bpf.c

#include <linux/bpf.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
#include <stdint.h>

#include "bpf_endian.h"
#include "bpf_helpers.h"

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

struct bpf_map_def SEC("maps") sock_map = {
  .type = BPF_MAP_TYPE_SOCKMAP,
  .key_size = sizeof(int),
  .value_size = sizeof(int),
  .max_entries = 2,
};


SEC("sk_skb_parser")
int _prog_parser(struct __sk_buff *skb)
{
  char debug_msg[] = "[_,_] prog_parser called. SKB length: %u\n";
  bpf_trace_printk(debug_msg, sizeof(debug_msg), skb->len);
  return skb->len;
}

SEC("sk_skb_verdict")
int _prog_verdict(struct __sk_buff *skb)
{
  char debug_msg[] = "[_,_] prog_parser verdict\n";
  uint32_t key;
  if (skb->local_port == 8000)
    key = 1;
  else
    key = 0;

  char msg[] = "local port %u\n";
  bpf_trace_printk(msg, sizeof(msg), skb->local_port);
  bpf_trace_printk(debug_msg, sizeof(debug_msg));

  return bpf_sk_redirect_map(skb, &sock_map, key, 0);
}