commit 3d8fa889b42f56c3e858bccbbc545595df5ff5e2
author Hungming Chen <nuccachen@google.com> Sun Apr 12 14:27:18 2020 +0800
committer Hungming Chen <nuccachen@google.com> Tue May 05 17:43:50 2020 +0800
tree b58bd4d99090a3b70e420c40140747d5004c32cc
parent 8bf2e7e05b11e5cfe708feebb60fe91c4bf8ac1f

Use device option to control BPF offload features

If BPF offload device config is not enabled:
- Does not add/remove offload forwarding rules through disabling IP
  neighbor monitor.
- Does not apply the RA MTU reduction.

Bug: 149997301
Test: atest IpServerTest
Change-Id: I2d6f80f0229f580c4b16243a064e889a6c37f77a

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

diff --git a/Tethering/src/android/net/ip/IpServer.java b/Tethering/src/android/net/ip/IpServer.java
index 83727bc..ca485f5 100644
--- a/Tethering/src/android/net/ip/IpServer.java
+++ b/Tethering/src/android/net/ip/IpServer.java
@@ -227,6 +227,7 @@
     private final int mInterfaceType;
     private final LinkProperties mLinkProperties;
     private final boolean mUsingLegacyDhcp;
+    private final boolean mUsingBpfOffload;
 
     private final Dependencies mDeps;
 
@@ -304,7 +305,8 @@
 
     public IpServer(
             String ifaceName, Looper looper, int interfaceType, SharedLog log,
-            INetd netd, Callback callback, boolean usingLegacyDhcp, Dependencies deps) {
+            INetd netd, Callback callback, boolean usingLegacyDhcp, boolean usingBpfOffload,
+            Dependencies deps) {
         super(ifaceName, looper);
         mLog = log.forSubComponent(ifaceName);
         mNetd = netd;
@@ -314,6 +316,7 @@
         mInterfaceType = interfaceType;
         mLinkProperties = new LinkProperties();
         mUsingLegacyDhcp = usingLegacyDhcp;
+        mUsingBpfOffload = usingBpfOffload;
         mDeps = deps;
         resetLinkProperties();
         mLastError = TetheringManager.TETHER_ERROR_NO_ERROR;
@@ -321,8 +324,15 @@
 
         mIpNeighborMonitor = mDeps.getIpNeighborMonitor(getHandler(), mLog,
                 new MyNeighborEventConsumer());
-        if (!mIpNeighborMonitor.start()) {
-            mLog.e("Failed to create IpNeighborMonitor on " + mIfaceName);
+
+        // IP neighbor monitor monitors the neighbor event for adding/removing offload
+        // forwarding rules per client. If BPF offload is not supported, don't start listening
+        // neighbor events. See updateIpv6ForwardingRules, addIpv6ForwardingRule,
+        // removeIpv6ForwardingRule.
+        if (mUsingBpfOffload) {
+            if (!mIpNeighborMonitor.start()) {
+                mLog.e("Failed to create IpNeighborMonitor on " + mIfaceName);
+            }
         }
 
         mInitialState = new InitialState();
@@ -715,12 +725,12 @@
             final String upstreamIface = v6only.getInterfaceName();
 
             params = new RaParams();
-            // We advertise an mtu lower by 16, which is the closest multiple of 8 >= 14,
-            // the ethernet header size.  This makes kernel ebpf tethering offload happy.
-            // This hack should be reverted once we have the kernel fixed up.
+            // When BPF offload is enabled, we advertise an mtu lower by 16, which is the closest
+            // multiple of 8 >= 14, the ethernet header size. This makes kernel ebpf tethering
+            // offload happy. This hack should be reverted once we have the kernel fixed up.
             // Note: this will automatically clamp to at least 1280 (ipv6 minimum mtu)
             // see RouterAdvertisementDaemon.java putMtu()
-            params.mtu = v6only.getMtu() - 16;
+            params.mtu = mUsingBpfOffload ? v6only.getMtu() - 16 : v6only.getMtu();
             params.hasDefaultRoute = v6only.hasIpv6DefaultRoute();
 
             if (params.hasDefaultRoute) params.hopLimit = getHopLimit(upstreamIface);
@@ -844,6 +854,11 @@
     }
 
     private void addIpv6ForwardingRule(Ipv6ForwardingRule rule) {
+        // Theoretically, we don't need this check because IP neighbor monitor doesn't start if BPF
+        // offload is disabled. Add this check just in case.
+        // TODO: Perhaps remove this protection check.
+        if (!mUsingBpfOffload) return;
+
         try {
             mNetd.tetherOffloadRuleAdd(rule.toTetherOffloadRuleParcel());
             mIpv6ForwardingRules.put(rule.address, rule);
@@ -853,6 +868,11 @@
     }
 
     private void removeIpv6ForwardingRule(Ipv6ForwardingRule rule, boolean removeFromMap) {
+        // Theoretically, we don't need this check because IP neighbor monitor doesn't start if BPF
+        // offload is disabled. Add this check just in case.
+        // TODO: Perhaps remove this protection check.
+        if (!mUsingBpfOffload) return;
+
         try {
             mNetd.tetherOffloadRuleRemove(rule.toTetherOffloadRuleParcel());
             if (removeFromMap) {

Tethering/src/com/android/networkstack/tethering/Tethering.java

diff --git a/Tethering/src/com/android/networkstack/tethering/Tethering.java b/Tethering/src/com/android/networkstack/tethering/Tethering.java
index 00b94a8..a31d547 100644
--- a/Tethering/src/com/android/networkstack/tethering/Tethering.java
+++ b/Tethering/src/com/android/networkstack/tethering/Tethering.java
@@ -2289,7 +2289,7 @@
         final TetherState tetherState = new TetherState(
                 new IpServer(iface, mLooper, interfaceType, mLog, mNetd,
                              makeControlCallback(), mConfig.enableLegacyDhcpServer,
-                             mDeps.getIpServerDependencies()));
+                             mConfig.enableBpfOffload, mDeps.getIpServerDependencies()));
         mTetherStates.put(iface, tetherState);
         tetherState.ipServer.start();
     }