ebtables: better version check regex

net/ebtables/ebtables.go

@@ -121,10 +121,17 @@ func getEbtablesVersionString(exec utilexec.Interface) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	versionMatcher := regexp.MustCompile(`v([0-9]+\.[0-9]+\.[0-9]+)`)
-	match := versionMatcher.FindStringSubmatch(string(bytes))
+	return parseVersion(string(bytes))
+}
+
+func parseVersion(version string) (string, error) {
+	// the regular expression contains `v?` at the beginning because
+	// different OS distros have different version format output i.e
+	// either starts with `v` or it doesn't
+	versionMatcher := regexp.MustCompile(`v?([0-9]+\.[0-9]+\.[0-9]+)`)
+	match := versionMatcher.FindStringSubmatch(version)
 	if match == nil {
-		return "", fmt.Errorf("no ebtables version found in string: %s", bytes)
+		return "", fmt.Errorf("no ebtables version found in string: %s", version)
 	}
 	return match[1], nil
 }

net/ebtables/ebtables_test.go

@@ -167,3 +167,61 @@ Bridge chain: TEST, entries: 0, policy: ACCEPT`), nil, nil
 		t.Errorf("expected err = nil")
 	}
 }
+
+func Test_parseVersion(t *testing.T) {
+	tests := []struct {
+		name    string
+		version string
+		want    string
+		wantErr bool
+	}{
+		{
+			name:    "version starting with `v`",
+			version: "v2.0.10",
+			want:    "2.0.10",
+			wantErr: false,
+		},
+		{
+			name:    "version without containing `v`",
+			version: "2.0.10",
+			want:    "2.0.10",
+			wantErr: false,
+		},
+		{
+			name:    "version containing `v` in between the regex expression match",
+			version: "2.0v.10",
+			want:    "",
+			wantErr: true,
+		},
+		{
+			name:    "version containing `v` after the regex expression match",
+			version: "2.0.10v",
+			want:    "2.0.10",
+			wantErr: false,
+		},
+		{
+			name:    "version starting with `v` and containing a symbol in between",
+			version: "v2.0.10-4",
+			want:    "2.0.10",
+			wantErr: false,
+		},
+		{
+			name:    "version starting with `v` and containing a symbol/alphabets in between",
+			version: "v2.0a.10-4",
+			want:    "",
+			wantErr: true,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got, err := parseVersion(tt.version)
+			if (err != nil) != tt.wantErr {
+				t.Errorf("parseVersion() error = %v, wantErr %v", err, tt.wantErr)
+				return
+			}
+			if got != tt.want {
+				t.Errorf("parseVersion() got = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}