Arnd Bergmann wrote:

+int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
+{
+	skb_orphan(skb);
+
+	if (!(dev->flags & IFF_UP))
+		return NET_RX_DROP;
+
+	if (skb->len > (dev->mtu + dev->hard_header_len))
+		return NET_RX_DROP;
+
+	skb_dst_drop(skb);
+	skb->tstamp.tv64 = 0;
+	skb->pkt_type = PACKET_HOST;
+	skb->protocol = eth_type_trans(skb, dev);
+	skb->mark = 0;

skb->mark clearing should stay private to veth since its usually
supposed to stay intact. The only exception is packets crossing
namespaces, where they should appear like a freshly received skbs.

+	secpath_reset(skb);
+	nf_reset(skb);
+	return netif_rx(skb);
+}
+EXPORT_SYMBOL_GPL(dev_forward_skb);