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Enhance DNS failover reliability (#1637)

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* Fix using wrong array index in log to avoid potential panic

* Increase gRPC connection timeout and add the timeout resolv.conf option

This makes sure the dns client is able to failover to a second
configured nameserver, if present. That is the case then when using the
dns `file` manager and a resolv.conf file generated for netbird.

* On file backup restore, remove the first NS if it's the netbird NS

* Bump dns mangager discovery message from debug to info to ease debugging
This commit is contained in:
Viktor Liu
2024-03-01 15:17:35 +01:00
committed by GitHub
parent a4b9e93217
commit 17b1099032
7 changed files with 224 additions and 15 deletions
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27
client/internal/dns/file_linux.go
View File

@ -8,6 +8,7 @@ import (
"net/netip"
"os"
"strings"
"time"
log "github.com/sirupsen/logrus"
)
@ -23,10 +24,16 @@ const (
fileMaxNumberOfSearchDomains = 6
)
const (
dnsFailoverTimeout = 4 * time.Second
dnsFailoverAttempts = 1
)
type fileConfigurator struct {
repair *repair
originalPerms os.FileMode
originalPerms os.FileMode
nbNameserverIP string
}
func newFileConfigurator() (hostManager, error) {
@ -64,7 +71,7 @@ func (f *fileConfigurator) applyDNSConfig(config HostDNSConfig) error {
}
nbSearchDomains := searchDomains(config)
nbNameserverIP := config.ServerIP
f.nbNameserverIP = config.ServerIP
resolvConf, err := parseBackupResolvConf()
if err != nil {
@ -73,11 +80,11 @@ func (f *fileConfigurator) applyDNSConfig(config HostDNSConfig) error {
f.repair.stopWatchFileChanges()
err = f.updateConfig(nbSearchDomains, nbNameserverIP, resolvConf)
err = f.updateConfig(nbSearchDomains, f.nbNameserverIP, resolvConf)
if err != nil {
return err
}
f.repair.watchFileChanges(nbSearchDomains, nbNameserverIP)
f.repair.watchFileChanges(nbSearchDomains, f.nbNameserverIP)
return nil
}
@ -85,10 +92,11 @@ func (f *fileConfigurator) updateConfig(nbSearchDomains []string, nbNameserverIP
searchDomainList := mergeSearchDomains(nbSearchDomains, cfg.searchDomains)
nameServers := generateNsList(nbNameserverIP, cfg)
options := prepareOptionsWithTimeout(cfg.others, int(dnsFailoverTimeout.Seconds()), dnsFailoverAttempts)
buf := prepareResolvConfContent(
searchDomainList,
nameServers,
cfg.others)
options)
log.Debugf("creating managed file %s", defaultResolvConfPath)
err := os.WriteFile(defaultResolvConfPath, buf.Bytes(), f.originalPerms)
@ -131,7 +139,12 @@ func (f *fileConfigurator) backup() error {
}
func (f *fileConfigurator) restore() error {
err := copyFile(fileDefaultResolvConfBackupLocation, defaultResolvConfPath)
err := removeFirstNbNameserver(fileDefaultResolvConfBackupLocation, f.nbNameserverIP)
if err != nil {
log.Errorf("Failed to remove netbird nameserver from %s on backup restore: %s", fileDefaultResolvConfBackupLocation, err)
}
err = copyFile(fileDefaultResolvConfBackupLocation, defaultResolvConfPath)
if err != nil {
return fmt.Errorf("restoring %s from %s: %w", defaultResolvConfPath, fileDefaultResolvConfBackupLocation, err)
}
@ -157,7 +170,7 @@ func (f *fileConfigurator) restoreUncleanShutdownDNS(storedDNSAddress *netip.Add
currentDNSAddress, err := netip.ParseAddr(resolvConf.nameServers[0])
// not a valid first nameserver -> restore
if err != nil {
log.Errorf("restoring unclean shutdown: parse dns address %s failed: %s", resolvConf.nameServers[1], err)
log.Errorf("restoring unclean shutdown: parse dns address %s failed: %s", resolvConf.nameServers[0], err)
return restoreResolvConfFile()
}