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 <net/if.h>
  17 #include <sys/resource.h>
  18 #include <arpa/inet.h>
  19 #include <netinet/ether.h>
  20 #include <unistd.h>
  21 #include <time.h>
  22 #include <bpf/bpf.h>
  23 #include <bpf/libbpf.h>
  24
  25 #define STATS_INTERVAL_S 2U
  26 #define MAX_PCKT_SIZE 600
  27
  28 static int ifindex = -1;
  29 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;
  30 static __u32 prog_id;
  31
  32 static void int_exit(int sig)
  33 {
  34         __u32 curr_prog_id = 0;
  35
  36         if (ifindex > -1) {
  37                 if (bpf_get_link_xdp_id(ifindex, &curr_prog_id, xdp_flags)) {
  38                         printf("bpf_get_link_xdp_id failed\n");
  39                         exit(1);
  40                 }
  41                 if (prog_id == curr_prog_id)
  42                         bpf_set_link_xdp_fd(ifindex, -1, xdp_flags);
  43                 else if (!curr_prog_id)
  44                         printf("couldn't find a prog id on a given iface\n");
  45                 else
  46                         printf("program on interface changed, not removing\n");
  47         }
  48         exit(0);
  49 }
  50
  51 /* simple "icmp packet too big sent" counter
  52  */
  53 static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)
  54 {
  55         time_t started_at = time(NULL);
  56         __u64 value = 0;
  57         int key = 0;
  58
  59
  60         while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {
  61                 sleep(STATS_INTERVAL_S);
  62
  63                 assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);
  64
  65                 printf("icmp \"packet too big\" sent: %10llu pkts\n", value);
  66         }
  67 }
  68
  69 static void usage(const char *cmd)
  70 {
  71         printf("Start a XDP prog which send ICMP \"packet too big\" \n"
  72                 "messages if ingress packet is bigger then MAX_SIZE bytes\n");
  73         printf("Usage: %s [...]\n", cmd);
  74         printf("    -i <ifname|ifindex> Interface\n");
  75         printf("    -T <stop-after-X-seconds> Default: 0 (forever)\n");
  76         printf("    -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);
  77         printf("    -S use skb-mode\n");
  78         printf("    -N enforce native mode\n");
  79         printf("    -F force loading prog\n");
  80         printf("    -h Display this help\n");
  81 }
  82
  83 int main(int argc, char **argv)
  84 {
  85         struct bpf_prog_load_attr prog_load_attr = {
  86                 .prog_type      = BPF_PROG_TYPE_XDP,
  87         };
  88         unsigned char opt_flags[256] = {};
  89         const char *optstr = "i:T:P:SNFh";
  90         struct bpf_prog_info info = {};
  91         __u32 info_len = sizeof(info);
  92         unsigned int kill_after_s = 0;
  93         int i, prog_fd, map_fd, opt;
  94         struct bpf_object *obj;
  95         __u32 max_pckt_size = 0;
  96         __u32 key = 0;
  97         char filename[256];
  98         int err;
  99
 100         for (i = 0; i < strlen(optstr); i++)
 101                 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
 102                         opt_flags[(unsigned char)optstr[i]] = 1;
 103
 104         while ((opt = getopt(argc, argv, optstr)) != -1) {
 105
 106                 switch (opt) {
 107                 case 'i':
 108                         ifindex = if_nametoindex(optarg);
 109                         if (!ifindex)
 110                                 ifindex = atoi(optarg);
 111                         break;
 112                 case 'T':
 113                         kill_after_s = atoi(optarg);
 114                         break;
 115                 case 'P':
 116                         max_pckt_size = atoi(optarg);
 117                         break;
 118                 case 'S':
 119                         xdp_flags |= XDP_FLAGS_SKB_MODE;
 120                         break;
 121                 case 'N':
 122                         /* default, set below */
 123                         break;
 124                 case 'F':
 125                         xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
 126                         break;
 127                 default:
 128                         usage(argv[0]);
 129                         return 1;
 130                 }
 131                 opt_flags[opt] = 0;
 132         }
 133
 134         if (!(xdp_flags & XDP_FLAGS_SKB_MODE))
 135                 xdp_flags |= XDP_FLAGS_DRV_MODE;
 136
 137         for (i = 0; i < strlen(optstr); i++) {
 138                 if (opt_flags[(unsigned int)optstr[i]]) {
 139                         fprintf(stderr, "Missing argument -%c\n", optstr[i]);
 140                         usage(argv[0]);
 141                         return 1;
 142                 }
 143         }
 144
 145         if (!ifindex) {
 146                 fprintf(stderr, "Invalid ifname\n");
 147                 return 1;
 148         }
 149
 150         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
 151         prog_load_attr.file = filename;
 152
 153         if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
 154                 return 1;
 155
 156         /* static global var 'max_pcktsz' is accessible from .data section */
 157         if (max_pckt_size) {
 158                 map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data");
 159                 if (map_fd < 0) {
 160                         printf("finding a max_pcktsz map in obj file failed\n");
 161                         return 1;
 162                 }
 163                 bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
 164         }
 165
 166         /* fetch icmpcnt map */
 167         map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");
 168         if (map_fd < 0) {
 169                 printf("finding a icmpcnt map in obj file failed\n");
 170                 return 1;
 171         }
 172
 173         signal(SIGINT, int_exit);
 174         signal(SIGTERM, int_exit);
 175
 176         if (bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 0) {
 177                 printf("link set xdp fd failed\n");
 178                 return 1;
 179         }
 180
 181         err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
 182         if (err) {
 183                 printf("can't get prog info - %s\n", strerror(errno));
 184                 return 1;
 185         }
 186         prog_id = info.id;
 187
 188         poll_stats(map_fd, kill_after_s);
 189         int_exit(0);
 190
 191         return 0;
 192 }