Commit 0bbc1df7 authored by Tomek Mrugalski's avatar Tomek Mrugalski 🛰

[5039] Parameters inheritance implemented, doc updated

parent a529c56d
......@@ -20,7 +20,8 @@ if HAVE_CQL
# This is a temporary workaround until we have Kea-wide support for C++11.
# The files in the subfolder must be explicitly specified here so
# as they are copied to the distribution. The other option would
......@@ -476,4 +476,92 @@ is used by DHCPv4 and DHCPv6 components.
DHCPv4-over-DHCPv6 which are relayed by a DHCPv6 relay are not yet supported.
@section dhcp6SimpleParser Simple JSON Parser
Since the early beginnings, our configuration parsing code was a mess. It
started back in 2011 when Tomek joined ISC recently and was told to implement
Kea configuration handling in similar way as DNS Auth module. The code grew
over time (DHCP configuration is significantly more complex than DNS, with
more interdependent values) and as of Kea 1.1 release it became very difficult
to manage. The decision has been made to significantly refactor or even
partially rewrite the parser code. The design for this effort is documented
here: It discusses the original issues
and the proposed architecture.
There are several aspects of this new approach. The base class for all parsers
is @ref isc::dhcp::SimpleParser. It simplifies the parser be rejecting the
concept of build/commit phases. Instead, there should be a single method
called parse that takes ConstElementPtr as a single parameter (that's the
JSON structures to be parsed) and returns the config structure to be used
in CfgMgr. An example of such a method can be the following:
std::pair<OptionDescriptor, std::string>
OptionDataParser::parse(isc::data::ConstElementPtr single_option)
Since each derived class will have the same parameter, but a different return
type, it's not possible to use virtual methods mechanism. That's perfectly
ok, though, as there is only a single instance of the class needed to parse
arbitrary number of parameters of the same type, so there is no need to
keep pointers to the parser object. As such there's fewer incentives to have
one generic way to handle all parsers.
@subsection dhcp6SimpleParserDefaults Default values in Simple Parser
Another simplification comes from the fact that almost all parameters
are mandatory in SimpleParser. One source of complexities in the old
parser was the necessity to deal with optional parameters. Simple
parser deals with that by explicitly requiring the input structure to
have all parameters filled. Obviously, it's not feasible to expect
everyone to always specify all parameters, therefore there's an easy
way to fill missing parameters with their default values. There are
several methods to do this, but the most generic one is:
static size_t
isc::dhcp::SimpleParser::setDefaults(isc::data::ElementPtr scope,
const SimpleDefaults& default_values);
It takes a pointer to element to be filled with default values and
vector of default values. Having those values specified in a single
place in a way that can easily be read even by non-programmers is a
big advantage of this approach. Here's an example from file:
/// This table defines default values for option definitions in DHCPv6
const SimpleDefaults OPTION6_DEF_DEFAULTS = {
{ "record-types", Element::string, ""},
{ "space", Element::string, "dhcp6"},
{ "array", Element::boolean, "false"},
{ "encapsulate", Element::string, "" }
This array (which technically is implemented as a vector and
initialized the C++11 way) can be passed to the aforementioned
setDefaults. That code will iterate over all default values and see if
there are explicit values provided. If not, the gaps will be filled
with default values. There are also convenience methods specified for
filling in option data defaults, option definition defaults and
setAllDefaults that sets all defaults (starts with global, but then
walks down the Element tree and fills defaults in subsequent scopes).
@subsection dhcp6SimpleParserInherits Inheriting parameters between scopes
SimpleParser provides a mechanism to inherit parameters between scopes,
e.g. to inherit global parameters in the subnet scope if more specific
values are not defined in the subnet scope. This is achieved by calling
static size_t SimpleParser::deriveParams(isc::data::ConstElementPtr parent,
isc::data::ElementPtr child,
const ParamsList& params);
ParamsList is a simple vector<string>. There will be more specific
methods implemented in the future, but for the time being only
@ref isc::dhcp::SimpleParser::inheritGlobalToSubnet is implemented.
......@@ -710,13 +710,11 @@ class OptionDefListParser : public SimpleParser {
/// @brief Constructor.
/// @param dummy first argument is ignored, all Parser constructors
/// accept string as first argument.
