istio.io/istio@v0.0.0-20240520182934-d79c90f27776/pkg/dns/client/proxy.go (about)

     1  // Copyright Istio Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package client
    16  
    17  import (
    18  	"net"
    19  	"time"
    20  
    21  	"github.com/miekg/dns"
    22  )
    23  
    24  type dnsProxy struct {
    25  	serveMux *dns.ServeMux
    26  	server   *dns.Server
    27  
    28  	// This is the upstream Client used to make upstream DNS queries
    29  	// in case the data is not in our name table.
    30  	upstreamClient *dns.Client
    31  	protocol       string
    32  	resolver       *LocalDNSServer
    33  }
    34  
    35  func newDNSProxy(protocol, addr string, resolver *LocalDNSServer) (*dnsProxy, error) {
    36  	p := &dnsProxy{
    37  		serveMux: dns.NewServeMux(),
    38  		server:   &dns.Server{},
    39  		upstreamClient: &dns.Client{
    40  			Net:          protocol,
    41  			DialTimeout:  5 * time.Second,
    42  			ReadTimeout:  5 * time.Second,
    43  			WriteTimeout: 5 * time.Second,
    44  		},
    45  		protocol: protocol,
    46  		resolver: resolver,
    47  	}
    48  
    49  	var err error
    50  	p.serveMux.Handle(".", p)
    51  	p.server.Handler = p.serveMux
    52  	if protocol == "udp" {
    53  		p.server.PacketConn, err = net.ListenPacket("udp", addr)
    54  	} else {
    55  		p.server.Listener, err = net.Listen("tcp", addr)
    56  	}
    57  	log.Infof("Starting local %s DNS server on %v", p.protocol, addr)
    58  	if err != nil {
    59  		log.Errorf("Failed to listen on %s port %s: %v", protocol, addr, err)
    60  		return nil, err
    61  	}
    62  	return p, nil
    63  }
    64  
    65  func (p *dnsProxy) start() {
    66  	err := p.server.ActivateAndServe()
    67  	if err != nil {
    68  		log.Errorf("Local %s DNS server terminated: %v", p.protocol, err)
    69  	}
    70  }
    71  
    72  func (p *dnsProxy) close() {
    73  	if p.server != nil {
    74  		if err := p.server.Shutdown(); err != nil {
    75  			log.Errorf("error in shutting down %s dns downstreamUDPServer :%v", p.protocol, err)
    76  		}
    77  	}
    78  }
    79  
    80  func (p *dnsProxy) Address() string {
    81  	if p.server != nil {
    82  		if p.server.Listener != nil {
    83  			return p.server.Listener.Addr().String()
    84  		}
    85  		if p.server.PacketConn != nil {
    86  			return p.server.PacketConn.LocalAddr().String()
    87  		}
    88  	}
    89  	return ""
    90  }
    91  
    92  func (p *dnsProxy) ServeDNS(w dns.ResponseWriter, req *dns.Msg) {
    93  	p.resolver.ServeDNS(p, w, req)
    94  }