iwlwifi: pcie: gen2: build A-MSDU only for GSO

If the incoming frame should be an A-MSDU, it may already be one,
for example in the case of NAN multicast being encapsulated in an
A-MSDU. Thus, use the GSO algorithm to build A-MSDU only if the
skb actually contains GSO data.

Fixes: 6ffe5de3 ("iwlwifi: pcie: add AMSDU to gen2")
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luca Coelho <luciano.coelho@intel.com>

drivers/net/wireless/intel/iwlwifi/pcie/tx-gen2.c

@@ -539,7 +539,12 @@ struct iwl_tfh_tfd *iwl_pcie_gen2_build_tfd(struct iwl_trans *trans,
 
 	hdr_len = ieee80211_hdrlen(hdr->frame_control);
 
-	if (amsdu)
+	/*
+	 * Only build A-MSDUs here if doing so by GSO, otherwise it may be
+	 * an A-MSDU for other reasons, e.g. NAN or an A-MSDU having been
+	 * built in the higher layers already.
+	 */
+	if (amsdu && skb_shinfo(skb)->gso_size)
 		return iwl_pcie_gen2_build_tx_amsdu(trans, txq, dev_cmd, skb,
 						    out_meta, hdr_len, len);