feat!: NetworkPolicy in the NodePort and game-server charts, on by default

garage, minecraft-router, minecraft-server, samba, teamspeak-server,
satisfactory. One major each. These are the charts the plan said to leave for
last, and they earned it - three of them changed the convention rather than
just consuming it.

GARAGE is the clearest illustration after keycloak. Its four ports split three
ways: s3 and web are RESTRICTED by source (no probe touches them), admin is the
probe path and stays open inside the cluster - which is uncomfortable, because
admin is also the admin API, and that is said out loud instead of glossed - and
rpc gets the narrowest rule the object can express, a podSelector with no
namespaceSelector. All four numbers come from garage.settings.

MINECRAFT-SERVER is the tightest policy in the repository, and the reason is
worth knowing: all three of its probes are EXEC probes, which put no packet on
the network, so no port has to stay open for the kubelet and no probeSources
value is needed at all. RCON and metrics are restricted outright. The game port
has two branches rendered from the same value the Service reads -
server.service.type NodePort means players arrive from the internet and the
rule must be open; anything else means the only path is in-cluster, so the rule
is restricted and the router's namespace has to be in allowedNamespaces.

MINECRAFT-ROUTER derives its egress from the routing table instead of guessing:
server.backendPort plus the "port" override of every mapping that sets one. Add
a backend on a non-standard port and the policy follows. What it cannot express
is the destination - mappings name hosts, and this object matches no hostname -
so the rule is wider than the routing table, and that is written down.

SATISFACTORY gets policyTypes: [Ingress] and no egress section, and the second
half of the reason is the deciding one. Steam's content delivery is not a
pinnable port set (SteamCMD over TCP 80/443/27015-27050, master servers over
UDP 27000-27100 and 4380, changed by Valve, re-downloaded on every update) -
and this is the ONE chart with no install-test at all, because the image is
multiple GB and the first start pulls over 10GB. An egress cap here would be
the only one in the sweep with no empirical check behind it, on the chart whose
correct port set is least knowable.

SAMBA and TEAMSPEAK-SERVER carry the NodePort lesson explicitly: the rules name
445/139 and the pod's voice and file-transfer ports, never the NodePorts, and
teamspeak's file is explicit that its pod port and NodePort happening to share a
number is a coincidence of its values rather than a pattern to copy. Teamspeak's
voice rule is UDP, and the file says why that matters: a TCP rule on the same
number is accepted, looks complete, and drops every voice packet.

THREE THINGS THE CHECKS CAUGHT WHILE THIS BATCH WAS WRITTEN, all of them real:

  - minecraft-server's RCON rule named a port the pod does not declare. The
    containerPort is gated on server.rcon.enabled and the rule was not, so
    assertion 2 rejected it. The rule now carries the same gate.
  - samba and satisfactory would have shipped allowedNamespaces and
    probeSources values that reach NO rule - every one of their inbound rules
    is open to any source. A value that silently does nothing is worse than one
    that is absent, because it reads as a control, so both are gone from those
    two charts and from their schemas, with the reason in values.yaml.
    teamspeak-server loses probeSources for the same reason and keeps
    allowedNamespaces, which its web-query rule uses.
  - the policy templates no longer declare template variables they do not use.
    samba keeps one, satisfactory none.

