From fc1adae2fd7d1964638d615e88d9bbb66245f6e9 Mon Sep 17 00:00:00 2001
From: Tomek Mrugalski <tomek@isc.org>
Date: Mon, 14 Feb 2022 16:15:35 +0100
Subject: [PATCH] [#2200] ddns_update hook added in v4

---
 src/bin/dhcp4/dhcp4_messages.mes |  5 ++++
 src/bin/dhcp4/dhcp4_srv.cc       | 39 ++++++++++++++++++++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/src/bin/dhcp4/dhcp4_messages.mes b/src/bin/dhcp4/dhcp4_messages.mes
index 28256e948e..0e2f2e7946 100644
--- a/src/bin/dhcp4/dhcp4_messages.mes
+++ b/src/bin/dhcp4/dhcp4_messages.mes
@@ -392,6 +392,11 @@ for decline4 hook point and one of the callouts set next step status to DROP.
 The server will now abort processing of the packet as if it was never
 received. The lease will continue to be assigned to this client.
 
+% DHCP4_HOOK_DDNS_UPDATE A hook has updated the DDNS parameters: hostname %1=>%2, forward update %3=>%4, reverse update %5=>%6
+This message indicates that there was a hook called on ddns_update hook point
+and that hook updated the DDNS update parameters: hostname, or whether to
+conduct forward (A record) or reverse (PTR record) DDNS updates.
+
 % DHCP4_HOOK_LEASE4_RELEASE_SKIP %1: lease was not released because a callout set the next step to SKIP
 This debug message is printed when a callout installed on lease4_release
 hook point set the next step status to SKIP. For this particular hook point, the
diff --git a/src/bin/dhcp4/dhcp4_srv.cc b/src/bin/dhcp4/dhcp4_srv.cc
index 62f957fcd7..4d645565db 100644
--- a/src/bin/dhcp4/dhcp4_srv.cc
+++ b/src/bin/dhcp4/dhcp4_srv.cc
@@ -94,6 +94,7 @@ struct Dhcp4Hooks {
     int hook_index_buffer4_send_;      ///< index for "buffer4_send" hook point
     int hook_index_lease4_decline_;    ///< index for "lease4_decline" hook point
     int hook_index_host4_identifier_;  ///< index for "host4_identifier" hook point
+    int hook_index_ddns_update_;       ///< index for "ddns_update" hook point
 
     /// Constructor that registers hook points for DHCPv4 engine
     Dhcp4Hooks() {
@@ -106,6 +107,7 @@ struct Dhcp4Hooks {
         hook_index_buffer4_send_      = HooksManager::registerHook("buffer4_send");
         hook_index_lease4_decline_    = HooksManager::registerHook("lease4_decline");
         hook_index_host4_identifier_  = HooksManager::registerHook("host4_identifier");
+        hook_index_ddns_update_       = HooksManager::registerHook("ddns_update");
     }
 };
 
@@ -2096,6 +2098,43 @@ Dhcpv4Srv::processClientName(Dhcpv4Exchange& ex) {
             }
         }
 
+        // Optionally, call a hook that may possibly override the decisions made
+        // earlier.
+        if (HooksManager::calloutsPresent(Hooks.hook_index_ddns_update_)) {
+            Pkt4Ptr query = ex.getQuery();
+
+            CalloutHandlePtr callout_handle = getCalloutHandle(query);
+
+            // Pass incoming packet as argument
+            callout_handle->setArgument("query4", query);
+            callout_handle->setArgument("response4", resp);
+            callout_handle->setArgument("hostname", hostname);
+            callout_handle->setArgument("fwd-update", fqdn_fwd);
+            callout_handle->setArgument("rev-update", fqdn_rev);
+
+            // Call callouts
+            HooksManager::callCallouts(Hooks.hook_index_ddns_update_, *callout_handle);
+
+            // Let's get the parameters returned by hook.
+            string hook_hostname;
+            bool hook_fqdn_fwd = false;
+            bool hook_fqdn_rev = false;
+            callout_handle->getArgument("hostname", hook_hostname);
+            callout_handle->getArgument("fwd-update", hook_fqdn_fwd);
+            callout_handle->getArgument("rev-update", hook_fqdn_rev);
+
+            // If there's anything changed by the hook, log it and then update the parameters
+            if ( (hostname != hook_hostname) || (fqdn_fwd != hook_fqdn_fwd) ||
+                 (fqdn_rev != hook_fqdn_rev)) {
+                LOG_DEBUG(hooks_logger, DBGLVL_PKT_HANDLING, DHCP4_HOOK_DDNS_UPDATE)
+                    .arg(hostname).arg(hook_hostname).arg(fqdn_fwd).arg(hook_fqdn_fwd)
+                    .arg(fqdn_rev).arg(hook_fqdn_rev);
+                hostname = hook_hostname;
+                fqdn_fwd = hook_fqdn_fwd;
+                fqdn_rev = hook_fqdn_rev;
+            }
+        }
+
         // Update the context
         auto ctx = ex.getContext();
         ctx->fwd_dns_update_ = fqdn_fwd;