ecen5273

ECEN5273 Coursework
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ingress.c (870B)

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// ingress.c
#include <vmlinux.h>

#include <bpf/bpf_endian.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_tracing.h>

#define TC_ACT_OK 0
#define ETH_P_IP 0x0800 /* Internet Protocol packet */

/// @tchook {"ifindex":2, "attach_point":"BPF_TC_INGRESS"}
/// @tcopts {"handle":1, "priority":1}
SEC("tc")
int tc_ingress(struct __sk_buff *ctx) {
  void *data_end = (void *)(__u64)ctx->data_end;
  void *data = (void *)(__u64)ctx->data;
  struct ethhdr *l2;
  struct iphdr *l3;

  if (ctx->protocol != bpf_htons(ETH_P_IP))
    return TC_ACT_OK;

  l2 = data;
  if ((void *)(l2 + 1) > data_end)
    return TC_ACT_OK;

  l3 = (struct iphdr *)(l2 + 1);
  if ((void *)(l3 + 1) > data_end)
    return TC_ACT_OK;

  bpf_printk("Got IP packet: tot_len: %d, ttl: %d", bpf_ntohs(l3->tot_len),
             l3->ttl);
  return TC_ACT_OK;
}

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