diff --git a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
index 40956f7..6550de2 100644
--- a/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
+++ b/Tethering/src/com/android/networkstack/tethering/BpfCoordinator.java
@@ -52,6 +52,7 @@
 import android.system.OsConstants;
 import android.text.TextUtils;
 import android.util.ArraySet;
+import android.util.Base64;
 import android.util.Log;
 import android.util.SparseArray;
 
@@ -118,6 +119,9 @@
     private static final String TETHER_ERROR_MAP_PATH = makeMapPath("error");
     private static final String TETHER_DEV_MAP_PATH = makeMapPath("dev");
 
+    // Using "," as a separator is safe because base64 characters are [0-9a-zA-Z/=+].
+    private static final String DUMP_BASE64_DELIMITER = ",";
+
     /** The names of all the BPF counters defined in bpf_tethering.h. */
     public static final String[] sBpfCounterNames = getBpfCounterNames();
 
@@ -1068,6 +1072,42 @@
         }
     }
 
+    private String ipv4RuleToBase64String(Tether4Key key, Tether4Value value) {
+        final byte[] keyBytes = key.writeToBytes();
+        final String keyBase64Str = Base64.encodeToString(keyBytes, Base64.DEFAULT)
+                .replace("\n", "");
+        final byte[] valueBytes = value.writeToBytes();
+        final String valueBase64Str = Base64.encodeToString(valueBytes, Base64.DEFAULT)
+                .replace("\n", "");
+
+        return keyBase64Str + DUMP_BASE64_DELIMITER + valueBase64Str;
+    }
+
+    private void dumpRawIpv4ForwardingRuleMap(
+            BpfMap<Tether4Key, Tether4Value> map, IndentingPrintWriter pw) throws ErrnoException {
+        if (map == null) {
+            pw.println("No IPv4 support");
+            return;
+        }
+        if (map.isEmpty()) {
+            pw.println("No rules");
+            return;
+        }
+        map.forEach((k, v) -> pw.println(ipv4RuleToBase64String(k, v)));
+    }
+
+    /**
+     * Dump raw BPF map in base64 encoded strings. For test only.
+     */
+    public void dumpRawMap(@NonNull IndentingPrintWriter pw) {
+        try (BpfMap<Tether4Key, Tether4Value> upstreamMap = mDeps.getBpfUpstream4Map()) {
+            // TODO: dump downstream map.
+            dumpRawIpv4ForwardingRuleMap(upstreamMap, pw);
+        } catch (ErrnoException e) {
+            pw.println("Error dumping IPv4 map: " + e);
+        }
+    }
+
     private String l4protoToString(int proto) {
         if (proto == OsConstants.IPPROTO_TCP) {
             return "tcp";
diff --git a/Tethering/src/com/android/networkstack/tethering/Tethering.java b/Tethering/src/com/android/networkstack/tethering/Tethering.java
index db9a64f..301a682 100644
--- a/Tethering/src/com/android/networkstack/tethering/Tethering.java
+++ b/Tethering/src/com/android/networkstack/tethering/Tethering.java
@@ -2479,6 +2479,13 @@
         @SuppressWarnings("resource") final IndentingPrintWriter pw = new IndentingPrintWriter(
                 writer, "  ");
 
+        // Used for testing instead of human debug.
+        // TODO: add options to choose which map to dump.
+        if (argsContain(args, "bpfRawMap")) {
+            mBpfCoordinator.dumpRawMap(pw);
+            return;
+        }
+
         if (argsContain(args, "bpf")) {
             dumpBpf(pw);
             return;