On 19/07/2025 11:30, Mohsin Bashir wrote:
> Test XDP_PASS/DROP in single buffer and multi buffer mode when
> XDP native support is available.
>
> ./drivers/net/xdp.py
> TAP version 13
> 1..4
> ok 1 xdp.test_xdp_native_pass_sb
> ok 2 xdp.test_xdp_native_pass_mb
> ok 3 xdp.test_xdp_native_drop_sb
> ok 4 xdp.test_xdp_native_drop_mb
> \# Totals: pass:4 fail:0 xfail:0 xpass:0 skip:0 error:0
>
> Signed-off-by: Jakub Kicinski <k...@kernel.org>
> Signed-off-by: Mohsin Bashir <mohsin.ba...@gmail.com>
> ---
> tools/testing/selftests/drivers/net/Makefile | 1 +
> tools/testing/selftests/drivers/net/xdp.py | 303 ++++++++++++++++++
> .../selftests/net/lib/xdp_native.bpf.c | 158 +++++++++
> 3 files changed, 462 insertions(+)
> create mode 100755 tools/testing/selftests/drivers/net/xdp.py
> create mode 100644 tools/testing/selftests/net/lib/xdp_native.bpf.c
>
...
> +
> +static struct udphdr *filter_udphdr(struct xdp_md *ctx, __u16 port)
> +{
> + void *data_end = (void *)(long)ctx->data_end;
> + void *data = (void *)(long)ctx->data;
> + struct udphdr *udph = NULL;
> + struct ethhdr *eth = data;
> +
> + if (data + sizeof(*eth) > data_end)
> + return NULL;
> +
This check assumes that the packet headers reside in the linear part of
the xdp_buff. However, this assumption does not hold across all drivers.
For example, in mlx5, the linear part is empty when using multi-buffer
mode with striding rq configuration. This causes all multi-buffer test
cases to fail over mlx5.
To ensure correctness across all drivers, all direct accesses to packet
data should use these safer helper functions instead:
bpf_xdp_load_bytes() and bpf_xdp_store_bytes().
Related discussion and context can be found here:
https://github.com/xdp-project/xdp-tools/pull/409
> + if (eth->h_proto == bpf_htons(ETH_P_IP)) {
> + struct iphdr *iph = data + sizeof(*eth);
> +
> + if (iph + 1 > (struct iphdr *)data_end ||
> + iph->protocol != IPPROTO_UDP)
> + return NULL;
> +
> + udph = (void *)eth + sizeof(*iph) + sizeof(*eth);
> + } else if (eth->h_proto == bpf_htons(ETH_P_IPV6)) {
> + struct ipv6hdr *ipv6h = data + sizeof(*eth);
> +
> + if (ipv6h + 1 > (struct ipv6hdr *)data_end ||
> + ipv6h->nexthdr != IPPROTO_UDP)
> + return NULL;
> +
> + udph = (void *)eth + sizeof(*ipv6h) + sizeof(*eth);
> + } else {
> + return NULL;
> + }
> +
> + if (udph + 1 > (struct udphdr *)data_end)
> + return NULL;
> +
> + if (udph->dest != bpf_htons(port))
> + return NULL;
> +
> + record_stats(ctx, STATS_RX);
> +
> + return udph;
> +}
