ie: Add ie_rsnxe_capable

Add convenience method for checking whether a given capability exists in
an RSN Extension element.

src/ie.c

@@ -2083,3 +2083,23 @@ int ie_build_hs20_indication(uint8_t version, uint8_t *to)
 
 	return 0;
 }
+
+bool ie_rsnxe_capable(const uint8_t *rsnxe, unsigned int bit)
+{
+	unsigned int field_len;
+
+	if (!rsnxe)
+		return false;
+
+	if (rsnxe[1] == 0)
+		return false;
+
+	field_len = bit_field(rsnxe[2], 0, 4);
+	if (field_len + 1 != rsnxe[1])
+		return false;
+
+	if ((bit / 8) > field_len)
+		return false;
+
+	return test_bit(rsnxe + 2, bit);
+}

src/ie.h

@@ -567,3 +567,10 @@ int ie_parse_hs20_indication_from_data(const uint8_t *data, size_t len,
 					uint8_t *version, uint16_t *pps_mo_id,
 					uint8_t *domain_id);
 int ie_build_hs20_indication(uint8_t version, uint8_t *to);
+
+enum ie_rsnx_capability {
+	IE_RSNX_PROTECTED_TWT                                = 4,
+	IE_RSNX_SAE_H2E                                      = 5,
+};
+
+bool ie_rsnxe_capable(const uint8_t *rsnxe, unsigned int bit);