Golang middleware.State類代碼示例

func (l Logger) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
	state := middleware.State{W: w, Req: r}
	for _, rule := range l.Rules {
		if middleware.Name(rule.NameScope).Matches(state.Name()) {
			responseRecorder := middleware.NewResponseRecorder(w)
			rcode, err := l.Next.ServeDNS(ctx, responseRecorder, r)

			if rcode > 0 {
				// There was an error up the chain, but no response has been written yet.
				// The error must be handled here so the log entry will record the response size.
				if l.ErrorFunc != nil {
					l.ErrorFunc(responseRecorder, r, rcode)
				} else {
					rc := middleware.RcodeToString(rcode)

					answer := new(dns.Msg)
					answer.SetRcode(r, rcode)
					state.SizeAndDo(answer)

					metrics.Report(state, metrics.Dropped, rc, answer.Len(), time.Now())
					w.WriteMsg(answer)
				}
				rcode = 0
			}
			rep := middleware.NewReplacer(r, responseRecorder, CommonLogEmptyValue)
			rule.Log.Println(rep.Replace(rule.Format))
			return rcode, err

		}
	}
	return l.Next.ServeDNS(ctx, w, r)
}

func (e Etcd) AAAA(zone string, state middleware.State, previousRecords []dns.RR) (records []dns.RR, debug []msg.Service, err error) {
	services, debug, err := e.records(state, false)
	if err != nil {
		return nil, debug, err
	}

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			// Try to resolve as CNAME if it's not an IP, but only if we don't create loops.
			if middleware.Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
				// x CNAME x is a direct loop, don't add those
				continue
			}

			newRecord := serv.NewCNAME(state.QName(), serv.Host)
			if len(previousRecords) > 7 {
				// don't add it, and just continue
				continue
			}
			if isDuplicateCNAME(newRecord, previousRecords) {
				continue
			}

			state1 := copyState(state, serv.Host, state.QType())
			nextRecords, nextDebug, err := e.AAAA(zone, state1, append(previousRecords, newRecord))

			if err == nil {
				// Not only have we found something we should add the CNAME and the IP addresses.
				if len(nextRecords) > 0 {
					records = append(records, newRecord)
					records = append(records, nextRecords...)
					debug = append(debug, nextDebug...)
				}
				continue
			}
			// This means we can not complete the CNAME, try to look else where.
			target := newRecord.Target
			if dns.IsSubDomain(zone, target) {
				// We should already have found it
				continue
			}
			m1, e1 := e.Proxy.Lookup(state, target, state.QType())
			if e1 != nil {
				continue
			}
			// Len(m1.Answer) > 0 here is well?
			records = append(records, newRecord)
			records = append(records, m1.Answer...)
			continue
			// both here again
		case ip.To4() != nil:
			// nada?
		case ip.To4() == nil:
			records = append(records, serv.NewAAAA(state.QName(), ip.To16()))
		}
	}
	return records, debug, nil
}

// NoData write a nodata response to the client.
func (k Kubernetes) Err(zone string, rcode int, state middleware.State) (int, error) {
	m := new(dns.Msg)
	m.SetRcode(state.Req, rcode)
	m.Ns = []dns.RR{k.SOA(zone, state)}
	state.SizeAndDo(m)
	state.W.WriteMsg(m)
	return rcode, nil
}

func (k Kubernetes) A(zone string, state middleware.State, previousRecords []dns.RR) (records []dns.RR, err error) {
	services, err := k.records(state, false)
	if err != nil {
		return nil, err
	}

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			// TODO(miek): lowercasing? Should lowercase in everything see #85
			if middleware.Name(state.Name()).Matches(dns.Fqdn(serv.Host)) {
				// x CNAME x is a direct loop, don't add those
				continue
			}

			newRecord := serv.NewCNAME(state.QName(), serv.Host)
			if len(previousRecords) > 7 {
				// don't add it, and just continue
				continue
			}
			if isDuplicateCNAME(newRecord, previousRecords) {
				continue
			}

			state1 := copyState(state, serv.Host, state.QType())
			nextRecords, err := k.A(zone, state1, append(previousRecords, newRecord))

			if err == nil {
				// Not only have we found something we should add the CNAME and the IP addresses.
				if len(nextRecords) > 0 {
					records = append(records, newRecord)
					records = append(records, nextRecords...)
				}
				continue
			}
			// This means we can not complete the CNAME, try to look else where.
			target := newRecord.Target
			if dns.IsSubDomain(zone, target) {
				// We should already have found it
				continue
			}
			m1, e1 := k.Proxy.Lookup(state, target, state.QType())
			if e1 != nil {
				continue
			}
			// Len(m1.Answer) > 0 here is well?
			records = append(records, newRecord)
			records = append(records, m1.Answer...)
			continue
		case ip.To4() != nil:
			records = append(records, serv.NewA(state.QName(), ip.To4()))
		case ip.To4() == nil:
			// nodata?
		}
	}
	return records, nil
}

func (k Kubernetes) records(state middleware.State, exact bool) ([]msg.Service, error) {
	services, err := k.Records(state.Name(), exact)
	if err != nil {
		return nil, err
	}
	// TODO: Do we want to support the SkyDNS (hacky) Group feature?
	services = msg.Group(services)
	return services, nil
}

