diff --git a/staticlibs/device/com/android/net/module/util/FdEventsReader.java b/staticlibs/device/com/android/net/module/util/FdEventsReader.java
index 4825992..f88883b 100644
--- a/staticlibs/device/com/android/net/module/util/FdEventsReader.java
+++ b/staticlibs/device/com/android/net/module/util/FdEventsReader.java
@@ -180,6 +180,17 @@
     }
 
     /**
+     * Called by the subclasses of FdEventsReader, decide whether it should stop reading from the
+     * socket or process the packet and continue to read upon receiving a zero-length packet.
+     *
+     * @return {@code true} if this FdEventsReader should process the zero-length packet.
+     *         {@code false} if it should stop reading from the socket.
+     */
+    protected boolean shouldProcessZeroLengthPacket() {
+        return false; // by default, stop reading upon receiving zero-length packet.
+    }
+
+    /**
      * Called by the main loop to log errors.  In some cases |e| may be null.
      */
     protected void logError(@NonNull String msg, @Nullable Exception e) {}
@@ -235,7 +246,7 @@
 
             try {
                 bytesRead = readPacket(mFd, mBuffer);
-                if (bytesRead < 1) {
+                if (bytesRead == 0 && !shouldProcessZeroLengthPacket()) {
                     if (isRunning()) logError("Socket closed, exiting", null);
                     break;
                 }
diff --git a/staticlibs/native/bpf_headers/include/bpf/BpfUtils.h b/staticlibs/native/bpf_headers/include/bpf/BpfUtils.h
index 99c7a91..9dd5822 100644
--- a/staticlibs/native/bpf_headers/include/bpf/BpfUtils.h
+++ b/staticlibs/native/bpf_headers/include/bpf/BpfUtils.h
@@ -28,7 +28,7 @@
 
 #include <log/log.h>
 
-#include "KernelVersion.h"
+#include "KernelUtils.h"
 
 namespace android {
 namespace bpf {
diff --git a/staticlibs/native/bpf_headers/include/bpf/KernelUtils.h b/staticlibs/native/bpf_headers/include/bpf/KernelUtils.h
new file mode 100644
index 0000000..3f82deb
--- /dev/null
+++ b/staticlibs/native/bpf_headers/include/bpf/KernelUtils.h
@@ -0,0 +1,104 @@
+/*
+ * Copyright (C) 2022 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#pragma once
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/personality.h>
+#include <sys/utsname.h>
+
+namespace android {
+namespace bpf {
+
+#define KVER(a, b, c) (((a) << 24) + ((b) << 16) + (c))
+
+static inline unsigned uncachedKernelVersion() {
+    struct utsname buf;
+    if (uname(&buf)) return 0;
+
+    unsigned kver_major = 0;
+    unsigned kver_minor = 0;
+    unsigned kver_sub = 0;
+    (void)sscanf(buf.release, "%u.%u.%u", &kver_major, &kver_minor, &kver_sub);
+    return KVER(kver_major, kver_minor, kver_sub);
+}
+
+static inline unsigned kernelVersion() {
+    static unsigned kver = uncachedKernelVersion();
+    return kver;
+}
+
+static inline __unused bool isAtLeastKernelVersion(unsigned major, unsigned minor, unsigned sub) {
+    return kernelVersion() >= KVER(major, minor, sub);
+}
+
+// Figure out the bitness of userspace.
+// Trivial and known at compile time.
+static constexpr bool isUserspace64bit() {
+    return sizeof(long) == 8;
+}
+
+// Figure out the bitness of the kernel.
+static inline __unused bool isKernel64Bit() {
+    // a 64-bit userspace requires a 64-bit kernel
+    if (isUserspace64bit()) return true;
+
+    static bool init = false;
+    static bool cache = false;
+    if (init) return cache;
+
+    // Retrieve current personality - on Linux this system call *cannot* fail.
+    int p = personality(0xffffffff);
+    // But if it does just assume kernel and userspace (which is 32-bit) match...
+    if (p == -1) return false;
+
+    // This will effectively mask out the bottom 8 bits, and switch to 'native'
+    // personality, and then return the previous personality of this thread
+    // (likely PER_LINUX or PER_LINUX32) with any extra options unmodified.
+    int q = personality((p & ~PER_MASK) | PER_LINUX);
+    // Per man page this theoretically could error out with EINVAL,
+    // but kernel code analysis suggests setting PER_LINUX cannot fail.
+    // Either way, assume kernel and userspace (which is 32-bit) match...
+    if (q != p) return false;
+
+    struct utsname u;
+    (void)uname(&u);  // only possible failure is EFAULT, but u is on stack.
+
+    // Switch back to previous personality.
+    // Theoretically could fail with EINVAL on arm64 with no 32-bit support,
+    // but then we wouldn't have fetched 'p' from the kernel in the first place.
+    // Either way there's nothing meaningful we can do in case of error.
+    // Since PER_LINUX32 vs PER_LINUX only affects uname.machine it doesn't
+    // really hurt us either.  We're really just switching back to be 'clean'.
+    (void)personality(p);
+
+    // Possible values of utsname.machine observed on x86_64 desktop (arm via qemu):
+    //   x86_64 i686 aarch64 armv7l
+    // additionally observed on arm device:
+    //   armv8l
+    // presumably also might just be possible:
+    //   i386 i486 i586
+    // and there might be other weird arm32 cases.
+    // We note that the 64 is present in both 64-bit archs,
+    // and in general is likely to be present in only 64-bit archs.
+    cache = !!strstr(u.machine, "64");
+    init = true;
+    return cache;
+}
+
+}  // namespace bpf
+}  // namespace android
diff --git a/staticlibs/native/bpf_headers/include/bpf/KernelVersion.h b/staticlibs/native/bpf_headers/include/bpf/KernelVersion.h
deleted file mode 100644
index 29a36e6..0000000
--- a/staticlibs/native/bpf_headers/include/bpf/KernelVersion.h
+++ /dev/null
@@ -1,48 +0,0 @@
-/*
- * Copyright (C) 2022 The Android Open Source Project
- *
- * Licensed under the Apache License, Version 2.0 (the "License");
- * you may not use this file except in compliance with the License.
- * You may obtain a copy of the License at
- *
- *      http://www.apache.org/licenses/LICENSE-2.0
- *
- * Unless required by applicable law or agreed to in writing, software
- * distributed under the License is distributed on an "AS IS" BASIS,
- * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
- * See the License for the specific language governing permissions and
- * limitations under the License.
- */
-
-#pragma once
-
-#include <stdio.h>
-#include <sys/utsname.h>
-
-namespace android {
-namespace bpf {
-
-#define KVER(a, b, c) (((a) << 24) + ((b) << 16) + (c))
-
-static inline unsigned uncachedKernelVersion() {
-    struct utsname buf;
-    if (uname(&buf)) return 0;
-
-    unsigned kver_major = 0;
-    unsigned kver_minor = 0;
-    unsigned kver_sub = 0;
-    (void)sscanf(buf.release, "%u.%u.%u", &kver_major, &kver_minor, &kver_sub);
-    return KVER(kver_major, kver_minor, kver_sub);
-}
-
-static inline unsigned kernelVersion() {
-    static unsigned kver = uncachedKernelVersion();
-    return kver;
-}
-
-static inline bool isAtLeastKernelVersion(unsigned major, unsigned minor, unsigned sub) {
-    return kernelVersion() >= KVER(major, minor, sub);
-}
-
-}  // namespace bpf
-}  // namespace android
diff --git a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
index 70c0f89..65c0b72 100644
--- a/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
+++ b/staticlibs/native/bpf_headers/include/bpf/bpf_helpers.h
@@ -99,6 +99,30 @@
 #define KVER(a, b, c) (((a) << 24) + ((b) << 16) + (c))
 #define KVER_INF 0xFFFFFFFFu
 
