Commit 0f3b07f0 authored by Johannes Berg's avatar Johannes Berg
Browse files

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: default avatarJohannes Berg <johannes.berg@intel.com>
parent 341203e7

include/linux/ieee80211.h

+53 −0
Original line number Diff line number Diff line
@@ -3243,4 +3243,57 @@ static inline bool ieee80211_action_contains_tpc(struct sk_buff *skb) 
	return true;

}



struct element {

	u8 id;

	u8 datalen;

	u8 data[];

};



/* element iteration helpers */

#define for_each_element(element, _data, _datalen)			\

	for (element = (void *)(_data);					\

	     (u8 *)(_data) + (_datalen) - (u8 *)element >=		\

		sizeof(*element) &&					\

	     (u8 *)(_data) + (_datalen) - (u8 *)element >=		\

		sizeof(*element) + element->datalen;			\

	     element = (void *)(element->data + element->datalen))



#define for_each_element_id(element, _id, data, datalen)		\

	for_each_element(element, data, datalen)			\

		if (element->id == (_id))



#define for_each_element_extid(element, extid, data, datalen)		\

	for_each_element(element, data, datalen)			\

		if (element->id == WLAN_EID_EXTENSION &&		\

		    element->datalen > 0 &&				\

		    element->data[0] == (extid))



#define for_each_subelement(sub, element)				\

	for_each_element(sub, (element)->data, (element)->datalen)



#define for_each_subelement_id(sub, id, element)			\

	for_each_element_id(sub, id, (element)->data, (element)->datalen)



#define for_each_subelement_extid(sub, extid, element)			\

	for_each_element_extid(sub, extid, (element)->data, (element)->datalen)



/**

 * for_each_element_completed - determine if element parsing consumed all data

 * @element: element pointer after for_each_element() or friends

 * @data: same data pointer as passed to for_each_element() or friends

 * @datalen: same data length as passed to for_each_element() or friends

 *

 * This function returns %true if all the data was parsed or considered

 * while walking the elements. Only use this if your for_each_element()

 * loop cannot be broken out of, otherwise it always returns %false.

 *

 * If some data was malformed, this returns %false since the last parsed

 * element will not fill the whole remaining data.

 */

static inline bool for_each_element_completed(const struct element *element,

					      const void *data, size_t datalen)

{

	return (u8 *)element == (u8 *)data + datalen;

}



#endif /* LINUX_IEEE80211_H */

net/wireless/scan.c

+6 −8
Original line number Diff line number Diff line
@@ -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;

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