From 50a69149072be4f66cbd05362fef9ec68f293323 Mon Sep 17 00:00:00 2001
From: Christian Hesse <mail@eworm.de>
Date: Fri, 1 Mar 2024 12:09:29 +0100
Subject: netwatch-notify: (mis-)use firewall address-list for lookup...
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... and drop the racy code querying dns cache. 😁
---
 doc/netwatch-notify.md |  4 ++--
 netwatch-notify.rsc    | 16 +++++-----------
 2 files changed, 7 insertions(+), 13 deletions(-)

diff --git a/doc/netwatch-notify.md b/doc/netwatch-notify.md
index a7cc2d6..e252d39 100644
--- a/doc/netwatch-notify.md
+++ b/doc/netwatch-notify.md
@@ -84,8 +84,8 @@ with a resolvable name:
     /tool/netwatch/add comment="notify, name=example.com, resolve=example.com";
 
 This supports multiple A or AAAA records for a name just fine, even a CNAME
-to those. But be warned: CNAME chains to multiple records will cause a high
-rate of configuration changes (and flash writes)!
+to those. An update happens only if no more record with the configured host
+address is found.
 
 ### No notification on host down
 
diff --git a/netwatch-notify.rsc b/netwatch-notify.rsc
index cd4fc0d..6501ea9 100644
--- a/netwatch-notify.rsc
+++ b/netwatch-notify.rsc
@@ -56,21 +56,15 @@
   :local Name     [ :tostr $1 ];
   :local Expected [ :tostr $2 ];
 
-  :delay 100ms;
+  :global GetRandom20CharAlNum;
 
-  :if ([ :len [ /ip/dns/cache/find where name=$Name data=$Expected ] ] > 0) do={
+  :local FwAddrList ($0 . "-" . [ $GetRandom20CharAlNum ]);
+  /ip/firewall/address-list/add address=$Name list=$FwAddrList dynamic=yes timeout=1s;
+  :delay 20ms;
+  :if ([ :len [ /ip/firewall/address-list/find where list=$FwAddrList address=$Expected ] ] > 0) do={
     :return true;
   }
 
-  :local Cname [ /ip/dns/cache/find where name=$Name type="CNAME" ];
-  :if ([ :len $Cname ] > 0) do={
-    :set Cname [ /ip/dns/cache/get $Cname data ];
-    :set Cname [ :pick $Cname 0 ([ :len $Cname ] - 1) ];
-    :if ([ :len [ /ip/dns/cache/find where name=$Cname data=$Expected ] ] > 0) do={
-      :return true;
-    }
-  }
-
   :return false;
 }
 
-- 
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