Levin Protocol
This chapter describes the levin protocol.
Buckets
A Bucket is a single piece of data that the levin protocol parser can decode, it will contain a p2p message or it will be part of a chain of buckets that will be combined into a single message.
Bucket Format
| Field | Type | Size (bytes) |
|---|---|---|
| Header | BucketHeader | 33 |
| Body | bytes | dynamic |
BucketHeader
Format1:
| Field | Type | Size (bytes) |
|---|---|---|
| Signature | LE u64 | 8 |
| Size | LE u64 | 8 |
| Expect Response | bool | 1 |
| Command | LE u32 | 4 |
| Return Code | LE i32 | 4 |
| Flags | LE u32 | 4 |
| Protocol Version | LE u32 | 4 |
Signature
The signature field is fixed for every bucket and is used to tell apart peers running different protocols.
Its value should be 0x0101010101012101 2
Size
This field represents the size of the buckets body.
Expect Response
Messages with the expect response field set must be responded to in order, other messages are still allowed in between responses.
Command
This field is an identifier for what specific message the bucket's body contains.
Return Code
This field represents the status of the response from the peer, requests and notifications should set this to 0 and successful
responses should be 1.
Flags
This is a bit-flag field that determines what type of bucket this is3:
| Type | Bits set |
|---|---|
| Request | 0000_0001 |
| Response | 0000_0010 |
| Start Fragment | 0000_0100 |
| End Fragment | 0000_1000 |
| Dummy | 0000_1100 |
Protocol Version
This is a fixed value of 1.
Bucket Body
All bucket bodies are serialized in the epee binary format which is described here: https://github.com/monero-project/monero/blob/cc73fe71162d564ffda8e549b79a350bca53c454/docs/PORTABLE_STORAGE.md
Exact message types are described in the next chapters.