use different protocol tag for unencrypted transport

p2p/net/conn/dial.go

@@ -63,7 +63,12 @@ func (d *Dialer) Dial(ctx context.Context, raddr ma.Multiaddr, remote peer.ID) (
 			maconn = d.Wrapper(maconn)
 		}
 
-		err = msmux.SelectProtoOrFail(SecioTag, maconn)
+		cryptoProtoChoice := SecioTag
+		if !EncryptConnections {
+			cryptoProtoChoice = NoEncryptionTag
+		}
+
+		err = msmux.SelectProtoOrFail(cryptoProtoChoice, maconn)
 		if err != nil {
 			errOut = err
 			return

p2p/net/conn/listen.go

@@ -18,6 +18,7 @@ import (
 )
 
 const SecioTag = "/secio"
+const NoEncryptionTag = "/plaintext"
 
 // ConnWrapper is any function that wraps a raw multiaddr connection
 type ConnWrapper func(transport.Conn) transport.Conn
@@ -164,7 +165,11 @@ func WrapTransportListener(ctx context.Context, ml transport.Listener, local pee
 	}
 	l.proc = goprocessctx.WithContextAndTeardown(ctx, l.teardown)
 
+	if EncryptConnections {
 		l.mux.AddHandler(SecioTag, nil)
+	} else {
+		l.mux.AddHandler(NoEncryptionTag, nil)
+	}
 
 	log.Debugf("Conn Listener on %s", l.Multiaddr())
 	log.Event(ctx, "swarmListen", l)