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cfg80211: add and use strongly typed element iteration macros

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commit 0f3b07f027f87a38ebe5c436490095df762819be upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Signed-off-by: Kevin F. Haggerty <haggertk@lineageos.org>
Change-Id: I88ed8b95701c3db932fddd0fcc1147b9b7ef7e54
This commit is contained in:
Johannes Berg
2020-08-08 16:42:49 +02:00
committed by matteo0026
parent 0682d533b0
commit d66f45c244
1 changed files with 53 additions and 0 deletions
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include/linux/ieee80211.h
+53
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@@ -1968,4 +1968,57 @@ static inline bool ieee80211_check_tim(struct ieee80211_tim_ie *tim,
return !!(tim->virtual_map[index] & mask);
}
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 */