Split implementations from generic code

core/pkg/net/dns/dns.go

@@ -0,0 +1,52 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+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 dns
+
+import (
+	"io/ioutil"
+	"strings"
+
+	"github.com/golang/glog"
+)
+
+// GetSystemNameServers returns the list of nameservers located in the file /etc/resolv.conf
+func GetSystemNameServers() ([]string, error) {
+	var nameservers []string
+	file, err := ioutil.ReadFile("/etc/resolv.conf")
+	if err != nil {
+		return nameservers, err
+	}
+
+	// Lines of the form "nameserver 1.2.3.4" accumulate.
+	lines := strings.Split(string(file), "\n")
+	for l := range lines {
+		trimmed := strings.TrimSpace(lines[l])
+		if strings.HasPrefix(trimmed, "#") {
+			continue
+		}
+		fields := strings.Fields(trimmed)
+		if len(fields) == 0 {
+			continue
+		}
+		if fields[0] == "nameserver" {
+			nameservers = append(nameservers, fields[1:]...)
+		}
+	}
+
+	glog.V(3).Infof("nameservers to use: %v", nameservers)
+	return nameservers, nil
+}

core/pkg/net/dns/dns_test.go

@@ -0,0 +1,31 @@
+/*
+Copyright 2015 The Kubernetes Authors.
+
+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 dns
+
+import (
+	"testing"
+)
+
+func TestGetDNSServers(t *testing.T) {
+	s, err := GetSystemNameServers()
+	if err != nil {
+		t.Fatalf("unexpected error reading /etc/resolv.conf file: %v", err)
+	}
+	if len(s) < 1 {
+		t.Error("expected at least 1 nameserver in /etc/resolv.conf")
+	}
+}