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576 lines
15 KiB
576 lines
15 KiB
package pex
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import (
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"bytes"
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"fmt"
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"math/rand"
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"reflect"
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"sort"
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"time"
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"github.com/pkg/errors"
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wire "github.com/tendermint/go-wire"
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cmn "github.com/tendermint/tmlibs/common"
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"github.com/tendermint/tendermint/p2p"
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"github.com/tendermint/tendermint/p2p/conn"
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)
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type Peer = p2p.Peer
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const (
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// PexChannel is a channel for PEX messages
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PexChannel = byte(0x00)
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maxPexMessageSize = 1048576 // 1MB
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// ensure we have enough peers
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defaultEnsurePeersPeriod = 30 * time.Second
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defaultMinNumOutboundPeers = 10
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// Seed/Crawler constants
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// TODO:
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// We want seeds to only advertise good peers.
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// Peers are marked by external mechanisms.
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// We need a config value that can be set to be
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// on the order of how long it would take before a good
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// peer is marked good.
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defaultSeedDisconnectWaitPeriod = 2 * time.Minute // disconnect after this
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defaultCrawlPeerInterval = 2 * time.Minute // dont redial for this. TODO: back-off
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defaultCrawlPeersPeriod = 30 * time.Second // check some peers every this
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)
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// PEXReactor handles PEX (peer exchange) and ensures that an
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// adequate number of peers are connected to the switch.
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//
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// It uses `AddrBook` (address book) to store `NetAddress`es of the peers.
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//
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// ## Preventing abuse
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//
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// Only accept pexAddrsMsg from peers we sent a corresponding pexRequestMsg too.
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// Only accept one pexRequestMsg every ~defaultEnsurePeersPeriod.
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type PEXReactor struct {
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p2p.BaseReactor
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book AddrBook
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config *PEXReactorConfig
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ensurePeersPeriod time.Duration
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// maps to prevent abuse
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requestsSent *cmn.CMap // ID->struct{}: unanswered send requests
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lastReceivedRequests *cmn.CMap // ID->time.Time: last time peer requested from us
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}
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// PEXReactorConfig holds reactor specific configuration data.
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type PEXReactorConfig struct {
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// Seed/Crawler mode
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SeedMode bool
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// Seeds is a list of addresses reactor may use
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// if it can't connect to peers in the addrbook.
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Seeds []string
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}
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// NewPEXReactor creates new PEX reactor.
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func NewPEXReactor(b AddrBook, config *PEXReactorConfig) *PEXReactor {
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r := &PEXReactor{
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book: b,
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config: config,
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ensurePeersPeriod: defaultEnsurePeersPeriod,
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requestsSent: cmn.NewCMap(),
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lastReceivedRequests: cmn.NewCMap(),
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}
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r.BaseReactor = *p2p.NewBaseReactor("PEXReactor", r)
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return r
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}
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// OnStart implements BaseService
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func (r *PEXReactor) OnStart() error {
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if err := r.BaseReactor.OnStart(); err != nil {
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return err
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}
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err := r.book.Start()
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if err != nil && err != cmn.ErrAlreadyStarted {
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return err
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}
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// return err if user provided a bad seed address
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if err := r.checkSeeds(); err != nil {
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return err
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}
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// Check if this node should run
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// in seed/crawler mode
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if r.config.SeedMode {
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go r.crawlPeersRoutine()
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} else {
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go r.ensurePeersRoutine()
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}
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return nil
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}
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// OnStop implements BaseService
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func (r *PEXReactor) OnStop() {
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r.BaseReactor.OnStop()
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r.book.Stop()
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}
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// GetChannels implements Reactor
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func (r *PEXReactor) GetChannels() []*conn.ChannelDescriptor {
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return []*conn.ChannelDescriptor{
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{
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ID: PexChannel,
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Priority: 1,
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SendQueueCapacity: 10,
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},
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}
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}
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// AddPeer implements Reactor by adding peer to the address book (if inbound)
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// or by requesting more addresses (if outbound).
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func (r *PEXReactor) AddPeer(p Peer) {
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if p.IsOutbound() {
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// For outbound peers, the address is already in the books -
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// either via DialPeersAsync or r.Receive.
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// Ask it for more peers if we need.
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if r.book.NeedMoreAddrs() {
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r.RequestAddrs(p)
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}
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} else {
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// For inbound peers, the peer is its own source,
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// and its NodeInfo has already been validated.
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// Let the ensurePeersRoutine handle asking for more
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// peers when we need - we don't trust inbound peers as much.
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addr := p.NodeInfo().NetAddress()
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r.book.AddAddress(addr, addr)
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}
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}
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// RemovePeer implements Reactor.
