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fix: prevent QUIC reload panic by lazily initializing the listener #7680

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Merged
yongtang merged 2 commits into from
Nov 18, 2025
Merged

fix: prevent QUIC reload panic by lazily initializing the listener #7680

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75c87c9
fix: prevent QUIC reload panic by lazily initializing the listener
nberlee Nov 15, 2025
c36ba51
test: add regression test for QUIC reload panic
nberlee Nov 18, 2025
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8 changes: 8 additions & 0 deletions core/dnsserver/server_quic.go
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Original file line number Diff line number Diff line change
Expand Up @@ -103,6 +103,14 @@ func NewServerQUIC(addr string, group []*Config) (*ServerQUIC, error) {
// ServePacket implements caddy.UDPServer interface.
func (s *ServerQUIC) ServePacket(p net.PacketConn) error {
s.m.Lock()
if s.quicListener == nil {
listener, err := quic.Listen(p, s.tlsConfig, s.quicConfig)
if err != nil {
s.m.Unlock()
return err
}
s.quicListener = listener
}
s.listenAddr = s.quicListener.Addr()
s.m.Unlock()

Expand Down
76 changes: 76 additions & 0 deletions test/quic_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -23,6 +23,12 @@ var quicCorefile = `quic://.:0 {
whoami
}`

var quicReloadCorefile = `quic://.:0 {
tls ../plugin/tls/test_cert.pem ../plugin/tls/test_key.pem ../plugin/tls/test_ca.pem
whoami
reload 2s
}`

// Corefile with custom stream limits
var quicLimitCorefile = `quic://.:0 {
tls ../plugin/tls/test_cert.pem ../plugin/tls/test_key.pem ../plugin/tls/test_ca.pem
Expand Down Expand Up @@ -89,6 +95,29 @@ func TestQUIC(t *testing.T) {
}
}

func TestQUICReloadDoesNotPanic(t *testing.T) {
inst, udp, _, err := CoreDNSServerAndPorts(quicCorefile)
if err != nil {
t.Fatalf("Could not get CoreDNS serving instance: %s", err)
}
t.Cleanup(func() { inst.Stop() })

assertQUICQuerySucceeds(t, udp)

restart, err := inst.Restart(NewInput(quicReloadCorefile))
if err != nil {
t.Fatalf("Failed to restart CoreDNS: %s", err)
}
t.Cleanup(func() { restart.Stop() })

udpReload, _ := CoreDNSServerPorts(restart, 0)
if udpReload == "" {
t.Fatal("Failed to determine QUIC listener address after reload")
}

assertQUICQuerySucceeds(t, udpReload)
}

func TestQUICProtocolError(t *testing.T) {
q, udp, _, err := CoreDNSServerAndPorts(quicCorefile)
if err != nil {
Expand Down Expand Up @@ -352,3 +381,50 @@ func createInvalidDOQMsg() []byte {
msg, _ := m.Pack()
return msg
}

func assertQUICQuerySucceeds(t *testing.T, address string) {
t.Helper()
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()

conn, err := quic.DialAddr(ctx, convertAddress(address), generateTLSConfig(), nil)
if err != nil {
t.Fatalf("Expected no error but got: %s", err)
}
defer func() { _ = conn.CloseWithError(0, "") }()

stream, err := conn.OpenStreamSync(ctx)
if err != nil {
t.Fatalf("Expected no error but got: %s", err)
}
defer func() { _ = stream.Close() }()

msg := createTestMsg()
if _, err = stream.Write(msg); err != nil {
t.Fatalf("Expected no error but got: %s", err)
}

sizeBuf := make([]byte, 2)
if _, err = io.ReadFull(stream, sizeBuf); err != nil {
t.Fatalf("Expected no error but got: %s", err)
}

size := binary.BigEndian.Uint16(sizeBuf)
buf := make([]byte, size)
if _, err = io.ReadFull(stream, buf); err != nil {
t.Fatalf("Expected no error but got: %s", err)
}

resp := new(dns.Msg)
if err = resp.Unpack(buf); err != nil {
t.Fatalf("Expected no error but got: %s", err)
}

if resp.Rcode != dns.RcodeSuccess {
t.Fatalf("Expected success but got %d", resp.Rcode)
}

if len(resp.Extra) != 2 {
t.Fatalf("Expected 2 RRs in additional section, but got %d", len(resp.Extra))
}
}