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swarm_dial.go
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swarm_dial.go
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package swarm
import (
"bytes"
"errors"
"fmt"
"sort"
"sync"
"time"
"github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr-net"
conn "github.com/ipfs/go-ipfs/p2p/net/conn"
addrutil "github.com/ipfs/go-ipfs/p2p/net/swarm/addr"
peer "github.com/ipfs/go-ipfs/p2p/peer"
lgbl "github.com/ipfs/go-ipfs/util/eventlog/loggables"
ma "github.com/ipfs/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
context "github.com/ipfs/go-ipfs/Godeps/_workspace/src/golang.org/x/net/context"
)
// 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 = errors.New("dial backoff")
ErrDialFailed = errors.New("dial attempt failed")
ErrDialToSelf = errors.New("dial to self attempted")
)
// 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
// number of concurrent outbound dials over transports that consume file descriptors
const concurrentFdDials = 160
// DialTimeout is the amount of time each dial attempt has. We can think about making
// this larger down the road, or putting more granular timeouts (i.e. within each
// subcomponent of Dial)
var DialTimeout time.Duration = time.Second * 10
// dialsync is a small object that helps manage ongoing dials.
// this way, if we receive many simultaneous dial requests, one
// can do its thing, while the rest wait.
//
// this interface is so would-be dialers can just:
//
// for {
// c := findConnectionToPeer(peer)
// if c != nil {
// return c
// }
//
// // ok, no connections. should we dial?
// if ok, wait := dialsync.Lock(peer); !ok {
// <-wait // can optionally wait
// continue
// }
// defer dialsync.Unlock(peer)
//
// c := actuallyDial(peer)
// return c
// }
//
type dialsync struct {
// ongoing is a map of tickets for the current peers being dialed.
// this way, we dont kick off N dials simultaneously.
ongoing map[peer.ID]chan struct{}
lock sync.Mutex
}
// Lock governs the beginning of a dial attempt.
// If there are no ongoing dials, it returns true, and the client is now
// scheduled to dial. Every other goroutine that calls startDial -- with
//the same dst -- will block until client is done. The client MUST call
// ds.Unlock(p) when it is done, to unblock the other callers.
// The client is not reponsible for achieving a successful dial, only for
// reporting the end of the attempt (calling ds.Unlock(p)).
//
// see the example below `dialsync`
func (ds *dialsync) Lock(dst peer.ID) (bool, chan struct{}) {
ds.lock.Lock()
if ds.ongoing == nil { // init if not ready
ds.ongoing = make(map[peer.ID]chan struct{})
}
wait, found := ds.ongoing[dst]
if !found {
ds.ongoing[dst] = make(chan struct{})
}
ds.lock.Unlock()
if found {
return false, wait
}
// ok! you're signed up to dial!
return true, nil
}
// Unlock releases waiters to a dial attempt. see Lock.
// if Unlock(p) is called without calling Lock(p) first, Unlock panics.
func (ds *dialsync) Unlock(dst peer.ID) {
ds.lock.Lock()
wait, found := ds.ongoing[dst]
if !found {
panic("called dialDone with no ongoing dials to peer: " + dst.Pretty())
}
delete(ds.ongoing, dst) // remove ongoing dial
close(wait) // release everyone else
ds.lock.Unlock()
}
// 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)
// }
//
type dialbackoff struct {
entries map[peer.ID]*backoffPeer
lock sync.RWMutex
}
type backoffPeer struct {
tries int
until time.Time
}
func (db *dialbackoff) init() {
if db.entries == nil {
db.entries = make(map[peer.ID]*backoffPeer)
}
}
// Backoff returns whether the client should backoff from dialing
// peer p
func (db *dialbackoff) Backoff(p peer.ID) (backoff bool) {
db.lock.Lock()
defer db.lock.Unlock()
db.init()
bp, found := db.entries[p]
if found && time.Now().Before(bp.until) {
return true
}
return false
}
const baseBackoffTime = time.Second * 5
const maxBackoffTime = 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.
