diff --git a/automotive/can/1.0/tools/libprotocan/Android.bp b/automotive/can/1.0/tools/libprotocan/Android.bp
new file mode 100644
index 0000000..76c238b
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/Android.bp
@@ -0,0 +1,42 @@
+//
+// Copyright (C) 2020 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.
+//
+
+package {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "hardware_interfaces_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["hardware_interfaces_license"],
+}
+
+cc_library_static {
+    name: "libprotocan",
+    defaults: ["android.hardware.automotive.vehicle@2.0-protocan-defaults"],
+    vendor: true,
+    srcs: [
+        "Checksum.cpp",
+        "MessageCounter.cpp",
+        "MessageDef.cpp",
+        "MessageInjector.cpp",
+        "Signal.cpp",
+    ],
+    export_include_dirs: ["include"],
+
+    shared_libs: [
+        "android.hardware.automotive.can@1.0",
+    ],
+}
diff --git a/automotive/can/1.0/tools/libprotocan/Checksum.cpp b/automotive/can/1.0/tools/libprotocan/Checksum.cpp
new file mode 100644
index 0000000..72fb0af
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/Checksum.cpp
@@ -0,0 +1,28 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/Checksum.h>
+
+namespace android::hardware::automotive::protocan {
+
+Checksum::Checksum(Signal signal, formula f) : mSignal(signal), mFormula(f) {}
+
+void Checksum::update(can::V1_0::CanMessage& msg) const {
+  mSignal.set(msg, 0);
+  mSignal.set(msg, mFormula(msg) % (mSignal.maxValue + 1));
+}
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/MessageCounter.cpp b/automotive/can/1.0/tools/libprotocan/MessageCounter.cpp
new file mode 100644
index 0000000..ef9882f
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/MessageCounter.cpp
@@ -0,0 +1,61 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/MessageCounter.h>
+
+#include <android-base/logging.h>
+
+namespace android::hardware::automotive::protocan {
+
+/** Whether to log counter state messages. */
+static constexpr bool kSuperVerbose = false;
+
+MessageCounter::MessageCounter(Signal signal) : upperBound(signal.maxValue + 1), mSignal(signal) {}
+
+Signal::value MessageCounter::next() const {
+  CHECK(mCurrent.has_value()) << "Counter not initialized. Did you call isReady?";
+  return (*mCurrent + 1) % upperBound;
+}
+
+void MessageCounter::read(const can::V1_0::CanMessage& msg) {
+    auto val = mSignal.get(msg);
+
+    if (!mCurrent.has_value()) {
+        LOG(VERBOSE) << "Got first counter val of " << val;
+        mCurrent = val;
+        return;
+    }
+
+    auto nextVal = next();
+    if (nextVal == val) {
+        if constexpr (kSuperVerbose) {
+            LOG(VERBOSE) << "Got next counter val of " << nextVal;
+        }
+        mCurrent = nextVal;
+    } else {
+        LOG(DEBUG) << "Ignoring next counter val of " << val << ", waiting for " << nextVal;
+    }
+}
+
+bool MessageCounter::isReady() const { return mCurrent.has_value(); }
+
+void MessageCounter::increment(can::V1_0::CanMessage& msg) {
+  auto newVal = next();
+  mCurrent = newVal;
+  mSignal.set(msg, newVal);
+}
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/MessageDef.cpp b/automotive/can/1.0/tools/libprotocan/MessageDef.cpp
new file mode 100644
index 0000000..23ce1df
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/MessageDef.cpp
@@ -0,0 +1,62 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/MessageDef.h>
+
+#include <android-base/logging.h>
+
+namespace android::hardware::automotive::protocan {
+
+using can::V1_0::CanMessage;
