mesh-controller/examples/modules/modules_test.go

package modules

import (
	"encoding/json"
	"os"
	"path/filepath"
	"strings"
	"testing"

	"github.com/novox/mesh-control/internal/catalogue"
	"github.com/novox/mesh-control/internal/overlay"
)

// The examples are manifests, so the thing to check is that the catalogue accepts them.
//
// A manifest that only ever appears in a document is a manifest nobody has run through the parser,
// and the parser refuses unknown keys — so a typo here would be discovered by whoever first tried
// to use one, which is the opposite of what an example is for.
func read(t *testing.T, name string) catalogue.Manifest {
	t.Helper()
	raw, err := os.ReadFile(filepath.Join(".", name))
	if err != nil {
		t.Fatal(err)
	}
	m, err := catalogue.ParseManifest(raw)
	if err != nil {
		t.Fatalf("%s is not a manifest this mesh accepts: %v", name, err)
	}
	return m
}

func TestEveryExampleIsAManifestTheMeshAccepts(t *testing.T) {
	found, err := filepath.Glob("*.json")
	if err != nil {
		t.Fatal(err)
	}
	if len(found) == 0 {
		t.Fatal("no examples, so this test proves nothing")
	}
	for _, name := range found {
		read(t, name)
	}
}

// The serving module reads what the mesh writes, and restarts when the mesh rewrites it.
//
// Without the second it would serve the names it started with for ever — every machine that
// joined afterwards unreachable by name, and every check passing.
func TestTheResolverReadsTheMeshsNamesAndFollowsThem(t *testing.T) {
	m := read(t, "dnsmasq.json")

	var config, service map[string]any
	for _, r := range m.Resources {
		switch r["id"] {
		case "config":
			config = r
		case "service":
			service = r
		}
	}
	if config == nil || service == nil {
		t.Fatal("the module has no configuration or no service")
	}
	if !strings.Contains(config["content"].(string), overlay.ResolverPath) {
		t.Fatalf("it does not read what the mesh writes at %s", overlay.ResolverPath)
	}

	var follows bool
	for _, id := range service["restart-on"].([]any) {
		if id.(string) == overlay.Resolver+".nodes" {
			follows = true
		}
	}
	if !follows {
		t.Fatalf("it does not restart when the mesh rewrites the names: %v", service["restart-on"])
	}
}

// It binds names the mesh chose, so it needs to know nothing about the machine it is on.
//
// That is the whole reason these can be static manifests: a resolver must bind somewhere and a
// stub must be pointed somewhere, and neither address is knowable in advance — unless the mesh
// named it.
func TestTheResolverNeedsToKnowNothingAboutItsMachine(t *testing.T) {
	config := read(t, "dnsmasq.json").Resources[1]["content"].(string)
	// The directive, not the word: the comment above it names the interface too, so a plain
	// Contains passes whatever the module actually binds. It did.
	if !strings.Contains(config, "interface="+overlay.Interface+"\n") {
		t.Fatalf("it does not bind the private network's interface %q:\n%s",
			overlay.Interface, config)
	}
	// That it binds one, not which. Which address it is belongs in the manifests, where the
	// asking modules can be checked against it — naming it here too would be a fourth place to
	// keep in step, and the one nobody would think to change.
	if !strings.Contains(config, "\nlisten-address=127.0.0.") {
		t.Fatalf("it answers on no address for the machine's own use:\n%s", config)
	}
	// Not an address that belongs to something else.
	//
	// **systemd-resolved holds .53 AND .54** — the stub and the proxy stub. This module asserted
	// .54 was free, in a comment that read as reasoned, and a machine said otherwise: dnsmasq
	// could not start at all. A unit test cannot know which addresses a machine has spare, but it
	// can hold on to what one has already told us.
	for _, taken := range []string{"127.0.0.1", "127.0.0.53", "127.0.0.54"} {
		if strings.Contains(config, "listen-address="+taken) {
			t.Fatalf("it takes %s, which belongs to something else:\n%s", taken, config)
		}
	}
}

