improve dial errors

dial_error.go

@@ -2,6 +2,7 @@ package swarm
 
 import (
 	"fmt"
+	"os"
 	"strings"
 
 	"github.com/libp2p/go-libp2p-core/peer"
@@ -20,6 +21,10 @@ type DialError struct {
 	Skipped    int
 }
 
+func (e *DialError) Timeout() bool {
+	return os.IsTimeout(e.Cause)
+}
+
 func (e *DialError) recordErr(addr ma.Multiaddr, err error) {
 	if len(e.DialErrors) >= maxDialDialErrors {
 		e.Skipped++
@@ -48,11 +53,7 @@ func (e *DialError) Error() string {
 
 // Unwrap implements https://godoc.org/golang.org/x/xerrors#Wrapper.
 func (e *DialError) Unwrap() error {
-	// If we have a context error, that's the "ultimate" error.
-	if e.Cause != nil {
-		return e.Cause
-	}
-	return nil
+	return e.Cause
 }
 
 var _ error = (*DialError)(nil)

dial_sync.go

@@ -2,11 +2,15 @@ package swarm
 
 import (
 	"context"
+	"errors"
 	"sync"
 
 	"github.com/libp2p/go-libp2p-core/peer"
 )
 
+// TODO: change this text when we fix the bug
+var errDialCanceled = errors.New("dial was aborted internally, likely due to https://git.io/Je2wW")
+
 // DialFunc is the type of function expected by DialSync.
 type DialFunc func(context.Context, peer.ID) (*Conn, error)
 
@@ -78,6 +82,16 @@ func (ad *activeDial) decref() {
 
 func (ad *activeDial) start(ctx context.Context) {
 	ad.conn, ad.err = ad.ds.dialFunc(ctx, ad.id)
+
+	// This isn't the user's context so we should fix the error.
+	switch ad.err {
+	case context.Canceled:
+		// The dial was canceled with `CancelDial`.
+		ad.err = errDialCanceled
+	case context.DeadlineExceeded:
+		// We hit an internal timeout, not a context timeout.
+		ad.err = ErrDialTimeout
+	}
 	close(ad.waitch)
 	ad.cancel()
 }

swarm.go

@@ -40,6 +40,9 @@ var ErrSwarmClosed = errors.New("swarm closed")
 // transport is misbehaving.
 var ErrAddrFiltered = errors.New("address filtered")
 
+// ErrDialTimeout is returned when one a dial times out due to the global timeout
+var ErrDialTimeout = errors.New("dial timed out")
+
 // Swarm is a connection muxer, allowing connections to other peers to
 // be opened and closed, while still using the same Chan for all
 // communication. The Chan sends/receives Messages, which note the

swarm_dial.go

@@ -221,12 +221,23 @@ func (s *Swarm) dialPeer(ctx context.Context, p peer.ID) (*Conn, error) {
 	defer cancel()
 
 	conn, err = s.dsync.DialLock(ctx, p)
-	if err != nil {
-		return nil, err
+	if err == nil {
+		return conn, nil
 	}
 
 	log.Debugf("network for %s finished dialing %s", s.local, p)
-	return conn, err
+
+	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
 }
 
 // doDial is an ugly shim method to retain all the logging and backoff logic
@@ -317,13 +328,14 @@ func (s *Swarm) dial(ctx context.Context, p peer.ID) (*Conn, error) {
 	connC, dialErr := s.dialAddrs(ctx, p, goodAddrsChan)
 	if dialErr != nil {
 		logdial["error"] = dialErr.Cause.Error()
-		if dialErr.Cause == context.Canceled {
-			// always prefer the "context canceled" error.
-			// we rely on behing able to check `err == context.Canceled`
+		switch dialErr.Cause {
+		case context.Canceled, context.DeadlineExceeded:
+			// Always prefer the context errors as we rely on being
+			// able to check them.
 			//
 			// Removing this will BREAK backoff (causing us to
 			// backoff when canceling dials).
-			return nil, context.Canceled
+			return nil, dialErr.Cause
 		}
 		return nil, dialErr
 	}