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 <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 #define MAX_PCKT_SIZE 600 26 27 static int ifindex = -1; 28 static __u32 xdp_flags = XDP_FLAGS_UPDATE_IF_NOEXIST; 29 static __u32 prog_id; 30 31 static 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 else 45 printf("program on interface changed, not removing\n"); 46 } 47 exit(0); 48 } 49 50 /* simple "icmp packet too big sent" counter 51 */ 52 static 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 68 static 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 82 int 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