wifi: mac80211: use cfg80211 defragmentation helper

Use the shared functionality rather than copying it into mac80211.
Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230616094949.7dcbf82baade.Ic68d1f547cb75d66037abdbb0f066db20ff41ba3@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/ieee80211_i.h

@@ -1752,6 +1752,8 @@ struct ieee802_11_elems {
 
 	/* mult-link element can be de-fragmented and thus u8 is not sufficient */
 	size_t multi_link_len;
+	/* The element in the original IEs */
+	const struct element *multi_link_elem;
 
 	/*
 	 * store the per station profile pointer and length in case that the

net/mac80211/util.c

@@ -984,6 +984,7 @@ ieee80211_parse_extension_element(u32 *crc,
 		break;
 	case WLAN_EID_EXT_EHT_MULTI_LINK:
 		if (ieee80211_mle_size_ok(data, len)) {
+			elems->multi_link_elem = (void *)elem;
 			elems->multi_link = (void *)data;
 			elems->multi_link_len = len;
 		}
@@ -1458,56 +1459,11 @@ static size_t ieee802_11_find_bssid_profile(const u8 *start, size_t len,
 	return found ? profile_len : 0;
 }
 
-static void ieee80211_defragment_element(struct ieee802_11_elems *elems,
-					 void **elem_ptr, size_t *len,
-					 size_t total_len, u8 frag_id)
-{
-	u8 *data = *elem_ptr, *pos, *start;
-	const struct element *elem;
-
-	/*
-	 * Since 'data' points to the data of the element, not the element
-	 * itself, allow 254 in case it was an extended element where the
-	 * extended ID isn't part of the data we see here and thus not part of
-	 * 'len' either.
-	 */
-	if (!data || (*len != 254 && *len != 255))
-		return;
-
-	start = elems->scratch_pos;
-
-	if (WARN_ON(*len > (elems->scratch + elems->scratch_len -
-			    elems->scratch_pos)))
-		return;
-
-	memcpy(elems->scratch_pos, data, *len);
-	elems->scratch_pos += *len;
-
-	pos = data + *len;
-	total_len -= *len;
-	for_each_element(elem, pos, total_len) {
-		if (elem->id != frag_id)
-			break;
-
-		if (WARN_ON(elem->datalen >
-			    (elems->scratch + elems->scratch_len -
-			     elems->scratch_pos)))
-			return;
-
-		memcpy(elems->scratch_pos, elem->data, elem->datalen);
-		elems->scratch_pos += elem->datalen;
-
-		*len += elem->datalen;
-	}
-
-	*elem_ptr = start;
-}
-
 static void ieee80211_mle_get_sta_prof(struct ieee802_11_elems *elems,
 				       u8 link_id)
 {
 	const struct ieee80211_multi_link_elem *ml = elems->multi_link;
-	size_t ml_len = elems->multi_link_len;
+	ssize_t ml_len = elems->multi_link_len;
 	const struct element *sub;
 
 	if (!ml || !ml_len)
@@ -1519,6 +1475,7 @@ static void ieee80211_mle_get_sta_prof(struct ieee802_11_elems *elems,
 
 	for_each_mle_subelement(sub, (u8 *)ml, ml_len) {
 		struct ieee80211_mle_per_sta_profile *prof = (void *)sub->data;
+		ssize_t sta_prof_len;
 		u16 control;
 
 		if (sub->id != IEEE80211_MLE_SUBELEM_PER_STA_PROFILE)
@@ -1536,14 +1493,23 @@ static void ieee80211_mle_get_sta_prof(struct ieee802_11_elems *elems,
 		if (!(control & IEEE80211_MLE_STA_CONTROL_COMPLETE_PROFILE))
 			return;
 
-		elems->prof = prof;
-		elems->sta_prof_len = sub->datalen;
-
 		/* the sub element can be fragmented */
-		ieee80211_defragment_element(elems, (void **)&elems->prof,
-					     &elems->sta_prof_len,
-					     ml_len - (sub->data - (u8 *)ml),
-					     IEEE80211_MLE_SUBELEM_FRAGMENT);
+		sta_prof_len =
+			cfg80211_defragment_element(sub,
+						    (u8 *)ml, ml_len,
+						    elems->scratch_pos,
+						    elems->scratch +
+							elems->scratch_len -
+							elems->scratch_pos,
+						    IEEE80211_MLE_SUBELEM_FRAGMENT);
+
+		if (sta_prof_len < 0)
+			return;
+
+		elems->prof = (void *)elems->scratch_pos;
+		elems->sta_prof_len = sta_prof_len;
+		elems->scratch_pos += sta_prof_len;
+
 		return;
 	}
 }
@@ -1557,17 +1523,28 @@ static void ieee80211_mle_parse_link(struct ieee802_11_elems *elems,
 		.from_ap = params->from_ap,
 		.link_id = -1,
 	};
+	ssize_t ml_len = elems->multi_link_len;
 	const struct element *non_inherit = NULL;
 	const u8 *end;
 
 	if (params->link_id == -1)
 		return;
 
-	ieee80211_defragment_element(elems, (void **)&elems->multi_link,
-				     &elems->multi_link_len,
-				     elems->total_len - ((u8 *)elems->multi_link -
-							 elems->ie_start),
-				     WLAN_EID_FRAGMENT);
+	ml_len = cfg80211_defragment_element(elems->multi_link_elem,
+					     elems->ie_start,
+					     elems->total_len,
+					     elems->scratch_pos,
+					     elems->scratch +
+						elems->scratch_len -
+						elems->scratch_pos,
+					     WLAN_EID_FRAGMENT);
+
+	if (ml_len < 0)
+		return;
+
+	elems->multi_link = (const void *)elems->scratch_pos;
+	elems->multi_link_len = ml_len;
+	elems->scratch_pos += ml_len;
 
 	ieee80211_mle_get_sta_prof(elems, params->link_id);
 	prof = elems->prof;