+using can::V1_0::CanMessageId;
+
+MessageDef::MessageDef(CanMessageId id, uint16_t len, std::map<std::string, Signal> signals,
+                       std::optional<Signal> counter, std::optional<Checksum> checksum)
+    : id(id), kLen(len), kSignals(std::move(signals)), kCounter(counter), kChecksum(checksum) {}
+
+const Signal& MessageDef::operator[](const std::string& signalName) const {
+  auto it = kSignals.find(signalName);
+  CHECK(it != kSignals.end()) << "Signal " << signalName << " doesn't exist";
+  return it->second;
+}
+
+CanMessage MessageDef::makeDefault() const {
+  CanMessage msg = {};
+  msg.id = id;
+  msg.payload.resize(kLen);
+
+  for (auto const& [name, signal] : kSignals) {
+    signal.setDefault(msg);
+  }
+
+  return msg;
+}
+
+MessageCounter MessageDef::makeCounter() const {
+  CHECK(kCounter.has_value()) << "Can't build a counter for message without such signal";
+  return MessageCounter(*kCounter);
+}
+
+void MessageDef::updateChecksum(can::V1_0::CanMessage& msg) const {
+  if (!kChecksum.has_value()) return;
+  kChecksum->update(msg);
+}
+
+bool MessageDef::validate(const can::V1_0::CanMessage& msg) const {
+    return msg.payload.size() >= kLen;
+}
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/MessageInjector.cpp b/automotive/can/1.0/tools/libprotocan/MessageInjector.cpp
new file mode 100644
index 0000000..7c45eaa
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/MessageInjector.cpp
@@ -0,0 +1,110 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/MessageInjector.h>
+
+#include <android-base/logging.h>
+
+#include <thread>
+
+namespace android::hardware::automotive::protocan {
+
+/** Whether to log injected messages. */
+static constexpr bool kSuperVerbose = true;
+
+using namespace std::literals::chrono_literals;
+
+using can::V1_0::CanMessage;
+using can::V1_0::CanMessageId;
+using can::V1_0::ICanBus;
+using can::V1_0::Result;
+
+MessageInjector::MessageInjector(MessageDef msgDef,
+                                 std::optional<std::chrono::milliseconds> interMessageDelay)
+    : kMsgDef(std::move(msgDef)),
+      kInterMessageDelay(interMessageDelay),
+      mCounter(msgDef.makeCounter()) {}
+
+void MessageInjector::inject(const CanMessage& msg) { inject({msg}); }
+
+void MessageInjector::inject(const std::initializer_list<can::V1_0::CanMessage> msgs) {
+  std::lock_guard<std::mutex> lock(mMessagesGuard);
+  for (const auto& msg : msgs) {
+    if constexpr (kSuperVerbose) {
+      LOG(VERBOSE) << "Message scheduled for injection: " << toString(msg);
+    }
+
+    mMessages.push(msg);
+  }
+}
+
+void MessageInjector::processQueueLocked(can::V1_0::ICanBus& bus) {
+  if (mMessages.empty() || !mCounter.isReady()) return;
+
+  auto paddingMessagesCount = mCounter.upperBound - (mMessages.size() % mCounter.upperBound);
+  auto padMessage = kMsgDef.makeDefault();
+  for (unsigned i = 0; i < paddingMessagesCount; i++) {
+    mMessages.push(padMessage);
+  }
+
+  while (!mMessages.empty()) {
+    auto&& outMsg = mMessages.front();
+
+    mCounter.increment(outMsg);
+    kMsgDef.updateChecksum(outMsg);
+
+    if constexpr (kSuperVerbose) {
+      LOG(VERBOSE) << "Injecting message: " << toString(outMsg);
+    }
+    auto result = bus.send(outMsg);
+    if (result != Result::OK) {
+      LOG(ERROR) << "Message injection failed: " << toString(result);
+    }
+
+    mMessages.pop();
+
+    // This would block onReceive, but the class is not supposed to be used in production anyway
+    // (see MessageInjector docstring).
