[Devel] Re: [PATCH] Correct data pointer offset calculation

[Oren Laadan]

... for v19-rc2, too. Thanks.

Oren.


Dan Smith wrote:
> The current data pointer offset calculation is not correct in all cases.
> This patch records the offset and resets it on restore.  With this patch,
> all of my test cases now pass and behave as they should.
> 
> Signed-off-by: Dan Smith <danms at us.ibm.com>
> ---
>  include/linux/checkpoint_hdr.h |    1 +
>  net/checkpoint.c               |   11 ++++++++++-
>  2 files changed, 11 insertions(+), 1 deletions(-)
> 
> diff --git a/include/linux/checkpoint_hdr.h b/include/linux/checkpoint_hdr.h
> index 95ea3dd..4e57d37 100644
> --- a/include/linux/checkpoint_hdr.h
> +++ b/include/linux/checkpoint_hdr.h
> @@ -605,6 +605,7 @@ struct ckpt_hdr_socket_buffer {
>  	__u32 skb_len; /* Length of skb (adjusted) */
>  	__u32 hdr_len; /* Length of skipped header */
>  	__u32 mac_len;
> +	__u32 data_offset; /* Offset of data pointer from head */
>  	__s32 sk_objref;
>  	__s32 pr_objref;
>  	__u16 protocol;
> diff --git a/net/checkpoint.c b/net/checkpoint.c
> index c9d5b1e..2ac6a42 100644
> --- a/net/checkpoint.c
> +++ b/net/checkpoint.c
> @@ -100,6 +100,8 @@ static void sock_record_header_info(struct sk_buff *skb,
>  	h->lin_len = (skb->tail - skb->head);
>  	h->frg_len = skb->data_len;
>  
> +	h->data_offset = (skb->data - skb->head);
> +
>  #ifdef NET_SKBUFF_DATA_USES_OFFSET
>  	h->transport_header = skb->transport_hdr;
>  	h->network_header = skb->network_header;
> @@ -140,6 +142,13 @@ int sock_restore_header_info(struct ckpt_ctx *ctx,
>  		return -EINVAL;
>  	}
>  
> +	if (h->data_offset > h->lin_len) {
> +		ckpt_err(ctx, -EINVAL,
> +			 "skb data offset %u > linear length %u\n",
> +			 h->data_offset, h->lin_len);
> +		return -EINVAL;
> +	}
> +
>  	if (h->skb_len > SKB_MAX_ALLOC) {
>  		ckpt_err(ctx, -EINVAL,
>  			 "skb total length %u larger than max of %lu\n",
> @@ -161,7 +170,7 @@ int sock_restore_header_info(struct ckpt_ctx *ctx,
>  	 */
>  	memcpy(skb->cb, h->cb, sizeof(skb->cb));
>  
> -	skb->data = skb->head + skb->hdr_len;
> +	skb->data = skb->head + h->data_offset;
>  	skb->len = h->skb_len;
>  
>  	skb_shinfo(skb)->gso_type = sk->sk_gso_type;
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