On Fri, Jul 26, 2024 at 4:34 AM Willem de Bruijn willemdebruijn.kernel@gmail.com wrote:
From: Willem de Bruijn willemb@google.com
...
/* 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())