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// Package routing provides interfaces for peer routing and content routing in libp2p.
package routing
import (
ci ""
cid ""
// ErrNotFound is returned when the router fails to find the requested record.
var ErrNotFound = errors.New("routing: not found")
// ErrNotSupported is returned when the router doesn't support the given record
// type/operation.
var ErrNotSupported = errors.New("routing: operation or key not supported")
// ContentRouting is a value provider layer of indirection. It is used to find
// information about who has what content.
// Content is identified by CID (content identifier), which encodes a hash
// of the identified content in a future-proof manner.
type ContentRouting interface {
// Provide adds the given cid to the content routing system. If 'true' is
// passed, it also announces it, otherwise it is just kept in the local
// accounting of which objects are being provided.
Provide(context.Context, cid.Cid, bool) error
// Search for peers who are able to provide a given key
FindProvidersAsync(context.Context, cid.Cid, int) <-chan peer.AddrInfo
// PeerRouting is a way to find address information about certain peers.
// This can be implemented by a simple lookup table, a tracking server,
// or even a DHT.
type PeerRouting interface {
// Find specific Peer
// FindPeer searches for a peer with given ID, returns a peer.AddrInfo
// with relevant addresses.
FindPeer(context.Context, peer.ID) (peer.AddrInfo, error)
// ValueStore is a basic Put/Get interface.
type ValueStore interface {
// PutValue adds value corresponding to given Key.
PutValue(context.Context, string, []byte, ...Option) error
// GetValue searches for the value corresponding to given Key.
GetValue(context.Context, string, ...Option) ([]byte, error)
// SearchValue searches for better and better values from this value
// store corresponding to the given Key. By default implementations must
// stop the search after a good value is found. A 'good' value is a value
// that would be returned from GetValue.
// Useful when you want a result *now* but still want to hear about
// better/newer results.
// Implementations of this methods won't return ErrNotFound. When a value
// couldn't be found, the channel will get closed without passing any results
SearchValue(context.Context, string, ...Option) (<-chan []byte, error)
// Routing is the combination of different routing types supported by libp2p.
// It can be satisfied by a single item (such as a DHT) or multiple different
// pieces that are more optimized to each task.
type Routing interface {
// Bootstrap allows callers to hint to the routing system to get into a
// Boostrapped state and remain there. It is not a synchronous call.
Bootstrap(context.Context) error
// TODO expose io.Closer or plain-old Close error
// PubKeyFetcher is an interfaces that should be implemented by value stores
// that can optimize retrieval of public keys.
// TODO(steb): Consider removing, see
type PubKeyFetcher interface {
// GetPublicKey returns the public key for the given peer.
GetPublicKey(context.Context, peer.ID) (ci.PubKey, error)
// KeyForPublicKey returns the key used to retrieve public keys
// from a value store.
func KeyForPublicKey(id peer.ID) string {
return "/pk/" + string(id)
// GetPublicKey retrieves the public key associated with the given peer ID from
// the value store.
// If the ValueStore is also a PubKeyFetcher, this method will call GetPublicKey
// (which may be better optimized) instead of GetValue.
func GetPublicKey(r ValueStore, ctx context.Context, p peer.ID) (ci.PubKey, error) {
switch k, err := p.ExtractPublicKey(); err {
case peer.ErrNoPublicKey:
// check the datastore
case nil:
return k, nil
return nil, err
if dht, ok := r.(PubKeyFetcher); ok {
// If we have a DHT as our routing system, use optimized fetcher
return dht.GetPublicKey(ctx, p)
key := KeyForPublicKey(p)
pkval, err := r.GetValue(ctx, key)
if err != nil {
return nil, err
// get PublicKey from node.Data
return ci.UnmarshalPublicKey(pkval)
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