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

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;
        __u64 ihl_len = 0;
        __u8 proto = 0;

        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("?tc")
int sk_lookup_success(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, BPF_F_CURRENT_NETNS, 0);
        bpf_printk("sk=%d\n", sk ? 1 : 0);
        if (sk)
                bpf_sk_release(sk);
        return sk ? TC_ACT_OK : TC_ACT_UNSPEC;
}

SEC("?tc")
int sk_lookup_success_simple(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};
        struct bpf_sock *sk;

        sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 0);
        if (sk)
                bpf_sk_release(sk);
        return 0;
}

SEC("?tc")
int err_use_after_free(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), BPF_F_CURRENT_NETNS, 0);
        if (sk) {
                bpf_sk_release(sk);
                family = sk->family;
        }
        return family;
}

SEC("?tc")
int err_modify_sk_pointer(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};
        struct bpf_sock *sk;

        sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 0);
        if (sk) {
                sk += 1;
                bpf_sk_release(sk);
        }
        return 0;
}

SEC("?tc")
int err_modify_sk_or_null_pointer(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};
        struct bpf_sock *sk;

        sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 0);
        sk += 1;
        if (sk)
                bpf_sk_release(sk);
        return 0;
}

SEC("?tc")
int err_no_release(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};

        bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 0);
        return 0;
}

SEC("?tc")
int err_release_twice(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};
        struct bpf_sock *sk;

        sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 0);
        bpf_sk_release(sk);
        bpf_sk_release(sk);
        return 0;
}

SEC("?tc")
int err_release_unchecked(struct __sk_buff *skb)
{
        struct bpf_sock_tuple tuple = {};
        struct bpf_sock *sk;

        sk = bpf_sk_lookup_tcp(skb, &tuple, sizeof(tuple), BPF_F_CURRENT_NETNS, 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), BPF_F_CURRENT_NETNS, 0);
}

SEC("?tc")
int err_no_release_subcall(struct __sk_buff *skb)
{
        lookup_no_release(skb);
        return 0;
}