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[client] Add TCP support to DNS forwarder service listener (#3790)

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[client] Add TCP support to DNS forwarder service listener
This commit is contained in:
hakansa 2025-05-09 15:06:34 +03:00 committed by GitHub
parent d5b52e86b6
commit 2f34e984b0
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GPG Key ID: B5690EEEBB952194
2 changed files with 98 additions and 20 deletions
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104
client/internal/dnsfwd/forwarder.go
View File

@ -33,6 +33,8 @@ type DNSForwarder struct {
dnsServer *dns.Server
mux *dns.ServeMux
tcpServer *dns.Server
tcpMux *dns.ServeMux
mutex sync.RWMutex
fwdEntries []*ForwarderEntry
@ -50,22 +52,41 @@ func NewDNSForwarder(listenAddress string, ttl uint32, firewall firewall.Manager
}
func (f *DNSForwarder) Listen(entries []*ForwarderEntry) error {
log.Infof("listen DNS forwarder on address=%s", f.listenAddress)
mux := dns.NewServeMux()
log.Infof("starting DNS forwarder on address=%s", f.listenAddress)
dnsServer := &dns.Server{
// UDP server
mux := dns.NewServeMux()
f.mux = mux
f.dnsServer = &dns.Server{
Addr: f.listenAddress,
Net: "udp",
Handler: mux,
}
f.dnsServer = dnsServer
f.mux = mux
// TCP server
tcpMux := dns.NewServeMux()
f.tcpMux = tcpMux
f.tcpServer = &dns.Server{
Addr: f.listenAddress,
Net: "tcp",
Handler: tcpMux,
}
f.UpdateDomains(entries)
return dnsServer.ListenAndServe()
}
errCh := make(chan error, 2)
go func() {
log.Infof("DNS UDP listener running on %s", f.listenAddress)
errCh <- f.dnsServer.ListenAndServe()
}()
go func() {
log.Infof("DNS TCP listener running on %s", f.listenAddress)
errCh <- f.tcpServer.ListenAndServe()
}()
// return the first error we get (e.g. bind failure or shutdown)
return <-errCh
}
func (f *DNSForwarder) UpdateDomains(entries []*ForwarderEntry) {
f.mutex.Lock()
defer f.mutex.Unlock()
@ -77,31 +98,41 @@ func (f *DNSForwarder) UpdateDomains(entries []*ForwarderEntry) {
}
oldDomains := filterDomains(f.fwdEntries)
for _, d := range oldDomains {
f.mux.HandleRemove(d.PunycodeString())
f.tcpMux.HandleRemove(d.PunycodeString())
}
newDomains := filterDomains(entries)
for _, d := range newDomains {
f.mux.HandleFunc(d.PunycodeString(), f.handleDNSQuery)
f.mux.HandleFunc(d.PunycodeString(), f.handleDNSQueryUDP)
f.tcpMux.HandleFunc(d.PunycodeString(), f.handleDNSQueryTCP)
}
f.fwdEntries = entries
log.Debugf("Updated domains from %v to %v", oldDomains, newDomains)
}
func (f *DNSForwarder) Close(ctx context.Context) error {
if f.dnsServer == nil {
return nil
var result *multierror.Error
if f.dnsServer != nil {
if err := f.dnsServer.ShutdownContext(ctx); err != nil {
result = multierror.Append(result, fmt.Errorf("UDP shutdown: %w", err))
}
}
if f.tcpServer != nil {
if err := f.tcpServer.ShutdownContext(ctx); err != nil {
result = multierror.Append(result, fmt.Errorf("TCP shutdown: %w", err))
}
return f.dnsServer.ShutdownContext(ctx)
}
func (f *DNSForwarder) handleDNSQuery(w dns.ResponseWriter, query *dns.Msg) {
return nberrors.FormatErrorOrNil(result)
}
func (f *DNSForwarder) handleDNSQuery(w dns.ResponseWriter, query *dns.Msg) *dns.Msg {
if len(query.Question) == 0 {
return
return nil
