[IPSEC]: Merge most of the output path

As part of the work on asynchrnous cryptographic operations, we need
to be able to resume from the spot where they occur.  As such, it
helps if we isolate them to one spot.

This patch moves most of the remaining family-specific processing into
the common output code.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/xfrm/xfrm_output.c

@@ -12,6 +12,7 @@
 #include <linux/errno.h>
 #include <linux/module.h>
 #include <linux/netdevice.h>
+#include <linux/netfilter.h>
 #include <linux/skbuff.h>
 #include <linux/spinlock.h>
 #include <net/dst.h>
@@ -40,7 +41,7 @@ err:
 	return err;
 }
 
-int xfrm_output(struct sk_buff *skb)
+static int xfrm_output_one(struct sk_buff *skb)
 {
 	struct dst_entry *dst = skb->dst;
 	struct xfrm_state *x = dst->xfrm;
@@ -87,10 +88,73 @@ int xfrm_output(struct sk_buff *skb)
 
 	err = 0;
 
-error_nolock:
+out_exit:
 	return err;
 error:
 	spin_unlock_bh(&x->lock);
-	goto error_nolock;
+error_nolock:
+	kfree_skb(skb);
+	goto out_exit;
+}
+
+static int xfrm_output2(struct sk_buff *skb)
+{
+	int err;
+
+	while (likely((err = xfrm_output_one(skb)) == 0)) {
+		struct xfrm_state *x;
+
+		nf_reset(skb);
+
+		err = skb->dst->ops->local_out(skb);
+		if (unlikely(err != 1))
+			break;
+
+		x = skb->dst->xfrm;
+		if (!x)
+			return dst_output(skb);
+
+		err = nf_hook(x->inner_mode->afinfo->family,
+			      x->inner_mode->afinfo->nf_post_routing, skb,
+			      NULL, skb->dst->dev, xfrm_output2);
+		if (unlikely(err != 1))
+			break;
+	}
+
+	return err;
+}
+
+int xfrm_output(struct sk_buff *skb)
+{
+	struct sk_buff *segs;
+
+	if (!skb_is_gso(skb))
+		return xfrm_output2(skb);
+
+	segs = skb_gso_segment(skb, 0);
+	kfree_skb(skb);
+	if (unlikely(IS_ERR(segs)))
+		return PTR_ERR(segs);
+
+	do {
+		struct sk_buff *nskb = segs->next;
+		int err;
+
+		segs->next = NULL;
+		err = xfrm_output2(segs);
+
+		if (unlikely(err)) {
+			while ((segs = nskb)) {
+				nskb = segs->next;
+				segs->next = NULL;
+				kfree_skb(segs);
+			}
+			return err;
+		}
+
+		segs = nskb;
+	} while (segs);
+
+	return 0;
 }
 EXPORT_SYMBOL_GPL(xfrm_output);