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common: Add strongly typed element iteration macros

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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 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.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
This commit is contained in:
Johannes Berg 2019-02-08 17:57:48 +01:00 committed by Jouni Malinen
parent 51c83edfca
commit 0e0c31bdc5
1 changed files with 53 additions and 0 deletions
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53
src/common/ieee802_11_common.h
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@ -12,6 +12,12 @@
#include "defs.h"
#include "ieee802_11_defs.h"
struct element {
u8 id;
u8 datalen;
u8 data[];
} STRUCT_PACKED;
struct hostapd_hw_modes;
#define MAX_NOF_MB_IES_SUPPORTED 5
@ -214,4 +220,51 @@ int ieee802_11_parse_candidate_list(const char *pos, u8 *nei_rep,
int ieee802_11_ext_capab(const u8 *ie, unsigned int capab);
/* element iteration helpers */
#define for_each_element(_elem, _data, _datalen) \
for (_elem = (const struct element *) (_data); \
(const u8 *) (_data) + (_datalen) - (const u8 *) _elem >= \
(int) sizeof(*_elem) && \
(const u8 *) (_data) + (_datalen) - (const u8 *) _elem >= \
(int) sizeof(*_elem) + _elem->datalen; \
_elem = (const struct element *) (_elem->data + _elem->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 1 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 0.
*
* If some data was malformed, this returns %false since the last parsed
* element will not fill the whole remaining data.
*/
static inline int for_each_element_completed(const struct element *element,
const void *data, size_t datalen)
{
return (const u8 *) element == (const u8 *) data + datalen;
}
#endif /* IEEE802_11_COMMON_H */