func (db *dialbackoff) AddBackoff(p peer.ID) {
db.lock.Lock()
defer db.lock.Unlock()
db.init()
bp, ok := db.entries[p]
if !ok {
db.entries[p] = &backoffPeer{
tries: 1,
until: time.Now().Add(baseBackoffTime),
}
return
}
expTimeAdd := time.Second * time.Duration(bp.tries*bp.tries)
if expTimeAdd > maxBackoffTime {
expTimeAdd = maxBackoffTime
}
bp.until = time.Now().Add(baseBackoffTime + expTimeAdd)
bp.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()
db.init()
delete(db.entries, p)
}
// Dial 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 achive connection.
func (s *Swarm) Dial(ctx context.Context, p peer.ID) (*Conn, error) {
var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
if p == s.local {
log.Event(ctx, "swarmDialSelf", logdial)
return nil, ErrDialToSelf
}
return s.gatedDialAttempt(ctx, p)
}
func (s *Swarm) bestConnectionToPeer(p peer.ID) *Conn {
cs := s.ConnectionsToPeer(p)
for _, conn := range cs {
if conn != nil { // dump out the first one we find. (TODO pick better)
return conn
}
}
return nil
}
// gatedDialAttempt is an attempt to dial a node. It is gated by the swarm's
// dial synchronization systems: dialsync and dialbackoff.
func (s *Swarm) gatedDialAttempt(ctx context.Context, p peer.ID) (*Conn, error) {
var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
defer log.EventBegin(ctx, "swarmDialAttemptSync", logdial).Done()
// check if we already have an open connection first
conn := s.bestConnectionToPeer(p)
if conn != nil {
return conn, nil
}
// check if there's an ongoing dial to this peer
if ok, wait := s.dsync.Lock(p); ok {
defer s.dsync.Unlock(p)
// if this peer has been backed off, lets get out of here
if s.backf.Backoff(p) {
log.Event(ctx, "swarmDialBackoff", logdial)
return nil, ErrDialBackoff
}
// ok, we have been charged to dial! let's do it.
// if it succeeds, dial will add the conn to the swarm itself.
defer log.EventBegin(ctx, "swarmDialAttemptStart", logdial).Done()
ctxT, cancel := context.WithTimeout(ctx, s.dialT)
conn, err := s.dial(ctxT, p)
cancel()
log.Debugf("dial end %s", conn)
if err != nil {
log.Event(ctx, "swarmDialBackoffAdd", logdial)
s.backf.AddBackoff(p) // let others know to backoff
// ok, we failed. try again. (if loop is done, our error is output)
return nil, fmt.Errorf("dial attempt failed: %s", err)
}
log.Event(ctx, "swarmDialBackoffClear", logdial)
s.backf.Clear(p) // okay, no longer need to backoff
return conn, nil
} else {
// we did not dial. we must wait for someone else to dial.
// check whether we should backoff first...
if s.backf.Backoff(p) {
log.Event(ctx, "swarmDialBackoff", logdial)
return nil, ErrDialBackoff
}
defer log.EventBegin(ctx, "swarmDialWait", logdial).Done()
select {
case <-wait: // wait for that other dial to finish.
// see if it worked, OR we got an incoming dial in the meantime...
conn := s.bestConnectionToPeer(p)
if conn != nil {
return conn, nil
}
return nil, ErrDialFailed
case <-ctx.Done(): // or we may have to bail...
return nil, ctx.Err()
}
}
}
// dial is the actual swarm's dial logic, gated by Dial.
func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
var logdial = lgbl.Dial("swarm", s.LocalPeer(), p, nil, nil)
if p == s.local {
log.Event(ctx, "swarmDialDoDialSelf", logdial)
return nil, ErrDialToSelf
}
defer log.EventBegin(ctx, "swarmDialDo", logdial).Done()
logdial["dial"] = "failure" // start off with failure. set to "success" at the end.
sk := s.peers.PrivKey(s.local)
logdial["encrypted"] = (sk != nil) // log wether this will be an encrypted dial or not.
if sk == nil {
// fine for sk to be nil, just log.
log.Debug("Dial not given PrivateKey, so WILL NOT SECURE conn.")
