netdev - [RFC PATCH v2 1/2] NET: Clone the sk_buff 'iif' field in __skb

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Date:	Mon, 07 Jan 2008 12:47:42 -0500
From:	Paul Moore <paul.moore@...com>
To:	netdev@...r.kernel.org
Cc:	davem@...emloft.net
Subject: [RFC PATCH v2 1/2] NET: Clone the sk_buff 'iif' field in __skb_clone()

Both NetLabel and SELinux (other LSMs may grow to use it as well) rely on the
'iif' field to determine the receiving network interface of inbound packets.
Unfortunately, at present this field is not preserved across a skb clone
operation which can lead to garbage values if the cloned skb is sent back
through the network stack.  This patch corrects this problem by properly
copying the 'iif' field in __skb_clone() and removing the 'iif' field
assignment from skb_act_clone() since it is no longer needed.

Also, while we are here, put the assignments in the same order as the offsets
to reduce cacheline bounces.

Signed-off-by: Paul Moore <paul.moore@...com>
---

 include/net/sch_generic.h |    1 -
 net/core/skbuff.c         |   11 ++++++-----
 2 files changed, 6 insertions(+), 6 deletions(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index c926551..4c3b351 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -325,7 +325,6 @@ static inline struct sk_buff *skb_act_clone(struct sk_buff *skb, gfp_t gfp_mask)
 		n->tc_verd = SET_TC_VERD(n->tc_verd, 0);
 		n->tc_verd = CLR_TC_OK2MUNGE(n->tc_verd);
 		n->tc_verd = CLR_TC_MUNGED(n->tc_verd);
-		n->iif = skb->iif;
 	}
 	return n;
 }
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 5b4ce9b..b628377 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -416,16 +416,17 @@ static struct sk_buff *__skb_clone(struct sk_buff *n, struct sk_buff *skb)
 	C(len);
 	C(data_len);
 	C(mac_len);
-	n->cloned = 1;
 	n->hdr_len = skb->nohdr ? skb_headroom(skb) : skb->hdr_len;
+	n->cloned = 1;
 	n->nohdr = 0;
 	n->destructor = NULL;
-	C(truesize);
-	atomic_set(&n->users, 1);
-	C(head);
-	C(data);
+	C(iif);
 	C(tail);
 	C(end);
+	C(head);
+	C(data);
+	C(truesize);
+	atomic_set(&n->users, 1);
 
 	atomic_inc(&(skb_shinfo(skb)->dataref));
 	skb->cloned = 1;

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