mirror of
https://github.com/netbirdio/netbird.git
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890e09b787
* keep existing nameserver as fallback when adding netbird resolver * fix resolvconf * fix imports
169 lines
5.1 KiB
Go
169 lines
5.1 KiB
Go
//go:build !android
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package dns
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import (
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"bytes"
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"fmt"
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"os"
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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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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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type fileConfigurator struct {
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originalPerms os.FileMode
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}
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func newFileConfigurator() (hostManager, error) {
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return &fileConfigurator{}, nil
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}
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func (f *fileConfigurator) supportCustomPort() bool {
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return false
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}
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func (f *fileConfigurator) applyDNSConfig(config hostDNSConfig) error {
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backupFileExist := false
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_, err := os.Stat(fileDefaultResolvConfBackupLocation)
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if err == nil {
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backupFileExist = true
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}
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if !config.routeAll {
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if backupFileExist {
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err = f.restore()
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if err != nil {
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return fmt.Errorf("unable to configure DNS for this peer using file manager without a Primary nameserver group. Restoring the original file return err: %s", err)
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}
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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 prefered 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 err != 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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}
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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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return nil
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}
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func (f *fileConfigurator) restoreHostDNS() error {
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return f.restore()
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}
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func (f *fileConfigurator) backup() error {
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stats, err := os.Stat(defaultResolvConfPath)
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if err != nil {
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return fmt.Errorf("got an error while checking stats for %s file. Error: %s", defaultResolvConfPath, err)
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}
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f.originalPerms = stats.Mode()
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err = copyFile(defaultResolvConfPath, fileDefaultResolvConfBackupLocation)
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if err != nil {
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return fmt.Errorf("got error while backing up the %s file. Error: %s", defaultResolvConfPath, err)
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}
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return nil
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}
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func (f *fileConfigurator) restore() error {
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err := copyFile(fileDefaultResolvConfBackupLocation, defaultResolvConfPath)
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if err != nil {
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return fmt.Errorf("got error while restoring the %s file from %s. Error: %s", defaultResolvConfPath, fileDefaultResolvConfBackupLocation, err)
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}
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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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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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}
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return nil
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}
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func copyFile(src, dest string) error {
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stats, err := os.Stat(src)
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if err != nil {
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return fmt.Errorf("got an error while checking stats for %s file when copying it. Error: %s", src, err)
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}
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bytesRead, err := os.ReadFile(src)
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if err != nil {
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return fmt.Errorf("got an error while reading the file %s file for copy. Error: %s", src, err)
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}
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err = os.WriteFile(dest, bytesRead, stats.Mode())
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if err != nil {
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return fmt.Errorf("got an writing the destination file %s for copy. Error: %s", dest, err)
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}
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return nil
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}
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