mac80211_hwsim: allow testing paged RX

Paged RX, i.e. SKBs with (some of) the data in pages instead
of the SKB header data (skb->data) can behave differently in
the stack and cause other bugs. To make debugging easier add
an option to hwsim to test with such SKBs.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

drivers/net/wireless/mac80211_hwsim.c

@@ -48,6 +48,10 @@ static int channels = 1;
 module_param(channels, int, 0444);
 MODULE_PARM_DESC(channels, "Number of concurrent channels");
 
+static bool paged_rx = false;
+module_param(paged_rx, bool, 0644);
+MODULE_PARM_DESC(paged_rx, "Use paged SKBs for RX instead of linear ones");
+
 /**
  * enum hwsim_regtest - the type of regulatory tests we offer
  *
@@ -755,9 +759,25 @@ static bool mac80211_hwsim_tx_frame_no_nl(struct ieee80211_hw *hw,
 		 * reserve some space for our vendor and the normal
 		 * radiotap header, since we're copying anyway
 		 */
-		nskb = skb_copy_expand(skb, 64, 0, GFP_ATOMIC);
-		if (nskb == NULL)
-			continue;
+		if (skb->len < PAGE_SIZE && paged_rx) {
+			struct page *page = alloc_page(GFP_ATOMIC);
+
+			if (!page)
+				continue;
+
+			nskb = dev_alloc_skb(128);
+			if (!nskb) {
+				__free_page(page);
+				continue;
+			}
+
+			memcpy(page_address(page), skb->data, skb->len);
+			skb_add_rx_frag(nskb, 0, page, 0, skb->len, skb->len);
+		} else {
+			nskb = skb_copy(skb, GFP_ATOMIC);
+			if (!nskb)
+				continue;
+		}
 
 		if (mac80211_hwsim_addr_match(data2, hdr->addr1))
 			ack = true;