+    if (kInterMessageDelay.has_value()) {
+      std::this_thread::sleep_for(*kInterMessageDelay);
+    }
+  }
+}
+
+void MessageInjector::onReceive(ICanBus& bus, const CanMessage& msg) {
+    if (!kMsgDef.validate(msg)) return;
+
+    std::lock_guard<std::mutex> lock(mMessagesGuard);
+
+    mCounter.read(msg);
+    processQueueLocked(bus);
+}
+
+MessageInjectorManager::MessageInjectorManager(
+    std::initializer_list<std::shared_ptr<MessageInjector>> injectors) {
+  std::transform(injectors.begin(), injectors.end(), std::inserter(mInjectors, mInjectors.end()),
+                 [](const std::shared_ptr<MessageInjector>& injector) {
+                   return std::make_pair(injector->kMsgDef.id, std::move(injector));
+                 });
+}
+
+void MessageInjectorManager::onReceive(sp<ICanBus> bus, const CanMessage& msg) {
+  auto it = mInjectors.find(msg.id);
+  if (it == mInjectors.end()) return;
+  it->second->onReceive(*bus, msg);
+}
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/Signal.cpp b/automotive/can/1.0/tools/libprotocan/Signal.cpp
new file mode 100644
index 0000000..bc3e070
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/Signal.cpp
@@ -0,0 +1,84 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/Signal.h>
+
+#include <android-base/logging.h>
+
+namespace android::hardware::automotive::protocan {
+
+static uint8_t calculateLastByteMask(uint16_t start, uint8_t length) {
+  unsigned lastByteBits = (start + length) % 8;
+  unsigned lastBytePadding = (8 - lastByteBits) % 8;
+  return 0xFF >> lastBytePadding;
+}
+
+static uint8_t calculateFirstByteMask(uint16_t firstByte, uint8_t firstBit, uint16_t lastByte,
+                                      uint8_t lastMask) {
+  uint8_t firstMask = 0xFF << firstBit;
+  if (firstByte == lastByte) firstMask &= lastMask;
+  return firstMask;
+}
+
+Signal::Signal(uint16_t start, uint8_t length, value defVal)
+    : maxValue((1u << length) - 1),
+      kFirstByte(start / 8),
+      kFirstBit(start % 8),
+      kFirstByteBits(8 - kFirstBit),
+      kLastByte((start + length - 1) / 8),
+      kLastMask(calculateLastByteMask(start, length)),
+      kFirstMask(calculateFirstByteMask(kFirstByte, kFirstBit, kLastByte, kLastMask)),
+      kDefVal(defVal) {
+  CHECK(length > 0) << "Signal length must not be zero";
+}
+
+Signal::value Signal::get(const can::V1_0::CanMessage& msg) const {
+    CHECK(msg.payload.size() > kLastByte)
+            << "Message is too short. Did you call MessageDef::validate?";
+
+    Signal::value v = 0;
+    if (kLastByte != kFirstByte) v = kLastMask & msg.payload[kLastByte];
+
+    for (int i = kLastByte - 1; i > kFirstByte; i--) {
+        v = (v << 8) | msg.payload[i];
+    }
+
+    return (v << kFirstByteBits) | ((msg.payload[kFirstByte] & kFirstMask) >> kFirstBit);
+}
+
+void Signal::set(can::V1_0::CanMessage& msg, Signal::value val) const {
+  CHECK(msg.payload.size() > kLastByte)
+      << "Signal requires message of length " << (kLastByte + 1)
+      << " which is beyond message length of " << msg.payload.size();
+
+  uint8_t firstByte = val << kFirstBit;
+  val >>= kFirstByteBits;
+
+  msg.payload[kFirstByte] = (msg.payload[kFirstByte] & ~kFirstMask) | (firstByte & kFirstMask);
+
+  for (int i = kFirstByte + 1; i < kLastByte; i++) {
+    msg.payload[i] = val & 0xFF;
+    val >>= 8;
+  }
+
+  if (kLastByte != kFirstByte) {
+    msg.payload[kLastByte] = (msg.payload[kLastByte] & ~kLastMask) | (val & kLastMask);
+  }
+}
+
+void Signal::setDefault(can::V1_0::CanMessage& msg) const { set(msg, kDefVal); }
