Add unit tests for default network creation.

Signed-off-by: Nashwan Azhari <[email protected]>

pkg/netutil/netutil_test.go

@@ -17,12 +17,44 @@
 package netutil
 
 import (
+	"bytes"
+	"fmt"
 	"net"
+	"os"
+	"path/filepath"
+	"strconv"
 	"testing"
+	"text/template"
+
+	ncdefaults "github.com/containerd/nerdctl/pkg/defaults"
+	"github.com/containerd/nerdctl/pkg/labels"
+	"github.com/containerd/nerdctl/pkg/rootlessutil"
+	"github.com/containerd/nerdctl/pkg/testutil"
 
 	"gotest.tools/v3/assert"
 )
 
+const preExistingNetworkConfigTemplate = `
+{
+    "cniVersion": "0.2.0",
+    "name": "{{ .network_name }}",
+    "type": "nat",
+    "master": "Ethernet",
+    "ipam": {
+        "subnet": "{{ .subnet }}",
+        "routes": [
+            {
+                "GW": "{{ .gateway }}"
+            }
+        ]
+    },
+    "capabilities": {
+        "portMappings": true,
+        "dns": true
+    }
+}
+`
+
 func TestParseIPAMRange(t *testing.T) {
 	t.Parallel()
 	type testCase struct {
@@ -97,3 +129,138 @@ func TestParseIPAMRange(t *testing.T) {
 		}
 	}
 }
+
+// Tests whether nerdctl properly creates the default network when required.
+func TestDefaultNetworkCreation(t *testing.T) {
+	if rootlessutil.IsRootless() {
+		t.Skip("must be superuser to create default network for this test")
+	}
+
+	// To prevent subnet collisions when attempting to recreate the default network
+	// in the isolated CNI config dir we'll be using, we must first delete
+	// the network in the default CNI config dir.
+	defaultCniEnv := CNIEnv{
+		Path:        ncdefaults.CNIPath(),
+		NetconfPath: ncdefaults.CNINetConfPath(),
+	}
+	defaultNet, err := defaultCniEnv.GetDefaultNetworkConfig()
+	assert.NilError(t, err)
+	if defaultNet != nil {
+		assert.NilError(t, defaultCniEnv.RemoveNetwork(defaultNet))
+	}
+
+	// We create a tempdir for the CNI conf path to ensure an empty env for this test.
+	cniConfTestDir := t.TempDir()
+	cniEnv := CNIEnv{
+		Path:        ncdefaults.CNIPath(),
+		NetconfPath: cniConfTestDir,
+	}
+	// Ensure no default network config is not present.
+	defaultNetConf, err := cniEnv.GetDefaultNetworkConfig()
+	assert.NilError(t, err)
+	assert.Assert(t, defaultNetConf == nil)
+
+	// Attempt to create the default network.
+	err = cniEnv.ensureDefaultNetworkConfig()
+	assert.NilError(t, err)
+
+	// Ensure no default network config is present now.
+	defaultNetConf, err = cniEnv.GetDefaultNetworkConfig()
+	assert.NilError(t, err)
+	assert.Assert(t, defaultNetConf != nil)
+
+	// Check network config file present.
+	stat, err := os.Stat(defaultNetConf.File)
+	assert.NilError(t, err)
+	firstConfigModTime := stat.ModTime()
+
+	// Check default network label present.
+	assert.Assert(t, defaultNetConf.NerdctlLabels != nil)
+	lstr, ok := (*defaultNetConf.NerdctlLabels)[labels.NerdctlDefaultNetwork]
+	assert.Assert(t, ok)
+	boolv, err := strconv.ParseBool(lstr)
+	assert.NilError(t, err)
+	assert.Assert(t, boolv)
+
+	// Ensure network isn't created twice or accidentally re-created.
+	err = cniEnv.ensureDefaultNetworkConfig()
+	assert.NilError(t, err)
+
+	// Check for any other network config files.
+	files := []os.FileInfo{}
+	walkF := func(p string, info os.FileInfo, err error) error {
+		files = append(files, info)
+		return nil
+	}
+	err = filepath.Walk(cniConfTestDir, walkF)
+	assert.NilError(t, err)
+	assert.Assert(t, len(files) == 2) // files[0] is the entry for '.'
+	assert.Assert(t, filepath.Join(cniConfTestDir, files[1].Name()) == defaultNetConf.File)
+	assert.Assert(t, firstConfigModTime == files[1].ModTime())
+}
+
+// Tests whether nerdctl skips the creation of the default network if a
+// network bearing the default network name already exists in a
+// non-nerdctl-managed network config file.
+func TestNetworkWithDefaultNameAlreadyExists(t *testing.T) {
+	// We create a tempdir for the CNI conf path to ensure an empty env for this test.
+	cniConfTestDir := t.TempDir()
+	cniEnv := CNIEnv{
+		Path:        t.TempDir(), // irrelevant for this test
+		NetconfPath: cniConfTestDir,
+	}
+
+	// Ensure no default network config is not present.
+	defaultNetConf, err := cniEnv.GetDefaultNetworkConfig()
+	assert.NilError(t, err)
+	assert.Assert(t, defaultNetConf == nil)
+
+	// Manually define and write a network config file.
+	values := map[string]string{
+		"network_name": DefaultNetworkName,
+		"subnet":       "10.7.1.1/24",
+		"gateway":      "10.7.1.1",
+	}
+	tpl, err := template.New("test").Parse(preExistingNetworkConfigTemplate)
+	assert.NilError(t, err)
+	buf := &bytes.Buffer{}
+	assert.NilError(t, tpl.ExecuteTemplate(buf, "test", values))
+
+	// Filename is irrelevant as long as it's not nerdctl's.
+	testConfFile := filepath.Join(cniConfTestDir, fmt.Sprintf("%s.conf", testutil.Identifier(t)))
+	err = os.WriteFile(testConfFile, buf.Bytes(), 0600)
+	assert.NilError(t, err)
+
+	// Check network is detected.
+	netConfs, err := cniEnv.NetworkList()
+	assert.NilError(t, err)
+	assert.Assert(t, len(netConfs) > 0)
+
+	var listedDefaultNetConf *NetworkConfig
+	for _, netConf := range netConfs {
+		if netConf.Name == DefaultNetworkName {
+			listedDefaultNetConf = netConf
+			break
+		}
+	}
+	assert.Assert(t, listedDefaultNetConf != nil)
+
+	defaultNetConf, err = cniEnv.GetDefaultNetworkConfig()
+	assert.NilError(t, err)
+	assert.Assert(t, defaultNetConf != nil)
+	assert.Assert(t, defaultNetConf.File == testConfFile)
+
+	err = cniEnv.ensureDefaultNetworkConfig()
+	assert.NilError(t, err)
+
+	netConfs, err = cniEnv.NetworkList()
+	assert.NilError(t, err)
+	defaultNamedNetworksFileDefinitions := []string{}
+	for _, netConf := range netConfs {
+		if netConf.Name == DefaultNetworkName {
+			defaultNamedNetworksFileDefinitions = append(defaultNamedNetworksFileDefinitions, netConf.File)
+		}
+	}
+	assert.Assert(t, len(defaultNamedNetworksFileDefinitions) == 1)
+	assert.Assert(t, defaultNamedNetworksFileDefinitions[0] == testConfFile)
+}