[CrOS PhoneHub] Fix MessageType endianness

Before this CL, MessageSenderImpl and MessageReceiverImpl assumed that
the phone and Chrome OS device had the same endianness. This CL fixes
the issue by converting from host to network endianness when sending
messages and converting from network to host endianness when receiving
messages.

Bug: 1106937
Change-Id: Idaa3b56f9450030aaf2c5460a2cae18ec4869d82
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2453271
Auto-Submit: Kyle Horimoto <khorimoto@chromium.org>
Commit-Queue: Regan Hsu <hsuregan@chromium.org>
Reviewed-by: Jimmy Gong <jimmyxgong@chromium.org>
Reviewed-by: Regan Hsu <hsuregan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#814370}

chromeos/components/phonehub/message_receiver_impl.cc

@@ -3,12 +3,13 @@
 // found in the LICENSE file.
 
 #include "chromeos/components/phonehub/message_receiver_impl.h"
-#include "chromeos/components/phonehub/proto/phonehub_api.pb.h"
 
+#include <netinet/in.h>
 #include <stdint.h>
 #include <string>
 
 #include "base/logging.h"
+#include "chromeos/components/phonehub/proto/phonehub_api.pb.h"
 
 namespace chromeos {
 namespace phonehub {
@@ -55,7 +56,8 @@ void MessageReceiverImpl::OnMessageReceived(const std::string& payload) {
   // proto::MessageType.
   uint16_t* ptr =
       reinterpret_cast<uint16_t*>(const_cast<char*>(payload.data()));
-  proto::MessageType message_type = static_cast<proto::MessageType>(*ptr);
+  proto::MessageType message_type =
+      static_cast<proto::MessageType>(ntohs(*ptr));
 
   PA_LOG(INFO) << "MessageReceiver received a "
                << GetMessageTypeName(message_type) << " message.";

chromeos/components/phonehub/message_receiver_unittest.cc

@@ -4,13 +4,14 @@
 
 #include "chromeos/components/phonehub/message_receiver_impl.h"
 
+#include <netinet/in.h>
+#include <memory>
+
 #include "base/strings/strcat.h"
 #include "chromeos/components/phonehub/fake_connection_manager.h"
 #include "chromeos/components/phonehub/proto/phonehub_api.pb.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
-#include <memory>
-
 namespace chromeos {
 namespace phonehub {
 namespace {
@@ -62,7 +63,7 @@ std::string SerializeMessage(proto::MessageType message_type,
   // Replace the first two characters with |message_type| as a 16-bit int.
   uint16_t* ptr =
       reinterpret_cast<uint16_t*>(const_cast<char*>(message.data()));
-  *ptr = static_cast<uint16_t>(message_type);
+  *ptr = htons(static_cast<uint16_t>(message_type));
   return message;
 }
 

chromeos/components/phonehub/message_sender_impl.cc

@@ -4,6 +4,8 @@
 
 #include "chromeos/components/phonehub/message_sender_impl.h"
 
+#include <netinet/in.h>
+
 #include "base/strings/strcat.h"
 #include "base/strings/utf_string_conversions.h"
 #include "chromeos/components/phonehub/connection_manager.h"
@@ -21,7 +23,7 @@ std::string SerializeMessage(proto::MessageType message_type,
   // Replace the first two characters with |message_type| as a 16-bit int.
   uint16_t* ptr =
       reinterpret_cast<uint16_t*>(const_cast<char*>(message.data()));
-  *ptr = static_cast<uint16_t>(message_type);
+  *ptr = htons(static_cast<uint16_t>(message_type));
   return message;
 }
 

chromeos/components/phonehub/message_sender_unittest.cc

@@ -4,6 +4,7 @@
 
 #include "chromeos/components/phonehub/message_sender_impl.h"
 
+#include <netinet/in.h>
 #include <stdint.h>
 #include <memory>
 #include <string>
@@ -39,7 +40,7 @@ class MessageSenderImplTest : public testing::Test {
     // bytes of |actual_message|.
     uint16_t* actual_message_uint16t_ptr =
         reinterpret_cast<uint16_t*>(const_cast<char*>(actual_message.data()));
-    EXPECT_EQ(static_cast<uint16_t>(expected_message_type),
+    EXPECT_EQ(ntohs(static_cast<uint16_t>(expected_message_type)),
               *actual_message_uint16t_ptr);
 
     const std::string& expected_proto_message =