/// @param global_context is a pointer to the global context which
/// stores global scope parameters, options, option defintions.
/// Stores address family that will be used to make certain decisions
/// during parsing.
/// @param address_family @c AF_INET or @c AF_INET6
OptionDefListParser(const uint16_t address_family);
//const std::string& dummy,
//ParserContextPtr global_context);
/// @brief Parses a list of option defintions, create them and store in cfg
......@@ -40,14 +40,30 @@ const SimpleDefaults OPTION6_DEFAULTS = {
{ "encapsulate", Element::string, "" }
/// This table defines default values for DHCPv4
const SimpleDefaults GLOBAL4_DEFAULTS = {
{ "renew-timer", Element::integer, "900" },
{ "rebind-timer", Element::integer, "1800" },
{ "valid-lifetime", Element::integer, "7200" }
/// This table defines default values for both DHCPv4 and DHCPv6
const SimpleDefaults GLOBAL_DEFAULTS = {
const SimpleDefaults GLOBAL6_DEFAULTS = {
{ "renew-timer", Element::integer, "900" },
{ "rebind-timer", Element::integer, "1800" },
{ "preferred-lifetime", Element::integer, "3600" },
{ "valid-lifetime", Element::integer, "7200" }
/// This list defines parameters that can be inherited from the global
/// scope to subnet scope.
SimpleParser::getString(isc::data::ConstElementPtr scope, const std::string& name) {
ConstElementPtr x = scope->get(name);
......@@ -162,8 +178,8 @@ size_t SimpleParser::setDefaults(isc::data::ElementPtr scope,
return (cnt);
size_t SimpleParser::setGlobalDefaults(isc::data::ElementPtr global) {
return (setDefaults(global, GLOBAL_DEFAULTS));
size_t SimpleParser::setGlobalDefaults(isc::data::ElementPtr global, bool v6) {
return (setDefaults(global, v6 ? GLOBAL6_DEFAULTS : GLOBAL4_DEFAULTS));
size_t SimpleParser::setOptionDefaults(isc::data::ElementPtr option, bool v6) {
......@@ -196,7 +212,8 @@ size_t SimpleParser::setAllDefaults(isc::data::ElementPtr global, bool v6) {
size_t cnt = 0;
// Set global defaults first.
//cnt = setGlobalDefaults(global);
/// @todo: Uncomment as part of the ticket 5019 work.
//cnt = setGlobalDefaults(global, v6);
// Now set option defintion defaults for each specified option definition
ConstElementPtr option_defs = global->get("option-def");
......@@ -249,5 +266,11 @@ SimpleParser::deriveParams(isc::data::ConstElementPtr parent,
return (cnt);
SimpleParser::inheritGlobalToSubnet(isc::data::ConstElementPtr global,
isc::data::ElementPtr subnet) {
return deriveParams(global, subnet, INHERIT_GLOBAL_TO_SUBNET);
}; // end of isc::dhcp namespace
}; // end of isc namespace
......@@ -62,6 +62,17 @@ class SimpleParser {
static size_t deriveParams(isc::data::ConstElementPtr parent,
isc::data::ElementPtr child,
const ParamsList& params);
/// @brief Derives (inherits) parameters from global to subnet scope
/// This method derives global parameters into subnet scope if they're
/// not defined there yet.
/// @param global parameters will be inherited from here
/// @param subnet parameters will be inserted here
/// @return number of parameters copied
static size_t
inheritGlobalToSubnet(isc::data::ConstElementPtr global,
isc::data::ElementPtr subnet);
/// @brief Sets the default values
......@@ -84,8 +95,9 @@ class SimpleParser {
/// for that.
/// @param global scope to be filled in with defaults.
/// @param v6 is it v6 (true) or v4 (false) option?
/// @return number of default values added
static size_t setGlobalDefaults(isc::data::ElementPtr global);
static size_t setGlobalDefaults(isc::data::ElementPtr global, bool v6);
/// @brief Sets option defaults for a single option
......@@ -131,6 +143,7 @@ class SimpleParser {
/// set the global defaults only, see @ref setGlobalDefaults for that.
/// @param global scope to be filled in with defaults.
