discover

Documentation

Overview

Package discover implements the Node Discovery Protocol.

The Node Discovery protocol provides a way to find RLPx nodes that can be connected to. It uses a Kademlia-like protocol to maintain a distributed database of the IDs and endpoints of all listening nodes.

Index

• Constants
• type Node
  • func MustParseNode(rawurl string) *Node
  • func NewNode(id NodeID, ip net.IP, udpPort, tcpPort uint16) *Node
  • func ParseNode(rawurl string) (*Node, error)
  • func (n *Node) Incomplete() bool
  • func (n *Node) String() string
• type NodeID
  • func HexID(in string) (NodeID, error)
  • func MustHexID(in string) NodeID
  • func PubkeyID(pub *ecdsa.PublicKey) NodeID
  • func (n NodeID) GoString() string
  • func (id NodeID) Pubkey() (*ecdsa.PublicKey, error)
  • func (n NodeID) String() string
• type Table
  • func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Table, error)
  • func (tab *Table) Close()
  • func (tab *Table) Lookup(targetID NodeID) []*Node
  • func (tab *Table) ReadRandomNodes(buf []*Node) (n int)
  • func (tab *Table) Resolve(targetID NodeID) *Node
  • func (tab *Table) Self() *Node
  • func (tab *Table) SetFallbackNodes(nodes []*Node) error

Examples

• NewNode

Constants

const NodeIDBits = 512

const Version = 4

Types

type Node

type Node struct {
	IP       net.IP // len 4 for IPv4 or 16 for IPv6
	UDP, TCP uint16 // port numbers
	ID       NodeID // the node's public key
	// contains filtered or unexported fields
}

Node represents a host on the network. The fields of Node may not be modified.

func MustParseNode

func MustParseNode(rawurl string) *Node

MustParseNode parses a node URL. It panics if the URL is not valid.

func NewNode

func NewNode(id NodeID, ip net.IP, udpPort, tcpPort uint16) *Node

NewNode creates a new node. It is mostly meant to be used for testing purposes.

Example

id := MustHexID("1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439")

// Complete nodes contain UDP and TCP endpoints:
n1 := NewNode(id, net.ParseIP("2001:db8:3c4d:15::abcd:ef12"), 52150, 30303)
fmt.Println("n1:", n1)
fmt.Println("n1.Incomplete() ->", n1.Incomplete())

// An incomplete node can be created by passing zero values
// for all parameters except id.
n2 := NewNode(id, nil, 0, 0)
fmt.Println("n2:", n2)
fmt.Println("n2.Incomplete() ->", n2.Incomplete())

Output:

n1: enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439@[2001:db8:3c4d:15::abcd:ef12]:30303?discport=52150
n1.Incomplete() -> false
n2: enode://1dd9d65c4552b5eb43d5ad55a2ee3f56c6cbc1c64a5c8d659f51fcd51bace24351232b8d7821617d2b29b54b81cdefb9b3e9c37d7fd5f63270bcc9e1a6f6a439
n2.Incomplete() -> true

func ParseNode

func ParseNode(rawurl string) (*Node, error)

ParseNode parses a node designator.

There are two basic forms of node designators

• incomplete nodes, which only have the public key (node ID)
• complete nodes, which contain the public key and IP/Port information

For incomplete nodes, the designator must look like one of these

enode://<hex node id>
<hex node id>

For complete nodes, the node ID is encoded in the username portion of the URL, separated from the host by an @ sign. The hostname can only be given as an IP address, DNS domain names are not allowed. The port in the host name section is the TCP listening port. If the TCP and UDP (discovery) ports differ, the UDP port is specified as query parameter "discport".

In the following example, the node URL describes a node with IP address 10.3.58.6, TCP listening port 30303 and UDP discovery port 30301.

enode://<hex node id>@10.3.58.6:30303?discport=30301

func (*Node) Incomplete

func (n *Node) Incomplete() bool

Incomplete returns true for nodes with no IP address.

func (*Node) String

func (n *Node) String() string

The string representation of a Node is a URL. Please see ParseNode for a description of the format.

type NodeID

type NodeID [NodeIDBits / 8]byte

NodeID is a unique identifier for each node. The node identifier is a marshaled elliptic curve public key.

func HexID

func HexID(in string) (NodeID, error)

HexID converts a hex string to a NodeID. The string may be prefixed with 0x.

func MustHexID

func MustHexID(in string) NodeID

MustHexID converts a hex string to a NodeID. It panics if the string is not a valid NodeID.

func PubkeyID

func PubkeyID(pub *ecdsa.PublicKey) NodeID

PubkeyID returns a marshaled representation of the given public key.

func (NodeID) GoString

func (n NodeID) GoString() string

The Go syntax representation of a NodeID is a call to HexID.

func (NodeID) Pubkey

func (id NodeID) Pubkey() (*ecdsa.PublicKey, error)

Pubkey returns the public key represented by the node ID. It returns an error if the ID is not a point on the curve.

func (NodeID) String

func (n NodeID) String() string

NodeID prints as a long hexadecimal number.

type Table

type Table struct {
	// contains filtered or unexported fields
}

func ListenUDP

func ListenUDP(priv *ecdsa.PrivateKey, laddr string, natm nat.Interface, nodeDBPath string) (*Table, error)

ListenUDP returns a new table that listens for UDP packets on laddr.

func (*Table) Close

func (tab *Table) Close()

Close terminates the network listener and flushes the node database.

func (*Table) Lookup

func (tab *Table) Lookup(targetID NodeID) []*Node

Lookup performs a network search for nodes close to the given target. It approaches the target by querying nodes that are closer to it on each iteration. The given target does not need to be an actual node identifier.

func (*Table) ReadRandomNodes

func (tab *Table) ReadRandomNodes(buf []*Node) (n int)

ReadRandomNodes fills the given slice with random nodes from the table. It will not write the same node more than once. The nodes in the slice are copies and can be modified by the caller.

func (*Table) Resolve

func (tab *Table) Resolve(targetID NodeID) *Node

Resolve searches for a specific node with the given ID. It returns nil if the node could not be found.

func (*Table) Self

func (tab *Table) Self() *Node

Self returns the local node. The returned node should not be modified by the caller.

func (*Table) SetFallbackNodes

func (tab *Table) SetFallbackNodes(nodes []*Node) error

SetFallbackNodes sets the initial points of contact. These nodes are used to connect to the network if the table is empty and there are no known nodes in the database.