+/*
+ * BPFFS (ie. /sys/fs/bpf) labelling is as follows:
+ *   subdirectory   selinux context      mainline  usecase / usable by
+ *   /              fs_bpf               no [*]    core operating system (ie. platform)
+ *   /loader        fs_bpf_loader        no, U+    (as yet unused)
+ *   /net_private   fs_bpf_net_private   yes, T+   network_stack
+ *   /net_shared    fs_bpf_net_shared    yes, T+   network_stack & system_server
+ *   /netd_readonly fs_bpf_netd_readonly yes, T+   network_stack & system_server & r/o to netd
+ *   /netd_shared   fs_bpf_netd_shared   yes, T+   network_stack & system_server & netd [**]
+ *   /tethering     fs_bpf_tethering     yes, S+   network_stack
+ *   /vendor        fs_bpf_vendor        no, T+    vendor
+ *
+ * [*] initial support for bpf was added back in P,
+ *     but things worked differently back then with no bpfloader,
+ *     and instead netd doing stuff by hand,
+ *     bpfloader with pinning into /sys/fs/bpf was (I believe) added in Q
+ *     (and was definitely there in R).
+ *
+ * [**] additionally bpf programs are accessible to netutils_wrapper
+ *      for use by iptables xt_bpf extensions.
+ *
+ * See cs/p:aosp-master%20-file:prebuilts/%20file:genfs_contexts%20"genfscon%20bpf"
+ */
+
 /* generic functions */
 
 /*
diff --git a/staticlibs/native/bpfmapjni/com_android_net_module_util_BpfMap.cpp b/staticlibs/native/bpfmapjni/com_android_net_module_util_BpfMap.cpp
index 2146d17..f93d6e1 100644
--- a/staticlibs/native/bpfmapjni/com_android_net_module_util_BpfMap.cpp
+++ b/staticlibs/native/bpfmapjni/com_android_net_module_util_BpfMap.cpp
@@ -25,7 +25,7 @@
 #define BPF_FD_JUST_USE_INT
 #include "BpfSyscallWrappers.h"
 
-#include "bpf/KernelVersion.h"
+#include "bpf/KernelUtils.h"
 
 namespace android {
 
diff --git a/staticlibs/native/tcutils/tcutils.cpp b/staticlibs/native/tcutils/tcutils.cpp
index 37a7ec8..c82390f 100644
--- a/staticlibs/native/tcutils/tcutils.cpp
+++ b/staticlibs/native/tcutils/tcutils.cpp
@@ -19,7 +19,7 @@
 #include "tcutils/tcutils.h"
 
 #include "logging.h"
-#include "bpf/KernelVersion.h"
+#include "bpf/KernelUtils.h"
 #include "scopeguard.h"
 
 #include <arpa/inet.h>
diff --git a/staticlibs/native/tcutils/tests/tcutils_test.cpp b/staticlibs/native/tcutils/tests/tcutils_test.cpp
index 53835d7..7732247 100644
--- a/staticlibs/native/tcutils/tests/tcutils_test.cpp
+++ b/staticlibs/native/tcutils/tests/tcutils_test.cpp
@@ -18,7 +18,7 @@
 
 #include <gtest/gtest.h>
 
-#include "bpf/KernelVersion.h"
+#include "bpf/KernelUtils.h"
 #include <tcutils/tcutils.h>
 
 #include <BpfSyscallWrappers.h>