Get wwid from interface not /proc/cmdline when wwid=[interface] is specified

Signed-off-by: Timothy Middelkoop <tmiddelkoop@internet2.edu>

internal/app/wwclient/root.go

@@ -141,6 +141,20 @@ func CobraRunE(cmd *cobra.Command, args []string) (err error) {
 	}
 
 	wwid := strings.Split(wwid_tmp[1], " ")[0]
+	wwid = strings.TrimSuffix(wwid, "\n")
+
+	// Dereference wwid from [interface] for cases that cannot have /proc/cmdline set by bootloader
+	if string(wwid[0]) == "[" {
+		iface := wwid[1:len(wwid)-1]
+		wwid_tmp, err := os.ReadFile(fmt.Sprintf("/sys/class/net/%s/address", iface))
+		if err != nil {
+			wwlog.Error("'wwid' cannot be dereferenced from /sys/class/net", iface)
+			os.Exit(1)
+		}
+		wwid = strings.TrimSuffix(string(wwid_tmp), "\n")
+		wwlog.Info("Dereferencing wwid from [%s] to %s", iface, wwid)
+	}
+
 
 	duration := 300
 	if conf.Warewulf.UpdateInterval > 0 {