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go-libp2p-daemon/specs/DHT.md

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libp2p Daemon DHT Protocol

The libp2p daemon DHT protocol allows clients to query and announce to the libp2p DHT.

At the moment, this is a living document. As such, it will be susceptible to changes until stabilization.

Protocol Specification

Data Types

The data structures are defined in pb/p2pd.proto. All messages are varint-delimited. For the DHT queries, the relevant data types are:

  • DHTRequest
  • DHTResponse

All DHT requests will be wrapped in a Request message with Type: DHT. Most DHT responses from the daemon will be wrapped in a Response with the DHTResponse field populated. Some responses will be basic Response messages to convey whether or not there was an error.

DHTRequest messages have a Type parameter that specifies the specific query the client wishes to execute.

The DHT protocol supports asynchronous stream responses with arbitrary numbers of results as well as responses that return a single value. DHTResponse messages have a Type parameter that specifies whether a response marks the BEGINning of a stream of messages, a VALUE within a stream of messages, or the END of a stream of messages. Single-value responses will simply return a single DHTResponse with type VALUE.

Protocol Requests

Protocols described in pseudo-go. Items of the form [item, ...] are lists of many items.

Errors

Any response that may be an error, will take the form of:

Response{
  Type: ERROR,
  ErrorResponse: {
    Msg: <error message>,
  },
}

FIND_PEER

Clients can issue a FIND_PEER request to query the DHT for a given peer's known addresses.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: FIND_PEER,
    Peer: <peer id>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: VALUE,
    Peer: PeerInfo{
      Id: <peer id>,
      Addrs: [<addr>, ...],
    }
  }
}

FIND_PEERS_CONNECTED_TO_PEER

Clients can issue a FIND_PEERS_CONNECTED_TO_PEER request to query the DHT for peers directly connected to a given peer in the DHT.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: FIND_PEERS_CONNECTED_TO_PEER,
    Peer: <peer id>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: BEGIN,
  }
}

Daemon Can return any number of responses like this, including 0

DHTResponse{
  Type: VALUE,
  Peer: PeerInfo{
    Id: <peer id>,
    Addrs: [<addr>, ...],
  },
}

Daemon Marks the end of the result stream

DHTResponse{
  Type: END,
}

FIND_PROVIDERS

Clients can issue a FIND_PROVIDERS request to query the DHT for peers that have a piece of content, identified by a CID. FIND_PROVIDERS optionally include a Count, specifying a maximum number of results to return.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: FIND_PROVIDERS,
    Cid: <content id>,
    Count: <number of results to include>,
  },
}

Daemon Can return an error if the CID is invalid

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: BEGIN,
  },
}

Daemon Can return any number of responses like this, including 0

DHTResponse{
  Type: VALUE,
  Peer: PeerInfo{
    Id: <peer id>,
    Addrs: [<addr>, ...],
  },
}

Daemon Marks the end of the result stream

DHTResponse{
  Type: END,
}

GET_CLOSEST_PEERS

Clients can issue a GET_CLOSEST_PEERS request to query the DHT routing table for peers that are closest to a provided key.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: GET_CLOSEST_PEERS,
    Key: <content id>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: BEGIN,
  }
}

Daemon Can return any number of responses like this, including 0

DHTResponse{
  Type: VALUE,
  Value: <peer id>,
}

Daemon Marks the end of the result stream

DHTResponse{
  Type: END,
}

GET_PUBLIC_KEY

Clients can issue a GET_PUBLIC_KEY request to query the DHT routing table for a given peer's public key.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: GET_PUBLIC_KEY,
    Peer: <peer id>,
  },
}

Daemon Can return an error if the peer is not found

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: VALUE,
    Value: <public key>,
  }
}

GET_VALUE

Clients can issue a GET_VALUE request to query the DHT for a value stored at a key in the DHT.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: GET_VALUE,
    Key: <key>,
  },
}

Daemon Can return an error if the key is not found

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: VALUE,
    Value: <value stored at key>,
  }
}

SEARCH_VALUE

Clients can issue a SEARCH_VALUE request to query the DHT for the best/most valid value stored at a given key. It will return a stream of values, terminating on the best/most valid value found. After the daemon finishes its query, it will update any peers in the DHT that returned stale or bad data for the given key with the better record.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: SEARCH_VALUE,
    Key: <key>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: BEGIN,
  }
}

Daemon Can return any number of responses like this, including 0

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: VALUE,
    Value: <value at key>,
  },
}

Daemon Marks the end of the result stream

Response{
  Type: OK,
  DHTResponse: DHTResponse{
    Type: END,
  }
}

PUT_VALUE

Clients can issue a PUT_VALUE request to write a value to a key in the DHT.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: PUT_VALUE,
    Key: <key>,
    Value: <value>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
}

PROVIDE

Clients can issue a PROVIDE request to announce that they have data addressed by a given CID.

Client

Request{
  Type: DHT,
  DHTRequest: DHTRequest{
    Type: PROVIDE,
    Cid: <cid>,
  },
}

Daemon Can return an error

Response{
  Type: OK,
}