Karl Hiramoto wrote, On 02/16/2009 04:02 PM:
...
> The problem ended up being the packet being corrupted when the vlan tag
> was being added and skb_cow_head() was being called.
>
> Anyone know why skb_cow_head() would corrupt the packet? Perhaps it was
> not allocated correctly? I'm using a big-endian ARM IXP435 board.
Hi,
Very nice debugging, but I think your patch doesn't look like enough:
1) it skips copy for cloned skbs,
2) this skb_cow_head() is needed anyway, sometimes.
So the real bug should be found in skb_cow_head() or elsewhere.
I attach here 2 patches for testing:
1) skb->mac_header update: it looks like needed, but I don't know if
it matters here,
2) an extention of your patch but with pskb_expand_head() called for
one to one copy.
BTW, if it's not a big problem it would be nice to try this e.g. on
2.6.29-rc5.
Thanks,
Jarek P.
---> patch #1
include/linux/if_vlan.h | 1 +
1 files changed, 1 insertions(+), 0 deletions(-)
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index f8ff918..e1ff5b1 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -210,6 +210,7 @@ static inline struct sk_buff *__vlan_put_tag(struct sk_buff *skb, u16 vlan_tci)
/* Move the mac addresses to the beginning of the new header. */
memmove(skb->data, skb->data + VLAN_HLEN, 2 * VLAN_ETH_ALEN);
+ skb->mac_header -= VLAN_HLEN;
/* first, the ethernet type */
veth->h_vlan_proto = htons(ETH_P_8021Q);
---> patch #2
include/linux/if_vlan.h | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/include/linux/if_vlan.h b/include/linux/if_vlan.h
index f8ff918..e9a5eb1 100644
--- a/include/linux/if_vlan.h
+++ b/include/linux/if_vlan.h
@@ -202,9 +202,16 @@ static inline struct sk_buff *__vlan_put_tag(struct sk_buff *skb, u16 vlan_tci)
{
struct vlan_ethhdr *veth;
- if (skb_cow_head(skb, VLAN_HLEN) < 0) {
- kfree_skb(skb);
- return NULL;
+ if (skb_headroom(skb) < VLAN_HLEN) {
+ if (skb_cow_head(skb, VLAN_HLEN) < 0) {
+ kfree_skb(skb);
+ return NULL;
+ }
+ } else {
+ if (pskb_expand_head(skb, 0, 0, GFP_ATOMIC) < 0) {
+ kfree_skb(skb);
+ return NULL;
+ }
}
veth = (struct vlan_ethhdr *)skb_push(skb, VLAN_HLEN);
--
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