plugin/forward: Allow Proxy to be used outside of forward plugin. (#5951)

* plugin/forward: Move Proxy into pkg/plugin/proxy, to allow forward.Proxy to be used outside of forward plugin.

Signed-off-by: Patrick Downey <patrick.downey@dioadconsulting.com>

plugin/pkg/proxy/proxy_test.go

@@ -0,0 +1,99 @@
+package proxy
+
+import (
+	"context"
+	"crypto/tls"
+	"testing"
+	"time"
+
+	"github.com/coredns/coredns/plugin/pkg/dnstest"
+	"github.com/coredns/coredns/plugin/pkg/transport"
+	"github.com/coredns/coredns/plugin/test"
+	"github.com/coredns/coredns/request"
+
+	"github.com/miekg/dns"
+)
+
+func TestProxy(t *testing.T) {
+	s := dnstest.NewServer(func(w dns.ResponseWriter, r *dns.Msg) {
+		ret := new(dns.Msg)
+		ret.SetReply(r)
+		ret.Answer = append(ret.Answer, test.A("example.org. IN A 127.0.0.1"))
+		w.WriteMsg(ret)
+	})
+	defer s.Close()
+
+	p := NewProxy(s.Addr, transport.DNS)
+	p.readTimeout = 10 * time.Millisecond
+	p.Start(5 * time.Second)
+	m := new(dns.Msg)
+
+	m.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnstest.NewRecorder(&test.ResponseWriter{})
+	req := request.Request{Req: m, W: rec}
+
+	resp, err := p.Connect(context.Background(), req, Options{PreferUDP: true})
+	if err != nil {
+		t.Errorf("Failed to connect to testdnsserver: %s", err)
+	}
+
+	if x := resp.Answer[0].Header().Name; x != "example.org." {
+		t.Errorf("Expected %s, got %s", "example.org.", x)
+	}
+}
+
+func TestProxyTLSFail(t *testing.T) {
+	// This is an udp/tcp test server, so we shouldn't reach it with TLS.
+	s := dnstest.NewServer(func(w dns.ResponseWriter, r *dns.Msg) {
+		ret := new(dns.Msg)
+		ret.SetReply(r)
+		ret.Answer = append(ret.Answer, test.A("example.org. IN A 127.0.0.1"))
+		w.WriteMsg(ret)
+	})
+	defer s.Close()
+
+	p := NewProxy(s.Addr, transport.TLS)
+	p.readTimeout = 10 * time.Millisecond
+	p.SetTLSConfig(&tls.Config{})
+	p.Start(5 * time.Second)
+	m := new(dns.Msg)
+
+	m.SetQuestion("example.org.", dns.TypeA)
+
+	rec := dnstest.NewRecorder(&test.ResponseWriter{})
+	req := request.Request{Req: m, W: rec}
+
+	_, err := p.Connect(context.Background(), req, Options{})
+	if err == nil {
+		t.Fatal("Expected *not* to receive reply, but got one")
+	}
+}
+
+func TestProtocolSelection(t *testing.T) {
+	p := NewProxy("bad_address", transport.DNS)
+	p.readTimeout = 10 * time.Millisecond
+
+	stateUDP := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
+	stateTCP := request.Request{W: &test.ResponseWriter{TCP: true}, Req: new(dns.Msg)}
+	ctx := context.TODO()
+
+	go func() {
+		p.Connect(ctx, stateUDP, Options{})
+		p.Connect(ctx, stateUDP, Options{ForceTCP: true})
+		p.Connect(ctx, stateUDP, Options{PreferUDP: true})
+		p.Connect(ctx, stateUDP, Options{PreferUDP: true, ForceTCP: true})
+		p.Connect(ctx, stateTCP, Options{})
+		p.Connect(ctx, stateTCP, Options{ForceTCP: true})
+		p.Connect(ctx, stateTCP, Options{PreferUDP: true})
+		p.Connect(ctx, stateTCP, Options{PreferUDP: true, ForceTCP: true})
+	}()
+
+	for i, exp := range []string{"udp", "tcp", "udp", "tcp", "tcp", "tcp", "udp", "tcp"} {
+		proto := <-p.transport.dial
+		p.transport.ret <- nil
+		if proto != exp {
+			t.Errorf("Unexpected protocol in case %d, expected %q, actual %q", i, exp, proto)
+		}
+	}
+}