text: /* SPDX-License-Identifier: GPL-2.0 */
  // Copyright (c) 2018 Covalent IO, Inc. http://covalent.io
  
  #include <stddef.h>
  #include <stdbool.h>
  #include <string.h>
  #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>
  #include <sys/socket.h>
  #include "bpf_helpers.h"
  #include "bpf_endian.h"
  
  int _version SEC("version") = 1;
  char _license[] SEC("license") = "GPL";
  
  /* Fill 'tuple' with L3 info, and attempt to find L4. On fail, return NULL. */
  static struct bpf_sock_tuple *get_tuple(void *data, __u64 nh_off,
  					void *data_end, __u16 eth_proto,
  					bool *ipv4)
  {
  	struct bpf_sock_tuple *result;
  	__u8 proto = 0;
  	__u64 ihl_len;
  
  	if (eth_proto == bpf_htons(ETH_P_IP)) {
  		struct iphdr *iph = (struct iphdr *)(data + nh_off);
  
  		if (iph + 1 > data_end)
  			return NULL;
  		ihl_len = iph->ihl * 4;
  		proto = iph->protocol;
  		*ipv4 = true;
  		result = (struct bpf_sock_tuple *)&iph->saddr;
  	} else if (eth_proto == bpf_htons(ETH_P_IPV6)) {
  		struct ipv6hdr *ip6h = (struct ipv6hdr *)(data + nh_off);
  
  		if (ip6h + 1 > data_end)
  			return NULL;
  		ihl_len = sizeof(*ip6h);
  		proto = ip6h->nexthdr;
  		*ipv4 = true;
  		result = (struct bpf_sock_tuple *)&ip6h->saddr;
  	}
  
  	if (data + nh_off + ihl_len > data_end || proto != IPPROTO_TCP)
  		return NULL;
  
  	return result;
  }
  
  SEC("sk_lookup_success")
  int bpf_sk_lookup_test0(struct __sk_buff *skb)
  {
  	void *data_end = (void *)(long)skb->data_end;
  	void *data = (void *)(long)skb->data;
  	struct ethhdr *eth = (struct ethhdr *)(data);
  	struct bpf_sock_tuple *tuple;
  	struct bpf_sock *sk;
  	size_t tuple_len;
  	bool ipv4;
  
  	if (eth + 1 > data_end)
  		return TC_ACT_SHOT;
  
  	tuple = get_tuple(data, sizeof(*eth), data_end, eth->h_proto, &ipv4);
  	if (!tuple || tuple + sizeof *tuple > data_end)
  		return TC_ACT_SHOT;
  
  	tuple_len = ipv4 ? sizeof(tuple->ipv4) : sizeof(tuple->ipv6);
  	sk = bpf_sk_lookup_tcp(skb, tuple, tuple_len, 0, 0);
  	if (sk)
  		bpf_sk_release(sk);
  	return sk ? TC_ACT_OK : TC_ACT_UNSPEC;
  }
  
  SEC("sk_lookup_success_simple")
  int bpf_sk_lookup_test1(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	if (sk)
  		bpf_sk_release(sk);
  	return 0;
  }
  
  SEC("fail_use_after_free")
  int bpf_sk_lookup_uaf(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  	__u32 family = 0;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	if (sk) {
  		bpf_sk_release(sk);
  		family = sk->family;
  	}
  	return family;
  }
  
  SEC("fail_modify_sk_pointer")
  int bpf_sk_lookup_modptr(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  	__u32 family;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	if (sk) {
  		sk += 1;
  		bpf_sk_release(sk);
  	}
  	return 0;
  }
  
  SEC("fail_modify_sk_or_null_pointer")
  int bpf_sk_lookup_modptr_or_null(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  	__u32 family;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	sk += 1;
  	if (sk)
  		bpf_sk_release(sk);
  	return 0;
  }
  
  SEC("fail_no_release")
  int bpf_sk_lookup_test2(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  
  	bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	return 0;
  }
  
  SEC("fail_release_twice")
  int bpf_sk_lookup_test3(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	bpf_sk_release(sk);
  	bpf_sk_release(sk);
  	return 0;
  }
  
  SEC("fail_release_unchecked")
  int bpf_sk_lookup_test4(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	struct bpf_sock *sk;
  
  	sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  	bpf_sk_release(sk);
  	return 0;
  }
  
  void lookup_no_release(struct __sk_buff *skb)
  {
  	struct bpf_sock_tuple tuple = {};
  	bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), 0, 0);
  }
  
  SEC("fail_no_release_subcall")
  int bpf_sk_lookup_test5(struct __sk_buff *skb)
  {
  	lookup_no_release(skb);
  	return 0;
  }
  