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func (r *PEXReactor) RemovePeer(p Peer, reason interface{}) {
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id := string(p.ID())
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r.requestsSent.Delete(id)
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r.lastReceivedRequests.Delete(id)
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}
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// Receive implements Reactor by handling incoming PEX messages.
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func (r *PEXReactor) Receive(chID byte, src Peer, msgBytes []byte) {
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_, msg, err := DecodeMessage(msgBytes)
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if err != nil {
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r.Logger.Error("Error decoding message", "err", err)
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return
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}
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r.Logger.Debug("Received message", "src", src, "chId", chID, "msg", msg)
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switch msg := msg.(type) {
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case *pexRequestMessage:
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// Check we're not receiving too many requests
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if err := r.receiveRequest(src); err != nil {
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r.Switch.StopPeerForError(src, err)
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return
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}
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// Seeds disconnect after sending a batch of addrs
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if r.config.SeedMode {
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// TODO: should we be more selective ?
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r.SendAddrs(src, r.book.GetSelection())
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r.Switch.StopPeerGracefully(src)
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} else {
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r.SendAddrs(src, r.book.GetSelection())
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}
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case *pexAddrsMessage:
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// If we asked for addresses, add them to the book
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if err := r.ReceiveAddrs(msg.Addrs, src); err != nil {
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r.Switch.StopPeerForError(src, err)
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return
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}
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default:
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r.Logger.Error(fmt.Sprintf("Unknown message type %v", reflect.TypeOf(msg)))
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}
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}
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func (r *PEXReactor) receiveRequest(src Peer) error {
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id := string(src.ID())
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v := r.lastReceivedRequests.Get(id)
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if v == nil {
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// initialize with empty time
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lastReceived := time.Time{}
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r.lastReceivedRequests.Set(id, lastReceived)
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return nil
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}
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lastReceived := v.(time.Time)
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if lastReceived.Equal(time.Time{}) {
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// first time gets a free pass. then we start tracking the time
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lastReceived = time.Now()
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r.lastReceivedRequests.Set(id, lastReceived)
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return nil
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}
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now := time.Now()
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if now.Sub(lastReceived) < r.ensurePeersPeriod/3 {
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return fmt.Errorf("Peer (%v) is sending too many PEX requests. Disconnecting", src.ID())
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}
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r.lastReceivedRequests.Set(id, now)
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return nil
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}
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// RequestAddrs asks peer for more addresses if we do not already
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// have a request out for this peer.
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func (r *PEXReactor) RequestAddrs(p Peer) {
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id := string(p.ID())
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if r.requestsSent.Has(id) {
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return
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}
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r.requestsSent.Set(id, struct{}{})
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p.Send(PexChannel, struct{ PexMessage }{&pexRequestMessage{}})
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}
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// ReceiveAddrs adds the given addrs to the addrbook if theres an open
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// request for this peer and deletes the open request.
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// If there's no open request for the src peer, it returns an error.
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func (r *PEXReactor) ReceiveAddrs(addrs []*p2p.NetAddress, src Peer) error {
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id := string(src.ID())
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if !r.requestsSent.Has(id) {
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return errors.New("Received unsolicited pexAddrsMessage")
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}
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r.requestsSent.Delete(id)
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srcAddr := src.NodeInfo().NetAddress()
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for _, netAddr := range addrs {
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if netAddr != nil {
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r.book.AddAddress(netAddr, srcAddr)
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}
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}
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return nil
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}
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// SendAddrs sends addrs to the peer.
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func (r *PEXReactor) SendAddrs(p Peer, netAddrs []*p2p.NetAddress) {
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p.Send(PexChannel, struct{ PexMessage }{&pexAddrsMessage{Addrs: netAddrs}})
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}
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// SetEnsurePeersPeriod sets period to ensure peers connected.
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func (r *PEXReactor) SetEnsurePeersPeriod(d time.Duration) {
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r.ensurePeersPeriod = d
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}
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// Ensures that sufficient peers are connected. (continuous)
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func (r *PEXReactor) ensurePeersRoutine() {
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var (
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seed = rand.New(rand.NewSource(time.Now().UnixNano()))
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jitter = seed.Int63n(r.ensurePeersPeriod.Nanoseconds())
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)
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// Randomize first round of communication to avoid thundering herd.
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// If no potential peers are present directly start connecting so we guarantee
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// swift setup with the help of configured seeds.
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if r.hasPotentialPeers() {
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time.Sleep(time.Duration(jitter))
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}
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// fire once immediately.
