From cfb31e844c39089046de1fc7021d5dedef14c145 Mon Sep 17 00:00:00 2001
From: Christian Hesse <mail@eworm.de>
Date: Thu, 6 May 2021 12:55:05 +0200
Subject: netwatch-notify: support dynamic address update

---
 doc/netwatch-notify.md |  9 +++++++++
 global-config          |  2 +-
 global-config-overlay  |  2 +-
 global-config.changes  |  1 +
 global-functions       |  2 +-
 netwatch-notify        | 15 +++++++++++++++
 6 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/doc/netwatch-notify.md b/doc/netwatch-notify.md
index a3d8ccd..ff1eae9 100644
--- a/doc/netwatch-notify.md
+++ b/doc/netwatch-notify.md
@@ -52,6 +52,15 @@ suppress notification if the parent host is down:
 Note that every configured parent in a chain increases the check count
 threshould by one.
 
+The host address can be updated dynamically. Give extra parameter `resolve`
+with a resolvable name:
+
+    / tool netwatch add comment="notify, hostname=example.com, resolve=example.com";
+
+But be warned: Dynamic updates will probably cause issues if the name has
+more than one record in dns - a high rate of configuration changes (and flash
+writes) at least.
+
 Also notification settings are required for e-mail and telegram.
 
 Tips & Tricks
diff --git a/global-config b/global-config
index 25d0496..77f41f6 100644
--- a/global-config
+++ b/global-config
@@ -8,7 +8,7 @@
 
 # Make sure all configuration properties are up to date and this
 # value is in sync with value in script 'global-functions'!
-:global GlobalConfigVersion 49;
+:global GlobalConfigVersion 50;
 
 # This is used for DNS and backup file.
 :global Domain "example.com";
diff --git a/global-config-overlay b/global-config-overlay
index 7057765..ac5e396 100644
--- a/global-config-overlay
+++ b/global-config-overlay
@@ -8,7 +8,7 @@
 # Make sure all configuration properties are up to date and this
 # value is in sync with value in script 'global-functions'!
 # Comment or remove to disable news and change notifications.
-:global GlobalConfigVersion 49;
+:global GlobalConfigVersion 50;
 
 # Copy configuration from global-config here and modify it.
 
diff --git a/global-config.changes b/global-config.changes
index 61850dd..74af117 100644
--- a/global-config.changes
+++ b/global-config.changes
@@ -53,6 +53,7 @@
   47="Removed obsolete intermediate certificate 'Let's Encrypt Authority X3' from store.";
   48="Added support for overriding e-mail and Telegram settings for every script.";
   49="Dropped '\$EmailBackupTo' & '\$EmailBackupCc' from configuration, use settings override if required.";
+  50="Added support for dynamic address update in 'netwatch-notify'.";
 };
 
 # Migration steps to be applied on script updates
diff --git a/global-functions b/global-functions
index 0c90ad8..2626c36 100644
--- a/global-functions
+++ b/global-functions
@@ -8,7 +8,7 @@
 # https://git.eworm.de/cgit/routeros-scripts/about/
 
 # expected configuration version
-:global ExpectedConfigVersion 49;
+:global ExpectedConfigVersion 50;
 
 # global variables not to be changed by user
 :global GlobalFunctionsReady false;
diff --git a/netwatch-notify b/netwatch-notify
index 9cb99bb..50441a9 100644
--- a/netwatch-notify
+++ b/netwatch-notify
@@ -33,6 +33,21 @@
     :set $Metric ($NetwatchNotify->$HostName);
   }
 
+  :if ([ :typeof ($HostInfo->"resolve") ] = "str") do={
+    :do {
+      :local Resolve [ :resolve ($HostInfo->"resolve") ];
+      :if ($Resolve != $HostVal->"host") do={
+         $LogPrintExit2 info $0 ("Name '" . $HostInfo->"resolve" . [ $IfThenElse ($HostInfo->"resolve" != \
+           $HostInfo->"hostname") ("' for host '" . $HostInfo->"hostname") "" ] . \
+           "' resolves to different address " . $Resolve . ", updating.") false;
+        / tool netwatch set host=$Resolve $Host;
+      }
+    } on-error={
+      $LogPrintExit2 warning $0 ("Resolving name '" . $HostInfo->"resolve" . [ $IfThenElse ($HostInfo->"resolve" != \
+        $HostInfo->"hostname") ("' for host '" . $HostInfo->"hostname") "" ] . "' failed.") false;
+    }
+  }
+
   :if ($HostVal->"status" = "up") do={
     :local Count ($Metric->"count");
     :if ($Count > 0) do={
-- 
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