Part of #5

minecraft-router/templates/NOTES.txt

@@ -138,3 +138,57 @@ server.env IS APPENDED TO WHAT THE CHART SETS
   in clear text, readable by everyone who can read pods in {{ .Release.Namespace }}; anything
   sensitive belongs in valueFrom.secretKeyRef.
 {{- end }}
+{{- if .Values.networkPolicy.enabled }}
+
+NETWORKPOLICY IS ACTIVE — WHAT IT CAPS, AND WHAT IT DOES NOT
+  {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy selects this workload's pods.
+  Inbound: the proxy port (TCP {{ .Values.server.port }}, open — it is published as NodePort
+  {{ .Values.server.outwardPort }} and the senders are players on the internet) and the API port
+  (TCP {{ .Values.server.apiPort }}, the probe path). Outbound: DNS plus the backend ports taken from
+  the routing table itself — TCP {{ $ports := list (int .Values.server.backendPort) }}{{ range .Values.mappings }}{{ if .port }}{{ $ports = append $ports (int .port) }}{{ end }}{{ end }}{{ join ", " ($ports | uniq) }}{{ with .Values.networkPolicy.egress }}{{ with .extraPorts }}, plus TCP {{ join ", " . }}{{ end }}{{ end }}.
+
+  THE BACKEND RULE IS BY PORT, NOT BY DESTINATION. mappings name hosts, and
+  this object cannot match a hostname — so the rule permits those ports to any
+  address, which is wider than your routing table. Adding a backend on a
+  non-standard port needs no change here: the policy reads the same value the
+  router does.
+
+  Three limits belong in the same breath, because none of them is visible in
+  the object itself:
+
+  - EGRESS IS BY PORT, NEVER BY DESTINATION. A NetworkPolicy matches CIDRs and
+    selectors and cannot express a hostname, so every egress rule permits its
+    port to ANY address. That is a limit of the object, not a shortcut — this
+    cluster's CNI (Canal: Flannel plus Calico) has no FQDN rule either. An
+    outbound port the chart does not know about is BLOCKED: add it to
+    networkPolicy.egress.extraPorts, and expect to find out through an
+    application-level connection error rather than through this object.
+{{- if .Values.networkPolicy.probeSources }}
+  - THE PROBE PATH IS RESTRICTED in this release, because
+    networkPolicy.probeSources is set to
+      {{ join ", " .Values.networkPolicy.probeSources }}
+    Probes come from the IP of the WORKER NODE running the pod. If none of those
+    CIDRs covers the node this pod lands on, the kubelet's probes are dropped
+    and THE POD NEVER BECOMES READY — the rollout then times out and the symptom
+    looks like a broken application. Compare
+
+      kubectl -n {{ .Release.Namespace }} describe pod -l app={{ .Release.Name }}-{{ .Chart.Name }}-deployment
+
+    against `kubectl get node -o wide`.
+{{- else }}
+  - THE PROBED PORT IS OPEN INSIDE THE CLUSTER. networkPolicy.probeSources is
+    empty, so that rule carries no source selector at all and any pod the CNI
+    routes to can reach it. Not from the internet — but this is NOT pod-level
+    isolation. Narrowing it means listing the worker node IPs in
+    networkPolicy.probeSources, because the kubelet probes from the node's own
+    address and the chart cannot know it; a wrong guess there leaves the pod
+    permanently un-Ready.
+{{- end }}
+  - IT IS ONLY A BOUNDARY WHERE THE CNI ENFORCES POLICIES. Where it does not,
+    this object is accepted and filters nothing, so everything reads as
+    configured while nothing is filtered. `kubectl -n {{ .Release.Namespace }} get networkpolicy`
+    shows the object exists; only a connection attempt from an unrelated
+    namespace shows that it bites.
+
+  Switch it off with networkPolicy.enabled: false.
+{{- end }}

