From 46e06d8fd1f1dd378c128fe87549bdba165f640a Mon Sep 17 00:00:00 2001
From: Ruben Herold <ruben@puettmann.net>
Date: Fri, 4 Sep 2026 11:17:26 +0200
Subject: dhcp-server: T9267: make client-class substring matching
 contains-anywhere

The Mikrotik configuration referenced by T9267 uses
matching-type=substring, documented to match the value anywhere within
the option string. This PR's "substring" match instead compared a
fixed-length slice at a fixed byte offset (default 0) for exact
equality - effectively an anchored prefix match, not a substring
search - which does not reliably reproduce the ticket's own use case
of picking a device model string (e.g. "T42S") out of a longer,
variably-formatted hostname.

Rebuild "hostname substring"/"vendor-class-id substring" on Kea's
match()+lcase() instead of substring()==, so a configured value now
matches anywhere in the option content and case-insensitively (options
like vendor-class-id are not guaranteed to arrive in a fixed case).
Drop the "offset" leaf together with it, since it has no remaining
purpose once matching is no longer anchored to a fixed position, and
there is no released behavior to preserve.

Raw hex input and values containing a literal single quote are
rejected for substring matching in verify(), since neither can be
safely embedded into the generated Kea regular expression; exact
"value" matching is unaffected and still accepts both.

Reported by alexk37 in review of PR #5436.
---
 .../include/dhcp/dhcp-server-common-config.xml.i   | 44 +++-------------------
 1 file changed, 6 insertions(+), 38 deletions(-)

(limited to 'interface-definitions/include')

diff --git a/interface-definitions/include/dhcp/dhcp-server-common-config.xml.i b/interface-definitions/include/dhcp/dhcp-server-common-config.xml.i
index e909adca3..f49f69856 100644
--- a/interface-definitions/include/dhcp/dhcp-server-common-config.xml.i
+++ b/interface-definitions/include/dhcp/dhcp-server-common-config.xml.i
@@ -62,31 +62,15 @@
         </leafNode>
         <node name="substring">
           <properties>
-            <help>Filters on part of the option contents</help>
+            <help>Filters on whether the option contents contain this text (case-insensitive)</help>
           </properties>
           <children>
-            <leafNode name="offset">
-              <properties>
-                <help>Byte offset from the start of the option value (default: 0)</help>
-                <valueHelp>
-                  <format>u32:0-255</format>
-                  <description>Byte offset</description>
-                </valueHelp>
-                <constraint>
-                  <validator name="numeric" argument="--range 0-255"/>
-                </constraint>
-              </properties>
-            </leafNode>
             <leafNode name="value">
               <properties>
-                <help>Filters on part of the option contents</help>
-                <valueHelp>
-                  <format>hex</format>
-                  <description>Values that start with 0x are interpreted as raw hex. This must only be hexadecimal characters e.g. 0x1234567890ABCDEF</description>
-                </valueHelp>
+                <help>Text that must appear anywhere in the option contents (case-insensitive)</help>
                 <valueHelp>
                   <format>txt</format>
-                  <description>Any other text string is interpreted as ASCII text</description>
+                  <description>ASCII text to search for; must not contain a single quote (')</description>
                 </valueHelp>
               </properties>
             </leafNode>
@@ -114,31 +98,15 @@
         </leafNode>
         <node name="substring">
           <properties>
-            <help>Filters on part of the option contents</help>
+            <help>Filters on whether the option contents contain this text (case-insensitive)</help>
           </properties>
           <children>
-            <leafNode name="offset">
-              <properties>
-                <help>Byte offset from the start of the option value (default: 0)</help>
-                <valueHelp>
-                  <format>u32:0-255</format>
-                  <description>Byte offset</description>
-                </valueHelp>
-                <constraint>
-                  <validator name="numeric" argument="--range 0-255"/>
-                </constraint>
-              </properties>
-            </leafNode>
             <leafNode name="value">
               <properties>
-                <help>Filters on part of the option contents</help>
-                <valueHelp>
-                  <format>hex</format>
-                  <description>Values that start with 0x are interpreted as raw hex. This must only be hexadecimal characters e.g. 0x1234567890ABCDEF</description>
-                </valueHelp>
+                <help>Text that must appear anywhere in the option contents (case-insensitive)</help>
                 <valueHelp>
                   <format>txt</format>
-                  <description>Any other text string is interpreted as ASCII text</description>
+                  <description>ASCII text to search for; must not contain a single quote (')</description>
                 </valueHelp>
               </properties>
             </leafNode>
-- 
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