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fix: ensure upstream health checks can handle large DNS responses

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- Add UpstreamConfig.VerifyMsg() method with proper EDNS0 support
- Replace hardcoded DNS messages in health checks with standardized verification method
- Set EDNS0 buffer size to 4096 bytes to handle large DNS responses
- Add test case for legacy resolver with extensive extra sections
This commit is contained in:
Cuong Manh Le
2025-08-15 15:49:06 +07:00
committed by Cuong Manh Le
parent 2c98b2c545
commit a72ff1e769
4 changed files with 102 additions and 5 deletions
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4
cmd/cli/dns_proxy.go
View File

@@ -1564,9 +1564,6 @@ func (p *prog) checkUpstreamOnce(upstream string, uc *ctrld.UpstreamConfig) erro
return err
}
msg := new(dns.Msg)
msg.SetQuestion(".", dns.TypeNS)
timeout := 1000 * time.Millisecond
if uc.Timeout > 0 {
timeout = time.Millisecond * time.Duration(uc.Timeout)
@@ -1580,6 +1577,7 @@ func (p *prog) checkUpstreamOnce(upstream string, uc *ctrld.UpstreamConfig) erro
p.Debug().Msgf("Rebootstrapping resolver for upstream: %s", upstream)
start := time.Now()
msg := uc.VerifyMsg()
_, err = resolver.Resolve(ctx, msg)
duration := time.Since(start)

9
config.go
View File

@@ -362,6 +362,15 @@ func (uc *UpstreamConfig) Init(ctx context.Context) {
}
}
// VerifyMsg creates and returns a new DNS message could be used for testing upstream health.
func (uc *UpstreamConfig) VerifyMsg() *dns.Msg {
msg := new(dns.Msg)
msg.RecursionDesired = true
msg.SetQuestion(".", dns.TypeNS)
msg.SetEdns0(4096, false) // ensure handling of large DNS response
return msg
}
// VerifyDomain returns the domain name that could be resolved by the upstream endpoint.
// It returns empty for non-ControlD upstream endpoint.
func (uc *UpstreamConfig) VerifyDomain() string {

3
internal/clientinfo/ptr_lookup.go
View File

@@ -119,8 +119,7 @@ func (p *ptrDiscover) lookupIPByHostname(name string, v6 bool) string {
// is reachable, set p.serverDown to false, so p.lookupHostname can continue working.
func (p *ptrDiscover) checkServer() {
bo := backoff.NewBackoff("ptrDiscover", func(format string, args ...any) {}, time.Minute*5)
m := new(dns.Msg)
m.SetQuestion(".", dns.TypeNS)
m := (&ctrld.UpstreamConfig{}).VerifyMsg()
ping := func() error {
ctx, cancel := context.WithTimeout(context.Background(), time.Second)
defer cancel()

91
resolver_test.go
View File

@@ -340,6 +340,35 @@ func Test_Edns0_CacheReply(t *testing.T) {
}
}
// https://github.com/Control-D-Inc/ctrld/issues/255
func Test_legacyResolverWithBigExtraSection(t *testing.T) {
lanPC, err := net.ListenPacket("udp", "127.0.0.1:0") // 127.0.0.1 is considered LAN (loopback)
if err != nil {
t.Fatalf("failed to listen on LAN address: %v", err)
}
lanServer, lanAddr, err := runLocalPacketConnTestServer(t, lanPC, bigExtraSectionHandler())
if err != nil {
t.Fatalf("failed to run LAN test server: %v", err)
}
defer lanServer.Shutdown()
uc := &UpstreamConfig{
Name: "Legacy",
Type: ResolverTypeLegacy,
Endpoint: lanAddr,
}
uc.Init()
r, err := NewResolver(uc)
if err != nil {
t.Fatal(err)
}
_, err = r.Resolve(context.Background(), uc.VerifyMsg())
if err != nil {
t.Fatal(err)
}
}
func Test_upstreamTypeFromEndpoint(t *testing.T) {
tests := []struct {
name string
@@ -428,6 +457,68 @@ func countHandler(call *atomic.Int64) dns.HandlerFunc {
}
}
func mustRR(s string) dns.RR {
r, err := dns.NewRR(s)
if err != nil {
panic(err)
}
return r
}
func bigExtraSectionHandler() dns.HandlerFunc {
return func(w dns.ResponseWriter, msg *dns.Msg) {
m := &dns.Msg{
Answer: []dns.RR{
mustRR(". 7149 IN NS m.root-servers.net."),
mustRR(". 7149 IN NS c.root-servers.net."),
mustRR(". 7149 IN NS e.root-servers.net."),
mustRR(". 7149 IN NS j.root-servers.net."),
mustRR(". 7149 IN NS g.root-servers.net."),
mustRR(". 7149 IN NS k.root-servers.net."),
mustRR(". 7149 IN NS l.root-servers.net."),
mustRR(". 7149 IN NS d.root-servers.net."),
mustRR(". 7149 IN NS h.root-servers.net."),
mustRR(". 7149 IN NS b.root-servers.net."),
mustRR(". 7149 IN NS a.root-servers.net."),
mustRR(". 7149 IN NS f.root-servers.net."),
mustRR(". 7149 IN NS i.root-servers.net."),
},
Extra: []dns.RR{
mustRR("m.root-servers.net. 656 IN A 202.12.27.33"),
mustRR("m.root-servers.net. 656 IN AAAA 2001:dc3::35"),
mustRR("c.root-servers.net. 656 IN A 192.33.4.12"),
mustRR("c.root-servers.net. 656 IN AAAA 2001:500:2::c"),
mustRR("e.root-servers.net. 656 IN A 192.203.230.10"),
mustRR("e.root-servers.net. 656 IN AAAA 2001:500:a8::e"),
mustRR("j.root-servers.net. 656 IN A 192.58.128.30"),
mustRR("j.root-servers.net. 656 IN AAAA 2001:503:c27::2:30"),
mustRR("g.root-servers.net. 656 IN A 192.112.36.4"),
mustRR("g.root-servers.net. 656 IN AAAA 2001:500:12::d0d"),
mustRR("k.root-servers.net. 656 IN A 193.0.14.129"),
mustRR("k.root-servers.net. 656 IN AAAA 2001:7fd::1"),
mustRR("l.root-servers.net. 656 IN A 199.7.83.42"),
mustRR("l.root-servers.net. 656 IN AAAA 2001:500:9f::42"),
mustRR("d.root-servers.net. 656 IN A 199.7.91.13"),
mustRR("d.root-servers.net. 656 IN AAAA 2001:500:2d::d"),
mustRR("h.root-servers.net. 656 IN A 198.97.190.53"),
mustRR("h.root-servers.net. 656 IN AAAA 2001:500:1::53"),
mustRR("b.root-servers.net. 656 IN A 170.247.170.2"),
mustRR("b.root-servers.net. 656 IN AAAA 2801:1b8:10::b"),
mustRR("a.root-servers.net. 656 IN A 198.41.0.4"),
mustRR("a.root-servers.net. 656 IN AAAA 2001:503:ba3e::2:30"),
mustRR("f.root-servers.net. 656 IN A 192.5.5.241"),
mustRR("f.root-servers.net. 656 IN AAAA 2001:500:2f::f"),
mustRR("i.root-servers.net. 656 IN A 192.36.148.17"),
mustRR("i.root-servers.net. 656 IN AAAA 2001:7fe::53"),
},
}
m.Compress = true
m.SetReply(msg)
w.WriteMsg(m)
}
}
func generateEdns0ClientCookie() string {
cookie := make([]byte, 8)
if _, err := rand.Read(cookie); err != nil {