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synced 2022-11-09 12:21:53 -05:00
92 lines
2.5 KiB
Go
92 lines
2.5 KiB
Go
package resolvconf
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import (
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"bytes"
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"io/ioutil"
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"regexp"
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"strings"
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)
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var (
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nsRegexp = regexp.MustCompile(`^\s*nameserver\s*(([0-9]+\.){3}([0-9]+))\s*$`)
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searchRegexp = regexp.MustCompile(`^\s*search\s*(([^\s]+\s*)*)$`)
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)
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func Get() ([]byte, error) {
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resolv, err := ioutil.ReadFile("/etc/resolv.conf")
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if err != nil {
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return nil, err
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}
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return resolv, nil
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}
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// getLines parses input into lines and strips away comments.
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func getLines(input []byte, commentMarker []byte) [][]byte {
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lines := bytes.Split(input, []byte("\n"))
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var output [][]byte
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for _, currentLine := range lines {
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var commentIndex = bytes.Index(currentLine, commentMarker)
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if commentIndex == -1 {
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output = append(output, currentLine)
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} else {
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output = append(output, currentLine[:commentIndex])
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}
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}
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return output
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}
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// GetNameservers returns nameservers (if any) listed in /etc/resolv.conf
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func GetNameservers(resolvConf []byte) []string {
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nameservers := []string{}
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for _, line := range getLines(resolvConf, []byte("#")) {
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var ns = nsRegexp.FindSubmatch(line)
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if len(ns) > 0 {
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nameservers = append(nameservers, string(ns[1]))
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}
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}
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return nameservers
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}
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// GetNameserversAsCIDR returns nameservers (if any) listed in
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// /etc/resolv.conf as CIDR blocks (e.g., "1.2.3.4/32")
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// This function's output is intended for net.ParseCIDR
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func GetNameserversAsCIDR(resolvConf []byte) []string {
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nameservers := []string{}
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for _, nameserver := range GetNameservers(resolvConf) {
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nameservers = append(nameservers, nameserver+"/32")
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}
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return nameservers
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}
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// GetSearchDomains returns search domains (if any) listed in /etc/resolv.conf
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// If more than one search line is encountered, only the contents of the last
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// one is returned.
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func GetSearchDomains(resolvConf []byte) []string {
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domains := []string{}
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for _, line := range getLines(resolvConf, []byte("#")) {
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match := searchRegexp.FindSubmatch(line)
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if match == nil {
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continue
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}
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domains = strings.Fields(string(match[1]))
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}
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return domains
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}
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func Build(path string, dns, dnsSearch []string) error {
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content := bytes.NewBuffer(nil)
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for _, dns := range dns {
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if _, err := content.WriteString("nameserver " + dns + "\n"); err != nil {
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return err
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}
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}
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if len(dnsSearch) > 0 {
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if searchString := strings.Join(dnsSearch, " "); strings.Trim(searchString, " ") != "." {
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if _, err := content.WriteString("search " + searchString + "\n"); err != nil {
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return err
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}
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}
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}
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return ioutil.WriteFile(path, content.Bytes(), 0644)
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}
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