net: xfrm: use skb_list_walk_safe helper for gso segments

This is converts xfrm segment iteration to use the new function, keeping
the flow of the existing code as intact as possible. One case is very
straight-forward, whereas the other case has some more subtle code that
likes to peak at ->next and relink skbs. By keeping the variables the
same as before, we can upgrade this code with minimal surgery required.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_device.c

@@ -78,7 +78,7 @@ struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t featur
 	int err;
 	unsigned long flags;
 	struct xfrm_state *x;
-	struct sk_buff *skb2;
+	struct sk_buff *skb2, *nskb;
 	struct softnet_data *sd;
 	netdev_features_t esp_features = features;
 	struct xfrm_offload *xo = xfrm_offload(skb);
@@ -148,11 +148,7 @@ struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t featur
 		return skb;
 	}
 
-	skb2 = skb;
-
-	do {
-		struct sk_buff *nskb = skb2->next;
-
+	skb_list_walk_safe(skb, skb2, nskb) {
 		esp_features |= skb->dev->gso_partial_features;
 		skb_mark_not_on_list(skb2);
 
@@ -176,14 +172,11 @@ struct sk_buff *validate_xmit_xfrm(struct sk_buff *skb, netdev_features_t featur
 			if (!skb)
 				return NULL;
 
-			goto skip_push;
+			continue;
 		}
 
 		skb_push(skb2, skb2->data - skb_mac_header(skb2));
-
-skip_push:
-		skb2 = nskb;
-	} while (skb2);
+	}
 
 	return skb;
 }

net/xfrm/xfrm_output.c

@@ -533,7 +533,7 @@ static int xfrm_output2(struct net *net, struct sock *sk, struct sk_buff *skb)
 
 static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb)
 {
-	struct sk_buff *segs;
+	struct sk_buff *segs, *nskb;
 
 	BUILD_BUG_ON(sizeof(*IPCB(skb)) > SKB_SGO_CB_OFFSET);
 	BUILD_BUG_ON(sizeof(*IP6CB(skb)) > SKB_SGO_CB_OFFSET);
@@ -544,8 +544,7 @@ static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb
 	if (segs == NULL)
 		return -EINVAL;
 
-	do {
-		struct sk_buff *nskb = segs->next;
+	skb_list_walk_safe(segs, segs, nskb) {
 		int err;
 
 		skb_mark_not_on_list(segs);
@@ -555,9 +554,7 @@ static int xfrm_output_gso(struct net *net, struct sock *sk, struct sk_buff *skb
 			kfree_skb_list(nskb);
 			return err;
 		}
-
-		segs = nskb;
-	} while (segs);
+	}
 
 	return 0;
 }