diff --git a/README b/README
index ac61a32..acb711a 100644
--- a/README
+++ b/README
@@ -2188,6 +2188,11 @@
 		serial# is unaffected by this, i. e. it remains
 		read-only.]
 
+		The same can be accomplished in a more flexible way
+		for any variable by configuring the type of access
+		to allow for those variables in the ".flags" variable
+		or define CONFIG_ENV_FLAGS_LIST_STATIC.
+
 - Protected RAM:
 		CONFIG_PRAM
 
@@ -3113,6 +3118,38 @@
 	cases. This setting can be used to tune behaviour; see
 	lib/hashtable.c for details.
 
+- CONFIG_ENV_FLAGS_LIST_DEFAULT
+- CONFIG_ENV_FLAGS_LIST_STATIC
+	Enable validation of the values given to enviroment variables when
+	calling env set.  Variables can be restricted to only decimal,
+	hexadecimal, or boolean.  If CONFIG_CMD_NET is also defined,
+	the variables can also be restricted to IP address or MAC address.
+
+	The format of the list is:
+		type_attribute = [s|d|x|b|i|m]
+		attributes = type_attribute
+		entry = variable_name[:attributes]
+		list = entry[,list]
+
+	The type attributes are:
+		s - String (default)
+		d - Decimal
+		x - Hexadecimal
+		b - Boolean ([1yYtT|0nNfF])
+		i - IP address
+		m - MAC address
+
+	- CONFIG_ENV_FLAGS_LIST_DEFAULT
+		Define this to a list (string) to define the ".flags"
+		envirnoment variable in the default or embedded environment.
+
+	- CONFIG_ENV_FLAGS_LIST_STATIC
+		Define this to a list (string) to define validation that
+		should be done if an entry is not found in the ".flags"
+		environment variable.  To override a setting in the static
+		list, simply add an entry for the same variable name to the
+		".flags" variable.
+
 The following definitions that deal with the placement and management
 of environment data (variable area); in general, we support the
 following configurations:
diff --git a/common/Makefile b/common/Makefile
index 04812e9..c774395 100644
--- a/common/Makefile
+++ b/common/Makefile
@@ -47,6 +47,7 @@
 COBJS-y += env_attr.o
 COBJS-y += env_callback.o
 COBJS-y += env_common.o
+COBJS-y += env_flags.o
 COBJS-$(CONFIG_ENV_IS_IN_DATAFLASH) += env_dataflash.o
 COBJS-$(CONFIG_ENV_IS_IN_EEPROM) += env_eeprom.o
 XCOBJS-$(CONFIG_ENV_IS_EMBEDDED) += env_embedded.o
@@ -212,6 +213,7 @@
 COBJS-$(CONFIG_SPL_NET_SUPPORT) += env_attr.o
 COBJS-$(CONFIG_SPL_NET_SUPPORT) += env_callback.o
 COBJS-$(CONFIG_SPL_NET_SUPPORT) += env_common.o
+COBJS-$(CONFIG_SPL_NET_SUPPORT) += env_flags.o
 COBJS-$(CONFIG_SPL_NET_SUPPORT) += env_nowhere.o
 COBJS-$(CONFIG_SPL_NET_SUPPORT) += miiphyutil.o
 endif
diff --git a/common/cmd_nvedit.c b/common/cmd_nvedit.c
index cb191cd..f645194 100644
--- a/common/cmd_nvedit.c
+++ b/common/cmd_nvedit.c
@@ -192,57 +192,9 @@
 #endif /* CONFIG_SPL_BUILD */
 
