From 2d055187980f9db07a2c4ea0a3171a8ad0dc7048 Mon Sep 17 00:00:00 2001
From: Szymon Sasin <szymon.sasin@gmail.com>
Date: Tue, 24 Sep 2024 15:02:16 +0300
Subject: [PATCH] fix: correlation-tag option number to be non-critical

---
 .../main/java/com/mbed/coap/packet/HeaderOptions.java | 11 ++++++++++-
 .../java/com/mbed/coap/packet/HeaderOptionsTest.java  |  7 +++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/coap-core/src/main/java/com/mbed/coap/packet/HeaderOptions.java b/coap-core/src/main/java/com/mbed/coap/packet/HeaderOptions.java
index 41cd4bd6..78db289e 100644
--- a/coap-core/src/main/java/com/mbed/coap/packet/HeaderOptions.java
+++ b/coap-core/src/main/java/com/mbed/coap/packet/HeaderOptions.java
@@ -25,6 +25,15 @@
  * - RFC 7959 (Block-Wise Transfers)
  * - draft-ietf-core-observe-09
  * - RFC 9175 (Echo, Request-Tag, and Token Processing)
+ * <p/>
+ * And custom:
+ * <pre>
+ *    +-----+---+---+---+---+----------------+--------+--------+----------+
+ *    | No. | C | U | N | R | Name           | Format | Length | Default  |
+ *    +-----+---+---+---+---+----------------+--------+--------+----------+
+ *    |29644|   |   |   |   | Correlation-tag| opaque | 0-36   | (none)   |
+ *    +-----+---+---+---+---+----------------+--------+--------+----------+
+ * </pre>
  */
 public class HeaderOptions extends BasicHeaderOptions {
 
@@ -34,7 +43,7 @@ public class HeaderOptions extends BasicHeaderOptions {
     private static final byte SIZE_2_RES = 28;
     private static final int ECHO = 252;
     private static final int REQUEST_TAG = 292;
-    private static final int OPEN_COAP_CORRELATION_TAG = 29643; // open-coap specific option for request tracing
+    public static final int OPEN_COAP_CORRELATION_TAG = 29644; // open-coap specific option for request tracing
     private Integer observe;
     private BlockOption block1Req;
     private BlockOption block2Res;
diff --git a/coap-core/src/test/java/com/mbed/coap/packet/HeaderOptionsTest.java b/coap-core/src/test/java/com/mbed/coap/packet/HeaderOptionsTest.java
index 9257e2ec..a138686a 100644
--- a/coap-core/src/test/java/com/mbed/coap/packet/HeaderOptionsTest.java
+++ b/coap-core/src/test/java/com/mbed/coap/packet/HeaderOptionsTest.java
@@ -522,6 +522,13 @@ void shouldUseQueryWithoutValue() throws CoapException, IOException {
         assertEquals("?param1=val1&q&param2=val2 Loc:?q", h2.toString());
     }
 
+    @Test
+    void correlationOptionShouldBeElectiveAndSafeToForward() {
+        assertFalse(isCritical(HeaderOptions.OPEN_COAP_CORRELATION_TAG));
+        assertFalse(isUnsave(HeaderOptions.OPEN_COAP_CORRELATION_TAG));
+        assertFalse(hasNoCacheKey(HeaderOptions.OPEN_COAP_CORRELATION_TAG));
+    }
+
     private static byte[] serialize(BasicHeaderOptions hdr) throws IOException, CoapException {
         ByteArrayOutputStream baos = new ByteArrayOutputStream();
         hdr.serialize(baos);