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/include/libprotocan/Checksum.h b/automotive/can/1.0/tools/libprotocan/include/libprotocan/Checksum.h
new file mode 100644
index 0000000..ff1dc91
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/include/libprotocan/Checksum.h
@@ -0,0 +1,37 @@
+/*
+ * Copyright (C) 2020 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 <android/hardware/automotive/can/1.0/types.h>
+#include <libprotocan/Signal.h>
+
+namespace android::hardware::automotive::protocan {
+
+class Checksum {
+ public:
+  using formula = std::function<Signal::value(const can::V1_0::CanMessage&)>;
+
+  Checksum(Signal signal, formula f);
+
+  void update(can::V1_0::CanMessage& msg) const;
+
+ private:
+  const Signal mSignal;
+  const formula mFormula;
+};
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageCounter.h b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageCounter.h
new file mode 100644
index 0000000..56113be
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageCounter.h
@@ -0,0 +1,55 @@
+/*
+ * Copyright (C) 2020 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 <android/hardware/automotive/can/1.0/types.h>
+#include <libprotocan/Signal.h>
+
+namespace android::hardware::automotive::protocan {
+
+class MessageCounter {
+ public:
+  const Signal::value upperBound;
+
+  MessageCounter(Signal signal);
+
+  /**
+   * Parse CAN message sent by external ECU to determine current counter value.
+   */
+  void read(const can::V1_0::CanMessage& msg);
+
+  /**
+   * States whether current counter value is determined.
+   */
+  bool isReady() const;
+
+  /**
+   * Increment current counter value and set it in a new message.
+   *
+   * Caller must check isReady() at least once before calling this method.
+   */
+  void increment(can::V1_0::CanMessage& msg);
+
+ private:
+  const Signal mSignal;
+
+  std::optional<Signal::value> mCurrent = std::nullopt;
+
+  Signal::value next() const;
+};
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageDef.h b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageDef.h
new file mode 100644
index 0000000..79b21e1
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageDef.h
@@ -0,0 +1,69 @@
+/*
+ * Copyright (C) 2020 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 <android/hardware/automotive/can/1.0/types.h>
+#include <libprotocan/Checksum.h>
+#include <libprotocan/MessageCounter.h>
+#include <libprotocan/Signal.h>
+
+namespace android::hardware::automotive::protocan {
+
+/**
+ * CAN message definition (not the actual message data).
+ *
+ * Describes static message properties (message ID, signals etc).
+ */
+class MessageDef {
+ public:
+  const can::V1_0::CanMessageId id;
+
+  /**
+   * Create message definition.
+   *
+   * Currently only constant length messages are supported.
+   *
+   * \param id CAN message ID
+   * \param len CAN message length
+   * \param signals CAN signal definitions
+   * \param counter Designated CAN signal definition for message counter, if the message has one
+   * \param checksum Designated CAN signal definition for payload checksum, if the message has one
+   */
+  MessageDef(can::V1_0::CanMessageId id, uint16_t len, std::map<std::string, Signal> signals,
+             std::optional<Signal> counter = std::nullopt,
+             std::optional<Checksum> checksum = std::nullopt);
+
+  const Signal& operator[](const std::string& signalName) const;
+
+  can::V1_0::CanMessage makeDefault() const;
+  MessageCounter makeCounter() const;
+
+  void updateChecksum(can::V1_0::CanMessage& msg) const;
+
+  /**
+   * Validate the message payload is large enough to hold all the signals.
