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swarm_dial.go
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swarm_dial.go
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package swarm
import (
"context"
"errors"
"fmt"
"sync"
"time"
"github.com/libp2p/go-libp2p-core/network"
"github.com/libp2p/go-libp2p-core/peer"
"github.com/libp2p/go-libp2p-core/transport"
ma "github.com/multiformats/go-multiaddr"
manet "github.com/multiformats/go-multiaddr/net"
)
// Diagram of dial sync:
//
// many callers of Dial() synched w. dials many addrs results to callers
// ----------------------\ dialsync use earliest /--------------
// -----------------------\ |----------\ /----------------
// ------------------------>------------<------- >---------<-----------------
// -----------------------| \----x \----------------
// ----------------------| \-----x \---------------
// any may fail if no addr at end
// retry dialAttempt x
var (
// ErrDialBackoff is returned by the backoff code when a given peer has
// been dialed too frequently
ErrDialBackoff = errors.New("dial backoff")
// ErrDialToSelf is returned if we attempt to dial our own peer
ErrDialToSelf = errors.New("dial to self attempted")
// ErrNoTransport is returned when we don't know a transport for the
// given multiaddr.
ErrNoTransport = errors.New("no transport for protocol")
// ErrAllDialsFailed is returned when connecting to a peer has ultimately failed
ErrAllDialsFailed = errors.New("all dials failed")
// ErrNoAddresses is returned when we fail to find any addresses for a
// peer we're trying to dial.
ErrNoAddresses = errors.New("no addresses")
// ErrNoGoodAddresses is returned when we find addresses for a peer but
// can't use any of them.
ErrNoGoodAddresses = errors.New("no good addresses")
// ErrGaterDisallowedConnection is returned when the gater prevents us from
// forming a connection with a peer.
ErrGaterDisallowedConnection = errors.New("gater disallows connection to peer")
)
// DialAttempts governs how many times a goroutine will try to dial a given peer.
// Note: this is down to one, as we have _too many dials_ atm. To add back in,
// add loop back in Dial(.)
const DialAttempts = 1
// ConcurrentFdDials is the number of concurrent outbound dials over transports
// that consume file descriptors
const ConcurrentFdDials = 160
// DefaultPerPeerRateLimit is the number of concurrent outbound dials to make
// per peer
var DefaultPerPeerRateLimit = 8
// dialbackoff is a struct used to avoid over-dialing the same, dead peers.
// Whenever we totally time out on a peer (all three attempts), we add them
// to dialbackoff. Then, whenevers goroutines would _wait_ (dialsync), they
// check dialbackoff. If it's there, they don't wait and exit promptly with
// an error. (the single goroutine that is actually dialing continues to
// dial). If a dial is successful, the peer is removed from backoff.
// Example:
//
// for {
// if ok, wait := dialsync.Lock(p); !ok {
// if backoff.Backoff(p) {
// return errDialFailed
// }
// <-wait
// continue
// }
// defer dialsync.Unlock(p)
// c, err := actuallyDial(p)
// if err != nil {
// dialbackoff.AddBackoff(p)
// continue
// }
// dialbackoff.Clear(p)
// }
//
// DialBackoff is a type for tracking peer dial backoffs.
//
// * It's safe to use its zero value.
// * It's thread-safe.
// * It's *not* safe to move this type after using.
type DialBackoff struct {
entries map[peer.ID]map[string]*backoffAddr
lock sync.RWMutex
}
type backoffAddr struct {
tries int
until time.Time
}
func (db *DialBackoff) init(ctx context.Context) {
if db.entries == nil {
db.entries = make(map[peer.ID]map[string]*backoffAddr)
}
go db.background(ctx)
}
func (db *DialBackoff) background(ctx context.Context) {
ticker := time.NewTicker(BackoffMax)
defer ticker.Stop()
for {
select {
case <-ctx.Done():
return
case <-ticker.C:
db.cleanup()
}
}
}
// Backoff returns whether the client should backoff from dialing
// peer p at address addr
func (db *DialBackoff) Backoff(p peer.ID, addr ma.Multiaddr) (backoff bool) {
db.lock.Lock()
defer db.lock.Unlock()
ap, found := db.entries[p][string(addr.Bytes())]
return found && time.Now().Before(ap.until)
}
// BackoffBase is the base amount of time to backoff (default: 5s).
var BackoffBase = time.Second * 5
// BackoffCoef is the backoff coefficient (default: 1s).
var BackoffCoef = time.Second
// BackoffMax is the maximum backoff time (default: 5m).
var BackoffMax = time.Minute * 5
// AddBackoff lets other nodes know that we've entered backoff with
// peer p, so dialers should not wait unnecessarily. We still will
// attempt to dial with one goroutine, in case we get through.
