netmaker/netclient/local/dns.go

package local

import (
	"io/ioutil"
	"os"
	"strings"
	//"github.com/davecgh/go-spew/spew"
        "log"
        "os/exec"
)

func SetDNS(nameserver string) error {
        bytes, err := ioutil.ReadFile("/etc/resolv.conf")
        if err != nil {
                return err
        }
        resolvstring := string(bytes)
        // //check whether s contains substring text
        hasdns := strings.Contains(resolvstring, nameserver)
        if hasdns {
                return nil
        }
        resolv, err := os.OpenFile("/etc/resolv.conf",os.O_APPEND|os.O_WRONLY, 0644)
        if err != nil {
                return err
        }
        defer resolv.Close()
        _, err = resolv.WriteString("nameserver " + nameserver + "\n")

        return err
}


func UpdateDNS(ifacename string, network string, nameserver string) error {
                _, err := exec.LookPath("resolvectl")
                if err != nil {
                        log.Println(err)
                        log.Println("WARNING: resolvectl not present. Unable to set dns. Install resolvectl or run manually.")
                } else {
                        _, err = exec.Command("resolvectl", "domain", ifacename, "~"+network).Output()
                        if err != nil {
                                log.Println(err)
                                log.Println("WARNING: Error encountered setting dns. Aborted setting dns.")
                        } else {
                                _, err = exec.Command("resolvectl", "default-route", ifacename, "false").Output()
                                if err != nil {
                                        log.Println(err)
                                        log.Println("WARNING: Error encountered setting dns. Aborted setting dns.")
                                } else {
                                        _, err = exec.Command("resolvectl", "dns", ifacename, nameserver).Output()
                                        if err!= nil {
						log.Println("WARNING: Error encountered running resolvectl dns " + ifacename + " " + nameserver)
						log.Println(err)
					}
                                }
                        }
                }
		return err
}