forked from cilium/cilium
/
helpers.go
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/
helpers.go
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// Copyright 2018 Authors of Cilium
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package dnsproxy
import (
"fmt"
"net"
"strings"
"github.com/miekg/dns"
)
// prepareNameMatch ensures that a name is an anchored regexp and that names
// with only "." (aka not a regexp) escape the "." so it does not match any
// character. DNS expects lowercase lookups (ignoring the highest ascii bit)
// and we mimic this by lowercasing the name here, and lookups later.
// Note: The trailing "." in a FQDN is assumed, and isn't added here.
func prepareNameMatch(name string) string {
name = strings.ToLower(name) // lowercase it
// anchor it
out := make([]string, 0, 3)
if !strings.HasPrefix(name, "^") {
out = append(out, "^")
}
out = append(out, name)
if !strings.HasSuffix(name, "$") {
out = append(out, "$")
}
return strings.Join(out, "")
}
// lookupTargetDNSServer finds the intended DNS target server for a specific
// request (passed in via ServeDNS). The IP:port combination is
// returned.
func lookupTargetDNSServer(w dns.ResponseWriter) (serverIP net.IP, serverPort uint16, addrStr string, err error) {
switch addr := (w.LocalAddr()).(type) {
case *net.UDPAddr:
return addr.IP, uint16(addr.Port), addr.String(), nil
case *net.TCPAddr:
return addr.IP, uint16(addr.Port), addr.String(), nil
default:
return nil, 0, addr.String(), fmt.Errorf("Cannot extract address information for type %T: %+v", addr, addr)
}
}