On Fri, Jul 26, 2024 at 4:34 AM Willem de Bruijn
<willemdebruijn.kernel@xxxxxxxxx> wrote:
>
> From: Willem de Bruijn <willemb@xxxxxxxxxx>
...
> /* Kernel has a special handling for GSO_BY_FRAGS. */
> diff --git a/net/ipv4/tcp_offload.c b/net/ipv4/tcp_offload.c
> index 4b791e74529e1..9e49ffcc77071 100644
> --- a/net/ipv4/tcp_offload.c
> +++ b/net/ipv4/tcp_offload.c
> @@ -140,6 +140,9 @@ struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
> if (thlen < sizeof(*th))
> goto out;
>
> + if (unlikely(skb->csum_start != skb->transport_header))
> + goto out;
> +
Using skb_transport_header() will make sure DEBUG_NET_WARN_ON_ONCE()
will fire for debug kernels,
with no additional costs for non debug kernels (compiler will generate
not use skb->head at all)
if (unlikely(skb->csum_start != skb_transport_header(skb) - skb->head))
goto out;
(This will match the corresponding initialization in __tcp_v4_send_check())
