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cmd/containerboot: refresh DNS config on SelfChange (#20236)

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364b952d6 switched containerboot to partial netmap fetching, but
stopped refreshing `DNS.ExtraRecords`, so Tailscale Services created
after pod boot were invisible to resolveTailnetFQDN. To fix we watch
for SelfChange ipn bus notifies, and refetch dns-config via LocalAPI
to get a fresh set of `DNS.ExtraRecords`.

Fixes #20233

Signed-off-by: chaosinthecrd <tom@tmlabs.co.uk>
This commit is contained in:
Tom Meadows
2026-06-25 14:50:25 +01:00
committed by GitHub
parent 9f92a4728e
commit 6e1de5b651
2 changed files with 76 additions and 1 deletions
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cmd/containerboot/main_test.go
+57
View File
@@ -7,6 +7,7 @@ package main
import (
"bytes"
"context"
_ "embed"
"encoding/base64"
"encoding/json"
@@ -32,6 +33,7 @@ import (
"github.com/google/go-cmp/cmp"
"golang.org/x/sys/unix"
"tailscale.com/client/local"
"tailscale.com/cmd/testwrapper/flakytest"
"tailscale.com/health"
"tailscale.com/ipn"
@@ -39,6 +41,7 @@ import (
"tailscale.com/kube/egressservices"
"tailscale.com/kube/kubeclient"
"tailscale.com/kube/kubetypes"
"tailscale.com/net/memnet"
"tailscale.com/tailcfg"
"tailscale.com/tstest"
"tailscale.com/types/key"
@@ -1945,3 +1948,57 @@ func newTestEnv(t *testing.T) testEnv {
healthAddrPort: healthAddrPort,
}
}
// TestProcessNotifyRefreshesDNSOnSelfChange verifies that a SelfChange
// notification triggers a DNS refresh; without it, VIPServices created
// after pod boot are invisible to resolveTailnetFQDN.
func TestProcessNotifyRefreshesDNSOnSelfChange(t *testing.T) {
extraRec := tailcfg.DNSRecord{
Name: "my-ingress.tailnet.ts.net.",
Type: "A",
Value: "100.99.10.20",
}
dnsCfg := &tailcfg.DNSConfig{
ExtraRecords: []tailcfg.DNSRecord{extraRec},
CertDomains: []string{"node.tailnet.ts.net"},
}
lal := memnet.Listen("local-tailscaled.sock:80")
defer lal.Close()
mux := http.NewServeMux()
mux.HandleFunc("/localapi/v0/dns-config", func(w http.ResponseWriter, r *http.Request) {
w.Header().Set("Content-Type", "application/json")
if err := json.NewEncoder(w).Encode(dnsCfg); err != nil {
t.Errorf("encoding dns config: %v", err)
}
})
srv := &http.Server{Handler: mux}
go srv.Serve(lal)
t.Cleanup(func() { srv.Shutdown(context.Background()) })
client := &local.Client{Dial: lal.Dial}
// Empty starting state, as if the InitialStatus captured at pod
// boot carried no ExtraRecords because the VIPService didn't exist
// yet at that time.
var s netmapState
n := ipn.Notify{
SelfChange: &tailcfg.Node{
ID: 1,
Name: "self.tailnet.ts.net.",
},
}
got := s.processNotify(context.Background(), client, n)
if got.dnsExtraRecords.Len() != 1 {
t.Fatalf("dnsExtraRecords.Len() = %d, want 1", got.dnsExtraRecords.Len())
}
if rec := got.dnsExtraRecords.At(0); rec.Name != extraRec.Name {
t.Errorf("dnsExtraRecords[0].Name = %q, want %q", rec.Name, extraRec.Name)
}
if got.certDomains.Len() != 1 || got.certDomains.At(0) != "node.tailnet.ts.net" {
t.Errorf("certDomains = %v, want [node.tailnet.ts.net]", got.certDomains.AsSlice())
}
}