[dataset] only master key is needed to attach (#4051)

examples/apps/cli/README.md

@@ -82,13 +82,11 @@ $ cd <path-to-openthread>/output/<platform>/bin
 $ ./ot-cli-ftd 2
 ```
 
-Configure Thread Master Key and PAN ID from Node 1's Active Operational Dataset:
+Configure Thread Master Key from Node 1's Active Operational Dataset:
 
 ```bash
 > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
 Done
-> dataset panid 0x8f28
-Done
 > dataset commit active
 Done
 ```

examples/platforms/efr32mg12/README.md

@@ -210,8 +210,6 @@ Click the Flash button located under the Browse... button.
    ```bash
    > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
    Done
-   > dataset panid 0x8f28
-   Done
    > dataset commit active
    Done
    > routerselectionjitter 1

examples/platforms/kw41z/README.md

@@ -97,8 +97,6 @@ The [NXP(Freescale) Test Tool][test-tool] provides a convenient method for flash
     ```bash
     > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
     Done
-    > dataset panid 0x8f28
-    Done
     > dataset commit active
     Done
     > ifconfig up

examples/platforms/nrf52811/README.md

@@ -205,8 +205,6 @@ To test the example:
    ```bash
    > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
    Done
-   > dataset panid 0x8f28
-   Done
    > dataset commit active
    Done
    > ifconfig up

examples/platforms/nrf52840/README.md

@@ -235,8 +235,6 @@ To test the example:
    ```bash
    > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
    Done
-   > dataset panid 0x8f28
-   Done
    > dataset commit active
    Done
    > ifconfig up

examples/platforms/samr21/README.md

@@ -158,8 +158,6 @@ $ (gdb) c
    ```bash
    > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
    Done
-   > dataset panid 0x8f28
-   Done
    > dataset commit active
    Done
    > routerselectionjitter 1

include/openthread/dataset.h

@@ -309,8 +309,8 @@ otError otDatasetGetActive(otInstance *aInstance, otOperationalDataset *aDataset
  * If the dataset does not include an Active Timestamp, the dataset is only partially complete.
  *
  * If Thread is enabled on a device that has a partially complete Active Dataset, the device will attempt to attach to
- * an existing Thread network using any existing information in the dataset. The minimum set of information needed to
- * attach is the PAN ID and Thread Master Key.
+ * an existing Thread network using any existing information in the dataset. Only the Thread Master Key is needed to
+ * attach to a network.
  *
  * If channel is not included in the dataset, the device will send MLE Announce messages across different channels to
  * find neighbors on other channels.

src/cli/README_DATASET.md

@@ -66,10 +66,7 @@ The Pending Operational Dataset is used to communicate changes to the Active Ope
 
 ### Attach to Existing Network
 
-The minimum set of parameters required for a device to attach a Thread network are:
-
-* Master Key
-* PAN ID
+Only the Master Key is required for a device to attach to a Thread network.
 
 While not required, specifying the channel avoids the need to search across multiple channels, improving both latency and efficiency of the attach process.
 
@@ -78,8 +75,6 @@ After the device successfully attaches to a Thread network, the device will retr
 1. Create a partial Active Operational Dataset.
 
     ```bash
-    > dataset panid 0x8f28
-    Done
     > dataset masterkey dfd34f0f05cad978ec4e32b0413038ff
     Done
     > dataset commit active

src/core/api/thread_api.cpp

@@ -405,7 +405,6 @@ otError otThreadSetEnabled(otInstance *aInstance, bool aEnabled)
 
     if (aEnabled)
     {
-        VerifyOrExit(instance.Get<Mac::Mac>().GetPanId() != Mac::kPanIdBroadcast, error = OT_ERROR_INVALID_STATE);
         error = instance.Get<Mle::MleRouter>().Start(/* aAnnounceAttach */ false);
     }
     else
@@ -413,7 +412,6 @@ otError otThreadSetEnabled(otInstance *aInstance, bool aEnabled)
         instance.Get<Mle::MleRouter>().Stop(true);
     }
 
-exit:
     return error;
 }
 

src/core/thread/mle.cpp

@@ -243,6 +243,20 @@ otError Mle::Start(bool aAnnounceAttach)
     VerifyOrExit(!otPlatRadioGetPromiscuous(&GetInstance()), error = OT_ERROR_INVALID_STATE);
     VerifyOrExit(Get<ThreadNetif>().IsUp(), error = OT_ERROR_INVALID_STATE);
 
+    if (Get<Mac::Mac>().GetPanId() == Mac::kPanIdBroadcast)
+    {
+        // if PAN ID is not configured, pick a random one to start
+
+        uint16_t panid;
+
+        do
+        {
+            panid = Random::NonCrypto::GetUint16();
+        } while (panid == Mac::kPanIdBroadcast);
+
+        Get<Mac::Mac>().SetPanId(panid);
+    }
+
     SetStateDetached();
 
     ApplyMeshLocalPrefix();