199 lines · c
1/* SPDX-License-Identifier: GPL-2.02 * Copyright (c) 2018 Facebook3 *4 * This program is free software; you can redistribute it and/or5 * modify it under the terms of version 2 of the GNU General Public6 * 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 <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 2U25#define MAX_PCKT_SIZE 60026 27static int ifindex = -1;28static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST;29static __u32 prog_id;30 31static void int_exit(int sig)32{33 __u32 curr_prog_id = 0;34 35 if (ifindex > -1) {36 if (bpf_xdp_query_id(ifindex, xdp_flags, &curr_prog_id)) {37 printf("bpf_xdp_query_id failed\n");38 exit(1);39 }40 if (prog_id == curr_prog_id)41 bpf_xdp_detach(ifindex, xdp_flags, NULL);42 else if (!curr_prog_id)43 printf("couldn't find a prog id on a given iface\n");44 else45 printf("program on interface changed, not removing\n");46 }47 exit(0);48}49 50/* simple "icmp packet too big sent" counter51 */52static void poll_stats(unsigned int map_fd, unsigned int kill_after_s)53{54 time_t started_at = time(NULL);55 __u64 value = 0;56 int key = 0;57 58 59 while (!kill_after_s || time(NULL) - started_at <= kill_after_s) {60 sleep(STATS_INTERVAL_S);61 62 assert(bpf_map_lookup_elem(map_fd, &key, &value) == 0);63 64 printf("icmp \"packet too big\" sent: %10llu pkts\n", value);65 }66}67 68static void usage(const char *cmd)69{70 printf("Start a XDP prog which send ICMP \"packet too big\" \n"71 "messages if ingress packet is bigger then MAX_SIZE bytes\n");72 printf("Usage: %s [...]\n", cmd);73 printf(" -i <ifname|ifindex> Interface\n");74 printf(" -T <stop-after-X-seconds> Default: 0 (forever)\n");75 printf(" -P <MAX_PCKT_SIZE> Default: %u\n", MAX_PCKT_SIZE);76 printf(" -S use skb-mode\n");77 printf(" -N enforce native mode\n");78 printf(" -F force loading prog\n");79 printf(" -h Display this help\n");80}81 82int main(int argc, char **argv)83{84 unsigned char opt_flags[256] = {};85 const char *optstr = "i:T:P:SNFh";86 struct bpf_prog_info info = {};87 __u32 info_len = sizeof(info);88 unsigned int kill_after_s = 0;89 int i, prog_fd, map_fd, opt;90 struct bpf_program *prog;91 struct bpf_object *obj;92 __u32 max_pckt_size = 0;93 __u32 key = 0;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 = if_nametoindex(optarg);106 if (!ifindex)107 ifindex = atoi(optarg);108 break;109 case 'T':110 kill_after_s = atoi(optarg);111 break;112 case 'P':113 max_pckt_size = atoi(optarg);114 break;115 case 'S':116 xdp_flags |= XDP_FLAGS_SKB_MODE;117 break;118 case 'N':119 /* default, set below */120 break;121 case 'F':122 xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;123 break;124 default:125 usage(argv[0]);126 return 1;127 }128 opt_flags[opt] = 0;129 }130 131 if (!(xdp_flags & XDP_FLAGS_SKB_MODE))132 xdp_flags |= XDP_FLAGS_DRV_MODE;133 134 for (i = 0; i < strlen(optstr); i++) {135 if (opt_flags[(unsigned int)optstr[i]]) {136 fprintf(stderr, "Missing argument -%c\n", optstr[i]);137 usage(argv[0]);138 return 1;139 }140 }141 142 if (!ifindex) {143 fprintf(stderr, "Invalid ifname\n");144 return 1;145 }146 147 snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);148 149 obj = bpf_object__open_file(filename, NULL);150 if (libbpf_get_error(obj))151 return 1;152 153 prog = bpf_object__next_program(obj, NULL);154 bpf_program__set_type(prog, BPF_PROG_TYPE_XDP);155 156 err = bpf_object__load(obj);157 if (err)158 return 1;159 160 prog_fd = bpf_program__fd(prog);161 162 /* static global var 'max_pcktsz' is accessible from .data section */163 if (max_pckt_size) {164 map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data");165 if (map_fd < 0) {166 printf("finding a max_pcktsz map in obj file failed\n");167 return 1;168 }169 bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);170 }171 172 /* fetch icmpcnt map */173 map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");174 if (map_fd < 0) {175 printf("finding a icmpcnt map in obj file failed\n");176 return 1;177 }178 179 signal(SIGINT, int_exit);180 signal(SIGTERM, int_exit);181 182 if (bpf_xdp_attach(ifindex, prog_fd, xdp_flags, NULL) < 0) {183 printf("link set xdp fd failed\n");184 return 1;185 }186 187 err = bpf_prog_get_info_by_fd(prog_fd, &info, &info_len);188 if (err) {189 printf("can't get prog info - %s\n", strerror(errno));190 return 1;191 }192 prog_id = info.id;193 194 poll_stats(map_fd, kill_after_s);195 int_exit(0);196 197 return 0;198}199