 /*
- * Perform consistency checking before setting, replacing, or deleting an
- * environment variable, then (if successful) apply the changes to internals so
- * to make them effective.  Code for this function was taken out of
- * _do_env_set(), which now calls it instead.
- * Also called as a callback function by himport_r().
- * Returns 0 in case of success, 1 in case of failure.
- * When (flag & H_FORCE) is set, do not print out any error message and force
- * overwriting of write-once variables.
- */
-
-int env_change_ok(const ENTRY *item, const char *newval, enum env_op op,
-	int flag)
-{
-#ifndef CONFIG_ENV_OVERWRITE
-	const char *name;
-#if defined(CONFIG_OVERWRITE_ETHADDR_ONCE) && defined(CONFIG_ETHADDR)
-	const char *oldval = NULL;
-
-	if (op != env_op_create)
-		oldval = item->data;
-#endif
-
-	name = item->key;
-#endif
-
-#ifndef CONFIG_ENV_OVERWRITE
-	/*
-	 * Some variables like "ethaddr" and "serial#" can be set only once and
-	 * cannot be deleted, unless CONFIG_ENV_OVERWRITE is defined.
-	 */
-	if (op != env_op_create &&		/* variable exists */
-		(flag & H_FORCE) == 0) {	/* and we are not forced */
-		if (strcmp(name, "serial#") == 0 ||
-		    (strcmp(name, "ethaddr") == 0
-#if defined(CONFIG_OVERWRITE_ETHADDR_ONCE) && defined(CONFIG_ETHADDR)
-		     && strcmp(oldval, __stringify(CONFIG_ETHADDR)) != 0
-#endif	/* CONFIG_OVERWRITE_ETHADDR_ONCE && CONFIG_ETHADDR */
-			)) {
-			printf("Can't overwrite \"%s\"\n", name);
-			return 1;
-		}
-	}
-#endif
-
-	return 0;
-}
-
-/*
  * Set a new environment variable,
  * or replace or delete an existing one.
-*/
+ */
 static int _do_env_set(int flag, int argc, char * const argv[])
 {
 	int   i, len;
diff --git a/common/env_common.c b/common/env_common.c
index 067fe3f..bb18070 100644
--- a/common/env_common.c
+++ b/common/env_common.c
@@ -40,7 +40,7 @@
 #include <env_default.h>
 
 struct hsearch_data env_htab = {
-	.change_ok = env_change_ok,
+	.change_ok = env_flags_validate,
 };
 
