_name: The key to delete from the htable
MI FIFO Command Format:
:sht_delete:_reply_fifo_file_ _hash_table_name_ _key_name_ _empty_line_
Example (note the quoting when executing it via FIFO):
kamctl fifo sht_delete auth '"user@example.org::last_auth"'
Lists one value in a hash table
Name: htable.get
Parameters:
htable : Name of the hash table to dump
key : Key name of the hash table value to dump
Example:
... # Dump $sht(students=>daniel) kamcmd htable.get students daniel # Dump first entry in array key course $sht(students=>course[0]) kamcmd htable.get students course[0] ...
Delete one value in a hash table
Name: htable.delete
Parameters:
htable : Name of the hash table to delete
key : Key name of the hash table value to delete
Example:
... # Delete $sht(students=>anna) kamcmd htable.delete students anna # Delete first entry in array key course $sht(students=>course[0]) kamcmd htable.delete students course[0] ...
Set an item in hash table to string value.
Name: htable.sets
Parameters:
htable : Name of the hash table
key : Key name in the hash table
Value : String value for the item
Example:
... # Set $sht(test=>x) as string kamcmd htable.sets test x abc # Set firsti entry in array key x $sht(test=>x[0]) as string kamcmd htable.sets test x[0] abc ...
Set an item in hash table to integer value.
Name: htable.seti
Parameters:
htable : Name of the hash table
key : Key name in the hash table
Value : Integer value for the item
Example:
... # Set $sht(test=>x) as integer kamcmd htable.seti test x 123 # Set firsti entry in array key x $sht(test=>x[0]) as integer kamcmd htable.sets test x[0] 123 ...
Lists all the values in a hash table
Name: dhtable.dump
Parameters:
htable : Name of the hash table to dump
Example:
... kamcmd htable.dump ipban ...
Reload hash table from database.
Name: dhtable.reload
Parameters:
htable : Name of the hash table to reload
Example:
... kamcmd htable.reload ipban ...
Lists all defined tables
Name: htable.listTables
Parameters:
None
Example:
... kamcmd htable.listTables ...
When defined, the module calls event_route[htable:mod-init] after all modules have been initialized. A typical use case is to initialise items in hash tables. The event route is executed only once, after core and module initialization, but before Kamailio forks any child processes.
...
event_route[htable:mod-init] {
$sht(a=>x) = 1;
}
...
When defined, the module calls event_route[htable:expired:<table>] when an entry in the given table expires. In this event route, the key and value of the expired record are available with the $shtrecord(key) and $shtrecord(value) pseudo-variables.
...
event_route[htable:expired:mytable] {
xlog("mytable record expired $shtrecord(key) => $shtrecord(value)\n");
}
...