//
// Backoff is not exponential, it's quadratic and computed according to the
// following formula:
//
// BackoffBase + BakoffCoef * PriorBackoffs^2
//
// Where PriorBackoffs is the number of previous backoffs.
func (db *DialBackoff) AddBackoff(p peer.ID, addr ma.Multiaddr) {
saddr := string(addr.Bytes())
db.lock.Lock()
defer db.lock.Unlock()
bp, ok := db.entries[p]
if !ok {
bp = make(map[string]*backoffAddr, 1)
db.entries[p] = bp
}
ba, ok := bp[saddr]
if !ok {
bp[saddr] = &backoffAddr{
tries: 1,
until: time.Now().Add(BackoffBase),
}
return
}
backoffTime := BackoffBase + BackoffCoef*time.Duration(ba.tries*ba.tries)
if backoffTime > BackoffMax {
backoffTime = BackoffMax
}
ba.until = time.Now().Add(backoffTime)
ba.tries++
}
// Clear removes a backoff record. Clients should call this after a
// successful Dial.
func (db *DialBackoff) Clear(p peer.ID) {
db.lock.Lock()
defer db.lock.Unlock()
delete(db.entries, p)
}
func (db *DialBackoff) cleanup() {
db.lock.Lock()
defer db.lock.Unlock()
now := time.Now()
for p, e := range db.entries {
good := false
for _, backoff := range e {
backoffTime := BackoffBase + BackoffCoef*time.Duration(backoff.tries*backoff.tries)
if backoffTime > BackoffMax {
backoffTime = BackoffMax
}
if now.Before(backoff.until.Add(backoffTime)) {
good = true
break
}
}
if !good {
delete(db.entries, p)
}
}
}
// DialPeer connects to a peer.
//
// The idea is that the client of Swarm does not need to know what network
// the connection will happen over. Swarm can use whichever it choses.
// This allows us to use various transport protocols, do NAT traversal/relay,
// etc. to achieve connection.
func (s *Swarm) DialPeer(ctx context.Context, p peer.ID) (network.Conn, error) {
if s.gater != nil && !s.gater.InterceptPeerDial(p) {
log.Debugf("gater disallowed outbound connection to peer %s", p.Pretty())
return nil, &DialError{Peer: p, Cause: ErrGaterDisallowedConnection}
}
// Avoid typed nil issues.
c, err := s.dialPeer(ctx, p)
if err != nil {
return nil, err
}
return c, nil
}
// internal dial method that returns an unwrapped conn
//
// It is gated by the swarm's dial synchronization systems: dialsync and
// dialbackoff.
func (s *Swarm) dialPeer(ctx context.Context, p peer.ID) (*Conn, error) {
log.Debugw("dialing peer", "from", s.local, "to", p)
err := p.Validate()
if err != nil {
return nil, err
}
if p == s.local {
return nil, ErrDialToSelf
}
// check if we already have an open (usable) connection first
conn := s.bestAcceptableConnToPeer(ctx, p)
if conn != nil {
return conn, nil
}
// apply the DialPeer timeout
ctx, cancel := context.WithTimeout(ctx, network.GetDialPeerTimeout(ctx))
defer cancel()
conn, err = s.dsync.Dial(ctx, p)
if err == nil {
return conn, nil
}
log.Debugf("network for %s finished dialing %s", s.local, p)
if ctx.Err() != nil {
// Context error trumps any dial errors as it was likely the ultimate cause.
return nil, ctx.Err()
}
if s.ctx.Err() != nil {
// Ok, so the swarm is shutting down.
return nil, ErrSwarmClosed
}
return nil, err
}
// dialWorkerLoop synchronizes and executes concurrent dials to a single peer
func (s *Swarm) dialWorkerLoop(p peer.ID, reqch <-chan dialRequest) {
w := newDialWorker(s, p, reqch)
w.loop()
}
func (s *Swarm) addrsForDial(ctx context.Context, p peer.ID) ([]ma.Multiaddr, error) {
peerAddrs := s.peers.Addrs(p)
if len(peerAddrs) == 0 {
return nil, ErrNoAddresses
}
goodAddrs := s.filterKnownUndialables(p, peerAddrs)
if forceDirect, _ := network.GetForceDirectDial(ctx); forceDirect {
goodAddrs = ma.FilterAddrs(goodAddrs, s.nonProxyAddr)
}
if len(goodAddrs) == 0 {
return nil, ErrNoGoodAddresses
}
return goodAddrs, nil
}
func (s *Swarm) dialNextAddr(ctx context.Context, p peer.ID, addr ma.Multiaddr, resch chan dialResult) error {
// check the dial backoff
if forceDirect, _ := network.GetForceDirectDial(ctx); !forceDirect {
if s.backf.Backoff(p, addr) {
return ErrDialBackoff
}
}
// start the dial
s.limitedDial(ctx, p, addr, resch)
return nil
}
func (s *Swarm) canDial(addr ma.Multiaddr) bool {
t := s.TransportForDialing(addr)
return t != nil && t.CanDial(addr)
}
func (s *Swarm) nonProxyAddr(addr ma.Multiaddr) bool {
t := s.TransportForDialing(addr)
return !t.Proxy()
}
// filterKnownUndialables takes a list of multiaddrs, and removes those
// that we definitely don't want to dial: addresses configured to be blocked,
// IPv6 link-local addresses, addresses without a dial-capable transport,
// and addresses that we know to be our own.
