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cmd/cli: remove old forwarder after adding new one on Windows Server

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Otherwise, the forwarders will keep piling up.
This commit is contained in:
Cuong Manh Le
2024-05-09 18:25:11 +07:00
committed by Cuong Manh Le
parent 3ddcb84db8
commit 0d6ca57536
1 changed files with 27 additions and 7 deletions
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34
cmd/cli/os_windows.go
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@@ -41,10 +41,12 @@ func setDNS(iface *net.Interface, nameservers []string) error {
// Configuring the Dns server to forward queries to ctrld instead.
if windowsHasLocalDnsServerRunning() {
file := absHomeDir(forwardersFilename)
oldForwardersContent, _ := os.ReadFile(file)
if err := os.WriteFile(file, []byte(strings.Join(nameservers, ",")), 0600); err != nil {
mainLog.Load().Warn().Err(err).Msg("could not save forwarders settings")
}
if err := addDnsServerForwarders(nameservers); err != nil {
oldForwarders := strings.Split(string(oldForwardersContent), ",")
if err := addDnsServerForwarders(nameservers, oldForwarders); err != nil {
mainLog.Load().Warn().Err(err).Msg("could not set forwarders settings")
}
}
@@ -206,14 +208,32 @@ func currentStaticDNS(iface *net.Interface) ([]string, error) {
return ns, nil
}
// addDnsServerForwarders adds given nameservers to DNS server forwarders list.
func addDnsServerForwarders(nameservers []string) error {
for _, ns := range nameservers {
cmd := fmt.Sprintf("Add-DnsServerForwarder -IPAddress %s", ns)
if out, err := powershell(cmd); err != nil {
return fmt.Errorf("%w: %s", err, string(out))
// addDnsServerForwarders adds given nameservers to DNS server forwarders list,
// and also removing old forwarders if provided.
func addDnsServerForwarders(nameservers, old []string) error {
newForwardersMap := make(map[string]struct{})
newForwarders := make([]string, len(nameservers))
for i := range nameservers {
newForwardersMap[nameservers[i]] = struct{}{}
newForwarders[i] = fmt.Sprintf("%q", nameservers[i])
}
oldForwarders := old[:0]
for _, fwd := range old {
if _, ok := newForwardersMap[fwd]; !ok {
oldForwarders = append(oldForwarders, fwd)
}
}
// NOTE: It is important to add new forwarder before removing old one.
// Testing on Windows Server 2022 shows that removing forwarder1
// then adding forwarder2 sometimes ends up adding both of them
// to the forwarders list.
cmd := fmt.Sprintf("Add-DnsServerForwarder -IPAddress %s", strings.Join(newForwarders, ","))
if len(oldForwarders) > 0 {
cmd = fmt.Sprintf("%s ; Remove-DnsServerForwarder -IPAddress %s -Force", cmd, strings.Join(oldForwarders, ","))
}
if out, err := powershell(cmd); err != nil {
return fmt.Errorf("%w: %s", err, string(out))
}
return nil
}