mirror of
https://github.com/netbirdio/netbird.git
synced 2025-08-17 10:31:45 +02:00
Parse original resolv.conf (#1270)
Handle original search domains in resolv.conf type implementations. - parse the original resolv.conf file - merge the search domains - ignore the domain keyword - append any other config lines (sortstlist, options) - fix read origin resolv.conf from bkp in resolvconf implementation - fix line length validation - fix number of search domains validation
This commit is contained in:
Zoltan Papp
GitHub
@ -3,29 +3,25 @@
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package dns
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import (
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"bufio"
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"bytes"
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"fmt"
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"os"
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"strings"
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log "github.com/sirupsen/logrus"
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)
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const (
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fileGeneratedResolvConfContentHeader = "# Generated by NetBird"
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fileGeneratedResolvConfSearchBeginContent = "search "
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fileGeneratedResolvConfContentFormat = fileGeneratedResolvConfContentHeader +
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"\n# If needed you can restore the original file by copying back %s\n\nnameserver %s\n" +
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fileGeneratedResolvConfSearchBeginContent + "%s\n\n" +
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"%s\n"
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)
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fileGeneratedResolvConfContentHeader = "# Generated by NetBird"
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fileGeneratedResolvConfContentHeaderNextLine = fileGeneratedResolvConfContentHeader + `
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# If needed you can restore the original file by copying back ` + fileDefaultResolvConfBackupLocation + "\n\n"
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const (
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fileDefaultResolvConfBackupLocation = defaultResolvConfPath + ".original.netbird"
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fileMaxLineCharsLimit = 256
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fileMaxNumberOfSearchDomains = 6
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)
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var fileSearchLineBeginCharCount = len(fileGeneratedResolvConfSearchBeginContent)
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fileMaxLineCharsLimit = 256
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fileMaxNumberOfSearchDomains = 6
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)
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type fileConfigurator struct {
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originalPerms os.FileMode
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@ -55,58 +51,39 @@ func (f *fileConfigurator) applyDNSConfig(config hostDNSConfig) error {
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}
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return fmt.Errorf("unable to configure DNS for this peer using file manager without a nameserver group with all domains configured")
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}
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managerType, err := getOSDNSManagerType()
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if err != nil {
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return err
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}
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switch managerType {
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case fileManager, netbirdManager:
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if !backupFileExist {
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err = f.backup()
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if err != nil {
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return fmt.Errorf("unable to backup the resolv.conf file")
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}
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}
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default:
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// todo improve this and maybe restart DNS manager from scratch
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return fmt.Errorf("something happened and file manager is not your preferred host dns configurator, restart the agent")
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}
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var searchDomains string
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appendedDomains := 0
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for _, dConf := range config.domains {
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if dConf.matchOnly || dConf.disabled {
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continue
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}
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if appendedDomains >= fileMaxNumberOfSearchDomains {
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// lets log all skipped domains
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log.Infof("already appended %d domains to search list. Skipping append of %s domain", fileMaxNumberOfSearchDomains, dConf.domain)
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continue
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}
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if fileSearchLineBeginCharCount+len(searchDomains) > fileMaxLineCharsLimit {
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// lets log all skipped domains
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log.Infof("search list line is larger than %d characters. Skipping append of %s domain", fileMaxLineCharsLimit, dConf.domain)
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continue
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}
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searchDomains += " " + dConf.domain
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appendedDomains++
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}
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originalContent, err := os.ReadFile(fileDefaultResolvConfBackupLocation)
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if err != nil {
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log.Errorf("Could not read existing resolv.conf")
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}
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content := fmt.Sprintf(fileGeneratedResolvConfContentFormat, fileDefaultResolvConfBackupLocation, config.serverIP, searchDomains, string(originalContent))
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err = writeDNSConfig(content, defaultResolvConfPath, f.originalPerms)
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if err != nil {
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err = f.restore()
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if !backupFileExist {
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err = f.backup()
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if err != nil {
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return fmt.Errorf("unable to backup the resolv.conf file")
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}
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}
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searchDomainList := searchDomains(config)
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originalSearchDomains, nameServers, others, err := originalDNSConfigs(fileDefaultResolvConfBackupLocation)
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if err != nil {
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log.Error(err)
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}
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searchDomainList = mergeSearchDomains(searchDomainList, originalSearchDomains)
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buf := prepareResolvConfContent(
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searchDomainList,
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append([]string{config.serverIP}, nameServers...),
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others)
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log.Debugf("creating managed file %s", defaultResolvConfPath)
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err = os.WriteFile(defaultResolvConfPath, buf.Bytes(), f.originalPerms)
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if err != nil {
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restoreErr := f.restore()
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if restoreErr != nil {
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log.Errorf("attempt to restore default file failed with error: %s", err)
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}
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return err
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return fmt.Errorf("got an creating resolver file %s. Error: %s", defaultResolvConfPath, err)
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}
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log.Infof("created a NetBird managed %s file with your DNS settings. Added %d search domains. Search list: %s", defaultResolvConfPath, appendedDomains, searchDomains)
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log.Infof("created a NetBird managed %s file with your DNS settings. Added %d search domains. Search list: %s", defaultResolvConfPath, len(searchDomainList), searchDomainList)
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return nil
