Adding simple resolver interface

resolver.go

@@ -0,0 +1,17 @@
+package socks5
+
+import (
+	"net"
+)
+
+// NameResolver is used to implement custom name resolution
+type NameResolver interface {
+	Resolve(name string) (*net.IPAddr, error)
+}
+
+// DNSResolver uses the system DNS to resolve host names
+type DNSResolver struct{}
+
+func (d DNSResolver) Resolve(name string) (*net.IPAddr, error) {
+	return net.ResolveIPAddr("ip", name)
+}

resolver_test.go

@@ -0,0 +1,18 @@
+package socks5
+
+import (
+	"testing"
+)
+
+func TestDNSResolver(t *testing.T) {
+	d := DNSResolver{}
+
+	addr, err := d.Resolve("localhost")
+	if err != nil {
+		t.Fatalf("err: %v", err)
+	}
+
+	if !addr.IP.IsLoopback() {
+		t.Fatalf("expected loopback")
+	}
+}