+   */
+  bool validate(const can::V1_0::CanMessage& msg) const;
+
+private:
+  const uint16_t kLen;
+  const std::map<std::string, Signal> kSignals;
+  const std::optional<Signal> kCounter;
+  const std::optional<Checksum> kChecksum;
+};
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageInjector.h b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageInjector.h
new file mode 100644
index 0000000..b0ea260
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/include/libprotocan/MessageInjector.h
@@ -0,0 +1,78 @@
+/*
+ * Copyright (C) 2020 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 <android-base/macros.h>
+#include <android/hardware/automotive/can/1.0/ICanBus.h>
+#include <libprotocan/MessageCounter.h>
+#include <libprotocan/MessageDef.h>
+#include <utils/Mutex.h>
+
+#include <queue>
+
+namespace android::hardware::automotive::protocan {
+
+class MessageInjectorManager;
+
+/**
+ * Injects CAN messages with a counter to an existing system.
+ *
+ * This class is NOT meant to use in production - there should be no need to inject counted CAN
+ * messages where the other sender is also broadcasting them. If this is the case, it may be a sign
+ * your CAN network needs a redesign. This tool is intended for use for testing and demo purposes.
+ */
+class MessageInjector {
+ public:
+  MessageInjector(MessageDef msgDef, std::optional<std::chrono::milliseconds> interMessageDelay);
+
+  void inject(const can::V1_0::CanMessage& msg);
+  void inject(const std::initializer_list<can::V1_0::CanMessage> msgs);
+
+ private:
+  const MessageDef kMsgDef;
+  const std::optional<std::chrono::milliseconds> kInterMessageDelay;
+  MessageCounter mCounter;
+
+  mutable std::mutex mMessagesGuard;
+  std::queue<can::V1_0::CanMessage> mMessages GUARDED_BY(mMessagesGuard);
+
+  void onReceive(can::V1_0::ICanBus& bus, const can::V1_0::CanMessage& msg);
+  void processQueueLocked(can::V1_0::ICanBus& bus);
+
+  friend class MessageInjectorManager;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageInjector);
+};
+
+/**
+ * Routes intercepted messages to MessageInjector instances configured to handle specific CAN
+ * message (CAN message ID). Intercepted messages from other nodes in CAN network are used to read
+ * current counter value in order to spoof the next packet.
+ */
+class MessageInjectorManager {
+ public:
+  MessageInjectorManager(std::initializer_list<std::shared_ptr<MessageInjector>> injectors);
+
+  void onReceive(sp<can::V1_0::ICanBus> bus, const can::V1_0::CanMessage& msg);
+
+ private:
+  std::map<can::V1_0::CanMessageId, std::shared_ptr<MessageInjector>> mInjectors;
+
+  DISALLOW_COPY_AND_ASSIGN(MessageInjectorManager);
+};
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/include/libprotocan/Signal.h b/automotive/can/1.0/tools/libprotocan/include/libprotocan/Signal.h
new file mode 100644
index 0000000..7c0f119
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/include/libprotocan/Signal.h
@@ -0,0 +1,50 @@
+/*
+ * Copyright (C) 2020 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 <android-base/macros.h>
+#include <android/hardware/automotive/can/1.0/types.h>
+
+namespace android::hardware::automotive::protocan {
+
+/**
+ * TODO(twasilczyk): right now, only Little Endian signals are supported.
+ */
+class Signal {
+ public:
+  using value = uint64_t;
+
+  const value maxValue;
+
+  Signal(uint16_t start, uint8_t length, value defVal = 0);
+
+  value get(const can::V1_0::CanMessage& msg) const;
+  void set(can::V1_0::CanMessage& msg, value val) const;
+  void setDefault(can::V1_0::CanMessage& msg) const;
+
+ private:
+  const uint16_t kFirstByte;     ///< Index of first byte that holds the signal
+  const uint8_t kFirstBit;       ///< Index of first bit within first byte
+  const uint8_t kFirstByteBits;  ///< How many bits of the first byte belong to the signal
+  const uint16_t kLastByte;      ///< Index of last byte that holds the signal
+  const uint8_t kLastMask;       ///< Bits of the last byte that belong to the signal
+  const uint8_t kFirstMask;      ///< Bits of the first byte that belong to the signal
+
+  const value kDefVal;
+};
+
+}  // namespace android::hardware::automotive::protocan
diff --git a/automotive/can/1.0/tools/libprotocan/tests/Android.bp b/automotive/can/1.0/tools/libprotocan/tests/Android.bp
new file mode 100644
index 0000000..251cc06
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/tests/Android.bp
@@ -0,0 +1,39 @@
+//
+// Copyright (C) 2020 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.
