// SPDX-License-Identifier: GPL-2.0
#include <error.h>
#include <errno.h>
#include <getopt.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <bpf/bpf.h>
#include <bpf/libbpf.h>

#include "flow_dissector_load.h"

const char *cfg_pin_path = "/sys/fs/bpf/flow_dissector";
const char *cfg_map_name = "jmp_table";
bool cfg_attach = true;
char *cfg_prog_name;
char *cfg_path_name;

static void load_and_attach_program(void)
{
        int prog_fd, ret;
        struct bpf_object *obj;

        /* Use libbpf 1.0 API mode */
        libbpf_set_strict_mode(LIBBPF_STRICT_ALL);

        ret = bpf_flow_load(&obj, cfg_path_name, cfg_prog_name,
                            cfg_map_name, NULL, &prog_fd, NULL);
        if (ret)
                error(1, 0, "bpf_flow_load %s", cfg_path_name);

        ret = bpf_prog_attach(prog_fd, 0 /* Ignore */, BPF_FLOW_DISSECTOR, 0);
        if (ret)
                error(1, 0, "bpf_prog_attach %s", cfg_path_name);

        ret = bpf_object__pin(obj, cfg_pin_path);
        if (ret)
                error(1, 0, "bpf_object__pin %s", cfg_pin_path);
}

static void detach_program(void)
{
        char command[64];
        int ret;

        ret = bpf_prog_detach(0, BPF_FLOW_DISSECTOR);
        if (ret)
                error(1, 0, "bpf_prog_detach");

        /* To unpin, it is necessary and sufficient to just remove this dir */
        sprintf(command, "rm -r %s", cfg_pin_path);
        ret = system(command);
        if (ret)
                error(1, errno, "%s", command);
}

static void parse_opts(int argc, char **argv)
{
        bool attach = false;
        bool detach = false;
        int c;

        while ((c = getopt(argc, argv, "adp:s:")) != -1) {
                switch (c) {
                case 'a':
                        if (detach)
                                error(1, 0, "attach/detach are exclusive");
                        attach = true;
                        break;
                case 'd':
                        if (attach)
                                error(1, 0, "attach/detach are exclusive");
                        detach = true;
                        break;
                case 'p':
                        if (cfg_path_name)
                                error(1, 0, "only one path can be given");

                        cfg_path_name = optarg;
                        break;
                case 's':
                        if (cfg_prog_name)
                                error(1, 0, "only one prog can be given");

                        cfg_prog_name = optarg;
                        break;
                }
        }

        if (detach)
                cfg_attach = false;

        if (cfg_attach && !cfg_path_name)
                error(1, 0, "must provide a path to the BPF program");

        if (cfg_attach && !cfg_prog_name)
                error(1, 0, "must provide a section name");
}

int main(int argc, char **argv)
{
        parse_opts(argc, argv);
        if (cfg_attach)
                load_and_attach_program();
        else
                detach_program();
        return 0;
}