Fix potential exceptions in FdEventReader users

In particular,
 - Fix a possible NPE In IpNeighborMonitor, if a NUD_FAILED is received
   for some neighbor before all other neighbors have received
   RTM_NEWNEIGH.
 - Add try / catch in IpNeighborMonitor, DhcpPacketListener,
   ConnectivityPacketTracker in case some unexpected exception is thrown
   while processing packets.
 - Add Log.wtf logging in FdEventsReader in case any such exception is
   missed.

Bug: 152842850
Test: atest NetworkStackTests
Original-Change: https://android-review.googlesource.com/1274609
Merged-In: Ia03fec358e98b3f218220e70fc3265e14ca15f78
Change-Id: Ia03fec358e98b3f218220e70fc3265e14ca15f78

1 files changed, 12 insertions, 3 deletions

diff --git a/src/android/net/ip/IpReachabilityMonitor.java b/src/android/net/ip/IpReachabilityMonitor.java
index db928d6..2a0ca5d 100644
--- a/src/android/net/ip/IpReachabilityMonitor.java
+++ b/src/android/net/ip/IpReachabilityMonitor.java
@@ -341,7 +341,14 @@ public class IpReachabilityMonitor {
             // TODO: Consider using NeighborEvent#isValid() here; it's more
             // strict but may interact badly if other entries are somehow in
             // NUD_INCOMPLETE (say, during network attach).
-            if (entry.getValue().nudState != StructNdMsg.NUD_FAILED) continue;
+            final NeighborEvent val = entry.getValue();
+
+            // Find all the neighbors that have gone into FAILED state.
+            // Ignore entries for which we have never received an event. If there are neighbors
+            // that never respond to ARP/ND, the kernel will send several FAILED event, then
+            // an INCOMPLETE event, and then more FAILED events. The INCOMPLETE event will
+            // populate the map and the subsequent FAILED event will be processed.
+            if (val == null || val.nudState != StructNdMsg.NUD_FAILED) continue;
 
             ip = entry.getKey();
             for (RouteInfo route : mLinkProperties.getRoutes()) {
@@ -378,10 +385,12 @@ public class IpReachabilityMonitor {
                 Log.d(TAG, "neighbour IPv4(v6): " + entry.getKey() + " neighbour state: "
                         + StructNdMsg.stringForNudState(entry.getValue().nudState));
             }
-            if (entry.getValue().nudState != StructNdMsg.NUD_REACHABLE) return;
+            final NeighborEvent val = entry.getValue();
+            // If an entry is null, consider that probing for that neighbour has completed.
+            if (val == null || val.nudState != StructNdMsg.NUD_REACHABLE) return;
         }
 
-        // All neighbours in the watchlist are in REACHABLE state and connection is stable,
+        // Probing for all neighbours in the watchlist is complete and the connection is stable,
         // restore NUD probe parameters to steadystate value. In the case where neighbours
         // are responsive, this code will run before the wakelock expires.
         setNeighbourParametersForSteadyState();