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}
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@ -138,15 +115,138 @@ func (f *fileConfigurator) restore() error {
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return os.RemoveAll(fileDefaultResolvConfBackupLocation)
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}
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func writeDNSConfig(content, fileName string, permissions os.FileMode) error {
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log.Debugf("creating managed file %s", fileName)
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func prepareResolvConfContent(searchDomains, nameServers, others []string) bytes.Buffer {
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var buf bytes.Buffer
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buf.WriteString(content)
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err := os.WriteFile(fileName, buf.Bytes(), permissions)
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if err != nil {
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return fmt.Errorf("got an creating resolver file %s. Error: %s", fileName, err)
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buf.WriteString(fileGeneratedResolvConfContentHeaderNextLine)
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for _, cfgLine := range others {
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buf.WriteString(cfgLine)
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buf.WriteString("\n")
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}
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return nil
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if len(searchDomains) > 0 {
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buf.WriteString("search ")
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buf.WriteString(strings.Join(searchDomains, " "))
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buf.WriteString("\n")
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}
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for _, ns := range nameServers {
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buf.WriteString("nameserver ")
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buf.WriteString(ns)
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buf.WriteString("\n")
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}
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return buf
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}
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func searchDomains(config hostDNSConfig) []string {
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listOfDomains := make([]string, 0)
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for _, dConf := range config.domains {
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if dConf.matchOnly || dConf.disabled {
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continue
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}
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listOfDomains = append(listOfDomains, dConf.domain)
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}
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return listOfDomains
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}
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func originalDNSConfigs(resolvconfFile string) (searchDomains, nameServers, others []string, err error) {
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file, err := os.Open(resolvconfFile)
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if err != nil {
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err = fmt.Errorf(`could not read existing resolv.conf`)
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return
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}
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defer file.Close()
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reader := bufio.NewReader(file)
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for {
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lineBytes, isPrefix, readErr := reader.ReadLine()
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if readErr != nil {
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break
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}
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if isPrefix {
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err = fmt.Errorf(`resolv.conf line too long`)
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return
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}
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line := strings.TrimSpace(string(lineBytes))
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if strings.HasPrefix(line, "#") {
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continue
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}
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if strings.HasPrefix(line, "domain") {
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continue
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}
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if strings.HasPrefix(line, "options") && strings.Contains(line, "rotate") {
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line = strings.ReplaceAll(line, "rotate", "")
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splitLines := strings.Fields(line)
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if len(splitLines) == 1 {
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continue
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}
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line = strings.Join(splitLines, " ")
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}
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if strings.HasPrefix(line, "search") {
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splitLines := strings.Fields(line)
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if len(splitLines) < 2 {
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continue
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}
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searchDomains = splitLines[1:]
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continue
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}
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if strings.HasPrefix(line, "nameserver") {
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splitLines := strings.Fields(line)
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if len(splitLines) != 2 {
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continue
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}
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nameServers = append(nameServers, splitLines[1])
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continue
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}
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others = append(others, line)
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}
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return
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}
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// merge search domains lists and cut off the list if it is too long
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func mergeSearchDomains(searchDomains []string, originalSearchDomains []string) []string {
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lineSize := len("search")
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searchDomainsList := make([]string, 0, len(searchDomains)+len(originalSearchDomains))
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lineSize = validateAndFillSearchDomains(lineSize, &searchDomainsList, searchDomains)
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_ = validateAndFillSearchDomains(lineSize, &searchDomainsList, originalSearchDomains)
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return searchDomainsList
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}
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// validateAndFillSearchDomains checks if the search domains list is not too long and if the line is not too long
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// extend s slice with vs elements
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// return with the number of characters in the searchDomains line
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func validateAndFillSearchDomains(initialLineChars int, s *[]string, vs []string) int {
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for _, sd := range vs {
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tmpCharsNumber := initialLineChars + 1 + len(sd)
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if tmpCharsNumber > fileMaxLineCharsLimit {
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// lets log all skipped domains
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log.Infof("search list line is larger than %d characters. Skipping append of %s domain", fileMaxLineCharsLimit, sd)
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continue
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}
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initialLineChars = tmpCharsNumber
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if len(*s) >= fileMaxNumberOfSearchDomains {
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// lets log all skipped domains
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log.Infof("already appended %d domains to search list. Skipping append of %s domain", fileMaxNumberOfSearchDomains, sd)
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continue
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}
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*s = append(*s, sd)
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}
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return initialLineChars
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}
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func copyFile(src, dest string) error {
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