// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>

#include <linux/ip.h>
#include <linux/in.h>
#include <linux/if_ether.h>
#include <linux/pkt_cls.h>
#include <stdbool.h>

int lookup_status;
bool test_xdp;
bool tcp_skc;

#define CUR_NS BPF_F_CURRENT_NETNS

static void socket_lookup(void *ctx, void *data_end, void *data)
{
        struct ethhdr *eth = data;
        struct bpf_sock_tuple *tp;
        struct bpf_sock *sk;
        struct iphdr *iph;
        int tplen;

        if (eth + 1 > data_end)
                return;

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

        iph = (struct iphdr *)(eth + 1);
        if (iph + 1 > data_end)
                return;

        tp = (struct bpf_sock_tuple *)&iph->saddr;
        tplen = sizeof(tp->ipv4);
        if ((void *)tp + tplen > data_end)
                return;

        switch (iph->protocol) {
        case IPPROTO_TCP:
                if (tcp_skc)
                        sk = bpf_skc_lookup_tcp(ctx, tp, tplen, CUR_NS, 0);
                else
                        sk = bpf_sk_lookup_tcp(ctx, tp, tplen, CUR_NS, 0);
                break;
        case IPPROTO_UDP:
                sk = bpf_sk_lookup_udp(ctx, tp, tplen, CUR_NS, 0);
                break;
        default:
                return;
        }

        lookup_status = 0;

        if (sk) {
                bpf_sk_release(sk);
                lookup_status = 1;
        }
}

SEC("tc")
int tc_socket_lookup(struct __sk_buff *skb)
{
        void *data_end = (void *)(long)skb->data_end;
        void *data = (void *)(long)skb->data;

        if (test_xdp)
                return TC_ACT_UNSPEC;

        socket_lookup(skb, data_end, data);
        return TC_ACT_UNSPEC;
}

SEC("xdp")
int xdp_socket_lookup(struct xdp_md *xdp)
{
        void *data_end = (void *)(long)xdp->data_end;
        void *data = (void *)(long)xdp->data;

        if (!test_xdp)
                return XDP_PASS;

        socket_lookup(xdp, data_end, data);
        return XDP_PASS;
}

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