Re: [PATCH net v3 2/2] selftests/bpf: cover AF_XDP multi-buffer TX software checksum

[Rongzheng Wang <testwrzwrz@gmail.com>]

Hi Maciej,

Thanks for the review and for the Reviewed-by on 1/2.

> nit: breaking RCT - I know it's test but Stan payed attention to keeping
> the order...

Fixed in v4. The declaration block now follows the width order used in this
file:

	struct xsk_tx_metadata *meta;
	struct xdp_desc *tx_desc;
	struct udphdr *udph;
	struct ethhdr *eth;
	struct iphdr *iph;
	u16 first_len;
	u16 pkt_len;
	u8 pkt[256];
	u32 offset;
	void *data;
	__u32 idx;
	u32 addr;
	int ret;
	u32 i;

> would it be worth exercising this up to MAX_SKB_FRAGS ?
> then instead of having this flat layout you would loop over the desc
> count.

Good point. I changed it to loop over the descriptor count and exercise 1,
2, and MAX_SKB_FRAGS + 1 (18) frames. The extra frame is the linear head;
the remaining MAX_SKB_FRAGS frames are skb frags, matching the copy-mode
limit documented in af_xdp.rst. The last descriptor takes the remaining
length so the fragments cannot overrun pkt_len. The updated selftest passes.

I'll send v4 as a new thread.

Thanks,
Rongzheng