 static uchar __env_get_char_spec(int index)
diff --git a/common/env_flags.c b/common/env_flags.c
new file mode 100644
index 0000000..a58d614
--- /dev/null
+++ b/common/env_flags.c
@@ -0,0 +1,319 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger@ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#include <linux/string.h>
+#include <linux/ctype.h>
+
+#include <common.h>
+#include <environment.h>
+
+#ifdef CONFIG_CMD_NET
+#define ENV_FLAGS_NET_VARTYPE_REPS "im"
+#else
+#define ENV_FLAGS_NET_VARTYPE_REPS ""
+#endif
+
+static const char env_flags_vartype_rep[] = "sdxb" ENV_FLAGS_NET_VARTYPE_REPS;
+
+/*
+ * Parse the flags string from a .flags attribute list into the vartype enum.
+ */
+enum env_flags_vartype env_flags_parse_vartype(const char *flags)
+{
+	char *type;
+
+	if (strlen(flags) <= ENV_FLAGS_VARTYPE_LOC)
+		return env_flags_vartype_string;
+
+	type = strchr(env_flags_vartype_rep,
+		flags[ENV_FLAGS_VARTYPE_LOC]);
+
+	if (type != NULL)
+		return (enum env_flags_vartype)
+			(type - &env_flags_vartype_rep[0]);
+
+	printf("## Warning: Unknown environment variable type '%c'\n",
+		flags[ENV_FLAGS_VARTYPE_LOC]);
+	return env_flags_vartype_string;
+}
+
+static inline int is_hex_prefix(const char *value)
+{
+	return value[0] == '0' && (value[1] == 'x' || value[1] == 'X');
+}
+
+static void skip_num(int hex, const char *value, const char **end,
+	int max_digits)
+{
+	int i;
+
+	if (hex && is_hex_prefix(value))
+		value += 2;
+
+	for (i = max_digits; i != 0; i--) {
+		if (hex && !isxdigit(*value))
+			break;
+		if (!hex && !isdigit(*value))
+			break;
+		value++;
+	}
+	if (end != NULL)
+		*end = value;
+}
+
+/*
+ * Based on the declared type enum, validate that the value string complies
+ * with that format
+ */
+static int _env_flags_validate_type(const char *value,
+	enum env_flags_vartype type)
+{
+	const char *end;
+#ifdef CONFIG_CMD_NET
+	const char *cur;
+	int i;
+#endif
+
+	switch (type) {
+	case env_flags_vartype_string:
+		break;
+	case env_flags_vartype_decimal:
+		skip_num(0, value, &end, -1);
+		if (*end != '\0')
+			return -1;
+		break;
+	case env_flags_vartype_hex:
+		skip_num(1, value, &end, -1);
+		if (*end != '\0')
+			return -1;
+		if (value + 2 == end && is_hex_prefix(value))
+			return -1;
+		break;
+	case env_flags_vartype_bool:
+		if (value[0] != '1' && value[0] != 'y' && value[0] != 't' &&
+		    value[0] != 'Y' && value[0] != 'T' &&
+		    value[0] != '0' && value[0] != 'n' && value[0] != 'f' &&
+		    value[0] != 'N' && value[0] != 'F')
+			return -1;
+		if (value[1] != '\0')
+			return -1;
+		break;
+#ifdef CONFIG_CMD_NET
+	case env_flags_vartype_ipaddr:
+		cur = value;
+		for (i = 0; i < 4; i++) {
+			skip_num(0, cur, &end, 3);
+			if (cur == end)
+				return -1;
+			if (i != 3 && *end != '.')
+				return -1;
+			if (i == 3 && *end != '\0')
+				return -1;
+			cur = end + 1;
+		}
+		break;
+	case env_flags_vartype_macaddr:
+		cur = value;
+		for (i = 0; i < 6; i++) {
+			skip_num(1, cur, &end, 2);
+			if (cur == end)
+				return -1;
+			if (cur + 2 == end && is_hex_prefix(cur))
+				return -1;
+			if (i != 5 && *end != ':')
+				return -1;
+			if (i == 5 && *end != '\0')
+				return -1;
+			cur = end + 1;
+		}
+		break;
+#endif
+	case env_flags_vartype_end:
+		return -1;
+	}
+
+	/* OK */
+	return 0;
+}
+
+/*
+ * Look for flags in a provided list and failing that the static list
+ */
+static inline int env_flags_lookup(const char *flags_list, const char *name,
+	char *flags)
+{
+	int ret = 1;
+
+	if (!flags)
+		/* bad parameter */
+		return -1;
+
+	/* try the env first */
+	if (flags_list)
+		ret = env_attr_lookup(flags_list, name, flags);
+
+	if (ret != 0)
+		/* if not found in the env, look in the static list */
+		ret = env_attr_lookup(ENV_FLAGS_LIST_STATIC, name, flags);
+
+	return ret;
+}
+
+/*
+ * Parse the flag charachters from the .flags attribute list into the binary
+ * form to be stored in the environment entry->flags field.
+ */
+static int env_parse_flags_to_bin(const char *flags)
