Re: problem with IPoA (CLIP), NAT, and VLANS
flat view
From: Jarek Poplawski <hidden>
Date: 2009-02-16 23:20:53
Also in:
lkml
Subsystem:
networking drivers, the rest · Maintainers:
Andrew Lunn, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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);