A minor followup change for BPF offload device option stuff

- Correct description and spelling in the code and xml files.
- Add a TODO for refactoring the IpServer constructor.
- Refine the if-statement for starting IP neighbor monitor.

Test: atest IpServerTest
Change-Id: If9c8bc6f785fa80575db56de4e223292e9807ace

Tethering/res/values/config.xml

@@ -57,7 +57,7 @@
 
     <!-- Use the BPF offload for tethering when the kernel has support. True by default.
          If the device doesn't want to support tether BPF offload, this should be false.
-         Note that this setting could be override by device config.
+         Note that this setting could be overridden by device config.
     -->
     <bool translatable="false" name="config_tether_enable_bpf_offload">true</bool>
 

Tethering/res/values/overlayable.xml

@@ -25,7 +25,7 @@
             <item type="array" name="config_tether_dhcp_range"/>
             <!-- Use the BPF offload for tethering when the kernel has support. True by default.
                  If the device doesn't want to support tether BPF offload, this should be false.
-                 Note that this setting could be override by device config.
+                 Note that this setting could be overridden by device config.
             -->
             <item type="bool" name="config_tether_enable_bpf_offload"/>
             <item type="bool" name="config_tether_enable_legacy_dhcp_server"/>

Tethering/src/android/net/ip/IpServer.java

@@ -303,6 +303,8 @@ public class IpServer extends StateMachine {
 
     private final IpNeighborMonitor mIpNeighborMonitor;
 
+    // TODO: Add a dependency object to pass the data members or variables from the tethering
+    // object. It helps to reduce the arguments of the constructor.
     public IpServer(
             String ifaceName, Looper looper, int interfaceType, SharedLog log,
             INetd netd, Callback callback, boolean usingLegacyDhcp, boolean usingBpfOffload,
@@ -325,15 +327,13 @@ public class IpServer extends StateMachine {
         mIpNeighborMonitor = mDeps.getIpNeighborMonitor(getHandler(), mLog,
                 new MyNeighborEventConsumer());
 
-        // IP neighbor monitor monitors the neighbor event for adding/removing offload
+        // IP neighbor monitor monitors the neighbor events for adding/removing offload
         // forwarding rules per client. If BPF offload is not supported, don't start listening
-        // neighbor events. See updateIpv6ForwardingRules, addIpv6ForwardingRule,
+        // for neighbor events. See updateIpv6ForwardingRules, addIpv6ForwardingRule,
         // removeIpv6ForwardingRule.
-        if (mUsingBpfOffload) {
-            if (!mIpNeighborMonitor.start()) {
+        if (mUsingBpfOffload && !mIpNeighborMonitor.start()) {
             mLog.e("Failed to create IpNeighborMonitor on " + mIfaceName);
         }
-        }
 
         mInitialState = new InitialState();
         mLocalHotspotState = new LocalHotspotState();