device: prepare skb_list_walk_safe for upstreaming

Author: zx2c4

src/device.c

@@ -171,8 +171,8 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
 		dev_kfree_skb(skb);
 		skb = segs;
 	}
-	do {
-		next = skb->next;
+
+	skb_list_walk_safe(skb, skb, next) {
 		skb_mark_not_on_list(skb);
 
 		skb = skb_share_check(skb, GFP_ATOMIC);
@@ -187,7 +187,7 @@ static netdev_tx_t wg_xmit(struct sk_buff *skb, struct net_device *dev)
 		PACKET_CB(skb)->mtu = mtu;
 
 		__skb_queue_tail(&packets, skb);
-	} while ((skb = next) != NULL);
+	}
 
 	spin_lock_bh(&peer->staged_packet_queue.lock);
 	/* If the queue is getting too big, we start removing the oldest packets

src/device.h

@@ -62,4 +62,12 @@ struct wg_device {
 int wg_device_init(void);
 void wg_device_uninit(void);
 
+/* Later after the dust settles, this can be moved into include/linux/sk_buff.h,
+ * where virtually all code that deals with GSO segs can benefit, around ~30
+ * drivers as of writing.
+ */
+#define skb_list_walk_safe(first, skb, next)                                   \
+	for (skb = first, next = skb->next; skb;                               \
+	     skb = next, next = skb ? skb->next : NULL)
+
 #endif /* _WG_DEVICE_H */

src/send.c

@@ -233,10 +233,6 @@ void wg_packet_send_keepalive(struct wg_peer *peer)
 	wg_packet_send_staged_packets(peer);
 }
 
-#define skb_walk_null_queue_safe(first, skb, next)                             \
-	for (skb = first, next = skb->next; skb;                               \
-	     skb = next, next = skb ? skb->next : NULL)
-
 static void wg_packet_create_data_done(struct sk_buff *first,
 				       struct wg_peer *peer)
 {
@@ -245,7 +241,7 @@ static void wg_packet_create_data_done(struct sk_buff *first,
 
 	wg_timers_any_authenticated_packet_traversal(peer);
 	wg_timers_any_authenticated_packet_sent(peer);
-	skb_walk_null_queue_safe(first, skb, next) {
+	skb_list_walk_safe(first, skb, next) {
 		is_keepalive = skb->len == message_data_len(0);
 		if (likely(!wg_socket_send_skb_to_peer(peer, skb,
 				PACKET_CB(skb)->ds) && !is_keepalive))
@@ -295,7 +291,7 @@ void wg_packet_encrypt_worker(struct work_struct *work)
 	while ((first = ptr_ring_consume_bh(&queue->ring)) != NULL) {
 		enum packet_state state = PACKET_STATE_CRYPTED;
 
-		skb_walk_null_queue_safe(first, skb, next) {
+		skb_list_walk_safe(first, skb, next) {
 			if (likely(encrypt_packet(skb,
 						  PACKET_CB(first)->keypair,
 						  &simd_context))) {