From: Johannes Berg <johannes.berg@xxxxxxxxx>
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@xxxxxxxxx>
---
src/common/ieee802_11_common.h | 53 ++++++++++++++++++++++++++++++++++
1 file changed, 53 insertions(+)
diff --git a/src/common/ieee802_11_common.h b/src/common/ieee802_11_common.h
index ce3bb8b9f5eb..a26b0ed1e5f8 100644
--- a/src/common/ieee802_11_common.h
+++ b/src/common/ieee802_11_common.h
@@ -12,6 +12,12 @@
#include "defs.h"
#include "ieee802_11_defs.h"
+struct element {
+ u8 id;
+ u8 datalen;
+ u8 data[];
+};
+
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(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 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 (u8 *)element == (u8 *)data + datalen;
+}
+
#endif /* IEEE802_11_COMMON_H */
--
2.17.2
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