fix host release name nil pointer (#2250)

* fix host release name nil pointer

* lint

* added host node to e2e test

---------

Co-authored-by: Roman Dodin <dodin.roman@gmail.com>

nodes/host/host.go

@@ -7,9 +7,6 @@ package host
 import (
 	"bytes"
 	"context"
-	"os"
-	"path/filepath"
-	"regexp"
 
 	osexec "os/exec"
 
@@ -19,6 +16,7 @@ import (
 	"github.com/srl-labs/containerlab/nodes/state"
 	"github.com/srl-labs/containerlab/runtime"
 	"github.com/srl-labs/containerlab/types"
+	"github.com/srl-labs/containerlab/utils"
 )
 
 var kindnames = []string{"host"}
@@ -59,30 +57,9 @@ func (*host) WithMgmtNet(*types.MgmtNet)                    {}
 // UpdateConfigWithRuntimeInfo is a noop for hosts.
 func (*host) UpdateConfigWithRuntimeInfo(_ context.Context) error { return nil }
 
-// getOSRelease returns the OS release of the host by inspecting /etc/*-release.
-func getOSRelease() string {
-	image := "N/A"
-
-	matches, err := filepath.Glob("/etc/*-release")
-	if err != nil {
-		return image
-	}
-	dat, err := os.ReadFile(matches[0])
-	if err != nil {
-		return image
-	}
-	// DISTRIB_DESCRIPTION exists in lsb-release, but not os-release.
-	// the lsb-release is coming first in the glob, so it works.
-	re := regexp.MustCompile(`DISTRIB_DESCRIPTION="(.*)"`)
-
-	regexres := re.FindSubmatch(dat)
-
-	return string(regexres[1])
-}
-
 // GetContainers returns a basic skeleton of a container to enable graphing of hosts kinds.
-func (*host) GetContainers(_ context.Context) ([]runtime.GenericContainer, error) {
-	image := getOSRelease()
+func (h *host) GetContainers(_ context.Context) ([]runtime.GenericContainer, error) {
+	image := utils.GetOSRelease()
 
 	return []runtime.GenericContainer{
 		{

tests/01-smoke/03-linux-nodes-to-bridge-and-host.clab.yml

@@ -14,6 +14,8 @@ topology:
       cmd: ash -c "sleep 9999"
     br-01-03-clab:
       kind: bridge
+    hostnode: # is not used, it is here for coverage
+      kind: host
 
   links:
     - endpoints: ["l1:eth1", "br-01-03-clab:l1-eth1"]

utils/file.go

@@ -19,6 +19,7 @@ import (
 	"os/exec"
 	"os/user"
 	"path/filepath"
+	"regexp"
 	"strconv"
 	"strings"
 
@@ -471,3 +472,37 @@ func recursiveChown(path string, uid, gid int) error {
 		return err
 	})
 }
+
+var osRelease string
+
+// GetOSRelease returns the OS release of the host by inspecting /etc/*-release files.
+func GetOSRelease() string {
+	// return cached result
+	if osRelease != "" {
+		return osRelease
+	}
+	osRelease = "N/A"
+
+	matches, err := filepath.Glob("/etc/*-release")
+	if err != nil {
+		return osRelease
+	}
+
+	re := regexp.MustCompile(`(DISTRIB_DESCRIPTION|PRETTY_NAME)="(.*)"`)
+
+	for _, match := range matches {
+		data, err := os.ReadFile(match)
+		if err != nil {
+			log.Error(err)
+		}
+
+		match := re.FindSubmatch(data)
+		// [0] = whole line match, [1] = left side of "=", [2] = right side of "="
+		if len(match) >= 3 {
+			osRelease = string(match[2])
+			break
+		}
+	}
+
+	return osRelease
+}