// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2017-18 David Ahern <dsahern@gmail.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of version 2 of the GNU General Public
 * License as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.
 */

#include <linux/bpf.h>
#include <linux/if_link.h>
#include <linux/limits.h>
#include <net/if.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <libgen.h>

#include <bpf/libbpf.h>
#include <bpf/bpf.h>

static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;

static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
{
        int err;

        err = bpf_xdp_attach(idx, prog_fd, xdp_flags, NULL);
        if (err < 0) {
                printf("ERROR: failed to attach program to %s\n", name);
                return err;
        }

        /* Adding ifindex as a possible egress TX port */
        err = bpf_map_update_elem(map_fd, &idx, &idx, 0);
        if (err)
                printf("ERROR: failed using device %s as TX-port\n", name);

        return err;
}

static int do_detach(int ifindex, const char *ifname, const char *app_name)
{
        LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
        struct bpf_prog_info prog_info = {};
        char prog_name[BPF_OBJ_NAME_LEN];
        __u32 info_len, curr_prog_id;
        int prog_fd;
        int err = 1;

        if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) {
                printf("ERROR: bpf_xdp_query_id failed (%s)\n",
                       strerror(errno));
                return err;
        }

        if (!curr_prog_id) {
                printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n",
                       xdp_flags, ifname);
                return err;
        }

        info_len = sizeof(prog_info);
        prog_fd = bpf_prog_get_fd_by_id(curr_prog_id);
        if (prog_fd < 0) {
                printf("ERROR: bpf_prog_get_fd_by_id failed (%s)\n",
                       strerror(errno));
                return prog_fd;
        }

        err = bpf_prog_get_info_by_fd(prog_fd, &prog_info, &info_len);
        if (err) {
                printf("ERROR: bpf_prog_get_info_by_fd failed (%s)\n",
                       strerror(errno));
                goto close_out;
        }
        snprintf(prog_name, sizeof(prog_name), "%s_prog", app_name);
        prog_name[BPF_OBJ_NAME_LEN - 1] = '\0';

        if (strcmp(prog_info.name, prog_name)) {
                printf("ERROR: %s isn't attached to %s\n", app_name, ifname);
                err = 1;
                goto close_out;
        }

        opts.old_prog_fd = prog_fd;
        err = bpf_xdp_detach(ifindex, xdp_flags, &opts);
        if (err < 0)
                printf("ERROR: failed to detach program from %s (%s)\n",
                       ifname, strerror(errno));
        /* TODO: Remember to cleanup map, when adding use of shared map
         *  bpf_map_delete_elem((map_fd, &idx);
         */
close_out:
        close(prog_fd);
        return err;
}

static void usage(const char *prog)
{
        fprintf(stderr,
                "usage: %s [OPTS] interface-list\n"
                "\nOPTS:\n"
                "    -d    detach program\n"
                "    -S    use skb-mode\n"
                "    -F    force loading prog\n"
                "    -D    direct table lookups (skip fib rules)\n",
                prog);
}

int main(int argc, char **argv)
{
        const char *prog_name = "xdp_fwd";
        struct bpf_program *prog = NULL;
        struct bpf_program *pos;
        const char *sec_name;
        int prog_fd = -1, map_fd = -1;
        char filename[PATH_MAX];
        struct bpf_object *obj;
        int opt, i, idx, err;
        int attach = 1;
        int ret = 0;

        while ((opt = getopt(argc, argv, ":dDSF")) != -1) {
                switch (opt) {
                case 'd':
                        attach = 0;
                        break;
                case 'S':
                        xdp_flags |= XDP_FLAGS_SKB_MODE;
                        break;
                case 'F':
                        xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
                        break;
                case 'D':
                        prog_name = "xdp_fwd_direct";
                        break;
                default:
                        usage(basename(argv[0]));
                        return 1;
                }
        }

        if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
                xdp_flags |= XDP_FLAGS_DRV_MODE;

        if (optind == argc) {
                usage(basename(argv[0]));
                return 1;
        }

        if (attach) {
                snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);

                if (access(filename, O_RDONLY) < 0) {
                        printf("error accessing file %s: %s\n",
                                filename, strerror(errno));
                        return 1;
                }

                obj = bpf_object__open_file(filename, NULL);
                if (libbpf_get_error(obj))
                        return 1;

                prog = bpf_object__next_program(obj, NULL);
                bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);

                err = bpf_object__load(obj);
                if (err) {
                        printf("Does kernel support devmap lookup?\n");
                        /* If not, the error message will be:
                         *  "cannot pass map_type 14 into func bpf_map_lookup_elem#1"
                         */
                        return 1;
                }

                bpf_object__for_each_program(pos, obj) {
                        sec_name = bpf_program__section_name(pos);
                        if (sec_name && !strcmp(sec_name, prog_name)) {
                                prog = pos;
                                break;
                        }
                }
                prog_fd = bpf_program__fd(prog);
                if (prog_fd < 0) {
                        printf("program not found: %s\n", strerror(prog_fd));
                        return 1;
                }
                map_fd = bpf_map__fd(bpf_object__find_map_by_name(obj,
                                                        "xdp_tx_ports"));
                if (map_fd < 0) {
                        printf("map not found: %s\n", strerror(map_fd));
                        return 1;
                }
        }

        for (i = optind; i < argc; ++i) {
                idx = if_nametoindex(argv[i]);
                if (!idx)
                        idx = strtoul(argv[i], NULL, 0);

                if (!idx) {
                        fprintf(stderr, "Invalid arg\n");
                        return 1;
                }
                if (!attach) {
                        err = do_detach(idx, argv[i], prog_name);
                        if (err)
                                ret = err;
                } else {
                        err = do_attach(idx, prog_fd, map_fd, argv[i]);
                        if (err)
                                ret = err;
                }
        }

        return ret;
}