Revert pkg/nonwriter changes (#1829)

The DoH work (#1619) made changes to pkg/nonwriter.Writer that in
hindsight were not backwards compatible; it added override for the
LocalAddr() and RemoteAddr(). Instead of rolling back that PR, this PR
reverts those changes and creates a DoHWriter for use in the
https-server.go side of things.

This was only caught in the integration test making this hard to catch,
so we add a upstream_file_test.go that tries (doesn't work yet) to test
this in the unit tests as well. Esp. helpful when 'git bisecting'.

Fixes #1826

core/dnsserver/https.go

@@ -4,8 +4,10 @@ import (
 	"encoding/base64"
 	"fmt"
 	"io/ioutil"
+	"net"
 	"net/http"
 
+	"github.com/coredns/coredns/plugin/pkg/nonwriter"
 	"github.com/miekg/dns"
 )
 
@@ -54,3 +56,19 @@ func base64ToMsg(b64 string) (*dns.Msg, error) {
 }
 
 var b64Enc = base64.RawURLEncoding
+
+// DoHWriter is a nonwriter.Writer that adds more specific LocalAddr and RemoteAddr methods.
+type DoHWriter struct {
+	nonwriter.Writer
+
+	// raddr is the remote's address. This can be optionally set.
+	raddr net.Addr
+	// laddr is our address. This can be optionally set.
+	laddr net.Addr
+}
+
+// RemoteAddr returns the remote address.
+func (d *DoHWriter) RemoteAddr() net.Addr { return d.raddr }
+
+// LocalAddr returns the local address.
+func (d *DoHWriter) LocalAddr() net.Addr { return d.laddr }

core/dnsserver/server-https.go

@@ -8,7 +8,6 @@ import (
 	"net/http"
 	"strconv"
 
-	"github.com/coredns/coredns/plugin/pkg/nonwriter"
 	"github.com/miekg/dns"
 )
 
@@ -119,12 +118,10 @@ func (s *ServerHTTPS) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
-	// Create a non-writer with the correct addresses in it.
-	dw := &nonwriter.Writer{Laddr: s.listenAddr}
+	// Create a DoHWriter with the correct addresses in it.
 	h, p, _ := net.SplitHostPort(r.RemoteAddr)
-	po, _ := strconv.Atoi(p)
-	ip := net.ParseIP(h)
-	dw.Raddr = &net.TCPAddr{IP: ip, Port: po}
+	port, _ := strconv.Atoi(p)
+	dw := &DoHWriter{laddr: s.listenAddr, raddr: &net.TCPAddr{IP: net.ParseIP(h), Port: port}}
 
 	// We just call the normal chain handler - all error handling is done there.
 	// We should expect a packet to be returned that we can send to the client.

plugin/pkg/nonwriter/nonwriter.go

@@ -2,8 +2,6 @@
 package nonwriter
 
 import (
-	"net"
-
 	"github.com/miekg/dns"
 )
 
@@ -11,11 +9,6 @@ import (
 type Writer struct {
 	dns.ResponseWriter
 	Msg *dns.Msg
-
-	// Raddr is the remote's address. This can be optionally set.
-	Raddr net.Addr
-	// Laddr is our address. This can be optionally set.
-	Laddr net.Addr
 }
 
 // New makes and returns a new NonWriter.
@@ -26,9 +19,3 @@ func (w *Writer) WriteMsg(res *dns.Msg) error {
 	w.Msg = res
 	return nil
 }
-
-// RemoteAddr returns the remote address.
-func (w *Writer) RemoteAddr() net.Addr { return w.Raddr }
-
-// LocalAddr returns the local address.
-func (w *Writer) LocalAddr() net.Addr { return w.Laddr }

test/file_upstream_test.go

+package test
+
+import (
+	"testing"
+
+	"github.com/miekg/dns"
+)
+
+// TODO(miek): this test needs to be fleshed out.
+
+func TestFileUpstream(t *testing.T) {
+	name, rm, err := TempFile(".", `$ORIGIN example.org.
+@	3600 IN	SOA sns.dns.icann.org. noc.dns.icann.org. (
+		2017042745 ; serial
+		7200       ; refresh (2 hours)
+		3600       ; retry (1 hour)
+		1209600    ; expire (2 weeks)
+		3600       ; minimum (1 hour)
+	)
+
+        3600 IN NS a.iana-servers.net.
+	3600 IN NS b.iana-servers.net.
+
+www 3600 IN CNAME   www.example.net.
+`)
+	if err != nil {
+		t.Fatalf("Failed to create zone: %s", err)
+	}
+	defer rm()
+
+	// Corefile with for example without proxy section.
+	corefile := `example.org:0 {
+       file ` + name + ` {
+	       upstream
+	}
+	hosts {
+		10.0.0.1 www.example.net.
+		fallthrough
+	}
+}
+`
+	i, udp, _, err := CoreDNSServerAndPorts(corefile)
+	if err != nil {
+		t.Fatalf("Could not get CoreDNS serving instance: %s", err)
+	}
+	defer i.Stop()
+
+	m := new(dns.Msg)
+	m.SetQuestion("www.example.org.", dns.TypeA)
+	m.SetEdns0(4096, true)
+
+	r, err := dns.Exchange(m, udp)
+	if err != nil {
+		t.Fatalf("Could not exchange msg: %s", err)
+	}
+	if r.Rcode == dns.RcodeServerFailure {
+		t.Fatalf("Rcode should not be dns.RcodeServerFailure")
+	}
+	t.Logf("%s", r)
+}