From: Of Konstantin Khlebnikov
> Sent: 08 January 2016 12:01
> Skb_gso_segment() uses skb control block during segmentation.
> This patch adds 32-bytes room for previous control block which
> will be copied into all resulting segments.
>
> This patch fixes kernel crash during fragmenting forwarded packets.
> Fragmentation requires valid IP CB in skb for clearing ip options.
> Also patch removes custom save/restore in ovs code, now it's redundant.
>
...
> diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
> index 4355129fff91..9147f9f34cbe 100644
> --- a/include/linux/skbuff.h
> +++ b/include/linux/skbuff.h
> @@ -3446,7 +3446,8 @@ struct skb_gso_cb {
> int encap_level;
> __u16 csum_start;
> };
> -#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)(skb)->cb)
> +#define SKB_SGO_CB_OFFSET 32
> +#define SKB_GSO_CB(skb) ((struct skb_gso_cb *)((skb)->cb +
> SKB_SGO_CB_OFFSET))
You could set SKB_SGO_CB_OFFSET to sizeof ((skb)->cb) - sizeof (struct
skb_gso_cb)
so that the end of 'cb' is always used.
(Assuming the former is a multiple of 4.)
It might be worth using an on-stack structure passed through as a separate
parameter - it doesn't look as though it has to be queued with the skb.
(Clearly a bigger change.)
David
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