github.com/elfadel/cilium@v1.6.12/pkg/fqdn/dnsproxy/helpers.go (about) 1 // Copyright 2018 Authors of Cilium 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 dnsproxy 16 17 import ( 18 "fmt" 19 "net" 20 "strings" 21 22 "github.com/miekg/dns" 23 ) 24 25 // prepareNameMatch ensures that a name is an anchored regexp and that names 26 // with only "." (aka not a regexp) escape the "." so it does not match any 27 // character. DNS expects lowercase lookups (ignoring the highest ascii bit) 28 // and we mimic this by lowercasing the name here, and lookups later. 29 // Note: The trailing "." in a FQDN is assumed, and isn't added here. 30 func prepareNameMatch(name string) string { 31 name = strings.ToLower(name) // lowercase it 32 33 // anchor it 34 out := make([]string, 0, 3) 35 if !strings.HasPrefix(name, "^") { 36 out = append(out, "^") 37 } 38 out = append(out, name) 39 if !strings.HasSuffix(name, "$") { 40 out = append(out, "$") 41 } 42 return strings.Join(out, "") 43 } 44 45 // lookupTargetDNSServer finds the intended DNS target server for a specific 46 // request (passed in via ServeDNS). The IP:port combination is 47 // returned. 48 func lookupTargetDNSServer(w dns.ResponseWriter) (serverIP net.IP, serverPort uint16, addrStr string, err error) { 49 switch addr := (w.LocalAddr()).(type) { 50 case *net.UDPAddr: 51 return addr.IP, uint16(addr.Port), addr.String(), nil 52 case *net.TCPAddr: 53 return addr.IP, uint16(addr.Port), addr.String(), nil 54 default: 55 return nil, 0, addr.String(), fmt.Errorf("Cannot extract address information for type %T: %+v", addr, addr) 56 } 57 }