}
// get remote peer addrs
remoteAddrs := s.peers.Addrs(p)
// make sure we can use the addresses.
remoteAddrs = addrutil.FilterUsableAddrs(remoteAddrs)
// drop out any addrs that would just dial ourselves. use ListenAddresses
// as that is a more authoritative view than localAddrs.
ila, _ := s.InterfaceListenAddresses()
remoteAddrs = addrutil.Subtract(remoteAddrs, ila)
remoteAddrs = addrutil.Subtract(remoteAddrs, s.peers.Addrs(s.local))
log.Debugf("%s swarm dialing %s -- local:%s remote:%s", s.local, p, s.ListenAddresses(), remoteAddrs)
if len(remoteAddrs) == 0 {
err := errors.New("peer has no addresses")
logdial["error"] = err
return nil, err
}
remoteAddrs = s.filterAddrs(remoteAddrs)
if len(remoteAddrs) == 0 {
err := errors.New("all adresses for peer have been filtered out")
logdial["error"] = err
return nil, err
}
// try to get a connection to any addr
connC, err := s.dialAddrs(ctx, p, remoteAddrs)
if err != nil {
logdial["error"] = err
return nil, err
}
logdial["netconn"] = lgbl.NetConn(connC)
// ok try to setup the new connection.
defer log.EventBegin(ctx, "swarmDialDoSetup", logdial, lgbl.NetConn(connC)).Done()
swarmC, err := dialConnSetup(ctx, s, connC)
if err != nil {
logdial["error"] = err
connC.Close() // close the connection. didn't work out :(
return nil, err
}
logdial["dial"] = "success"
return swarmC, nil
}
func (s *Swarm) dialAddrs(ctx context.Context, p peer.ID, remoteAddrs []ma.Multiaddr) (conn.Conn, error) {
// sort addresses so preferred addresses are dialed sooner
sort.Sort(AddrList(remoteAddrs))
// try to connect to one of the peer's known addresses.
// we dial concurrently to each of the addresses, which:
// * makes the process faster overall
// * attempts to get the fastest connection available.
// * mitigates the waste of trying bad addresses
log.Debugf("%s swarm dialing %s %s", s.local, p, remoteAddrs)
ctx, cancel := context.WithCancel(ctx)
defer cancel() // cancel work when we exit func
conns := make(chan conn.Conn)
errs := make(chan error, len(remoteAddrs))
// dialSingleAddr is used in the rate-limited async thing below.
dialSingleAddr := func(addr ma.Multiaddr) {
// rebind chans in scope so we can nil them out easily
connsout := conns
errsout := errs
connC, err := s.dialAddr(ctx, p, addr)
if err != nil {
connsout = nil
} else if connC == nil {
// NOTE: this really should never happen
log.Errorf("failed to dial %s %s and got no error!", p, addr)
err = fmt.Errorf("failed to dial %s %s", p, addr)
connsout = nil
} else {
errsout = nil
}
// check parent still wants our results
select {
case <-ctx.Done():
if connC != nil {
connC.Close()
}
case errsout <- err:
case connsout <- connC:
}
}
// this whole thing is in a goroutine so we can use foundConn
// to end early.
go func() {
limiter := make(chan struct{}, 8)
for _, addr := range remoteAddrs {
// returns whatever ratelimiting is acceptable for workerAddr.
