Merge remote-tracking branch 'origin/master' into feature/envoy

integration/internal/netutil/netutil.go

@@ -0,0 +1,50 @@
+// Package netutil has helper types for working with network connections.
+package netutil
+
+import (
+	"context"
+	"net"
+)
+
+// Dialer is a type that has a DialContext method for making a network connection.
+type Dialer = interface {
+	DialContext(ctx context.Context, network, addr string) (net.Conn, error)
+}
+
+type localDialer struct {
+	underlying Dialer
+	portToAddr map[string]string
+}
+
+// NewLocalDialer creates a new Dialer which routes localhost traffic to the remote destinations
+// defined by `portToAddr`.
+func NewLocalDialer(underlying Dialer, portToAddr map[string]string) Dialer {
+	d := &localDialer{underlying: underlying, portToAddr: portToAddr}
+	return d
+}
+
+func (d *localDialer) DialContext(ctx context.Context, network, addr string) (net.Conn, error) {
+	addr = d.remapHost(ctx, addr)
+	return d.underlying.DialContext(ctx, network, addr)
+}
+
+func (d *localDialer) remapHost(ctx context.Context, hostport string) string {
+	host, port, err := net.SplitHostPort(hostport)
+	if err != nil {
+		host = hostport
+		port = "443"
+	}
+
+	dst, ok := d.portToAddr[port]
+	if !ok {
+		return hostport
+	}
+
+	ips, err := net.DefaultResolver.LookupIPAddr(ctx, host)
+	if err != nil || len(ips) == 0 || ips[0].String() != "127.0.0.1" {
+		return hostport
+	}
+
+	return dst
+
+}