+{
+	return env_flags_parse_vartype(flags) & ENV_FLAGS_VARTYPE_BIN_MASK;
+}
+
+/*
+ * Look for possible flags for a newly added variable
+ * This is called specifically when the variable did not exist in the hash
+ * previously, so the blanket update did not find this variable.
+ */
+void env_flags_init(ENTRY *var_entry)
+{
+	const char *var_name = var_entry->key;
+	const char *flags_list = getenv(ENV_FLAGS_VAR);
+	char flags[ENV_FLAGS_ATTR_MAX_LEN + 1] = "";
+	int ret = 1;
+
+	/* look in the ".flags" and static for a reference to this variable */
+	ret = env_flags_lookup(flags_list, var_name, flags);
+
+	/* if any flags were found, set the binary form to the entry */
+	if (!ret && strlen(flags))
+		var_entry->flags = env_parse_flags_to_bin(flags);
+}
+
+/*
+ * Called on each existing env var prior to the blanket update since removing
+ * a flag in the flag list should remove its flags.
+ */
+static int clear_flags(ENTRY *entry)
+{
+	entry->flags = 0;
+
+	return 0;
+}
+
+/*
+ * Call for each element in the list that defines flags for a variable
+ */
+static int set_flags(const char *name, const char *value)
+{
+	ENTRY e, *ep;
+
+	e.key	= name;
+	e.data	= NULL;
+	hsearch_r(e, FIND, &ep, &env_htab, 0);
+
+	/* does the env variable actually exist? */
+	if (ep != NULL) {
+		/* the flag list is empty, so clear the flags */
+		if (value == NULL || strlen(value) == 0)
+			ep->flags = 0;
+		else
+			/* assign the requested flags */
+			ep->flags = env_parse_flags_to_bin(value);
+	}
+
+	return 0;
+}
+
+static int on_flags(const char *name, const char *value, enum env_op op,
+	int flags)
+{
+	/* remove all flags */
+	hwalk_r(&env_htab, clear_flags);
+
+	/* configure any static flags */
+	env_attr_walk(ENV_FLAGS_LIST_STATIC, set_flags);
+	/* configure any dynamic flags */
+	env_attr_walk(value, set_flags);
+
+	return 0;
+}
+U_BOOT_ENV_CALLBACK(flags, on_flags);
+
+/*
+ * Perform consistency checking before creating, overwriting, or deleting an
+ * environment variable. Called as a callback function by hsearch_r() and
+ * hdelete_r(). Returns 0 in case of success, 1 in case of failure.
+ * When (flag & H_FORCE) is set, do not print out any error message and force
+ * overwriting of write-once variables.
+ */
+
+int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
+	int flag)
+{
+	const char *name;
+#if !defined(CONFIG_ENV_OVERWRITE) && defined(CONFIG_OVERWRITE_ETHADDR_ONCE) \
+&& defined(CONFIG_ETHADDR)
+	const char *oldval = NULL;
+
+	if (op != env_op_create)
+		oldval = item->data;
+#endif
+
+	name = item->key;
+
+	/* Default value for NULL to protect string-manipulating functions */
+	newval = newval ? : "";
+
+#ifndef CONFIG_ENV_OVERWRITE
+	/*
+	 * Some variables like "ethaddr" and "serial#" can be set only once and
+	 * cannot be deleted, unless CONFIG_ENV_OVERWRITE is defined.
+	 */
+	if (op != env_op_create &&		/* variable exists */
+		(flag & H_FORCE) == 0) {	/* and we are not forced */
+		if (strcmp(name, "serial#") == 0 ||
+		    (strcmp(name, "ethaddr") == 0
+#if defined(CONFIG_OVERWRITE_ETHADDR_ONCE) && defined(CONFIG_ETHADDR)
+		     && strcmp(oldval, __stringify(CONFIG_ETHADDR)) != 0
+#endif	/* CONFIG_OVERWRITE_ETHADDR_ONCE && CONFIG_ETHADDR */
+			)) {
+			printf("Can't overwrite \"%s\"\n", name);
+			return 1;
+		}
+	}
+#endif
+
+	/* validate the value to match the variable type */
+	if (op != env_op_delete) {
+		enum env_flags_vartype type = (enum env_flags_vartype)
+			(ENV_FLAGS_VARTYPE_BIN_MASK & item->flags);
+
+		if (_env_flags_validate_type(newval, type) < 0) {
+			printf("## Error: flags type check failure for "
+				"\"%s\" <= \"%s\" (type: %c)\n",
+				name, newval, env_flags_vartype_rep[type]);
+			return -1;
+		}
+	}
+
+	return 0;
+}
diff --git a/include/env_callback.h b/include/env_callback.h
index f52e133..47fdc6f 100644
--- a/include/env_callback.h
+++ b/include/env_callback.h
@@ -24,6 +24,7 @@
 #ifndef __ENV_CALLBACK_H__
 #define __ENV_CALLBACK_H__
 