minecraft-router/templates/minecraft-router.networkpolicy.yaml

@@ -0,0 +1,184 @@
+{{- /*
+NetworkPolicy for minecraft-router (Gitea #5).
+
+The router is the one chart here whose whole job is to forward traffic to OTHER
+releases, so its egress rule is the interesting one and it is DERIVED from the
+routing table rather than guessed: server.backendPort, plus the per-mapping
+"port" override for every entry of mappings that has one. Add a backend on a
+non-standard port and the policy follows it, because both come from the same
+value.
+
+What it does NOT express is the destination. The mappings name hosts
+(internalUrl), and a NetworkPolicy matches CIDRs and selectors and never
+hostnames - so the rule permits those PORTS to any address, not those services.
+A backend in another namespace is reachable through this rule; so is anything
+else listening on 25565.
+
+Inbound splits in two: the proxy port is a NodePort and faces the internet, the
+API port is the probe path.
+
+WHAT THIS OBJECT IS: a ceiling on reachability, not an authentication layer.
+Only the ports declared below are reachable at all - whatever else the process
+binds, now or after the next app update, is blocked without anyone having to
+notice it exists.
+
+WHAT IT IS NOT:
+  - EGRESS IS COARSE. A NetworkPolicy matches CIDRs and selectors and NEVER
+    hostnames, so "only to the database host" cannot be expressed at all. This
+    cluster's CNI is Canal (Flannel plus Calico for policy) and has no FQDN
+    rule; Calico's GlobalNetworkSet could express one but would bind this chart
+    to Calico, the same argument that kept implementation-specific objects out
+    of the Gateway-API sweep (#114). Each egress rule therefore permits its
+    PORT to any destination.
+  - NOT A BOUNDARY WHERE THE CNI DOES NOT ENFORCE ONE. An unenforced policy is
+    accepted by the API server and filters nothing, so everything reads as
+    configured while nothing is filtered.
+  - THE REASONING IS IN TEMPLATE COMMENTS, not in "#" comments: those are part
+    of the rendered object, travel into the cluster and appear in every release
+    diff. ci/run-networkpolicy-test.sh fails on a rendered "#".
+
+THE PORT NUMBERS BELOW ARE POD PORTS, NEVER NODEPORTS. A NetworkPolicy is
+evaluated at the pod's network interface, after kube-proxy has already
+translated a NodePort to the targetPort, so a NodePort number here would match
+nothing while looking strict - and, being the only rule for that port, would
+block every inbound connection instead. ci/run-networkpolicy-test.sh asserts
+every port here against the containerPorts of the pod spec this policy
+selects.
+*/ -}}
+{{- if .Values.networkPolicy.enabled }}
+{{- $backendPorts := list (int .Values.server.backendPort) }}
+{{- range .Values.mappings }}
+{{- if .port }}{{- $backendPorts = append $backendPorts (int .port) }}{{- end }}
+{{- end }}
+{{- $np := .Values.networkPolicy }}
+{{- $ns := .Release.Namespace }}
+{{- $probeSources := $np.probeSources | default list }}
+{{- $allowedNs := $np.allowedNamespaces | default list }}
+apiVersion: networking.k8s.io/v1
+kind: NetworkPolicy
+metadata:
+  name: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
+  labels:
+    app: {{ .Release.Name }}-{{ .Chart.Name }}-networkpolicy
+spec:
+  {{- /*
+  Selects the Deployment's pods. ci/run-networkpolicy-test.sh fails if
+  this matches no pod spec of the same render - which is the mistake that
+  would otherwise leave a policy in the namespace filtering nothing, and
+  its usual cause is a label renamed in the workload template.
+  */}}
+  podSelector:
+    matchLabels:
+      app: {{ .Release.Name }}-{{ .Chart.Name }}-deployment
+  policyTypes:
+    - Ingress
+    {{- /*
+    Egress is listed because the router's outbound traffic is exactly known for
+    once - DNS, and the backend ports from its own routing table. That makes this
+    one of the few egress caps in the sweep that is derived rather than guessed.
+    */}}
+    - Egress
+  ingress:
+    {{- /*
+    THE PROXY PORT, and deliberately open with no "from" at all: it is published
+    as a NodePort (server.outwardPort) and the senders are Minecraft clients on the
+    internet. After NodePort masquerading the source address is a cluster node
+    anyway, so a source selector here could only ever be a list of node IPs - which
+    would be a restriction in appearance and a maintenance trap in fact.
+
+    NOTE THE NUMBER: this is the POD port (server.port), not server.outwardPort.
+    The NodePort is translated by kube-proxy before the packet reaches the pod, so
+    writing 30565 here would match nothing while looking strict - and being the
+    only rule for this port, it would block every player instead.
+    ci/run-networkpolicy-test.sh asserts exactly this.
+    */}}
+    - ports:
+        - protocol: TCP
+          port: {{ .Values.server.port | int64 }}
+    {{- /*
+    THE API PORT - the router's own HTTP interface, and the port all three probes
+    address. So it is the probe path and stays open inside the cluster by default.
+
+    No ingress-controller entry: this chart renders no Ingress, and nothing should
+    route to the router's API from outside.
+    */}}
+    - ports:
+        - protocol: TCP
+          port: {{ .Values.server.apiPort | int64 }}
+      {{- if $probeSources }}
+      {{- /*
+      RESTRICTED, because the operator supplied probeSources. The kubelet's probes
+      come from the IP of the WORKER NODE running the pod, so that address has to be
+      in the list or the pod never becomes Ready - and a pod that is never Ready
+      reads as a broken application rather than as a policy.
+      */}}
+      from:
+        - namespaceSelector:
+            matchLabels:
+              {{- /*
+              Set by Kubernetes itself on every namespace (>= 1.21), so this needs no
+              labelling work on a namespace this chart does not own.
+              */}}
+              kubernetes.io/metadata.name: {{ $ns }}
+        {{- range $allowedNs }}
+        - namespaceSelector:
+            matchLabels:
+              kubernetes.io/metadata.name: {{ . | quote }}
+        {{- end }}
+        {{- range $probeSources }}
+        - ipBlock:
+            cidr: {{ . | quote }}
+        {{- end }}
+      {{- else }}
+      {{- /*
+      NO "from" SELECTOR, WHICH MEANS OPEN - deliberately, and only inside the
+      cluster, because this port carries no NodePort. The alternative was to guess
+      the worker node CIDRs, and a wrong guess blocks every kubelet probe: the pod
+      stays un-Ready, the rollout times out, and the cause looks like the
+      application. An empty "from: []" would be worse than either - it allows
+      everything too, but while reading as a restriction. Narrow it with
+      networkPolicy.probeSources.
+      */}}
+      {{- end }}
+  egress:
+    {{- /*
+    DNS, unconditionally. There is no value to switch this off, and that is
+    deliberate: a knob whose only other setting breaks every name lookup in
+    the pod is a trap and not a feature.
+    */}}
+    - ports:
+        - protocol: UDP
+          port: 53
+        - protocol: TCP
+          port: 53
+    {{- /*
+    THE BACKENDS, by port, derived from the routing table: server.backendPort plus
+    the "port" override of every mapping that sets one. So a backend on a
+    non-standard port is covered automatically, and there is no second list to keep
+    in step with mappings.
+
+    Ports and not destinations: the mappings name hosts (internalUrl) and this
+    object cannot match a hostname, so this rule permits those ports to ANY
+    address. That is wider than the routing table and is the honest description of
+    what the object can do.
+    */}}
+    - ports:
+        {{- range $backendPorts | uniq }}
+        - protocol: TCP
+          port: {{ . }}
+        {{- end }}
+    {{- with $np.egress }}
+    {{- with .extraPorts }}
+    {{- /*
+    Ports only, to any destination - see the header. This is the operator's
+    escape hatch from the egress cap, and the only alternative to switching
+    the whole policy off.
+    */}}
+    - ports:
+        {{- range . }}
+        - protocol: TCP
+          port: {{ int . }}
+        {{- end }}
+    {{- end }}
+    {{- end }}
+{{- end }}