skb: allow skb_scrub_packet() to be used by tunnels

This function was only used when a packet was sent to another netns. Now, it can
also be used after tunnel encapsulation or decapsulation.

Only skb_orphan() should not be done when a packet is not crossing netns.
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -2392,7 +2392,7 @@ extern void	       skb_split(struct sk_buff *skb,
 				 struct sk_buff *skb1, const u32 len);
 extern int	       skb_shift(struct sk_buff *tgt, struct sk_buff *skb,
 				 int shiftlen);
-extern void	       skb_scrub_packet(struct sk_buff *skb);
+extern void	       skb_scrub_packet(struct sk_buff *skb, bool xnet);
 
 extern struct sk_buff *skb_segment(struct sk_buff *skb,
 				   netdev_features_t features);

net/core/dev.c

@@ -1697,7 +1697,7 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
 	 * call skb_scrub_packet() after it to clear pkt_type _after_ calling
 	 * eth_type_trans().
 	 */
-	skb_scrub_packet(skb);
+	skb_scrub_packet(skb, true);
 
 	return netif_rx(skb);
 }

net/core/skbuff.c

@@ -3500,17 +3500,22 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
 EXPORT_SYMBOL(skb_try_coalesce);
 
 /**
- * skb_scrub_packet - scrub an skb before sending it to another netns
+ * skb_scrub_packet - scrub an skb
  *
  * @skb: buffer to clean
- *
- * skb_scrub_packet can be used to clean an skb before injecting it in
- * another namespace. We have to clear all information in the skb that
- * could impact namespace isolation.
+ * @xnet: packet is crossing netns
+ *
+ * skb_scrub_packet can be used after encapsulating or decapsulting a packet
+ * into/from a tunnel. Some information have to be cleared during these
+ * operations.
+ * skb_scrub_packet can also be used to clean a skb before injecting it in
+ * another namespace (@xnet == true). We have to clear all information in the
+ * skb that could impact namespace isolation.
  */
-void skb_scrub_packet(struct sk_buff *skb)
+void skb_scrub_packet(struct sk_buff *skb, bool xnet)
 {
-	skb_orphan(skb);
+	if (xnet)
+		skb_orphan(skb);
 	skb->tstamp.tv64 = 0;
 	skb->pkt_type = PACKET_HOST;
 	skb->skb_iif = 0;

net/ipv4/ip_tunnel.c

@@ -462,7 +462,7 @@ int ip_tunnel_rcv(struct ip_tunnel *tunnel, struct sk_buff *skb,
 	}
 
 	if (!net_eq(tunnel->net, dev_net(tunnel->dev)))
-		skb_scrub_packet(skb);
+		skb_scrub_packet(skb, true);
 
 	gro_cells_receive(&tunnel->gro_cells, skb);
 	return 0;
@@ -615,7 +615,7 @@ void ip_tunnel_xmit(struct sk_buff *skb, struct net_device *dev,
 	}
 
 	if (!net_eq(tunnel->net, dev_net(dev)))
-		skb_scrub_packet(skb);
+		skb_scrub_packet(skb, true);
 
 	if (tunnel->err_count > 0) {
 		if (time_before(jiffies,

net/ipv6/ip6_tunnel.c

@@ -830,7 +830,7 @@ static int ip6_tnl_rcv(struct sk_buff *skb, __u16 protocol,
 		tstats->rx_bytes += skb->len;
 
 		if (!net_eq(t->net, dev_net(t->dev)))
-			skb_scrub_packet(skb);
+			skb_scrub_packet(skb, true);
 
 		netif_rx(skb);
 
@@ -1002,7 +1002,7 @@ static int ip6_tnl_xmit2(struct sk_buff *skb,
 	}
 
 	if (!net_eq(t->net, dev_net(dev)))
-		skb_scrub_packet(skb);
+		skb_scrub_packet(skb, true);
 
 	/*
 	 * Okay, now see if we can stuff it in the buffer as-is.

net/ipv6/sit.c

@@ -622,7 +622,7 @@ static int ipip6_rcv(struct sk_buff *skb)
 		tstats->rx_bytes += skb->len;
 
 		if (!net_eq(tunnel->net, dev_net(tunnel->dev)))
-			skb_scrub_packet(skb);
+			skb_scrub_packet(skb, true);
 		netif_rx(skb);
 
 		return 0;
@@ -861,7 +861,7 @@ static netdev_tx_t ipip6_tunnel_xmit(struct sk_buff *skb,
 	}
 
 	if (!net_eq(tunnel->net, dev_net(dev)))
-		skb_scrub_packet(skb);
+		skb_scrub_packet(skb, true);
 
 	/*
 	 * Okay, now see if we can stuff it in the buffer as-is.