implement insertOrReplace()
Test: atest com.android.networkstack.tethering.BpfMapTest
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Change-Id: I4a40898f03293d6d79b57c35f743271c669a8ea7
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfMap.java b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
index e9b4ccf..1363dc5 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfMap.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfMap.java
@@ -98,6 +98,7 @@
/**
* Update an existing or create a new key -> value entry in an eBbpf map.
+ * (use insertOrReplaceEntry() if you need to know whether insert or replace happened)
*/
public void updateEntry(K key, V value) throws ErrnoException {
writeToMapEntry(mMapFd, key.writeToBytes(), value.writeToBytes(), BPF_ANY);
@@ -133,6 +134,35 @@
}
}
+ /**
+ * Update an existing or create a new key -> value entry in an eBbpf map.
+ * Returns true if inserted, false if replaced.
+ * (use updateEntry() if you don't care whether insert or replace happened)
+ * Note: see inline comment below if running concurrently with delete operations.
+ */
+ public boolean insertOrReplaceEntry(K key, V value)
+ throws ErrnoException {
+ try {
+ writeToMapEntry(mMapFd, key.writeToBytes(), value.writeToBytes(), BPF_NOEXIST);
+ return true; /* insert succeeded */
+ } catch (ErrnoException e) {
+ if (e.errno != EEXIST) throw e;
+ }
+ try {
+ writeToMapEntry(mMapFd, key.writeToBytes(), value.writeToBytes(), BPF_EXIST);
+ return false; /* replace succeeded */
+ } catch (ErrnoException e) {
+ if (e.errno != ENOENT) throw e;
+ }
+ /* If we reach here somebody deleted after our insert attempt and before our replace:
+ * this implies a race happened. The kernel bpf delete interface only takes a key,
+ * and not the value, so we can safely pretend the replace actually succeeded and
+ * was immediately followed by the other thread's delete, since the delete cannot
+ * observe the potential change to the value.
+ */
+ return false; /* pretend replace succeeded */
+ }
+
/** Remove existing key from eBpf map. Return false if map was not modified. */
public boolean deleteEntry(K key) throws ErrnoException {
return deleteMapEntry(mMapFd, key.writeToBytes());
diff --git a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
index 62302c3..d24c35a 100644
--- a/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
+++ b/Tethering/tests/privileged/src/com/android/networkstack/tethering/BpfMapTest.java
@@ -209,7 +209,7 @@
}
@Test
- public void testUpdateBpfMap() throws Exception {
+ public void testUpdateEntry() throws Exception {
final TetherDownstream6Key key = mTestData.keyAt(0);
final Tether6Value value = mTestData.valueAt(0);
final Tether6Value value2 = mTestData.valueAt(1);
@@ -232,6 +232,29 @@
}
@Test
+ public void testInsertOrReplaceEntry() throws Exception {
+ final TetherDownstream6Key key = mTestData.keyAt(0);
+ final Tether6Value value = mTestData.valueAt(0);
+ final Tether6Value value2 = mTestData.valueAt(1);
+ assertFalse(mTestMap.deleteEntry(key));
+
+ // insertOrReplaceEntry will create an entry if it does not exist already.
+ assertTrue(mTestMap.insertOrReplaceEntry(key, value));
+ assertTrue(mTestMap.containsKey(key));
+ final Tether6Value result = mTestMap.getValue(key);
+ assertEquals(value, result);
+
+ // updateEntry will update an entry that already exists.
+ assertFalse(mTestMap.insertOrReplaceEntry(key, value2));
+ assertTrue(mTestMap.containsKey(key));
+ final Tether6Value result2 = mTestMap.getValue(key);
+ assertEquals(value2, result2);
+
+ assertTrue(mTestMap.deleteEntry(key));
+ assertFalse(mTestMap.containsKey(key));
+ }
+
+ @Test
public void testInsertReplaceEntry() throws Exception {
final TetherDownstream6Key key = mTestData.keyAt(0);
final Tether6Value value = mTestData.valueAt(0);
