[#3084] Use callout argument instead of status

src/bin/dhcp4/dhcp4_messages.mes
    DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING - new message

src/bin/dhcp4/dhcp4_srv.cc
    Dhcpv4Srv::processDhcp4Query() - look for offer-address-in-use
    argument in lease4_offer unpark lambda

src/bin/dhcp4/dhcp4_messages.cc

@@ -83,6 +83,7 @@ extern const isc::log::MessageID DHCP4_HOOK_BUFFER_RCVD_SKIP = "DHCP4_HOOK_BUFFE
 extern const isc::log::MessageID DHCP4_HOOK_BUFFER_SEND_SKIP = "DHCP4_HOOK_BUFFER_SEND_SKIP";
 extern const isc::log::MessageID DHCP4_HOOK_DDNS_UPDATE = "DHCP4_HOOK_DDNS_UPDATE";
 extern const isc::log::MessageID DHCP4_HOOK_DECLINE_SKIP = "DHCP4_HOOK_DECLINE_SKIP";
+extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING = "DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING";
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_DROP = "DHCP4_HOOK_LEASE4_OFFER_DROP";
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_PARK = "DHCP4_HOOK_LEASE4_OFFER_PARK";
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_PARKING_LOT_FULL = "DHCP4_HOOK_LEASE4_OFFER_PARKING_LOT_FULL";
@@ -263,6 +264,7 @@ const char* values[] = {
     "DHCP4_HOOK_BUFFER_SEND_SKIP", "%1: prepared response is dropped because a callout set the next step to SKIP.",
     "DHCP4_HOOK_DDNS_UPDATE", "A hook has updated the DDNS parameters: hostname %1=>%2, forward update %3=>%4, reverse update %5=>%6",
     "DHCP4_HOOK_DECLINE_SKIP", "Decline4 hook callouts set status to DROP, ignoring packet.",
+    "DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING", "hook callouts did not set an argument as expected %1 for %2",
     "DHCP4_HOOK_LEASE4_OFFER_DROP", "%1: packet is dropped, because a callout set the next step to DROP",
     "DHCP4_HOOK_LEASE4_OFFER_PARK", "%1: packet is parked, because a callout set the next step to PARK",
     "DHCP4_HOOK_LEASE4_OFFER_PARKING_LOT_FULL", "The parked-packet-limit %1, has been reached, dropping query: %2",

src/bin/dhcp4/dhcp4_messages.h

@@ -84,6 +84,7 @@ extern const isc::log::MessageID DHCP4_HOOK_BUFFER_RCVD_SKIP;
 extern const isc::log::MessageID DHCP4_HOOK_BUFFER_SEND_SKIP;
 extern const isc::log::MessageID DHCP4_HOOK_DDNS_UPDATE;
 extern const isc::log::MessageID DHCP4_HOOK_DECLINE_SKIP;
+extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING;
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_DROP;
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_PARK;
 extern const isc::log::MessageID DHCP4_HOOK_LEASE4_OFFER_PARKING_LOT_FULL;

src/bin/dhcp4/dhcp4_messages.mes

@@ -1073,3 +1073,9 @@ in a network or more likely a device that is using an address that it is not
 supposed to use. The server will fully recover from this situation, but if
 the underlying problem of a misconfigured or rogue device is not solved, this
 address may be declined again in the future.
+
+% DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING hook callouts did not set an argument as expected %1 for %2
+This debug message is printed when none of the callouts installed on the
+lease4_offer hook point set an expected argument in the callout status.
+This is a programming error in the installed hook libraries.  Details of
+the argument and the query in process at the time are provided log arguments.

src/bin/dhcp4/dhcp4_srv.cc

@@ -1502,6 +1502,7 @@ Dhcpv4Srv::processDhcp4Query(Pkt4Ptr& query, Pkt4Ptr& rsp,
                                                                   static_cast<int64_t>(1));
                         rsp.reset();
                         return;
+
                     }
                 }
 
@@ -1513,8 +1514,17 @@ Dhcpv4Srv::processDhcp4Query(Pkt4Ptr& query, Pkt4Ptr& rsp,
                     hook_label, query,
                     [this, callout_handle, query, rsp, callout_handle_state, hook_idx, ctx]() mutable {
                         if (hook_idx == Hooks.hook_index_lease4_offer_) {
-                            auto status = callout_handle->getStatus();
+                            bool offer_address_in_use = false;
-                            if (status == CalloutHandle::NEXT_STEP_DROP) {
+                            try {
+                                callout_handle->getArgument("offer-address-in-use", offer_address_in_use);
+                            } catch (const NoSuchArgument& ex) {
+                                /// @todo consider logging this
+                                LOG_DEBUG(hooks_logger, DBG_DHCP4_HOOKS,
+                                          DHCP4_HOOK_LEASE4_OFFER_ARGUMENT_MISSING)
+                                          .arg(query->getLabel());
+                            }
+
+                            if (offer_address_in_use) {
                                 Lease4Ptr lease = ctx->new_lease_;
                                 bool lease_exists = (ctx->offer_lft_ > 0);
                                 if (MultiThreadingMgr::instance().getMode()) {