Ejemplo n.º 1
0
func serve(w dns.ResponseWriter, r *dns.Msg, c *Cache) {
	switch {
	case r.IsNotify():
		if *flaglog {
			log.Printf("fks-shield: notify/update")
		}
		fallthrough
	case r.IsUpdate():
		client := new(dns.Client)
		if p, e := client.Exchange(r, *server); e == nil {
			w.WriteMsg(p)
		}
		return
	}
	if p := c.Find(r); p != nil {
		b := []byte{byte(r.MsgHdr.Id >> 8), byte(r.MsgHdr.Id)}
		p = append(b, p...)
		w.Write(p)
		return
	}
	// Cache miss
	client := new(dns.Client)
	if p, e := client.Exchange(r, *server); e == nil {
		// TODO(mg): If r has edns0 and p has not we create a mismatch here
		w.WriteMsg(p)
		c.Insert(p)
		return
	} else {
		log.Printf("fks-shield: failed to get answer " + e.Error())
		m := new(dns.Msg)
		m.SetRcode(r, dns.RcodeServerFailure)
		w.WriteMsg(m)
	}
}