diff --git a/quic/qbone/platform/internet_checksum.cc b/quic/qbone/platform/internet_checksum.cc
new file mode 100644
index 0000000..9cbe227
--- /dev/null
+++ b/quic/qbone/platform/internet_checksum.cc
@@ -0,0 +1,32 @@
+// Copyright (c) 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/third_party/quiche/src/quic/qbone/platform/internet_checksum.h"
+#include "net/third_party/quiche/src/quic/platform/api/quic_endian.h"
+
+namespace quic {
+
+void InternetChecksum::Update(const char* data, size_t size) {
+  const char* current;
+  for (current = data; current + 1 < data + size; current += 2) {
+    accumulator_ += *reinterpret_cast<const uint16_t*>(current);
+  }
+  if (current < data + size) {
+    accumulator_ += *reinterpret_cast<const uint8_t*>(current);
+  }
+}
+
+void InternetChecksum::Update(const uint8_t* data, size_t size) {
+  Update(reinterpret_cast<const char*>(data), size);
+}
+
+uint16_t InternetChecksum::Value() const {
+  uint32_t total = accumulator_;
+  while (total & 0xffff0000u) {
+    total = (total >> 16u) + (total & 0xffffu);
+  }
+  return ~static_cast<uint16_t>(total);
+}
+
+}  // namespace quic