samples/bpf/xdp_adjust_tail_user.c

   1 /* SPDX-License-Identifier: GPL-2.0
   2  * Copyright (c) 2018 Facebook
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of version 2 of the GNU General Public
   6  * License as published by the Free Software Foundation.
   7  */
   8 #include <linux/bpf.h>
   9 #include <linux/if_link.h>
  10 #include <assert.h>
  11 #include <errno.h>
  12 #include <signal.h>
  13 #include <stdio.h>
  14 #include <stdlib.h>
  15 #include <string.h>
  16 #include <sys/resource.h>
  17 #include <arpa/inet.h>
  18 #include <netinet/ether.h>
  19 #include <unistd.h>
  20 #include <time.h>
  21 #include "bpf/bpf.h"
  22 #include "bpf/libbpf.h"
  23
  24 #define STATS_INTERVAL_S 2U
  25
  26 static int ifindex = -1;
  27 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
  28 static __u32 prog_id;
  29
  30 static void int_exit(int sig)
  31 {
  32         __u32 curr_prog_id = 0;
  33
  34         if (ifindex > -1) {
  35                 if (bpf_get_link_xdp_id(ifindex, &curr_prog_id, xdp_flags)) {
  36                         printf("bpf_get_link_xdp_id failed\n");
  37                         exit(1);
  38                 }
  39                 if (prog_id == curr_prog_id)
  40                         bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
  41                 else if (!curr_prog_id)
  42                         printf("couldn't find a prog id on a given iface\n");
  43                 else
  44                         printf("program on interface changed, not removing\n");
  45         }
  46         exit(0);
  47 }
  48
  49 /* simple "icmp packet too big sent" counter
  50  */
  51 static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)
  52 {
  53         time_t started_at = time(NULL);
  54         __u64 value = 0;
  55         int key = 0;
  56
  57
  58         while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
  59                 sleep(STATS_INTERVAL_S);
  60
  61                 assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
  62
  63                 printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
  64         }
  65 }
  66
  67 static void usage(const char *cmd)
  68 {
  69         printf("Start a XDP prog which send ICMP \"packet too big\" \n"
  70                 "messages if ingress packet is bigger then MAX_SIZE bytes\n");
  71         printf("Usage: %s [...]\n", cmd);
  72         printf("    -i <ifindex> Interface Index\n");
  73         printf("    -T <stop-after-X-seconds> Default: 0 (forever)\n");
  74         printf("    -S use skb-mode\n");
  75         printf("    -N enforce native mode\n");
  76         printf("    -F force loading prog\n");
  77         printf("    -h Display this help\n");
  78 }
  79
  80 int main(int argc, char **argv)
  81 {
  82         struct rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
  83         struct bpf_prog_load_attr prog_load_attr = {
  84                 .prog_type      = BPF_PROG_TYPE_XDP,
  85         };
  86         unsigned char opt_flags[256] = {};
  87         const char *optstr = "i:T:SNFh";
  88         struct bpf_prog_info info = {};
  89         __u32 info_len = sizeof(info);
  90         unsigned int kill_after_s = 0;
  91         int i, prog_fd, map_fd, opt;
  92         struct bpf_object *obj;
  93         struct bpf_map *map;
  94         char filename[256];
  95         int err;
  96
  97         for (i = 0; i < strlen(optstr); i++)
  98                 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
  99                         opt_flags[(unsigned char)optstr[i]] = 1;
 100
 101         while ((opt = getopt(argc, argv, optstr)) != -1) {
 102
 103                 switch (opt) {
 104                 case 'i':
 105                         ifindex = atoi(optarg);
 106                         break;
 107                 case 'T':
 108                         kill_after_s = atoi(optarg);
 109                         break;
 110                 case 'S':
 111                         xdp_flags |= XDP_FLAGS_SKB_MODE;
 112                         break;
 113                 case 'N':
 114                         xdp_flags |= XDP_FLAGS_DRV_MODE;
 115                         break;
 116                 case 'F':
 117                         xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
 118                         break;
 119                 default:
 120                         usage(argv[0]);
 121                         return 1;
 122                 }
 123                 opt_flags[opt] = 0;
 124         }
 125
 126         for (i = 0; i < strlen(optstr); i++) {
 127                 if (opt_flags[(unsigned int)optstr[i]]) {
 128                         fprintf(stderr, "Missing argument -%c\n", optstr[i]);
 129                         usage(argv[0]);
 130                         return 1;
 131                 }
 132         }
 133
 134         if (setrlimit(RLIMIT_MEMLOCK, &r)) {
 135                 perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
 136                 return 1;
 137         }
 138
 139         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 140         prog_load_attr.file = filename;
 141
 142         if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
 143                 return 1;
 144
 145         map = bpf_map__next(NULL, obj);
 146         if (!map) {
 147                 printf("finding a map in obj file failed\n");
 148                 return 1;
 149         }
 150         map_fd = bpf_map__fd(map);
 151
 152         if (!prog_fd) {
 153                 printf("load_bpf_file: %s\n", strerror(errno));
 154                 return 1;
 155         }
 156
 157         signal(SIGINT, int_exit);
 158         signal(SIGTERM, int_exit);
 159
 160         if (bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 0) {
 161                 printf("link set xdp fd failed\n");
 162                 return 1;
 163         }
 164
 165         err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
 166         if (err) {
 167                 printf("can't get prog info - %s\n", strerror(errno));
 168                 return 1;
 169         }
 170         prog_id = info.id;
 171
 172         poll_stats(map_fd, kill_after_s);
 173         int_exit(0);
 174
 175         return 0;
 176 }