bpf.c

#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/in.h>
#include <linux/ip.h>
#include <linux/ipv6.h>
#include <linux/pkt_cls.h>
#include <linux/tcp.h>

/* struct bpf_map_def reuseport_map = { */
/*      .type = BPF_MAP_TYPE_ARRAY, */
/*      .key_size = sizeof(__u32), */
/*      .value_size = sizeof(__u64), */
/*      .max_entries = 16, */
/* }; */
BPF_HASH(reuse_map, u32, u64, 1024);


int handler(struct sk_reuseport_md *ctx)
{
    int err;

    u32 key=12;
    u32 value = 0, *val;
    reuse_map.lookup(&key);

    void *data = ctx->data;
    void *data_end = ctx->data_end;

    u32 skb_addrs[8];

    bpf_skb_load_bytes_relative(ctx, offsetof(struct iphdr, saddr), skb_addrs, 8, BPF_HDR_START_NET);
    return SK_DROP;
}

handler.py

from bcc import BPF

device = "wg0"
flags = 0
flags |= (1 << 1)

b = BPF(src_file="./bpf.c")
fn = b.load_func("handler", BPF.XDP, None)

b.attach_xdp(device, fn, flags)