Revert "Cache DNS lookups when resolving safebrowsing or parental servers, also cache replacement hostnames as well."

This reverts commit a5d1053520.

This cache had unintended side effects.

coredns_plugin/coredns_plugin.go

@@ -41,16 +41,6 @@ func init() {
 	})
 }
 
-type cacheEntry struct {
-	answer      []dns.RR
-	lastUpdated time.Time
-}
-
-var (
-	lookupCacheTime = time.Minute * 30
-	lookupCache     = map[string]cacheEntry{}
-)
-
 type plugFilter struct {
 	ID   int64
 	Path string
@@ -345,8 +335,6 @@ func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWri
 		records = append(records, result)
 	} else {
 		// this is a domain name, need to look it up
-		cacheentry := lookupCache[val]
-		if time.Since(cacheentry.lastUpdated) > lookupCacheTime {
 		req := new(dns.Msg)
 		req.SetQuestion(dns.Fqdn(val), question.Qtype)
 		req.RecursionDesired = true
@@ -361,13 +349,6 @@ func (p *plug) replaceHostWithValAndReply(ctx context.Context, w dns.ResponseWri
 				answer.Header().Name = question.Name
 			}
 			records = result.Answer
-				cacheentry.answer = result.Answer
-				cacheentry.lastUpdated = time.Now()
-				lookupCache[val] = cacheentry
-			}
-		} else {
-			// get from cache
-			records = cacheentry.answer
 		}
 	}
 	m := new(dns.Msg)

dnsfilter/dnsfilter.go

@@ -17,7 +17,6 @@ import (
 	"sync/atomic"
 	"time"
 
-	_ "github.com/benburkert/dns/init"
 	"github.com/bluele/gcache"
 	"golang.org/x/net/publicsuffix"
 )