[#566,!304] kea-dhcp6 now removes objects deleted from config backend

src/lib/dhcpsrv/cb_ctl_dhcp6.cc
    CBControlDHCPv6::databaseConfigApply() - revamped to
    delete objects based on DELETE audit entries

src/lib/dhcpsrv/unittests
    Renamed cb_ctl_dhcp_unittest.cc to cb_ctl_dhcp4_unittest.cc
    cb_ctl_dhcp6_unittest.cc - new file

Added proposed ChangeLog

ChangeLog

+1560.	[func]		tmark
+	kea-dhcp6 now automatically deletes configuration elements
+	that have been deleted from configuration backends.
+	(Gitlab #566,!304, git TBD)
+
 1559.	[func]		fdupont
 	Added DHCPv6 support to the MySQL Config Backend hook.
 	(Gitlab #397,!244, git 980091ecd717e41a61f0d7f6808213e450647d8e)

src/lib/dhcpsrv/cb_ctl_dhcp6.cc

@@ -9,6 +9,7 @@
 #include <dhcpsrv/cfgmgr.h>
 #include <dhcpsrv/dhcpsrv_log.h>
 
+using namespace isc::db;
 using namespace isc::data;
 using namespace isc::process;
 
@@ -20,11 +21,99 @@ CBControlDHCPv6::databaseConfigApply(const db::BackendSelector& backend_selector
                                      const db::ServerSelector& server_selector,
                                      const boost::posix_time::ptime& lb_modification_time,
                                      const db::AuditEntryCollection& audit_entries) {
+    bool globals_fetched = false;
+
+    // Let's first delete all the configuration elements for which DELETE audit
+    // entries are found. Although, this may break chronology of the audit in
+    // some cases it should not affect the end result of the data fetch. If the
+    // object was created and then subsequently deleted, we will first try to
+    // delete this object from the local configuration (which will fail because
+    // the object does not exist) and then we will try to fetch it from the
+    // database which will return no result.
+    if (!audit_entries.empty()) {
+
+        auto cfg = CfgMgr::instance().getCurrentCfg();
+        auto external_cfg = CfgMgr::instance().createExternalCfg();
+
+        // Get audit entries for deleted global parameters.
+        const auto& index = audit_entries.get<AuditEntryObjectTypeTag>();
+        auto range = index.equal_range(boost::make_tuple("dhcp6_global_parameter",
+                                                         AuditEntry::ModificationType::DELETE));
+        if (range.first != range.second) {
+            // Some globals have been deleted. Since we currently don't track database
+            // identifiers of the global parameters we have to fetch all global
+            // parameters for this server. Next, we simply replace existing
+            // global parameters with the new parameters. This is slightly
+            // inefficient but only slightly. Note that this is a single
+            // database query and the number of global parameters is small.
+            data::StampedValueCollection globals;
+            globals = getMgr().getPool()->getAllGlobalParameters6(backend_selector, server_selector);
+            addGlobalsToConfig(external_cfg, globals);
+
+            // Now that we successfully fetched the new global parameters, let's
+            // remove existing ones and merge them into the current configuration.
+            cfg->clearConfiguredGlobals();
+            CfgMgr::instance().mergeIntoCurrentCfg(external_cfg->getSequence());
+            globals_fetched = true;
+        }
+
+        try {
+            // Get audit entries for deleted option definitions and delete each
+            // option definition from the current configuration for which the
+            // audit entry is found.
+            range = index.equal_range(boost::make_tuple("dhcp6_option_def",
+                                                        AuditEntry::ModificationType::DELETE));
+            for (auto entry = range.first; entry != range.second; ++entry) {
+                cfg->getCfgOptionDef()->del((*entry)->getObjectId());
+            }
+
+            // Repeat the same for other configuration elements.
+
+            range = index.equal_range(boost::make_tuple("dhcp6_options",
+                                                        AuditEntry::ModificationType::DELETE));
+            for (auto entry = range.first; entry != range.second; ++entry) {
+                cfg->getCfgOption()->del((*entry)->getObjectId());
+            }
+
+            range = index.equal_range(boost::make_tuple("dhcp6_shared_network",
+                                                        AuditEntry::ModificationType::DELETE));
+            for (auto entry = range.first; entry != range.second; ++entry) {
+                cfg->getCfgSharedNetworks6()->del((*entry)->getObjectId());
+            }
+
+            range = index.equal_range(boost::make_tuple("dhcp6_subnet",
+                                                        AuditEntry::ModificationType::DELETE));
+            for (auto entry = range.first; entry != range.second; ++entry) {
+                // If the deleted subnet belongs to a shared network and the
+                // shared network is not being removed, we need to detach the
+                // subnet from the shared network.
+                auto subnet = cfg->getCfgSubnets6()->getBySubnetId((*entry)->getObjectId());
+                if (subnet) {
+                    // Check if the subnet belongs to a shared network.
+                    SharedNetwork6Ptr network;
+                    subnet->getSharedNetwork(network);
+                    if (network) {
+                        // Detach the subnet from the shared network.
+                        network->del(subnet->getID());
+                    }
+                    // Actually delete the subnet from the configuration.
+                    cfg->getCfgSubnets6()->del((*entry)->getObjectId());
+                }
+            }
+
+        } catch (...) {
+            // Ignore errors thrown when attempting to delete a non-existing
+            // configuration entry. There is no guarantee that the deleted
+            // entry is actually there as we're not processing the audit
+            // chronologically.
+        }
+    }
+
     // Create the external config into which we'll fetch backend config data.
     SrvConfigPtr external_cfg = CfgMgr::instance().createExternalCfg();
 
