plugin/forward: remove truncate logic (#2320)

I think this is causing problem and it will actually clash with the
scrubbing that now happens for all plugins anyway. We're assuming the
returned message will be valid even with tc being set. request.Scrub
follows that same logic.
Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/forward/truncated_test.go

-package forward
-
-import (
-	"sync/atomic"
-	"testing"
-
-	"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 TestLookupTruncated(t *testing.T) {
-	i := int32(0)
-	s := dnstest.NewServer(func(w dns.ResponseWriter, r *dns.Msg) {
-		j := atomic.LoadInt32(&i)
-		atomic.AddInt32(&i, 1)
-
-		if j == 0 {
-			ret := new(dns.Msg)
-			ret.SetReply(r)
-			ret.Truncated = true
-			ret.Answer = append(ret.Answer, test.A("example.org. IN A 127.0.0.1"))
-			w.WriteMsg(ret)
-			return
-
-		}
-
-		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)
-	f := New()
-	f.SetProxy(p)
-	defer f.Close()
-
-	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
-
-	resp, err := f.Lookup(state, "example.org.", dns.TypeA)
-	if err != nil {
-		t.Fatal("Expected to receive reply, but didn't")
-	}
-	// expect answer with TC
-	if !resp.Truncated {
-		t.Error("Expected to receive reply with TC bit set, but didn't")
-	}
-	if len(resp.Answer) != 1 {
-		t.Error("Expected to receive original reply, but answer is missing")
-	}
-
-	resp, err = f.Lookup(state, "example.org.", dns.TypeA)
-	if err != nil {
-		t.Fatal("Expected to receive reply, but didn't")
-	}
-	// expect answer without TC
-	if resp.Truncated {
-		t.Error("Expected to receive reply without TC bit set, but didn't")
-	}
-}
-
-func TestForwardTruncated(t *testing.T) {
-	i := int32(0)
-	s := dnstest.NewServer(func(w dns.ResponseWriter, r *dns.Msg) {
-		j := atomic.LoadInt32(&i)
-		atomic.AddInt32(&i, 1)
-
-		if j == 0 {
-			ret := new(dns.Msg)
-			ret.SetReply(r)
-			ret.Truncated = true
-			ret.Answer = append(ret.Answer, test.A("example.org. IN A 127.0.0.1"))
-			w.WriteMsg(ret)
-			return
-
-		}
-
-		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()
-
-	f := New()
-
-	p1 := NewProxy(s.Addr, transport.DNS)
-	f.SetProxy(p1)
-	p2 := NewProxy(s.Addr, transport.DNS)
-	f.SetProxy(p2)
-	defer f.Close()
-
-	state := request.Request{W: &test.ResponseWriter{}, Req: new(dns.Msg)}
-	state.Req.SetQuestion("example.org.", dns.TypeA)
-	resp, err := f.Forward(state)
-	if err != nil {
-		t.Fatal("Expected to receive reply, but didn't")
-	}
-
-	// expect answer with TC
-	if !resp.Truncated {
-		t.Error("Expected to receive reply with TC bit set, but didn't")
-	}
-	if len(resp.Answer) != 1 {
-		t.Error("Expected to receive original reply, but answer is missing")
-	}
-
-	resp, err = f.Forward(state)
-	if err != nil {
-		t.Fatal("Expected to receive reply, but didn't")
-	}
-	// expect answer without TC
-	if resp.Truncated {
-		t.Error("Expected to receive reply without TC bit set, but didn't")
-	}
-}