works better

ex/fks-shield/cache.go

@@ -12,7 +12,7 @@ import (
 // Cache elements, we using to key (toRadixKey) to distinguish between dns and dnssec
 type Packet struct {
 	ttl time.Time // insertion time
-	d   []byte    // raw packet
+	d   []byte    // raw packet, except the first two bytes
 }
 
 func toRadixKey(d *dns.Msg) string {
@@ -31,14 +31,6 @@ type Cache struct {
 	*radix.Radix
 }
 
-// Make an as-is copy, except for the first two bytes, as these hold
-// the DNS id.
-func quickCopy(p []byte) []byte {
-	q := make([]byte, 2)
-	q = append(q, p[2:]...)
-	return q
-}
-
 func NewCache() *Cache {
 	return &Cache{Radix: radix.New()}
 }
@@ -67,7 +59,7 @@ func (c *Cache) Find(d *dns.Msg) []byte {
 		}
 		return nil
 	}
-	return quickCopy(p.Value.(*Packet).d)
+	return p.Value.(*Packet).d
 }
 
 func (c *Cache) Insert(d *dns.Msg) {
@@ -75,7 +67,7 @@ func (c *Cache) Insert(d *dns.Msg) {
 		log.Printf("fsk-shield: inserting " + toRadixKey(d))
 	}
 	buf, _ := d.Pack() // Should always work
-	c.Radix.Insert(toRadixKey(d), &Packet{d: buf, ttl: time.Now().UTC()})
+	c.Radix.Insert(toRadixKey(d), &Packet{d: buf[2:], ttl: time.Now().UTC()})
 }
 
 func (c *Cache) Remove(d *dns.Msg) {

ex/fks-shield/shield.go

@@ -36,7 +36,9 @@ func serve(w dns.ResponseWriter, r *dns.Msg, c *Cache) {
 		return
 	}
 	if p := c.Find(r); p != nil {
-		dns.RawSetId(p, r.MsgHdr.Id)
+		b := []byte{0, 0}
+		dns.RawSetId(b, r.MsgHdr.Id)
+		p = append(b, p...)
 		w.WriteBuf(p)
 		return
 	}

ex/fksd/main.go

@@ -5,7 +5,7 @@ import (
 	"flag"
 	"log"
 	"os"
-	"os/Signal"
+	"os/signal"
 	"strings"
 )