// This is an optimization to avoid wasting time on dials that we know are going to fail.
func (s *Swarm) filterKnownUndialables(p peer.ID, addrs []ma.Multiaddr) []ma.Multiaddr {
lisAddrs, _ := s.InterfaceListenAddresses()
var ourAddrs []ma.Multiaddr
for _, addr := range lisAddrs {
protos := addr.Protocols()
// we're only sure about filtering out /ip4 and /ip6 addresses, so far
if protos[0].Code == ma.P_IP4 || protos[0].Code == ma.P_IP6 {
ourAddrs = append(ourAddrs, addr)
}
}
return ma.FilterAddrs(addrs,
func(addr ma.Multiaddr) bool {
for _, a := range ourAddrs {
if a.Equal(addr) {
return false
}
}
return true
},
s.canDial,
// TODO: Consider allowing link-local addresses
func(addr ma.Multiaddr) bool { return !manet.IsIP6LinkLocal(addr) },
func(addr ma.Multiaddr) bool {
return s.gater == nil || s.gater.InterceptAddrDial(p, addr)
},
)
}
// limitedDial will start a dial to the given peer when
// it is able, respecting the various different types of rate
// limiting that occur without using extra goroutines per addr
func (s *Swarm) limitedDial(ctx context.Context, p peer.ID, a ma.Multiaddr, resp chan dialResult) {
timeout := s.dialTimeout
if lowTimeoutFilters.AddrBlocked(a) && s.dialTimeoutLocal < s.dialTimeout {
timeout = s.dialTimeoutLocal
}
s.limiter.AddDialJob(&dialJob{
addr: a,
peer: p,
resp: resp,
ctx: ctx,
timeout: timeout,
})
}
// dialAddr is the actual dial for an addr, indirectly invoked through the limiter
func (s *Swarm) dialAddr(ctx context.Context, p peer.ID, addr ma.Multiaddr) (transport.CapableConn, error) {
// Just to double check. Costs nothing.
if s.local == p {
return nil, ErrDialToSelf
}
log.Debugf("%s swarm dialing %s %s", s.local, p, addr)
tpt := s.TransportForDialing(addr)
if tpt == nil {
return nil, ErrNoTransport
}
connC, err := tpt.Dial(ctx, addr, p)
if err != nil {
return nil, err
}
// Trust the transport? Yeah... right.
if connC.RemotePeer() != p {
connC.Close()
err = fmt.Errorf("BUG in transport %T: tried to dial %s, dialed %s", p, connC.RemotePeer(), tpt)
log.Error(err)
return nil, err
}
// success! we got one!
return connC, nil
}
// TODO We should have a `IsFdConsuming() bool` method on the `Transport` interface in go-libp2p-core/transport.
// This function checks if any of the transport protocols in the address requires a file descriptor.
// For now:
// A Non-circuit address which has the TCP/UNIX protocol is deemed FD consuming.
// For a circuit-relay address, we look at the address of the relay server/proxy
// and use the same logic as above to decide.
func isFdConsumingAddr(addr ma.Multiaddr) bool {
first, _ := ma.SplitFunc(addr, func(c ma.Component) bool {
return c.Protocol().Code == ma.P_CIRCUIT
})
// for safety
if first == nil {
return true
}
_, err1 := first.ValueForProtocol(ma.P_TCP)
_, err2 := first.ValueForProtocol(ma.P_UNIX)
return err1 == nil || err2 == nil
}
func isExpensiveAddr(addr ma.Multiaddr) bool {
_, err1 := addr.ValueForProtocol(ma.P_WS)
_, err2 := addr.ValueForProtocol(ma.P_WSS)
return err1 == nil || err2 == nil
}
func isRelayAddr(addr ma.Multiaddr) bool {
_, err := addr.ValueForProtocol(ma.P_CIRCUIT)
return err == nil
}