Re: [PATCH bpf-next v3 4/4] selftests/bpf: add icmp_send_unreach kfunc tests

Martin KaFai Lau
2025-07-29T01:18:41Z

On 7/28/25 2:43 AM, Mahe Tardy wrote:
> +SEC("cgroup_skb/egress")
> +int egress(struct __sk_buff *skb)
> +{
> + void *data = (void *)(long)skb->data;
> + void *data_end = (void *)(long)skb->data_end;
> + struct iphdr *iph;
> + struct tcphdr *tcph;
> +
> + iph = data;
> + if ((void *)(iph + 1) > data_end || iph->version != 4 ||
> + iph->protocol != IPPROTO_TCP || iph->daddr != bpf_htonl(SERVER_IP))
> + return SK_PASS;
> +
> + tcph = (void *)iph + iph->ihl * 4;
> + if ((void *)(tcph + 1) > data_end ||
> + tcph->dest != bpf_htons(SERVER_PORT))
> + return SK_PASS;
> +
> + kfunc_ret = bpf_icmp_send_unreach(skb, unreach_code);
> +
> + /* returns SK_PASS to execute the test case quicker */

Do you know why the user space is slower if 0 (SK_DROP) is used?

> + return SK_PASS;