// ServeDNS implements the middleware.Handler interface.
func (c Cache) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (int, error) {
	state := middleware.State{W: w, Req: r}

	qname := state.Name()
	qtype := state.QType()
	zone := middleware.Zones(c.Zones).Matches(qname)
	if zone == "" {
		return c.Next.ServeDNS(ctx, w, r)
	}

	do := state.Do() // might need more from OPT record?

	if i, ok := c.get(qname, qtype, do); ok {
		resp := i.toMsg(r)
		state.SizeAndDo(resp)
		w.WriteMsg(resp)

		cacheHitCount.WithLabelValues(zone).Inc()
		return dns.RcodeSuccess, nil
	}
	cacheMissCount.WithLabelValues(zone).Inc()

	crr := NewCachingResponseWriter(w, c.cache, c.cap)
	return c.Next.ServeDNS(ctx, crr, r)
}

// DefaultErrorFunc responds to an DNS request with an error.
func DefaultErrorFunc(w dns.ResponseWriter, r *dns.Msg, rcode int) {
	state := middleware.State{W: w, Req: r}
	rc := middleware.RcodeToString(rcode)

	answer := new(dns.Msg)
	answer.SetRcode(r, rcode)
	state.SizeAndDo(answer)

	metrics.Report(state, metrics.Dropped, rc, answer.Len(), time.Now())
	w.WriteMsg(answer)
}

// PTR returns the PTR records, only services that have a domain name as host are included.
func (e Etcd) PTR(zone string, state middleware.State) (records []dns.RR, debug []msg.Service, err error) {
	services, debug, err := e.records(state, true)
	if err != nil {
		return nil, debug, err
	}

	for _, serv := range services {
		if ip := net.ParseIP(serv.Host); ip == nil {
			records = append(records, serv.NewPTR(state.QName(), serv.Host))
		}
	}
	return records, debug, nil
}

func (e Etcd) CNAME(zone string, state middleware.State) (records []dns.RR, debug []msg.Service, err error) {
	services, debug, err := e.records(state, true)
	if err != nil {
		return nil, debug, err
	}

	if len(services) > 0 {
		serv := services[0]
		if ip := net.ParseIP(serv.Host); ip == nil {
			records = append(records, serv.NewCNAME(state.QName(), serv.Host))
		}
	}
	return records, debug, nil
}

func (e Etcd) TXT(zone string, state middleware.State) (records []dns.RR, debug []msg.Service, err error) {
	services, debug, err := e.records(state, false)
	if err != nil {
		return nil, debug, err
	}

	for _, serv := range services {
		if serv.Text == "" {
			continue
		}
		records = append(records, serv.NewTXT(state.QName()))
	}
	return records, debug, nil
}

func (e Etcd) NS(zone string, state middleware.State) (records, extra []dns.RR, debug []msg.Service, err error) {
	// NS record for this zone live in a special place, ns.dns.<zone>. Fake our lookup.
	// only a tad bit fishy...
	old := state.QName()

	state.Clear()
	state.Req.Question[0].Name = "ns.dns." + zone
	services, debug, err := e.records(state, false)
	if err != nil {
		return nil, nil, debug, err
	}
	// ... and reset
	state.Req.Question[0].Name = old

	for _, serv := range services {
		ip := net.ParseIP(serv.Host)
		switch {
		case ip == nil:
			return nil, nil, debug, fmt.Errorf("NS record must be an IP address: %s", serv.Host)
		case ip.To4() != nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(state.QName()))
			extra = append(extra, serv.NewA(serv.Host, ip.To4()))
		case ip.To4() == nil:
			serv.Host = msg.Domain(serv.Key)
			records = append(records, serv.NewNS(state.QName()))
			extra = append(extra, serv.NewAAAA(serv.Host, ip.To16()))
		}
	}
	return records, extra, debug, nil
}

// isNotify checks if state is a notify message and if so, will *also* check if it
// is from one of the configured masters. If not it will not be a valid notify
// message. If the zone z is not a secondary zone the message will also be ignored.
func (z *Zone) isNotify(state middleware.State) bool {
	if state.Req.Opcode != dns.OpcodeNotify {
		return false
	}
	if len(z.TransferFrom) == 0 {
		return false
	}
	remote := middleware.Addr(state.IP()).Normalize()
	for _, from := range z.TransferFrom {
		if from == remote {
			return true
		}
	}
	return false
}

