Dump underlying BPF traffic stats as well as higher-level stats.

This provides a better way to tell whether traffic is flowing.

Test: manual
Bug: 190783768
Original-Change: https://android-review.googlesource.com/1737393
Merged-In: If557b0a18fc0aea1bf6a65d91547fc1930098ed0
Change-Id: If557b0a18fc0aea1bf6a65d91547fc1930098ed0
diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index 8adcbd9..0ce8898 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -773,6 +773,12 @@
         }
         pw.decreaseIndent();
 
+        pw.println("BPF stats:");
+        pw.increaseIndent();
+        dumpBpfStats(pw);
+        pw.decreaseIndent();
+        pw.println();
+
         pw.println("Forwarding rules:");
         pw.increaseIndent();
         dumpIpv6UpstreamRules(pw);
@@ -800,6 +806,22 @@
                     upstreamIfindex), stats.toString()));
         }
     }
+    private void dumpBpfStats(@NonNull IndentingPrintWriter pw) {
+        try (BpfMap<TetherStatsKey, TetherStatsValue> map = mDeps.getBpfStatsMap()) {
+            if (map == null) {
+                pw.println("No BPF stats map");
+                return;
+            }
+            if (map.isEmpty()) {
+                pw.println("<empty>");
+            }
+            map.forEach((k, v) -> {
+                pw.println(String.format("%s: %s", k, v));
+            });
+        } catch (ErrnoException e) {
+            pw.println("Error dumping BPF stats map: " + e);
+        }
+    }
 
     private void dumpIpv6ForwardingRules(@NonNull IndentingPrintWriter pw) {
         if (mIpv6ForwardingRules.size() == 0) {