// may not rate limit at all.
rl := s.addrDialRateLimit(addr)
select {
case <-ctx.Done(): // our context was cancelled
return
case rl <- struct{}{}:
// take the token, move on
}
select {
case <-ctx.Done(): // our context was cancelled
return
case limiter <- struct{}{}:
// take the token, move on
}
go func(rlc <-chan struct{}, a ma.Multiaddr) {
dialSingleAddr(a)
<-limiter
<-rlc
}(rl, addr)
}
}()
// wair for the results.
exitErr := fmt.Errorf("failed to dial %s", p)
for range remoteAddrs {
select {
case exitErr = <-errs: //
log.Debug("dial error: ", exitErr)
case connC := <-conns:
// take the first + return asap
return connC, nil
case <-ctx.Done():
// break out and return error
break
}
}
return nil, exitErr
}
func (s *Swarm) dialAddr(ctx context.Context, p peer.ID, addr ma.Multiaddr) (conn.Conn, error) {
log.Debugf("%s swarm dialing %s %s", s.local, p, addr)
connC, err := s.dialer.Dial(ctx, addr, p)
if err != nil {
return nil, fmt.Errorf("%s --> %s dial attempt failed: %s", s.local, p, err)
}
// if the connection is not to whom we thought it would be...
remotep := connC.RemotePeer()
if remotep != p {
connC.Close()
return nil, fmt.Errorf("misdial to %s through %s (got %s)", p, addr, remotep)
}
// if the connection is to ourselves...
// this can happen TONS when Loopback addrs are advertized.
// (this should be caught by two checks above, but let's just make sure.)
if remotep == s.local {
connC.Close()
return nil, fmt.Errorf("misdial to %s through %s (got self)", p, addr)
}
// success! we got one!
return connC, nil
}
func (s *Swarm) filterAddrs(addrs []ma.Multiaddr) []ma.Multiaddr {
var out []ma.Multiaddr
for _, a := range addrs {
if !s.Filters.AddrBlocked(a) {
out = append(out, a)
}
}
return out
}
// dialConnSetup is the setup logic for a connection from the dial side. it
// needs to add the Conn to the StreamSwarm, then run newConnSetup
func dialConnSetup(ctx context.Context, s *Swarm, connC conn.Conn) (*Conn, error) {
psC, err := s.swarm.AddConn(connC)
if err != nil {
// connC is closed by caller if we fail.
return nil, fmt.Errorf("failed to add conn to ps.Swarm: %s", err)
}
// ok try to setup the new connection. (newConnSetup will add to group)
swarmC, err := s.newConnSetup(ctx, psC)
if err != nil {
psC.Close() // we need to make sure psC is Closed.
return nil, err
}
return swarmC, err
}
// addrDialRateLimit returns a ratelimiting channel for dialing transport
// addrs like a. for example, tcp is fd-ratelimited. utp is not ratelimited.
func (s *Swarm) addrDialRateLimit(a ma.Multiaddr) chan struct{} {
if isFDCostlyTransport(a) {
return s.fdRateLimit
}
// do not rate limit it at all
return make(chan struct{}, 1)
}
func isFDCostlyTransport(a ma.Multiaddr) bool {
return isTCPMultiaddr(a)
}
func isTCPMultiaddr(a ma.Multiaddr) bool {
p := a.Protocols()
return len(p) == 2 && (p[0].Name == "ip4" || p[0].Name == "ip6") && p[1].Name == "tcp"
}
type AddrList []ma.Multiaddr
func (al AddrList) Len() int {
return len(al)
}
func (al AddrList) Swap(i, j int) {
al[i], al[j] = al[j], al[i]
}
func (al AddrList) Less(i, j int) bool {
a := al[i]
b := al[j]
// dial localhost addresses next, they should fail immediately
lba := manet.IsIPLoopback(a)
lbb := manet.IsIPLoopback(b)
if lba {
if !lbb {
return true
}
}
// dial utp and similar 'non-fd-consuming' addresses first
fda := isFDCostlyTransport(a)
fdb := isFDCostlyTransport(b)
if !fda {
if fdb {
return true
}
// if neither consume fd's, assume equal ordering
return false
}
// if 'b' doesnt take a file descriptor
if !fdb {
return false
}
// if 'b' is loopback and both take file descriptors
if lbb {
return false
}
// for the rest, just sort by bytes
return bytes.Compare(a.Bytes(), b.Bytes()) > 0
}