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// ensures we dial the seeds right away if the book is empty
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r.ensurePeers()
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// fire periodically
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ticker := time.NewTicker(r.ensurePeersPeriod)
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for {
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select {
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case <-ticker.C:
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r.ensurePeers()
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case <-r.Quit():
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ticker.Stop()
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return
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}
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}
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}
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// ensurePeers ensures that sufficient peers are connected. (once)
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//
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// heuristic that we haven't perfected yet, or, perhaps is manually edited by
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// the node operator. It should not be used to compute what addresses are
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// already connected or not.
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func (r *PEXReactor) ensurePeers() {
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var (
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out, in, dial = r.Switch.NumPeers()
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numToDial = defaultMinNumOutboundPeers - (out + dial)
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)
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r.Logger.Info(
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"Ensure peers",
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"numOutPeers", out,
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"numInPeers", in,
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"numDialing", dial,
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"numToDial", numToDial,
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)
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if numToDial <= 0 {
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return
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}
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// bias to prefer more vetted peers when we have fewer connections.
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// not perfect, but somewhate ensures that we prioritize connecting to more-vetted
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// NOTE: range here is [10, 90]. Too high ?
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newBias := cmn.MinInt(out, 8)*10 + 10
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toDial := make(map[p2p.ID]*p2p.NetAddress)
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// Try maxAttempts times to pick numToDial addresses to dial
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maxAttempts := numToDial * 3
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for i := 0; i < maxAttempts && len(toDial) < numToDial; i++ {
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try := r.book.PickAddress(newBias)
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if try == nil {
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continue
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}
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if _, selected := toDial[try.ID]; selected {
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continue
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}
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if dialling := r.Switch.IsDialing(try.ID); dialling {
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continue
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}
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if connected := r.Switch.Peers().Has(try.ID); connected {
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continue
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}
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r.Logger.Info("Will dial address", "addr", try)
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toDial[try.ID] = try
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}
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// Dial picked addresses
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for _, item := range toDial {
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go func(picked *p2p.NetAddress) {
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err := r.Switch.DialPeerWithAddress(picked, false)
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if err != nil {
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r.Logger.Error("Dialing failed", "err", err)
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// TODO: detect more "bad peer" scenarios
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if _, ok := err.(p2p.ErrSwitchAuthenticationFailure); ok {
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r.book.MarkBad(picked)
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} else {
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r.book.MarkAttempt(picked)
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}
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}
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}(item)
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}
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// If we need more addresses, pick a random peer and ask for more.
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if r.book.NeedMoreAddrs() {
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peers := r.Switch.Peers().List()
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peersCount := len(peers)
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if peersCount > 0 {
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peer := peers[rand.Int()%peersCount] // nolint: gas
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r.Logger.Info("We need more addresses. Sending pexRequest to random peer", "peer", peer)
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r.RequestAddrs(peer)
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}
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}
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// If we are not connected to nor dialing anybody, fallback to dialing a seed.
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if out+in+dial+len(toDial) == 0 {
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r.Logger.Info("No addresses to dial nor connected peers. Falling back to seeds")
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r.dialSeeds()
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}
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}
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// check seed addresses are well formed
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func (r *PEXReactor) checkSeeds() error {
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lSeeds := len(r.config.Seeds)
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if lSeeds == 0 {
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return nil
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}
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_, errs := p2p.NewNetAddressStrings(r.config.Seeds)
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for _, err := range errs {
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if err != nil {
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return err
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}
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}
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return nil
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}
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// randomly dial seeds until we connect to one or exhaust them
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func (r *PEXReactor) dialSeeds() {
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lSeeds := len(r.config.Seeds)
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if lSeeds == 0 {
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return
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}
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seedAddrs, _ := p2p.NewNetAddressStrings(r.config.Seeds)
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perm := rand.Perm(lSeeds)
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// perm := r.Switch.rng.Perm(lSeeds)
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for _, i := range perm {
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// dial a random seed
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seedAddr := seedAddrs[i]
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err := r.Switch.DialPeerWithAddress(seedAddr, false)
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if err == nil {
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return
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}
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r.Switch.Logger.Error("Error dialing seed", "err", err, "seed", seedAddr)
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}
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r.Switch.Logger.Error("Couldn't connect to any seeds")
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}
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//----------------------------------------------------------
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// Explores the network searching for more peers. (continuous)
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// Seed/Crawler Mode causes this node to quickly disconnect
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// from peers, except other seed nodes.
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func (r *PEXReactor) crawlPeersRoutine() {
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// Do an initial crawl
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r.crawlPeers()
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// Fire periodically
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ticker := time.NewTicker(defaultCrawlPeersPeriod)
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for {
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select {
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case <-ticker.C:
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r.attemptDisconnects()
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r.crawlPeers()
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case <-r.Quit():
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return
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}
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}
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}
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// hasPotentialPeers indicates if there is a potential peer to connect to, by
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// consulting the Switch as well as the AddrBook.
