cfg80211: add and use strongly typed element iteration macros

Rather than always iterating elements from frames with pure
u8 pointers, add a type "struct element" that encapsulates
the id/datalen/data format of them.

Then, add the element iteration macros
 * for_each_element
 * for_each_element_id
 * for_each_element_extid

which take, as their first 'argument', such a structure and
iterate through a given u8 array interpreting it as elements.

While at it and since we'll need it, also add
 * for_each_subelement
 * for_each_subelement_id
 * for_each_subelement_extid

which instead of taking data/length just take an outer element
and use its data/datalen.

Also add for_each_element_completed() to determine if any of
the loops above completed, i.e. it was able to parse all of
the elements successfully and no data remained.

Use for_each_element_id() in cfg80211_find_ie_match() as the
first user of this.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>

1 files changed, 6 insertions, 8 deletions

diff --git a/net/wireless/scan.c b/net/wireless/scan.c
index 5123667f4569..c7f64bb9c581 100644
--- a/net/wireless/scan.c
+++ b/net/wireless/scan.c
@@ -484,6 +484,8 @@ const u8 *cfg80211_find_ie_match(u8 eid, const u8 *ies, int len,
 				 const u8 *match, int match_len,
 				 int match_offset)
 {
+	const struct element *elem;
+
 	/* match_offset can't be smaller than 2, unless match_len is
 	 * zero, in which case match_offset must be zero as well.
 	 */
@@ -491,14 +493,10 @@ const u8 *cfg80211_find_ie_match(u8 eid, const u8 *ies, int len,
 		    (!match_len && match_offset)))
 		return NULL;
 
-	while (len >= 2 && len >= ies[1] + 2) {
-		if ((ies[0] == eid) &&
-		    (ies[1] + 2 >= match_offset + match_len) &&
-		    !memcmp(ies + match_offset, match, match_len))
-			return ies;
-
-		len -= ies[1] + 2;
-		ies += ies[1] + 2;
+	for_each_element_id(elem, eid, ies, len) {
+		if (elem->datalen >= match_offset - 2 + match_len &&
+		    !memcmp(elem->data + match_offset - 2, match, match_len))
+			return (void *)elem;
 	}
 
 	return NULL;