// Everything that points resolution at the mesh points at the same place.
//
// Three files name this address — one binds it and two send queries to it — and a change to one
// of them alone is a resolver answering where nobody asks.
func TestTheAskingModulesPointAtWhereTheResolverAnswers(t *testing.T) {
	serving := read(t, "dnsmasq.json").Resources[1]["content"].(string)
	var at string
	for _, line := range strings.Split(serving, "\n") {
		if rest, found := strings.CutPrefix(strings.TrimSpace(line), "listen-address="); found {
			at = rest
		}
	}
	if at == "" {
		t.Fatal("the resolver binds no address for the machine's own use")
	}
	for _, asking := range []string{"resolved-split-dns.json", "resolv-conf.json"} {
		m := read(t, asking)
		var mentions bool
		for _, r := range m.Resources {
			if content, ok := r["content"].(string); ok && strings.Contains(content, at) {
				mentions = true
			}
		}
		if !mentions {
			t.Fatalf("%s does not point at %s, where the resolver answers", asking, at)
		}
	}
}

// The two ways of deciding what a machine asks claim the same thing, so the mesh refuses the pair.
func TestTwoWaysOfOwningTheResolverCannotBothBeAssigned(t *testing.T) {
	shelf := map[string]catalogue.Manifest{}
	for _, name := range []string{"resolved-split-dns.json", "resolv-conf.json", "dnsmasq.json"} {
		m := read(t, name)
		shelf[m.Module] = m
	}
	// Something has to answer `wildcard-resolution`, or they are refused for that instead and the
	// test would pass without ever reaching the claim.
	shelf["dnsmasq"] = read(t, "dnsmasq.json")

	_, err := catalogue.Resolve(shelf,
		[]string{"dnsmasq", "resolved-split-dns", "resolv-conf"},
		catalogue.Node{Name: "anchor", Capabilities: map[string]bool{}},
		catalogue.World{Unchecked: true})
	if err == nil {
		t.Fatal("both ways of owning the resolver were assigned to one machine")
	}
	said := err.Error()
	if !strings.Contains(said, "the-resolver-configuration") {
		t.Fatalf("the refusal does not name what they both want: %v", said)
	}
}

// And the two roles are not the same claim: a machine runs one resolver AND one thing deciding
// what it asks, so serving and asking must be assignable together.
func TestServingAndAskingAreAssignableTogether(t *testing.T) {
	shelf := map[string]catalogue.Manifest{}
	for _, name := range []string{"dnsmasq.json", "resolved-split-dns.json"} {
		m := read(t, name)
		shelf[m.Module] = m
	}
	if _, err := catalogue.Resolve(shelf,
		[]string{"dnsmasq", "resolved-split-dns"},
		catalogue.Node{Name: "anchor", Capabilities: map[string]bool{}},
		catalogue.World{Unchecked: true}); err != nil {
		t.Fatalf("a resolver and the thing pointing at it cannot both be assigned: %v", err)
	}
}

// The examples are JSON a person edits, so a stray comma is worth catching here rather than on a
// machine.
func TestTheExamplesAreWellFormed(t *testing.T) {
	found, _ := filepath.Glob("*.json")
	for _, name := range found {
		raw, err := os.ReadFile(name)
		if err != nil {
			t.Fatal(err)
		}
		var any map[string]any
		if err := json.Unmarshal(raw, &any); err != nil {
			t.Fatalf("%s is not JSON: %v", name, err)
		}
	}
}

// The resolver must not look up its own upstreams.
//
// Whatever points a machine at the mesh writes that address into resolv.conf, so a resolver that
// read it would find itself — and every query it could not answer locally would loop until its
// receive queue filled. It did: 15KB of queries backed up and every lookup on the machine hung.
//
// It needs no upstream because it is never asked for anything else: the asking module routes only
// the mesh's suffix here and leaves the rest where the machine already sent it.
func TestTheResolverDoesNotAskItselfForUpstreams(t *testing.T) {
	config := read(t, "dnsmasq.json").Resources[1]["content"].(string)
	if !strings.Contains(config, "\nno-resolv\n") {
		t.Fatalf("it reads resolv.conf for upstreams, which now points at itself:\n%s", config)
	}
	// And names no upstream of its own: choosing one would send every query this machine cannot
	// answer somewhere nobody agreed to.
	for _, line := range strings.Split(config, "\n") {
		if strings.HasPrefix(strings.TrimSpace(line), "server=") {
			t.Fatalf("it forwards to %q, which is not the mesh's to choose", line)
		}
	}
}