netfilter: add and use nf_fwd_netdev_egress

... so we can use current skb instead of working with a clone.
Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

include/net/netfilter/nf_dup_netdev.h

@@ -2,5 +2,6 @@
 #define _NF_DUP_NETDEV_H_
 
 void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif);
+void nf_fwd_netdev_egress(const struct nft_pktinfo *pkt, int oif);
 
 #endif

net/netfilter/nf_dup_netdev.c

@@ -14,6 +14,29 @@
 #include <linux/netfilter/nf_tables.h>
 #include <net/netfilter/nf_tables.h>
 
+static void nf_do_netdev_egress(struct sk_buff *skb, struct net_device *dev)
+{
+	if (skb_mac_header_was_set(skb))
+		skb_push(skb, skb->mac_len);
+
+	skb->dev = dev;
+	dev_queue_xmit(skb);
+}
+
+void nf_fwd_netdev_egress(const struct nft_pktinfo *pkt, int oif)
+{
+	struct net_device *dev;
+
+	dev = dev_get_by_index_rcu(nft_net(pkt), oif);
+	if (!dev) {
+		kfree_skb(pkt->skb);
+		return;
+	}
+
+	nf_do_netdev_egress(pkt->skb, dev);
+}
+EXPORT_SYMBOL_GPL(nf_fwd_netdev_egress);
+
 void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif)
 {
 	struct net_device *dev;
@@ -24,14 +47,8 @@ void nf_dup_netdev_egress(const struct nft_pktinfo *pkt, int oif)
 		return;
 
 	skb = skb_clone(pkt->skb, GFP_ATOMIC);
-	if (skb == NULL)
-		return;
-
-	if (skb_mac_header_was_set(skb))
-		skb_push(skb, skb->mac_len);
-
-	skb->dev = dev;
-	dev_queue_xmit(skb);
+	if (skb)
+		nf_do_netdev_egress(skb, dev);
 }
 EXPORT_SYMBOL_GPL(nf_dup_netdev_egress);
 

net/netfilter/nft_fwd_netdev.c

@@ -26,8 +26,8 @@ static void nft_fwd_netdev_eval(const struct nft_expr *expr,
 	struct nft_fwd_netdev *priv = nft_expr_priv(expr);
 	int oif = regs->data[priv->sreg_dev];
 
-	nf_dup_netdev_egress(pkt, oif);
-	regs->verdict.code = NF_DROP;
+	nf_fwd_netdev_egress(pkt, oif);
+	regs->verdict.code = NF_STOLEN;
 }
 
 static const struct nla_policy nft_fwd_netdev_policy[NFTA_FWD_MAX + 1] = {