}
question := query.Question[0]
log.Tracef("received DNS request for DNS forwarder: domain=%v type=%v class=%v",
@ -123,20 +154,53 @@ func (f *DNSForwarder) handleDNSQuery(w dns.ResponseWriter, query *dns.Msg) {
if err := w.WriteMsg(resp); err != nil {
log.Errorf("failed to write DNS response: %v", err)
}
return
return nil
}
ctx, cancel := context.WithTimeout(context.Background(), upstreamTimeout)
defer cancel()
ips, err := net.DefaultResolver.LookupNetIP(ctx, network, domain)
if err != nil {
f.handleDNSError(w, resp, domain, err)
return
f.handleDNSError(w, query, resp, domain, err)
return nil
}
f.updateInternalState(domain, ips)
f.addIPsToResponse(resp, domain, ips)
return resp
}
func (f *DNSForwarder) handleDNSQueryUDP(w dns.ResponseWriter, query *dns.Msg) {
resp := f.handleDNSQuery(w, query)
if resp == nil {
return
}
opt := query.IsEdns0()
maxSize := dns.MinMsgSize
if opt != nil {
// client advertised a larger EDNS0 buffer
maxSize = int(opt.UDPSize())
}
// if our response is too big, truncate and set the TC bit
if resp.Len() > maxSize {
resp.Truncate(maxSize)
}
if err := w.WriteMsg(resp); err != nil {
log.Errorf("failed to write DNS response: %v", err)
}
}
func (f *DNSForwarder) handleDNSQueryTCP(w dns.ResponseWriter, query *dns.Msg) {
resp := f.handleDNSQuery(w, query)
if resp == nil {
return
}
if err := w.WriteMsg(resp); err != nil {
log.Errorf("failed to write DNS response: %v", err)
}
@ -179,7 +243,7 @@ func (f *DNSForwarder) updateFirewall(matchingEntries []*ForwarderEntry, prefixe
}
// handleDNSError processes DNS lookup errors and sends an appropriate error response
func (f *DNSForwarder) handleDNSError(w dns.ResponseWriter, resp *dns.Msg, domain string, err error) {
func (f *DNSForwarder) handleDNSError(w dns.ResponseWriter, query, resp *dns.Msg, domain string, err error) {
var dnsErr *net.DNSError
switch {
@ -191,7 +255,7 @@ func (f *DNSForwarder) handleDNSError(w dns.ResponseWriter, resp *dns.Msg, domai
}
if dnsErr.Server != "" {
log.Warnf("failed to resolve query for domain=%s server=%s: %v", domain, dnsErr.Server, err)
log.Warnf("failed to resolve query for type=%s domain=%s server=%s: %v", dns.TypeToString[query.Question[0].Qtype], domain, dnsErr.Server, err)
} else {
log.Warnf(errResolveFailed, domain, err)
}

14
client/internal/dnsfwd/manager.go
View File

@ -33,6 +33,7 @@ type Manager struct {
statusRecorder *peer.Status
fwRules []firewall.Rule
tcpRules []firewall.Rule
dnsForwarder *DNSForwarder
}
@ -107,6 +108,13 @@ func (m *Manager) allowDNSFirewall() error {
}
m.fwRules = dnsRules
tcpRules, err := m.firewall.AddPeerFiltering(nil, net.IP{0, 0, 0, 0}, firewall.ProtocolTCP, nil, dport, firewall.ActionAccept, "")
if err != nil {
log.Errorf("failed to add allow DNS router rules, err: %v", err)
return err
}
m.tcpRules = tcpRules
return nil
}
@ -117,7 +125,13 @@ func (m *Manager) dropDNSFirewall() error {
mErr = multierror.Append(mErr, fmt.Errorf("failed to delete DNS router rules, err: %v", err))
}
}
for _, rule := range m.tcpRules {
if err := m.firewall.DeletePeerRule(rule); err != nil {
mErr = multierror.Append(mErr, fmt.Errorf("failed to delete DNS router rules, err: %v", err))
}
}
m.fwRules = nil
m.tcpRules = nil
return nberrors.FormatErrorOrNil(mErr)
}