torsvc: add support for stream isolation

In this commit, we extend the TorDial function and add a new attribute
to the TorProxyNet struct to allow the caller to opt for stream
isolation or not. Using stream isolation, we ensure that each new
connection uses a distinct circuit.

torsvc/net.go

@@ -39,6 +39,12 @@ type TorProxyNet struct {
 	// This is used for an outbound-only mode, so the node will not listen for
 	// incoming connections
 	TorSocks string
+
+	// StreamIsolation is a bool that determines if we should force the
+	// creation of a new circuit for this connection. If true, then this
+	// means that our traffic may be harder to correlate as each connection
+	// will now use a distinct circuit.
+	StreamIsolation bool
 }
 
 // Dial on the Tor network uses the torsvc TorDial() function, and requires
@@ -47,7 +53,7 @@ func (t *TorProxyNet) Dial(network, address string) (net.Conn, error) {
 	if network != "tcp" {
 		return nil, fmt.Errorf("Cannot dial non-tcp network via Tor")
 	}
-	return TorDial(address, t.TorSocks)
+	return TorDial(address, t.TorSocks, t.StreamIsolation)
 }
 
 // LookupHost on Tor network uses the torsvc TorLookupHost function.

torsvc/torsvc.go

@@ -44,9 +44,16 @@ var (
 )
 
 // TorDial returns a connection to a remote peer via Tor's socks proxy. Only
-// TCP is supported over Tor.
-func TorDial(address, socksPort string) (net.Conn, error) {
-	p := &socks.Proxy{Addr: localhost + ":" + socksPort}
+// TCP is supported over Tor. The final argument determines if we should force
+// stream isolation for this new connection. If we do, then this means this new
+// connection will use a fresh circuit, rather than possibly re-using an
+// existing circuit.
+func TorDial(address, socksPort string, streamIsolation bool) (net.Conn, error) {
+	p := &socks.Proxy{
+		Addr:         localhost + ":" + socksPort,
+		TorIsolation: streamIsolation,
+	}
+
 	return p.Dial("tcp", address)
 }