// Sign signs the message m. it takes care of negative or nodata responses. It
// uses NSEC black lies for authenticated denial of existence. Signatures
// creates will be cached for a short while. By default we sign for 8 days,
// starting 3 hours ago.
func (d Dnssec) Sign(state middleware.State, zone string, now time.Time) *dns.Msg {
	req := state.Req
	mt, _ := middleware.Classify(req) // TODO(miek): need opt record here?
	if mt == middleware.Delegation {
		return req
	}

	incep, expir := incepExpir(now)

	if mt == middleware.NameError {
		if req.Ns[0].Header().Rrtype != dns.TypeSOA || len(req.Ns) > 1 {
			return req
		}

		ttl := req.Ns[0].Header().Ttl

		if sigs, err := d.sign(req.Ns, zone, ttl, incep, expir); err == nil {
			req.Ns = append(req.Ns, sigs...)
		}
		if sigs, err := d.nsec(state.Name(), zone, ttl, incep, expir); err == nil {
			req.Ns = append(req.Ns, sigs...)
		}
		if len(req.Ns) > 1 { // actually added nsec and sigs, reset the rcode
			req.Rcode = dns.RcodeSuccess
		}
		return req
	}

	for _, r := range rrSets(req.Answer) {
		ttl := r[0].Header().Ttl
		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
			req.Answer = append(req.Answer, sigs...)
		}
	}
	for _, r := range rrSets(req.Ns) {
		ttl := r[0].Header().Ttl
		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
			req.Ns = append(req.Ns, sigs...)
		}
	}
	for _, r := range rrSets(req.Extra) {
		ttl := r[0].Header().Ttl
		if sigs, err := d.sign(r, zone, ttl, incep, expir); err == nil {
			req.Extra = append(sigs, req.Extra...) // prepend to leave OPT alone
		}
	}
	return req
}

func (h ErrorHandler) recovery(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) {
	rec := recover()
	if rec == nil {
		return
	}

	state := middleware.State{W: w, Req: r}
	// Obtain source of panic
	// From: https://gist.github.com/swdunlop/9629168
	var name, file string // function name, file name
	var line int
	var pc [16]uintptr
	n := runtime.Callers(3, pc[:])
	for _, pc := range pc[:n] {
		fn := runtime.FuncForPC(pc)
		if fn == nil {
			continue
		}
		file, line = fn.FileLine(pc)
		name = fn.Name()
		if !strings.HasPrefix(name, "runtime.") {
			break
		}
	}

	// Trim file path
	delim := "/coredns/"
	pkgPathPos := strings.Index(file, delim)
	if pkgPathPos > -1 && len(file) > pkgPathPos+len(delim) {
		file = file[pkgPathPos+len(delim):]
	}

	panicMsg := fmt.Sprintf("%s [PANIC %s %s] %s:%d - %v", time.Now().Format(timeFormat), r.Question[0].Name, dns.Type(r.Question[0].Qtype), file, line, rec)
	if h.Debug {
		// Write error and stack trace to the response rather than to a log
		var stackBuf [4096]byte
		stack := stackBuf[:runtime.Stack(stackBuf[:], false)]
		answer := debugMsg(dns.RcodeServerFailure, r)
		// add stack buf in TXT, limited to 255 chars for now.
		txt, _ := dns.NewRR(". IN 0 TXT " + string(stack[:255]))
		answer.Answer = append(answer.Answer, txt)
		state.SizeAndDo(answer)
		w.WriteMsg(answer)
	} else {
		// Currently we don't use the function name, since file:line is more conventional
		h.Log.Printf(panicMsg)
	}
}

func (p Proxy) lookup(state middleware.State, r *dns.Msg) (*dns.Msg, error) {
	var (
		reply *dns.Msg
		err   error
	)
	for _, upstream := range p.Upstreams {
		// allowed bla bla bla TODO(miek): fix full proxy spec from caddy?
		start := time.Now()

		// Since Select() should give us "up" hosts, keep retrying
		// hosts until timeout (or until we get a nil host).
		for time.Now().Sub(start) < tryDuration {
			host := upstream.Select()

			if host == nil {
				return nil, errUnreachable
			}

			atomic.AddInt64(&host.Conns, 1)
			// tls+tcp ?
			if state.Proto() == "tcp" {
				reply, err = middleware.Exchange(p.Client.TCP, r, host.Name)
			} else {
				reply, err = middleware.Exchange(p.Client.UDP, r, host.Name)
			}
			atomic.AddInt64(&host.Conns, -1)

			if err == nil {
				return reply, nil
			}
			timeout := host.FailTimeout
			if timeout == 0 {
				timeout = 10 * time.Second
			}
			atomic.AddInt32(&host.Fails, 1)
			go func(host *UpstreamHost, timeout time.Duration) {
				time.Sleep(timeout)
				atomic.AddInt32(&host.Fails, -1)
			}(host, timeout)
		}
		return nil, errUnreachable
	}
	return nil, errUnreachable
}