#include <linux/bpf.h>
#include <linux/if_ether.h>
#include <linux/ip.h>

SEC("xdp")
int xdp_drop_tcp(struct xdp_md *ctx)
{
    void *data_end = (void *)(long)ctx->data_end;
    void *data = (void *)(long)ctx->data;
    struct ethhdr *eth = data;

    if ((void *)(eth + 1) > data_end)
        return XDP_PASS;

    if (eth->h_proto != __constant_htons(ETH_P_IP))
        return XDP_PASS;

    struct iphdr *ip = (void *)(eth + 1);
    if ((void *)(ip + 1) > data_end)
        return XDP_PASS;

    if (ip->protocol == IPPROTO_TCP)
        return XDP_DROP;

    return XDP_PASS;
}

char _license[] SEC("license") = "GPL";