dev: introduce skb_scrub_packet()

The goal of this new function is to perform all needed cleanup before sending
an skb into another netns.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 24 insertions, 10 deletions

diff --git a/net/core/dev.c b/net/core/dev.c
index 722f633926e0..370354a9c5f6 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -1652,22 +1652,13 @@ int dev_forward_skb(struct net_device *dev, struct sk_buff *skb)
                 }
         }
 
-        skb_orphan(skb);
-
         if (unlikely(!is_skb_forwardable(dev, skb))) {
                 atomic_long_inc(&dev->rx_dropped);
                 kfree_skb(skb);
                 return NET_RX_DROP;
         }
-        skb->skb_iif = 0;
-        skb_dst_drop(skb);
-        skb->tstamp.tv64 = 0;
-        skb->pkt_type = PACKET_HOST;
+        skb_scrub_packet(skb);
         skb->protocol = eth_type_trans(skb, dev);
-        skb->mark = 0;
-        secpath_reset(skb);
-        nf_reset(skb);
-        nf_reset_trace(skb);
         return netif_rx(skb);
 }
 EXPORT_SYMBOL_GPL(dev_forward_skb);
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 9f73eca29fbe..b1fcb8727e56 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -3492,3 +3492,26 @@ bool skb_try_coalesce(struct sk_buff *to, struct sk_buff *from,
         return true;
 }
 EXPORT_SYMBOL(skb_try_coalesce);
+
+/**
+ * skb_scrub_packet - scrub an skb before sending it to another netns
+ *
+ * @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.
+ */
+void skb_scrub_packet(struct sk_buff *skb)
+{
+        skb_orphan(skb);
+        skb->tstamp.tv64 = 0;
+        skb->pkt_type = PACKET_HOST;
+        skb->skb_iif = 0;
+        skb_dst_drop(skb);
+        skb->mark = 0;
+        secpath_reset(skb);
+        nf_reset(skb);
+        nf_reset_trace(skb);
+}
+EXPORT_SYMBOL_GPL(skb_scrub_packet);