Subnet-EVM Warp messages: message encoding in SendWarpMessage event logs

[Nuttymoon]

Hi, I am currently working on an experimental tool to monitor Avalanche Warp Messaging: Avalanche Warp Navigator. The navigator feature is added to the Ash CLI which is written in Rust.

To achieve this goal my first step was to decode the data of SendWarpMessage event logs to extract the UnsignedMessage and the AddressedPayload.

I managed to decode the messages and extract all the information:

Yet, I have some questions about the way the UnsignedMessage is encoded in the SendWarpMessage event data:

• What are the first 2 bytes of the UnsignedMessage used for? Is this for the codec version? (I saw a reference to codecVersion in the code)
• What are the 6 bytes after the length of the AddressedPayload used for?

Here is my current understanding of the encoding, which I validated by the messages I generated:

'0000'     # 2B: CodecVersion?
'00003039' # 4B: NetworkID
'76dccb39c21a43aad4ffa98d4dd86a9ca29f5038a13b87658ef856bc161dbb47' # 32B: SourceChainID
# AddressesPayload
'00000062'     # 4B: AddressedPayload length
'000000000000' # 6B: ???
'8db97c7cece249c2b98bdc0226cc4c2a57bf52fc'                         # 20B: SourceAddress
'a4277d59ef210782b0b2a8043877a8bfcbc385942924c5547d3cd45493448b01' # 32B: DestinationChainID
'9632a79656af553f58738b0fb750320158495942'                         # 20B: DestinationAddress
'00000010466f722074686520456d7065726f7221'                         # XXB: Payload (ABI encoded)

Thanks!

[patrick-ogrady]

(side note: super cool project ❤️ )

[aaronbuchwald]

You can find the AWM message format here: https://github.com/ava-labs/avalanchego/blob/master/vms/platformvm/warp/README.md#awm-serialization and the Subnet-EVM payload serializations here: https://github.com/ava-labs/subnet-evm/blob/master/warp/payload/README.md.

[aaronbuchwald]

The message formats are still subject to change, so heads up that they are not set in stone yet.

[Nuttymoon]

Thanks for the links. I missed those READMEs somehow...