package dns import ( "strings" "github.com/Dreamacro/clash/component/fakeip" "github.com/Dreamacro/clash/log" D "github.com/miekg/dns" ) type handler func(w D.ResponseWriter, r *D.Msg) type middleware func(next handler) handler func withFakeIP(fakePool *fakeip.Pool) middleware { return func(next handler) handler { return func(w D.ResponseWriter, r *D.Msg) { q := r.Question[0] if q.Qtype == D.TypeAAAA { D.HandleFailed(w, r) return } else if q.Qtype != D.TypeA { next(w, r) return } host := strings.TrimRight(q.Name, ".") if fakePool.LookupHost(host) { next(w, r) return } rr := &D.A{} rr.Hdr = D.RR_Header{Name: q.Name, Rrtype: D.TypeA, Class: D.ClassINET, Ttl: dnsDefaultTTL} ip := fakePool.Lookup(host) rr.A = ip msg := r.Copy() msg.Answer = []D.RR{rr} setMsgTTL(msg, 1) msg.SetReply(r) w.WriteMsg(msg) return } } } func withResolver(resolver *Resolver) handler { return func(w D.ResponseWriter, r *D.Msg) { msg, err := resolver.Exchange(r) if err != nil { q := r.Question[0] log.Debugln("[DNS Server] Exchange %s failed: %v", q.String(), err) D.HandleFailed(w, r) return } msg.SetReply(r) w.WriteMsg(msg) return } } func compose(middlewares []middleware, endpoint handler) handler { length := len(middlewares) h := endpoint for i := length - 1; i >= 0; i-- { middleware := middlewares[i] h = middleware(h) } return h } func newHandler(resolver *Resolver) handler { middlewares := []middleware{} if resolver.IsFakeIP() { middlewares = append(middlewares, withFakeIP(resolver.pool)) } return compose(middlewares, withResolver(resolver)) }