+#include <env_flags.h>
 #include <linker_lists.h>
 #include <search.h>
 
@@ -45,6 +46,7 @@
  * a new association in the ".callbacks" environment variable.
  */
 #define ENV_CALLBACK_LIST_STATIC ENV_CALLBACK_VAR ":callbacks," \
+	ENV_FLAGS_VAR ":flags," \
 	"baudrate:baudrate," \
 	"bootfile:bootfile," \
 	"loadaddr:loadaddr," \
diff --git a/include/env_default.h b/include/env_default.h
index d05eba1..39c5b7c 100644
--- a/include/env_default.h
+++ b/include/env_default.h
@@ -41,6 +41,9 @@
 #ifdef	CONFIG_ENV_CALLBACK_LIST_DEFAULT
 	ENV_CALLBACK_VAR "=" CONFIG_ENV_CALLBACK_LIST_DEFAULT "\0"
 #endif
+#ifdef	CONFIG_ENV_FLAGS_LIST_DEFAULT
+	ENV_FLAGS_VAR "=" CONFIG_ENV_FLAGS_LIST_DEFAULT "\0"
+#endif
 #ifdef	CONFIG_BOOTARGS
 	"bootargs="	CONFIG_BOOTARGS			"\0"
 #endif
diff --git a/include/env_flags.h b/include/env_flags.h
new file mode 100644
index 0000000..bf25f27
--- /dev/null
+++ b/include/env_flags.h
@@ -0,0 +1,76 @@
+/*
+ * (C) Copyright 2012
+ * Joe Hershberger, National Instruments, joe.hershberger@ni.com
+ *
+ * See file CREDITS for list of people who contributed to this
+ * project.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 of
+ * the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston,
+ * MA 02111-1307 USA
+ */
+
+#ifndef __ENV_FLAGS_H__
+#define __ENV_FLAGS_H__
+
+enum env_flags_vartype {
+	env_flags_vartype_string,
+	env_flags_vartype_decimal,
+	env_flags_vartype_hex,
+	env_flags_vartype_bool,
+#ifdef CONFIG_CMD_NET
+	env_flags_vartype_ipaddr,
+	env_flags_vartype_macaddr,
+#endif
+	env_flags_vartype_end
+};
+
+#define ENV_FLAGS_VAR ".flags"
+#define ENV_FLAGS_ATTR_MAX_LEN 2
+#define ENV_FLAGS_VARTYPE_LOC 0
+
+#ifndef CONFIG_ENV_FLAGS_LIST_STATIC
+#define CONFIG_ENV_FLAGS_LIST_STATIC ""
+#endif
+
+#define ENV_FLAGS_LIST_STATIC \
+	CONFIG_ENV_FLAGS_LIST_STATIC
+
+/*
+ * Parse the flags string from a .flags attribute list into the vartype enum.
+ */
+enum env_flags_vartype env_flags_parse_vartype(const char *flags);
+
+#include <search.h>
+
+/*
+ * When adding a variable to the environment, initialize the flags for that
+ * variable.
+ */
+void env_flags_init(ENTRY *var_entry);
+
+/*
+ * Validate the newval for to conform with the requirements defined by its flags
+ */
+int env_flags_validate(const ENTRY *item, const char *newval, enum env_op op,
+	int flag);
+
+/*
+ * These are the binary flags used in the environment entry->flags variable to
+ * decribe properties of veriables in the table
+ */
+#define ENV_FLAGS_VARTYPE_BIN_MASK	0x00000007
+/* The actual variable type values use the enum value (within the mask) */
+
+#endif /* __ENV_FLAGS_H__ */
diff --git a/include/environment.h b/include/environment.h
index 6c30215..00e59ba 100644
--- a/include/environment.h
+++ b/include/environment.h
@@ -166,6 +166,7 @@
 
 #include <env_attr.h>
 #include <env_callback.h>
+#include <env_flags.h>
 #include <search.h>
 
 extern struct hsearch_data env_htab;
@@ -189,14 +190,6 @@
 /* Import from binary representation into hash table */
 int env_import(const char *buf, int check);
 
-/*
- * Check if variable "item" can be changed to newval
- * When (flag & H_FORCE) is set, it does not print out any error
- * message and forces overwriting of write-once variables.
- */
-int env_change_ok(const ENTRY *item, const char *newval, enum env_op op,
-	int flag);
-
 #endif /* DO_DEPS_ONLY */
 
 #endif /* _ENVIRONMENT_H_ */
diff --git a/include/search.h b/include/search.h
index d68e24a..13d3be6 100644
--- a/include/search.h
+++ b/include/search.h
@@ -49,6 +49,7 @@
 	char *data;
 	int (*callback)(const char *name, const char *value, enum env_op op,
 		int flags);
+	int flags;
 } ENTRY;
 
 /* Opaque type for internal use.  */
diff --git a/lib/hashtable.c b/lib/hashtable.c
index e922666..07ebfb2 100644
--- a/lib/hashtable.c
+++ b/lib/hashtable.c
@@ -55,6 +55,7 @@
 #endif
 
 #include <env_callback.h>
+#include <env_flags.h>
 #include <search.h>
 
 /*
@@ -412,6 +413,8 @@
 
 		/* This is a new entry, so look up a possible callback */
 		env_callback_init(&htab->table[idx].entry);
+		/* Also look for flags */
+		env_flags_init(&htab->table[idx].entry);
 
 		/* check for permission */
 		if (htab->change_ok != NULL && htab->change_ok(
@@ -465,6 +468,7 @@
 	free((void *)ep->key);
 	free(ep->data);
 	ep->callback = NULL;
+	ep->flags = 0;
 	htab->table[idx].used = -1;
 
 	--htab->filled;