[PATCH v9 net-next 1/7] net: add skb_vlan_deaccel helper

[Simon Horman]

This breaks out the bulk of skb_vlan_push into a separate helper.
This new helper moves any vlan tag present in metadata into packet data.
The existing skb_vlan_push uses this new helper and then pushes a new
vlan tag (into metadata).

The motivation is to allow deaccelerating VLAN tags without adding a new
one. This is in preparation for a push ethernet header support in Open
vSwitch.

Signed-off-by: Simon Horman <simon.hor...@netronome.com>

---
v9 [Simon Horman]
* New patch
---
 include/linux/skbuff.h |  1 +
 net/core/skbuff.c      | 50 ++++++++++++++++++++++++++++++++------------------
 2 files changed, 33 insertions(+), 18 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index c413c588a24f..fa504d28c7e4 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2994,6 +2994,7 @@ int skb_vlan_pop(struct sk_buff *skb);
 int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci);
 struct sk_buff *pskb_extract(struct sk_buff *skb, int off, int to_copy,
                             gfp_t gfp);
+int skb_vlan_deaccel(struct sk_buff *skb);
 
 static inline int memcpy_from_msg(void *data, struct msghdr *msg, int len)
 {
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
index 7a1d48983f81..84a3f8cc4b0a 100644
--- a/net/core/skbuff.c
+++ b/net/core/skbuff.c
@@ -4516,30 +4516,44 @@ int skb_vlan_pop(struct sk_buff *skb)
 }
 EXPORT_SYMBOL(skb_vlan_pop);
 
-int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
+int skb_vlan_deaccel(struct sk_buff *skb)
 {
-       if (skb_vlan_tag_present(skb)) {
-               unsigned int offset = skb->data - skb_mac_header(skb);
-               int err;
+       unsigned int offset;
+       int err;
 
-               /* __vlan_insert_tag expect skb->data pointing to mac header.
-                * So change skb->data before calling it and change back to
-                * original position later
-                */
-               __skb_push(skb, offset);
-               err = __vlan_insert_tag(skb, skb->vlan_proto,
-                                       skb_vlan_tag_get(skb));
-               if (err) {
-                       __skb_pull(skb, offset);
-                       return err;
-               }
+       if (!skb_vlan_tag_present(skb))
+               return 0;
 
-               skb->protocol = skb->vlan_proto;
-               skb->mac_len += VLAN_HLEN;
+       offset = skb->data - skb_mac_header(skb);
 
-               skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
+       /* __vlan_insert_tag expect skb->data pointing to mac header.
+        * So change skb->data before calling it and change back to
+        * original position later
+        */
+       __skb_push(skb, offset);
+       err = __vlan_insert_tag(skb, skb->vlan_proto, skb_vlan_tag_get(skb));
+       if (err) {
                __skb_pull(skb, offset);
+               return err;
        }
+
+       skb->protocol = skb->vlan_proto;
+       skb->mac_len += VLAN_HLEN;
+
+       skb_postpush_rcsum(skb, skb->data + (2 * ETH_ALEN), VLAN_HLEN);
+       __skb_pull(skb, offset);
+
+       return 0;
+}
+EXPORT_SYMBOL(skb_vlan_deaccel);
+
+int skb_vlan_push(struct sk_buff *skb, __be16 vlan_proto, u16 vlan_tci)
+{
+       int err;
+
+       err = skb_vlan_deaccel(skb);
+       if (err)
+               return err;
        __vlan_hwaccel_put_tag(skb, vlan_proto, vlan_tci);
        return 0;
 }
-- 
2.7.0.rc3.207.g0ac5344