coredns/core/dnsserver/server_tls.go

package dnsserver

import (
	"context"
	"crypto/tls"
	"fmt"
	"net"
	"time"

	"github.com/coredns/caddy"
	"github.com/coredns/coredns/plugin/pkg/reuseport"
	"github.com/coredns/coredns/plugin/pkg/transport"

	"github.com/miekg/dns"
)

// ServerTLS represents an instance of a TLS-over-DNS-server.
type ServerTLS struct {
	*Server
	tlsConfig *tls.Config
}

// NewServerTLS returns a new CoreDNS TLS server and compiles all plugin in to it.
func NewServerTLS(addr string, group []*Config) (*ServerTLS, error) {
	s, err := NewServer(addr, group)
	if err != nil {
		return nil, err
	}
	// The *tls* plugin must make sure that multiple conflicting
	// TLS configuration returns an error: it can only be specified once.
	var tlsConfig *tls.Config
	for _, z := range s.zones {
		for _, conf := range z {
			// Should we error if some configs *don't* have TLS?
			tlsConfig = conf.TLSConfig
		}
	}

	return &ServerTLS{Server: s, tlsConfig: tlsConfig}, nil
}

// Compile-time check to ensure Server implements the caddy.GracefulServer interface
var _ caddy.GracefulServer = &Server{}

// Serve implements caddy.TCPServer interface.
func (s *ServerTLS) Serve(l net.Listener) error {
	s.m.Lock()

	if s.tlsConfig != nil {
		l = tls.NewListener(l, s.tlsConfig)
	}

	// Only fill out the TCP server for this one.
	s.server[tcp] = &dns.Server{Listener: l,
		Net:           "tcp-tls",
		MaxTCPQueries: tlsMaxQueries,
		ReadTimeout:   s.readTimeout,
		WriteTimeout:  s.writeTimeout,
		IdleTimeout: func() time.Duration {
			return s.idleTimeout
		},
		Handler: dns.HandlerFunc(func(w dns.ResponseWriter, r *dns.Msg) {
			ctx := context.WithValue(context.Background(), Key{}, s.Server)
			ctx = context.WithValue(ctx, LoopKey{}, 0)
			s.ServeDNS(ctx, w, r)
		})}

	s.m.Unlock()

	return s.server[tcp].ActivateAndServe()
}

// ServePacket implements caddy.UDPServer interface.
func (s *ServerTLS) ServePacket(p net.PacketConn) error { return nil }

// Listen implements caddy.TCPServer interface.
func (s *ServerTLS) Listen() (net.Listener, error) {
	l, err := reuseport.Listen("tcp", s.Addr[len(transport.TLS+"://"):])
	if err != nil {
		return nil, err
	}
	return l, nil
}

// ListenPacket implements caddy.UDPServer interface.
func (s *ServerTLS) ListenPacket() (net.PacketConn, error) { return nil, nil }

// OnStartupComplete lists the sites served by this server
// and any relevant information, assuming Quiet is false.
func (s *ServerTLS) OnStartupComplete() {
	if Quiet {
		return
	}

	out := startUpZones(transport.TLS+"://", s.Addr, s.zones)
	if out != "" {
		fmt.Print(out)
	}
}

const (
	tlsMaxQueries = -1
)