+//
+
+package {
+    // See: http://go/android-license-faq
+    // A large-scale-change added 'default_applicable_licenses' to import
+    // all of the 'license_kinds' from "hardware_interfaces_license"
+    // to get the below license kinds:
+    //   SPDX-license-identifier-Apache-2.0
+    default_applicable_licenses: ["hardware_interfaces_license"],
+}
+
+cc_test {
+    name: "libprotocan_signal_test",
+    defaults: ["android.hardware.automotive.can@defaults"],
+    vendor: true,
+    gtest: true,
+    srcs: ["libprotocan_signal_test.cpp"],
+    static_libs: [
+        "libprotocan",
+    ],
+    shared_libs: [
+        "android.hardware.automotive.can@1.0",
+        "libhidlbase",
+    ],
+}
diff --git a/automotive/can/1.0/tools/libprotocan/tests/libprotocan_signal_test.cpp b/automotive/can/1.0/tools/libprotocan/tests/libprotocan_signal_test.cpp
new file mode 100644
index 0000000..19c1209
--- /dev/null
+++ b/automotive/can/1.0/tools/libprotocan/tests/libprotocan_signal_test.cpp
@@ -0,0 +1,218 @@
+/*
+ * Copyright (C) 2020 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.
+ */
+
+#include <libprotocan/Signal.h>
+
+#include <gtest/gtest.h>
+
+namespace android::hardware::automotive::protocan::unittest {
+
+TEST(SignalTest, TestGetSingleBytes) {
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+  for (unsigned i = 0; i < msg.payload.size(); i++) {
+    Signal signal(8 * i, 8);
+    ASSERT_EQ(i, signal.get(msg));
+  }
+}
+
+TEST(SignalTest, TestSetSingleBytes) {
+  std::vector<can::V1_0::CanMessage> msgs = {{}, {}, {}};
+  msgs[0].payload = {0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF, 0xFF};
+  msgs[1].payload = {0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB, 0xAB};
+  msgs[2].payload = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
+  for (unsigned i = 0; i < msgs[0].payload.size(); i++) {
+    Signal signal(8 * i, 8);
+
+    for (auto&& msgOriginal : msgs) {
+      auto msgModified = msgOriginal;
+      signal.set(msgModified, 0xBA);
+
+      auto msgExpected = msgOriginal;
+      msgExpected.payload[i] = 0xBA;
+
+      ASSERT_EQ(msgExpected, msgModified) << "i=" << i;
+    }
+  }
+}
+
+TEST(SignalTest, TestGetStart4) {
+  /* Data generated with Python3:
+   *
+   * from cantools.database.can import *
+   * hex(Message(1, 'm', 4, [Signal('s', 4, 16, byte_order='little_endian')]).
