plugin/cache: Fix filtering (#4148)

The filtering of DNSSEC records in the cache plugin was not done
correctly. Also the change to introduced this bug didn't take into
account that the cache - by virtue of differentiating between DNSSEC and
no-DNSSEC - relied on not copying the data from the cache.

This change copies and then filters the data and factors the filtering
into a function that is used in two places (albeit with on ugly boolean
parameters to prevent copying things twice).

Add tests, do_test.go is moved to test/cache_test.go because the OPT
handing is done outside of the cache plugin. The core server re-attaches
the correct OPT when replying, so that makes for a better e2e test.

Added small unit test for filterRRslice and an explicit test that asks
for DNSSEC first and then plain, and vice versa to test cache behavior.

Fixes: #4146

Signed-off-by: Miek Gieben <miek@miek.nl>

1 files changed, 0 insertions, 75 deletions

diff --git a/plugin/cache/do_test.go b/plugin/cache/do_test.go
deleted file mode 100644
index 3cf87cabe..000000000
--- a/plugin/cache/do_test.go
+++ /dev/null
@@ -1,75 +0,0 @@
-package cache
-
-import (
-	"context"
-	"testing"
-
-	"github.com/coredns/coredns/plugin"
-	"github.com/coredns/coredns/plugin/pkg/dnstest"
-	"github.com/coredns/coredns/plugin/test"
-
-	"github.com/miekg/dns"
-)
-
-func TestDo(t *testing.T) {
-	// cache sets Do and requests that don't have them.
-	c := New()
-	c.Next = echoHandler()
-	req := new(dns.Msg)
-	req.SetQuestion("example.org.", dns.TypeA)
-	rec := dnstest.NewRecorder(&test.ResponseWriter{})
-
-	// No DO set.
-	c.ServeDNS(context.TODO(), rec, req)
-	reply := rec.Msg
-	opt := reply.Extra[len(reply.Extra)-1]
-	if x, ok := opt.(*dns.OPT); !ok {
-		t.Fatalf("Expected OPT RR, got %T", x)
-	}
-	if !opt.(*dns.OPT).Do() {
-		t.Errorf("Expected DO bit to be set, got false")
-	}
-	if x := opt.(*dns.OPT).UDPSize(); x != defaultUDPBufSize {
-		t.Errorf("Expected %d bufsize, got %d", defaultUDPBufSize, x)
-	}
-
-	// Do set - so left alone.
-	const mysize = defaultUDPBufSize * 2
-	setDo(req)
-	// set bufsize to something else than default to see cache doesn't touch it
-	req.Extra[len(req.Extra)-1].(*dns.OPT).SetUDPSize(mysize)
-	c.ServeDNS(context.TODO(), rec, req)
-	reply = rec.Msg
-	opt = reply.Extra[len(reply.Extra)-1]
-	if x, ok := opt.(*dns.OPT); !ok {
-		t.Fatalf("Expected OPT RR, got %T", x)
-	}
-	if !opt.(*dns.OPT).Do() {
-		t.Errorf("Expected DO bit to be set, got false")
-	}
-	if x := opt.(*dns.OPT).UDPSize(); x != mysize {
-		t.Errorf("Expected %d bufsize, got %d", mysize, x)
-	}
-
-	// edns0 set, but not DO, so _not_ left alone.
-	req.Extra[len(req.Extra)-1].(*dns.OPT).SetDo(false)
-	c.ServeDNS(context.TODO(), rec, req)
-	reply = rec.Msg
-	opt = reply.Extra[len(reply.Extra)-1]
-	if x, ok := opt.(*dns.OPT); !ok {
-		t.Fatalf("Expected OPT RR, got %T", x)
-	}
-	if !opt.(*dns.OPT).Do() {
-		t.Errorf("Expected DO bit to be set, got false")
-	}
-	if x := opt.(*dns.OPT).UDPSize(); x != defaultUDPBufSize {
-		t.Errorf("Expected %d bufsize, got %d", defaultUDPBufSize, x)
-	}
-}
-
-func echoHandler() plugin.Handler {
-	return plugin.HandlerFunc(func(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
-		w.WriteMsg(r)
-		return dns.RcodeSuccess, nil
-	})
-}