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 } 193