mirror of https://github.com/knative/pkg.git
76 lines
1.8 KiB
Go
76 lines
1.8 KiB
Go
/*
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Copyright 2019 The Knative Authors
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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*/
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package network
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import (
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"bufio"
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"fmt"
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"io"
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"os"
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"strings"
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"sync"
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)
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const (
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resolverFileName = "/etc/resolv.conf"
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defaultDomainName = "cluster.local"
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)
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var (
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domainName string
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once sync.Once
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)
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// GetServiceHostname returns the fully qualified service hostname
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func GetServiceHostname(name string, namespace string) string {
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return fmt.Sprintf("%s.%s.svc.%s", name, namespace, GetClusterDomainName())
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}
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// GetClusterDomainName returns cluster's domain name or an error
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// Closes issue: https://github.com/knative/eventing/issues/714
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func GetClusterDomainName() string {
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once.Do(func() {
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f, err := os.Open(resolverFileName)
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if err == nil {
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defer f.Close()
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domainName = getClusterDomainName(f)
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} else {
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domainName = defaultDomainName
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}
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})
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return domainName
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}
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func getClusterDomainName(r io.Reader) string {
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scanner := bufio.NewScanner(r)
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for scanner.Scan() {
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elements := strings.Split(scanner.Text(), " ")
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if elements[0] != "search" {
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continue
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}
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for i := 1; i < len(elements)-1; i++ {
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if strings.HasPrefix(elements[i], "svc.") {
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return strings.TrimSuffix(elements[i][4:], ".")
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}
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}
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}
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// For all abnormal cases return default domain name
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return defaultDomainName
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}
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