From f92be97bf23e55999a801e250b39eca76c0a71af Mon Sep 17 00:00:00 2001
From: Martin Turon <mturon@google.com>
Date: Wed, 23 Jun 2021 18:21:19 -0700
Subject: [PATCH] [msg] Reorder header bits to match spec.

---
 src/transport/SecureMessageCodec.cpp |  2 +-
 src/transport/SecureSessionMgr.cpp   |  2 +-
 src/transport/raw/MessageHeader.cpp  | 18 ++++++------------
 src/transport/raw/MessageHeader.h    | 17 +++++++++--------
 4 files changed, 17 insertions(+), 22 deletions(-)

diff --git a/src/transport/SecureMessageCodec.cpp b/src/transport/SecureMessageCodec.cpp
index 1e44b57ee262b5..ff3481fcc66572 100644
--- a/src/transport/SecureMessageCodec.cpp
+++ b/src/transport/SecureMessageCodec.cpp
@@ -58,7 +58,7 @@ CHIP_ERROR Encode(NodeId localNodeId, Transport::PeerConnectionState * state, Pa
         packetHeader.SetDestinationNodeId(state->GetPeerNodeId());
     }
 
-    packetHeader.GetFlags().Set(Header::FlagValues::kSecure);
+    packetHeader.GetFlags().Set(Header::FlagValues::kEncryptedMessage);
 
     ReturnErrorOnFailure(payloadHeader.EncodeBeforeData(msgBuf));
 
diff --git a/src/transport/SecureSessionMgr.cpp b/src/transport/SecureSessionMgr.cpp
index b13e23670ce4a5..3b599332d5752e 100644
--- a/src/transport/SecureSessionMgr.cpp
+++ b/src/transport/SecureSessionMgr.cpp
@@ -315,7 +315,7 @@ void SecureSessionMgr::OnMessageReceived(const PeerAddress & peerAddress, System
 
     ReturnOnFailure(packetHeader.DecodeAndConsume(msg));
 
-    if (packetHeader.GetFlags().Has(Header::FlagValues::kSecure))
+    if (packetHeader.GetFlags().Has(Header::FlagValues::kEncryptedMessage))
     {
         SecureMessageDispatch(packetHeader, peerAddress, std::move(msg));
     }
diff --git a/src/transport/raw/MessageHeader.cpp b/src/transport/raw/MessageHeader.cpp
index a94fadf2fe7914..fc3e312715c444 100644
--- a/src/transport/raw/MessageHeader.cpp
+++ b/src/transport/raw/MessageHeader.cpp
@@ -78,14 +78,14 @@ constexpr size_t kVendorIdSizeBytes = 2;
 constexpr size_t kAckIdSizeBytes = 4;
 
 /// Mask to extract just the version part from a 16bit header prefix.
-constexpr uint16_t kVersionMask = 0xF000;
+constexpr uint16_t kVersionMask = 0x00F0;
 /// Shift to convert to/from a masked version 16bit value to a 4bit version.
-constexpr int kVersionShift = 12;
+constexpr int kVersionShift = 4;
 
 /// Mask to extract just the encryption type part from a 16bit header prefix.
-constexpr uint16_t kEncryptionTypeMask = 0xF0;
-/// Shift to convert to/from a masked encryption type 16bit value to a 4bit encryption type.
-constexpr int kEncryptionTypeShift = 4;
+constexpr uint16_t kEncryptionTypeMask = 0x3000;
+/// Shift to convert to/from a masked encryption type 16bit value to a 2bit encryption type.
+constexpr int kEncryptionTypeShift = 12;
 
 } // namespace
 
@@ -131,12 +131,6 @@ uint16_t MessageAuthenticationCode::TagLenForEncryptionType(Header::EncryptionTy
 {
     switch (encType)
     {
-    case Header::EncryptionType::kAESCCMTagLen8:
-        return 8;
-
-    case Header::EncryptionType::kAESCCMTagLen12:
-        return 12;
-
     case Header::EncryptionType::kAESCCMTagLen16:
         return 16;
 
@@ -158,8 +152,8 @@ CHIP_ERROR PacketHeader::Decode(const uint8_t * const data, uint16_t size, uint1
     version = ((header & kVersionMask) >> kVersionShift);
     VerifyOrExit(version == kHeaderVersion, err = CHIP_ERROR_VERSION_MISMATCH);
 
+    mFlags.SetRaw(header);
     mEncryptionType = static_cast<Header::EncryptionType>((header & kEncryptionTypeMask) >> kEncryptionTypeShift);
-    mFlags.SetRaw(header & Header::kFlagsMask);
 
     err = reader.Read32(&mMessageId).StatusCode();
     SuccessOrExit(err);
diff --git a/src/transport/raw/MessageHeader.h b/src/transport/raw/MessageHeader.h
index 4ec89c18dc6322..3a4809aabfdbd2 100644
--- a/src/transport/raw/MessageHeader.h
+++ b/src/transport/raw/MessageHeader.h
@@ -47,9 +47,8 @@ namespace Header {
 
 enum class EncryptionType
 {
-    kAESCCMTagLen8  = 0,
-    kAESCCMTagLen12 = 1,
-    kAESCCMTagLen16 = 2,
+    kEncryptionTypeNone  = 0,
+    kAESCCMTagLen16 = 1,
 };
 
 /**
@@ -74,16 +73,19 @@ enum class ExFlagValues : uint8_t
 enum class FlagValues : uint16_t
 {
     /// Header flag specifying that a destination node id is included in the header.
-    kDestinationNodeIdPresent = 0x0100,
+    kDestinationNodeIdPresent = 0x0001,
+
+    /// Header flag specifying that a destination group id is included in the header.
+    kDestinationGroupIdPresent = 0x0002,
 
     /// Header flag specifying that a source node id is included in the header.
-    kSourceNodeIdPresent = 0x0200,
+    kSourceNodeIdPresent = 0x0004,
 
     /// Header flag specifying that it is a control message for secure session.
-    kSecureSessionControlMessage = 0x0800,
+    kSecureSessionControlMessage = 0x4000,
 
     /// Header flag specifying that it is a encrypted message.
-    kSecure = 0x0001,
+    kEncryptedMessage = 0x0100,
 
 };
 
@@ -97,7 +99,6 @@ using ExFlags = BitFlags<ExFlagValues>;
 //                      |   |            +---Encrypted
 //                      |   +----------------Control message (TODO: Implement this)
 //                      +--------------------Privacy enhancements (TODO: Implement this)
-static constexpr uint16_t kFlagsMask = 0x0F01;
 
 } // namespace Header