netwatch-notify: handle CNAME to multiple records

2 files changed, 12 insertions, 3 deletions

diff --git a/doc/netwatch-notify.md b/doc/netwatch-notify.md
index 6925ca5..a7cc2d6 100644
--- a/doc/netwatch-notify.md
+++ b/doc/netwatch-notify.md
@@ -83,9 +83,9 @@ 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, but be
-warned: A CNAME to multiple records will cause a high rate of configuration
-changes (and flash writes)!
+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)!
 
 ### No notification on host down
 
diff --git a/netwatch-notify.rsc b/netwatch-notify.rsc
index 1b6a005..cd4fc0d 100644
--- a/netwatch-notify.rsc
+++ b/netwatch-notify.rsc
@@ -62,6 +62,15 @@
     :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;
 }