fix setting memcache counters for the first time

dos.go

@@ -13,6 +13,7 @@ var (
 	dosKeyNamespace = "dos"
 
 	memcacheAddr = flag.String("memcache", "127.0.0.1:11211", "Memcache address")
+	whitelistedAddrs = flag.String("whitelist-addrs", "127.0.0.1", "Whitelisted addresses (no rate limiting), comma separated")
 )
 
 type Limiter struct {
@@ -31,7 +32,7 @@ func NewLimiter(param string, count int, period int, extractfn func(*http.Reques
 		Count: count,
 		Period: period,
 		extractValue: extractfn,
-		whitelistedValues: make([]string, 0),
+		whitelistedValues: strings.Split(*whitelistedAddrs, ","),
 		mc: memcache.New(*memcacheAddr),
 	}
 }
@@ -58,7 +59,7 @@ func (l *Limiter) Limit(handler http.Handler) http.Handler {
 		result, err := l.mc.Increment(key, 1)
 		if err != nil {
 			result = 1
-			if err = l.mc.Add(&memcache.Item{Key: key, Value: []byte{0, 0, 0, 0}, Expiration: int32(l.Period)}); err != nil {
+			if err = l.mc.Add(&memcache.Item{Key: key, Value: []byte("1"), Expiration: int32(l.Period)}); err != nil {
 				// Possible race for who adds to the cache first.
 				if result, err = l.mc.Increment(key, 1); err != nil {
 					log.Printf("Memcache failed for '%s': %s", key, err)