Re: [PATCH net v2] udp: fix skb_copy_and_csum_datagram with odd segment sizes

[Eric Dumazet <eric.dumazet@gmail.com>]

On 2/3/21 8:29 PM, Willem de Bruijn wrote:
> From: Willem de Bruijn <willemb@google.com>
> 
> When iteratively computing a checksum with csum_block_add, track the
> offset "pos" to correctly rotate in csum_block_add when offset is odd.
> 
> The open coded implementation of skb_copy_and_csum_datagram did this.
> With the switch to __skb_datagram_iter calling csum_and_copy_to_iter,
> pos was reinitialized to 0 on each call.
> 
> Bring back the pos by passing it along with the csum to the callback.
> 
> Changes v1->v2
>   - pass csum value, instead of csump pointer (Alexander Duyck)
> 
> Link: https://lore.kernel.org/netdev/20210128152353.GB27281@optiplex/
> Fixes: 950fcaecd5cc ("datagram: consolidate datagram copy to iter helpers")
> Reported-by: Oliver Graute <oliver.graute@gmail.com>
> Signed-off-by: Willem de Bruijn <willemb@google.com>
> ---
>

Reviewed-by: Eric Dumazet <edumazet@google.com>