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Linux/samples/bpf/xdp_adjust_tail_user.c

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  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.h"
 23 #include "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 rlimit r = {RLIM_INFINITY, RLIM_INFINITY};
 86         struct bpf_prog_load_attr prog_load_attr = {
 87                 .prog_type      = BPF_PROG_TYPE_XDP,
 88         };
 89         unsigned char opt_flags[256] = {};
 90         const char *optstr = "i:T:P:SNFh";
 91         struct bpf_prog_info info = {};
 92         __u32 info_len = sizeof(info);
 93         unsigned int kill_after_s = 0;
 94         int i, prog_fd, map_fd, opt;
 95         struct bpf_object *obj;
 96         __u32 max_pckt_size = 0;
 97         __u32 key = 0;
 98         char filename[256];
 99         int err;
100 
101         for (i = 0; i < strlen(optstr); i++)
102                 if (optstr[i] != 'h' && 'a' <= optstr[i] && optstr[i] <= 'z')
103                         opt_flags[(unsigned char)optstr[i]] = 1;
104 
105         while ((opt = getopt(argc, argv, optstr)) != -1) {
106 
107                 switch (opt) {
108                 case 'i':
109                         ifindex = if_nametoindex(optarg);
110                         if (!ifindex)
111                                 ifindex = atoi(optarg);
112                         break;
113                 case 'T':
114                         kill_after_s = atoi(optarg);
115                         break;
116                 case 'P':
117                         max_pckt_size = atoi(optarg);
118                         break;
119                 case 'S':
120                         xdp_flags |= XDP_FLAGS_SKB_MODE;
121                         break;
122                 case 'N':
123                         xdp_flags |= XDP_FLAGS_DRV_MODE;
124                         break;
125                 case 'F':
126                         xdp_flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
127                         break;
128                 default:
129                         usage(argv[0]);
130                         return 1;
131                 }
132                 opt_flags[opt] = 0;
133         }
134 
135         for (i = 0; i < strlen(optstr); i++) {
136                 if (opt_flags[(unsigned int)optstr[i]]) {
137                         fprintf(stderr, "Missing argument -%c\n", optstr[i]);
138                         usage(argv[0]);
139                         return 1;
140                 }
141         }
142 
143         if (setrlimit(RLIMIT_MEMLOCK, &r)) {
144                 perror("setrlimit(RLIMIT_MEMLOCK, RLIM_INFINITY)");
145                 return 1;
146         }
147 
148         if (!ifindex) {
149                 fprintf(stderr, "Invalid ifname\n");
150                 return 1;
151         }
152 
153         snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
154         prog_load_attr.file = filename;
155 
156         if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
157                 return 1;
158 
159         /* static global var 'max_pcktsz' is accessible from .data section */
160         if (max_pckt_size) {
161                 map_fd = bpf_object__find_map_fd_by_name(obj, "xdp_adju.data");
162                 if (map_fd < 0) {
163                         printf("finding a max_pcktsz map in obj file failed\n");
164                         return 1;
165                 }
166                 bpf_map_update_elem(map_fd, &key, &max_pckt_size, BPF_ANY);
167         }
168 
169         /* fetch icmpcnt map */
170         map_fd = bpf_object__find_map_fd_by_name(obj, "icmpcnt");
171         if (map_fd < 0) {
172                 printf("finding a icmpcnt map in obj file failed\n");
173                 return 1;
174         }
175 
176         signal(SIGINT, int_exit);
177         signal(SIGTERM, int_exit);
178 
179         if (bpf_set_link_xdp_fd(ifindex, prog_fd, xdp_flags) < 0) {
180                 printf("link set xdp fd failed\n");
181                 return 1;
182         }
183 
184         err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
185         if (err) {
186                 printf("can't get prog info - %s\n", strerror(errno));
187                 return 1;
188         }
189         prog_id = info.id;
190 
191         poll_stats(map_fd, kill_after_s);
192         int_exit(0);
193 
194         return 0;
195 }
196 

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