+   *     decode(b'\xde\xad\xbe\xef')['s'])
+   */
+
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0xDE, 0xAD, 0xBE, 0xEF};
+  can::V1_0::CanMessage msg2 = {};
+  msg2.payload = {0xDE, 0xAD, 0xBE, 0xEF, 0xDE, 0xAD};
+
+  Signal s0_4(0, 4);
+  Signal s4_4(4, 4);
+  Signal s4_8(4, 8);
+  Signal s4_16(4, 16);
+  Signal s4_28(4, 28);
+  Signal s12_8(12, 8);
+  Signal s12_12(12, 12);
+  Signal s12_16(12, 16);
+  Signal s12_20(12, 20);
+  Signal s12_32(12, 32);
+
+  ASSERT_EQ(0xEu, s0_4.get(msg));
+  ASSERT_EQ(0xDu, s4_4.get(msg));
+  ASSERT_EQ(0xDDu, s4_8.get(msg));
+  ASSERT_EQ(0xEADDu, s4_16.get(msg));
+  ASSERT_EQ(0xEFBEADDu, s4_28.get(msg));
+  ASSERT_EQ(0xEAu, s12_8.get(msg));
+  ASSERT_EQ(0xBEAu, s12_12.get(msg));
+  ASSERT_EQ(0xFBEAu, s12_16.get(msg));
+  ASSERT_EQ(0xEFBEAu, s12_20.get(msg));
+  ASSERT_EQ(0xDDEEFBEAu, s12_32.get(msg2));
+}
+
+TEST(SignalTest, TestGet64) {
+  /* Data generated with Python3:
+   *
+   * from cantools.database.can import *
+   * hex(Message(1, 'm', 9, [Signal('s', 4, 64, byte_order='little_endian')]).
+   *     decode(b'\xde\xad\xbe\xef\xab\xbc\xcd\xde\xef')['s'])
+   */
+
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0xDE, 0xAD, 0xBE, 0xEF, 0xAB, 0xBC, 0xCD, 0xDE, 0xEF};
+
+  Signal s0_64(0, 64);
+  Signal s8_64(8, 64);
+  Signal s4_64(4, 64);
+  Signal s1_64(1, 64);
+
+  ASSERT_EQ(0xDECDBCABEFBEADDEu, s0_64.get(msg));
+  ASSERT_EQ(0xEFDECDBCABEFBEADu, s8_64.get(msg));
+  ASSERT_EQ(0xFDECDBCABEFBEADDu, s4_64.get(msg));
+  ASSERT_EQ(0xEF66DE55F7DF56EFu, s1_64.get(msg));
+}
+
+TEST(SignalTest, TestGetAllStarts) {
+  /* Data generated with Python3:
+   *
+   * from cantools.database.can import *
+   * hex(Message(1, 'm', 6, [Signal('s', 0, 20, byte_order='little_endian')]).
+   *     decode(b'\xde\xad\xbe\xef\xde\xad')['s'])
+   */
+
+  std::map<int, Signal::value> shifts = {
+      {0, 0xEADDEu}, {1, 0xF56EFu}, {2, 0xFAB77u}, {3, 0x7D5BBu}, {4, 0xBEADDu},  {5, 0xDF56Eu},
+      {6, 0xEFAB7u}, {7, 0xF7D5Bu}, {8, 0xFBEADu}, {9, 0x7DF56u}, {10, 0xBEFABu}, {11, 0xDF7D5u},
+  };
+
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0xDE, 0xAD, 0xBE, 0xEF, 0xCC, 0xCC};
+
+  for (auto const& [start, expected] : shifts) {
+    Signal s(start, 20);
+    ASSERT_EQ(expected, s.get(msg)) << "shift of " << start << " failed";
+  }
+}
+
+TEST(SignalTest, TestSetStart4) {
+  /* Data generated with Python3:
+   *
+   * from cantools.database.can import *
+   * so=4 ; sl=8
+   * md = Message(1, 'm', 4, [Signal('a1', 0, so), Signal('a2', so+sl, 32-so-sl),
+   *     Signal('s', so, sl, byte_order='little_endian')])
+   * m = md.decode(b'\xcc\xcc\xcc\xcc')
+   * m['s'] = 0xDE
+   * binascii.hexlify(md.encode(m)).upper()
+   */
+  typedef struct {
+    int start;
+    int length;
+    Signal::value setValue;