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func (r *PEXReactor) hasPotentialPeers() bool {
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out, in, dial := r.Switch.NumPeers()
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return out+in+dial > 0 && len(r.book.ListOfKnownAddresses()) > 0
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}
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// crawlPeerInfo handles temporary data needed for the
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// network crawling performed during seed/crawler mode.
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type crawlPeerInfo struct {
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// The listening address of a potential peer we learned about
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Addr *p2p.NetAddress
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// The last time we attempt to reach this address
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LastAttempt time.Time
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// The last time we successfully reached this address
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LastSuccess time.Time
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}
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// oldestFirst implements sort.Interface for []crawlPeerInfo
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// based on the LastAttempt field.
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type oldestFirst []crawlPeerInfo
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func (of oldestFirst) Len() int { return len(of) }
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func (of oldestFirst) Swap(i, j int) { of[i], of[j] = of[j], of[i] }
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func (of oldestFirst) Less(i, j int) bool { return of[i].LastAttempt.Before(of[j].LastAttempt) }
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// getPeersToCrawl returns addresses of potential peers that we wish to validate.
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// NOTE: The status information is ordered as described above.
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func (r *PEXReactor) getPeersToCrawl() []crawlPeerInfo {
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var of oldestFirst
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// TODO: be more selective
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addrs := r.book.ListOfKnownAddresses()
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for _, addr := range addrs {
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if len(addr.ID()) == 0 {
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continue // dont use peers without id
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}
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of = append(of, crawlPeerInfo{
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Addr: addr.Addr,
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LastAttempt: addr.LastAttempt,
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LastSuccess: addr.LastSuccess,
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})
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}
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sort.Sort(of)
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return of
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}
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// crawlPeers will crawl the network looking for new peer addresses. (once)
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func (r *PEXReactor) crawlPeers() {
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peerInfos := r.getPeersToCrawl()
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now := time.Now()
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// Use addresses we know of to reach additional peers
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for _, pi := range peerInfos {
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// Do not attempt to connect with peers we recently dialed
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if now.Sub(pi.LastAttempt) < defaultCrawlPeerInterval {
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continue
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}
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// Otherwise, attempt to connect with the known address
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err := r.Switch.DialPeerWithAddress(pi.Addr, false)
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if err != nil {
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r.book.MarkAttempt(pi.Addr)
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continue
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}
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}
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// Crawl the connected peers asking for more addresses
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for _, pi := range peerInfos {
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// We will wait a minimum period of time before crawling peers again
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if now.Sub(pi.LastAttempt) >= defaultCrawlPeerInterval {
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peer := r.Switch.Peers().Get(pi.Addr.ID)
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if peer != nil {
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r.RequestAddrs(peer)
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}
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}
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}
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}
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// attemptDisconnects checks if we've been with each peer long enough to disconnect
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func (r *PEXReactor) attemptDisconnects() {
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for _, peer := range r.Switch.Peers().List() {
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status := peer.Status()
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if status.Duration < defaultSeedDisconnectWaitPeriod {
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continue
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}
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if peer.IsPersistent() {
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continue
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}
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r.Switch.StopPeerGracefully(peer)
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}
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}
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//-----------------------------------------------------------------------------
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// Messages
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const (
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msgTypeRequest = byte(0x01)
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msgTypeAddrs = byte(0x02)
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)
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// PexMessage is a primary type for PEX messages. Underneath, it could contain
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// either pexRequestMessage, or pexAddrsMessage messages.
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type PexMessage interface{}
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var _ = wire.RegisterInterface(
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struct{ PexMessage }{},
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wire.ConcreteType{&pexRequestMessage{}, msgTypeRequest},
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wire.ConcreteType{&pexAddrsMessage{}, msgTypeAddrs},
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)
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// DecodeMessage implements interface registered above.
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func DecodeMessage(bz []byte) (msgType byte, msg PexMessage, err error) {
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msgType = bz[0]
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n := new(int)
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r := bytes.NewReader(bz)
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msg = wire.ReadBinary(struct{ PexMessage }{}, r, maxPexMessageSize, n, &err).(struct{ PexMessage }).PexMessage
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return
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}
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/*
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A pexRequestMessage requests additional peer addresses.
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*/
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type pexRequestMessage struct {
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}
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func (m *pexRequestMessage) String() string {
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return "[pexRequest]"
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}
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/*
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A message with announced peer addresses.
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*/
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type pexAddrsMessage struct {
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Addrs []*p2p.NetAddress
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}
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func (m *pexAddrsMessage) String() string {
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return fmt.Sprintf("[pexAddrs %v]", m.Addrs)
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}
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