veth: move loopback logic to common location

The veth driver contains code to forward an skb
from the start_xmit function of one network
device into the receive path of another device.

Moving that code into a common location lets us
reuse the code for direct forwarding of data
between macvlan ports, and possibly in other
drivers.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 40 insertions, 0 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index e65af60..7775e8b 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -105,6 +105,7 @@
 #include <net/dst.h>
 #include <net/pkt_sched.h>
 #include <net/checksum.h>
+#include <net/xfrm.h>
 #include <linux/highmem.h>
 #include <linux/init.h>
 #include <linux/kmod.h>
@@ -1419,6 +1420,45 @@ static inline void net_timestamp(struct sk_buff *skb)
 		skb->tstamp.tv64 = 0;
 }
 
+/**
+ * dev_forward_skb - loopback an skb to another netif
+ *
+ * @dev: destination network device
+ * @skb: buffer to forward
+ *
+ * return values:
+ *	NET_RX_SUCCESS	(no congestion)
+ *	NET_RX_DROP     (packet was dropped)
+ *
+ * dev_forward_skb can be used for injecting an skb from the
+ * start_xmit function of one device into the receive queue
+ * of another device.
+ *
+ * The receiving device may be in another namespace, so
+ * we have to clear all information in the skb that could
+ * impact namespace isolation.
+ */
+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;
+	secpath_reset(skb);
+	nf_reset(skb);
+	return netif_rx(skb);
+}
+EXPORT_SYMBOL_GPL(dev_forward_skb);
+
 /*
  *	Support routine. Sends outgoing frames to any network
  *	taps currently in use.