+    hidl_vec<uint8_t> payload;
+  } case_t;
+
+  std::vector<case_t> cases = {
+      {0, 4, 0xDu, {0xCD, 0xCC, 0xCC, 0xCC}},       {4, 4, 0xDu, {0xDC, 0xCC, 0xCC, 0xCC}},
+      {4, 8, 0xDEu, {0xEC, 0xCD, 0xCC, 0xCC}},      {4, 16, 0xDEADu, {0xDC, 0xEA, 0xCD, 0xCC}},
+      {4, 24, 0xDEADBEu, {0xEC, 0xDB, 0xEA, 0xCD}}, {4, 28, 0xDEADBEEu, {0xEC, 0xBE, 0xAD, 0xDE}},
+      {12, 8, 0xDEu, {0xCC, 0xEC, 0xCD, 0xCC}},     {12, 12, 0xDEAu, {0xCC, 0xAC, 0xDE, 0xCC}},
+      {12, 16, 0xDEADu, {0xCC, 0xDC, 0xEA, 0xCD}},  {12, 20, 0xDEADBu, {0xCC, 0xBC, 0xAD, 0xDE}},
+  };
+
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0xCC, 0xCC, 0xCC, 0xCC};
+
+  for (auto const& tcase : cases) {
+    Signal s(tcase.start, tcase.length);
+
+    can::V1_0::CanMessage expectedMsg = {};
+    expectedMsg.payload = tcase.payload;
+
+    can::V1_0::CanMessage editedMsg = msg;
+    s.set(editedMsg, tcase.setValue);
+
+    ASSERT_EQ(expectedMsg, editedMsg) << " set(" << tcase.start << ", " << tcase.length << ")";
+  }
+}
+
+TEST(SignalTest, TestSetAllStarts) {
+  /* Data generated with Python3:
+   * from cantools.database.can import *
+   * import binascii
+   * import textwrap
+   *
+   * length = 20
+   * for start in range(0, 32 - length):
+   *     signals = [Signal('s', start, length, byte_order='little_endian')]
+   *     if start > 0: signals.append(Signal('a', 0, start, byte_order='little_endian'))
+   *     signals.append(Signal('b', start + length, 32 - start - length,
+   *         byte_order='little_endian'))
+   *
+   *     md = Message(1, 'm', 4, signals)
+   *     m = md.decode(b'\xcc\xcc\xcc\xcc')
+   *     m['s'] = 0xDEADB
+   *     out = binascii.hexlify(md.encode(m)).decode('ascii').upper()
+   *     out = ', '.join(['0x{}'.format(v) for v in textwrap.wrap(out, 2)])
+   *     print('{{ {:d}, {{ {:s} }}}},'.format(start, out))
+   */
+
+  std::map<int, hidl_vec<uint8_t>> shifts = {
+      {0, {0xDB, 0xEA, 0xCD, 0xCC}}, {1, {0xB6, 0xD5, 0xDB, 0xCC}},  {2, {0x6C, 0xAB, 0xF7, 0xCC}},
+      {3, {0xDC, 0x56, 0xEF, 0xCC}}, {4, {0xBC, 0xAD, 0xDE, 0xCC}},  {5, {0x6C, 0x5B, 0xBD, 0xCD}},
+      {6, {0xCC, 0xB6, 0x7A, 0xCF}}, {7, {0xCC, 0x6D, 0xF5, 0xCE}},  {8, {0xCC, 0xDB, 0xEA, 0xCD}},
+      {9, {0xCC, 0xB6, 0xD5, 0xDB}}, {10, {0xCC, 0x6C, 0xAB, 0xF7}}, {11, {0xCC, 0xDC, 0x56, 0xEF}},
+  };
+
+  can::V1_0::CanMessage msg = {};
+  msg.payload = {0xCC, 0xCC, 0xCC, 0xCC};
+
+  for (auto const& [start, expectedPayload] : shifts) {
+    Signal s(start, 20);
+
+    can::V1_0::CanMessage expectedMsg = {};
+    expectedMsg.payload = expectedPayload;
+
+    can::V1_0::CanMessage editedMsg = msg;
+    s.set(editedMsg, 0xDEADB);
+
+    ASSERT_EQ(expectedMsg, editedMsg) << "shift of " << start << " failed";
+  }
+}
+
+}  // namespace android::hardware::automotive::protocan::unittest