changes from PR

net/conn/dial.go

@@ -8,7 +8,6 @@ import (
 	manet "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr/net"
 
 	peer "github.com/jbenet/go-ipfs/peer"
-	"github.com/jbenet/go-ipfs/util"
 )
 
 // Dial connects to a particular peer, over a given network
@@ -24,10 +23,6 @@ func (d *Dialer) Dial(ctx context.Context, network string, remote peer.Peer) (Co
 		return nil, fmt.Errorf("No remote address for network %s", network)
 	}
 
-	if util.IsLoopbackAddr(raddr.String()) {
-		return nil, fmt.Errorf("Attempted to connect to loopback address: %s", raddr)
-	}
-
 	remote, err := d.Peerstore.Add(remote)
 	if err != nil {
 		log.Errorf("Error putting peer into peerstore: %s", remote)

net/conn/handshake.go

@@ -106,18 +106,28 @@ func Handshake3(ctx context.Context, c Conn) error {
 		return err
 	}
 
-	nat, err := CheckNAT(remoteH.GetObservedAddr())
+	// If we are behind a NAT, inform the user that certain things might not work yet
+	nat, err := checkNAT(remoteH.GetObservedAddr())
 	if err != nil {
 		log.Errorf("Error in NAT detection: %s", err)
 	}
 	if nat {
-		log.Warning("We are probably behind a NAT!")
+		msg := `Remote peer observed our address to be: %s
+		The local addresses are: %s
+		Thus, connection is going through NAT, and other connections may fail.
+
+		IPFS NAT traversal is still under development. Please bug us on github or irc to fix this.
+		Baby steps: http://jbenet.static.s3.amazonaws.com/271dfcf/baby-steps.gif
+		`
+		addrs, _ := u.GetLocalAddresses()
+		log.Warning(fmt.Sprintf(msg, remoteH.GetObservedAddr(), addrs))
 	}
 
 	return nil
 }
 
-func CheckNAT(obsaddr string) (bool, error) {
+// checkNAT returns whether or not we might be behind a NAT
+func checkNAT(obsaddr string) (bool, error) {
 	oma, err := ma.NewMultiaddr(obsaddr)
 	if err != nil {
 		return false, err

net/handshake/pb/handshake.proto

@@ -30,5 +30,9 @@ message Handshake3 {
   // repeated mux.ProtocolID services = 3;
 
   // we'll have more fields here later.
+
+  // oservedAddr is the multiaddr of the remote endpoint that the local node perceives
+  // this is useful information to convey to the other side, as it helps the remote endpoint
+  // determine whether its connection to the local peer goes through NAT.
   optional string observedAddr = 4;
 }

net/swarm/swarm.go

@@ -3,6 +3,7 @@ package swarm
 import (
 	"errors"
 	"fmt"
+	"strings"
 	"sync"
 
 	conn "github.com/jbenet/go-ipfs/net/conn"
@@ -127,6 +128,16 @@ func (s *Swarm) Dial(peer peer.Peer) (conn.Conn, error) {
 		Peerstore: s.peers,
 	}
 
+	// If we are attempting to connect to a loopback addr, fail out early
+	raddr := peer.NetAddress("tcp")
+	if raddr == nil {
+		return nil, fmt.Errorf("No remote address for network tcp")
+	}
+
+	if strings.HasPrefix(raddr.String(), "/ip4/0.0.0.0") {
+		return nil, fmt.Errorf("Attempted to connect to loopback address: %s", raddr)
+	}
+
 	c, err = d.Dial(s.Context(), "tcp", peer)
 	if err != nil {
 		return nil, err

util/util.go

@@ -112,6 +112,8 @@ func GetenvBool(name string) bool {
 	return v == "true" || v == "t" || v == "1"
 }
 
+// IsLoopbackAddr returns whether or not the ip portion of the passed in multiaddr
+// string is a loopback address
 func IsLoopbackAddr(addr string) bool {
 	loops := []string{"/ip4/127.0.0.1", "/ip6/::1", "/ip4/0.0.0.0"}
 	for _, loop := range loops {
@@ -122,7 +124,10 @@ func IsLoopbackAddr(addr string) bool {
 	return false
 }
 
+// GetLocalAddresses returns a list of ip addresses associated with
+// the local machine
 func GetLocalAddresses() ([]ma.Multiaddr, error) {
+	// Enumerate interfaces on this machine
 	ifaces, err := net.Interfaces()
 	if err != nil {
 		return nil, err
@@ -135,19 +140,25 @@ func GetLocalAddresses() ([]ma.Multiaddr, error) {
 			log.Warningf("Skipping addr: %s", err)
 			continue
 		}
+		// Check each address and convert to a multiaddr
 		for _, addr := range addrs {
 			switch v := addr.(type) {
 			case *net.IPNet:
+
+				// Build multiaddr
 				maddr, err := manet.FromIP(v.IP)
 				if err != nil {
 					log.Errorf("maddr parsing error: %s", err)
 					continue
 				}
+
+				// Dont list loopback addresses
 				if IsLoopbackAddr(maddr.String()) {
 					continue
 				}
 				maddrs = append(maddrs, maddr)
 			default:
+				// Not sure if any other types will show up here
 				log.Errorf("Got '%s' type = '%s'", v, reflect.TypeOf(v))
 			}
 		}