/// @param v6 true = v6, false = v4
/// @return number of default values added
static size_t setAllDefaults(isc::data::ElementPtr global, bool v6);
......@@ -145,7 +158,7 @@ class SimpleParser {
getPosition(const std::string& name, const data::ConstElementPtr parent =
data::ConstElementPtr()) const;
/// @destructor
/// Destructor
/// It's really simple, isn't it?
virtual ~SimpleParser() {}
......@@ -318,6 +318,16 @@ public:
(config_pair.first == "option-def")) {
// We also don't care about the default values that may be been
// inserted
if ( (config_pair.first == "preferred-lifetime") ||
(config_pair.first == "valid-lifetime") ||
(config_pair.first == "renew-timer") ||
(config_pair.first == "rebind-timer")) {
// Remaining ones are old style parsers. Need go do
// the build/commit dance with them.
......@@ -477,6 +487,28 @@ public:
/// @brief Checks if specified map has an integer parameter with expected value
/// @param map map to be checked
/// @param param_name name of the parameter to be checked
/// @param exp_value expected value of the parameter.
void checkIntegerValue(const ConstElementPtr& map, const std::string& param_name,
int64_t exp_value) {
// First check if the passed element is a map.
ASSERT_EQ(Element::map, map->getType());
// Now try to get the element being checked
ConstElementPtr elem = map->get(param_name);
// Now check if it's indeed integer
ASSERT_EQ(Element::integer, elem->getType());
// Finally, check if its value meets expectation.
EXPECT_EQ(exp_value, elem->intValue());
/// @brief Parsers used in the parsing of the configuration
/// Allows the tests to interrogate the state of the parsers (if required).
......@@ -2393,4 +2425,65 @@ TEST_F(ParseConfigTest, validRelayInfo6) {
// (see CtrlDhcpv4SrvTest.commandSocketBasic in
// src/bin/dhcp4/tests/
// This test checks if global defaults are properly set for DHCPv6.
TEST_F(ParseConfigTest, globalDefaults6) {
ElementPtr empty = Element::fromJSON("{ }");
size_t num;
EXPECT_NO_THROW(num = SimpleParser::setGlobalDefaults(empty, true));
// We expect at least 4 parameters to be inserted.
EXPECT_TRUE(num >= 4);
checkIntegerValue(empty, "valid-lifetime", 7200);
checkIntegerValue(empty, "preferred-lifetime", 3600);
checkIntegerValue(empty, "rebind-timer", 1800);
checkIntegerValue(empty, "renew-timer", 900);
// This test checks if global defaults are properly set for DHCPv4.
TEST_F(ParseConfigTest, DISABLED_globalDefaults4) {
ElementPtr empty = Element::fromJSON("{ }");
size_t num;
EXPECT_NO_THROW(num = SimpleParser::setGlobalDefaults(empty, false));
// We expect at least 3 parameters to be inserted.
EXPECT_TRUE(num >= 3);
checkIntegerValue(empty, "valid-lifetime", 7200);
checkIntegerValue(empty, "rebind-timer", 1800);
checkIntegerValue(empty, "renew-timer", 900);
// Make sure that preferred-lifetime is not set for v4 (it's v6 only
// parameter)
// This test checks if the parameters can be inherited from the global
// scope to the subnet scope.
TEST_F(ParseConfigTest, inheritGlobalToSubnet) {
ElementPtr global = Element::fromJSON("{ \"renew-timer\": 1,"
" \"rebind-timer\": 2,"
" \"preferred-lifetime\": 3,"
" \"valid-lifetime\": 4"
ElementPtr subnet = Element::fromJSON("{ \"renew-timer\": 100 }");
// we should inherit 3 parameters. Renew-timer should remain intact,
// as it was already defined in the subnet scope.
size_t num;
EXPECT_NO_THROW(num = SimpleParser::inheritGlobalToSubnet(global, subnet));
EXPECT_EQ(3, num);
// Check the values. 3 of them are interited, while the fourth one
// was already defined in the subnet, so should not be inherited.
checkIntegerValue(subnet, "renew-timer", 100);
checkIntegerValue(subnet, "rebind-timer", 2);
checkIntegerValue(subnet, "preferred-lifetime", 3);
checkIntegerValue(subnet, "valid-lifetime", 4);
}; // Anonymous namespace
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