     // First let's fetch the globals and add them to external config.
-    if (fetchConfigElement(audit_entries, "dhcp6_global_parameter")) {
+    if (!globals_fetched && fetchConfigElement(audit_entries, "dhcp6_global_parameter")) {
         data::StampedValueCollection globals;
         globals = getMgr().getPool()->getModifiedGlobalParameters6(backend_selector, server_selector,
                                                                    lb_modification_time);
@@ -57,6 +146,12 @@ CBControlDHCPv6::databaseConfigApply(const db::BackendSelector& backend_selector
             getMgr().getPool()->getModifiedSharedNetworks6(backend_selector, server_selector,
                                                            lb_modification_time);
         for (auto network = networks.begin(); network != networks.end(); ++network) {
+            // In order to take advantage of the dynamic inheritance of global
+            // parameters to a shared network we need to set a callback function
+            // for each network to allow for fetching global parameters.
+            (*network)->setFetchGlobalsFn([] () -> ConstElementPtr {
+                return (CfgMgr::instance().getCurrentCfg()->getConfiguredGlobals());
+            });
             external_cfg->getCfgSharedNetworks6()->add((*network));
         }
     }
@@ -67,6 +162,12 @@ CBControlDHCPv6::databaseConfigApply(const db::BackendSelector& backend_selector
                                                                             server_selector,
                                                                             lb_modification_time);
         for (auto subnet = subnets.begin(); subnet != subnets.end(); ++subnet) {
+            // In order to take advantage of the dynamic inheritance of global
+            // parameters to a subnet we need to set a callback function for each
+            // subnet to allow for fetching global parameters.
+            (*subnet)->setFetchGlobalsFn([] () -> ConstElementPtr {
+                return (CfgMgr::instance().getCurrentCfg()->getConfiguredGlobals());
+            });
             external_cfg->getCfgSubnets6()->add((*subnet));
         }
     }

src/lib/dhcpsrv/tests/Makefile.am

@@ -63,7 +63,8 @@ libdhcpsrv_unittests_SOURCES += alloc_engine_hooks_unittest.cc
 libdhcpsrv_unittests_SOURCES += alloc_engine4_unittest.cc
 libdhcpsrv_unittests_SOURCES += alloc_engine6_unittest.cc
 libdhcpsrv_unittests_SOURCES += callout_handle_store_unittest.cc
-libdhcpsrv_unittests_SOURCES += cb_ctl_dhcp_unittest.cc
+libdhcpsrv_unittests_SOURCES += cb_ctl_dhcp4_unittest.cc
+libdhcpsrv_unittests_SOURCES += cb_ctl_dhcp6_unittest.cc
 libdhcpsrv_unittests_SOURCES += cfg_db_access_unittest.cc
 libdhcpsrv_unittests_SOURCES += cfg_duid_unittest.cc
 libdhcpsrv_unittests_SOURCES += cfg_expiration_unittest.cc