package main import ( "github.com/miekg/dns" ) type Question struct { qname string qtype string qclass string } func (q *Question) String() string { return q.qname + " " + q.qclass + " " + q.qtype } type GODNSHandler struct { resolver *Resolver cache Cache } func NewHandler() *GODNSHandler { var ( clientConfig *dns.ClientConfig cacheConfig CacheSettings resolver *Resolver cache Cache ) resolvConfig := settings.ResolvConfig clientConfig, err := dns.ClientConfigFromFile(resolvConfig.ResolvFile) if err != nil { logger.Printf(":%s is not a valid resolv.conf file\n", resolvConfig.ResolvFile) logger.Println(err) panic(err) } clientConfig.Timeout = resolvConfig.Timeout resolver = &Resolver{clientConfig} cacheConfig = settings.Cache switch cacheConfig.Backend { case "memory": cache = &MemoryCache{ backend: make(map[string]*dns.Msg), expire: cacheConfig.Expire, maxcount: cacheConfig.Maxcount, } case "redis": // cache = &MemoryCache{ // backend: make(map[string]*dns.Msg), // serializer: new(JsonSerializer), // expire: cacheConfig.Expire, // maxcount: cacheConfig.Maxcount, // } panic("Redis cache backend not implement yet") default: logger.Printf("Invalid cache backend %s", cacheConfig.Backend) panic("Invalid cache backend") } return &GODNSHandler{resolver, cache} } func (h *GODNSHandler) do(net string, w dns.ResponseWriter, req *dns.Msg) { q := req.Question[0] Q := Question{q.Name, dns.TypeToString[q.Qtype], dns.ClassToString[q.Qclass]} Debug("Question: %s", Q.String()) key := KeyGen(Q) // Only query cache when qtype == 'A' , qclass == 'IN' if q.Qtype == dns.TypeA && q.Qclass == dns.ClassINET { mesg, err := h.cache.Get(key) if err != nil { Debug("%s didn't hit cache: %s", Q.String(), err) } else { Debug("%s hit cache", Q.String()) mesg.Id = req.Id w.WriteMsg(mesg) return } } mesg, err := h.resolver.Lookup(net, req) if err != nil { Debug("%s", err) dns.HandleFailed(w, req) return } w.WriteMsg(mesg) if q.Qtype == dns.TypeA && q.Qclass == dns.ClassINET { err = h.cache.Set(key, mesg) if err != nil { Debug("Set %s cache failed: %s", Q.String(), err.Error()) } Debug("Insert %s into cache", Q.String()) } } func (h *GODNSHandler) DoTCP(w dns.ResponseWriter, req *dns.Msg) { h.do("tcp", w, req) } func (h *GODNSHandler) DoUDP(w dns.ResponseWriter, req *dns.Msg) { h.do("udp", w, req) }