mac80211: allow segmentation offloads

Implement the necessary software segmentation on the normal
TX path so that fast-xmit can use segmentation offload if
the hardware (or driver) supports it.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/main.c

@@ -840,7 +840,8 @@ int ieee80211_register_hw(struct ieee80211_hw *hw)
 
 	/* Only HW csum features are currently compatible with mac80211 */
 	feature_whitelist = NETIF_F_IP_CSUM | NETIF_F_IPV6_CSUM |
-			    NETIF_F_HW_CSUM | NETIF_F_SG | NETIF_F_HIGHDMA;
+			    NETIF_F_HW_CSUM | NETIF_F_SG | NETIF_F_HIGHDMA |
+			    NETIF_F_GSO_SOFTWARE;
 	if (WARN_ON(hw->netdev_features & ~feature_whitelist))
 		return -EINVAL;
 

net/mac80211/tx.c

@@ -2843,6 +2843,7 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 {
 	struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
 	struct sta_info *sta;
+	struct sk_buff *next;
 
 	if (unlikely(skb->len < ETH_HLEN)) {
 		kfree_skb(skb);
@@ -2864,15 +2865,26 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 			goto out;
 	}
 
+	if (skb_is_gso(skb)) {
+		struct sk_buff *segs;
+
+		segs = skb_gso_segment(skb, 0);
+		if (IS_ERR(segs)) {
+			goto out_free;
+		} else if (segs) {
+			consume_skb(skb);
+			skb = segs;
+		}
+	} else {
 		/* we cannot process non-linear frames on this path */
 		if (skb_linearize(skb)) {
 			kfree_skb(skb);
 			goto out;
 		}
 
-	/* the frame could be fragmented, software-encrypted, and other things
-	 * so we cannot really handle checksum offload with it - fix it up in
-	 * software before we handle anything else.
+		/* the frame could be fragmented, software-encrypted, and other
+		 * things so we cannot really handle checksum offload with it -
+		 * fix it up in software before we handle anything else.
 		 */
 		if (skb->ip_summed == CHECKSUM_PARTIAL) {
 			if (skb->encapsulation)
@@ -2884,6 +2896,15 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 			if (skb_checksum_help(skb))
 				goto out_free;
 		}
+	}
+
+	next = skb;
+	while (next) {
+		skb = next;
+		next = skb->next;
+
+		skb->prev = NULL;
+		skb->next = NULL;
 
 		skb = ieee80211_build_hdr(sdata, skb, info_flags, sta);
 		if (IS_ERR(skb))
@@ -2894,6 +2915,7 @@ void __ieee80211_subif_start_xmit(struct sk_buff *skb,
 		dev->trans_start = jiffies;
 
 		ieee80211_xmit(sdata, sta, skb);
+	}
 	goto out;
  out_free:
 	kfree_skb(skb);