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Linux/samples/bpf/bpf_load.c

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  1 #include <stdio.h>
  2 #include <sys/types.h>
  3 #include <sys/stat.h>
  4 #include <fcntl.h>
  5 #include <libelf.h>
  6 #include <gelf.h>
  7 #include <errno.h>
  8 #include <unistd.h>
  9 #include <string.h>
 10 #include <stdbool.h>
 11 #include <stdlib.h>
 12 #include <linux/bpf.h>
 13 #include <linux/filter.h>
 14 #include <linux/perf_event.h>
 15 #include <linux/netlink.h>
 16 #include <linux/rtnetlink.h>
 17 #include <linux/types.h>
 18 #include <sys/types.h>
 19 #include <sys/socket.h>
 20 #include <sys/syscall.h>
 21 #include <sys/ioctl.h>
 22 #include <sys/mman.h>
 23 #include <poll.h>
 24 #include <ctype.h>
 25 #include <assert.h>
 26 #include "libbpf.h"
 27 #include "bpf_load.h"
 28 #include "perf-sys.h"
 29 
 30 #define DEBUGFS "/sys/kernel/debug/tracing/"
 31 
 32 static char license[128];
 33 static int kern_version;
 34 static bool processed_sec[128];
 35 char bpf_log_buf[BPF_LOG_BUF_SIZE];
 36 int map_fd[MAX_MAPS];
 37 int prog_fd[MAX_PROGS];
 38 int event_fd[MAX_PROGS];
 39 int prog_cnt;
 40 int prog_array_fd = -1;
 41 
 42 struct bpf_map_data map_data[MAX_MAPS];
 43 int map_data_count = 0;
 44 
 45 static int populate_prog_array(const char *event, int prog_fd)
 46 {
 47         int ind = atoi(event), err;
 48 
 49         err = bpf_map_update_elem(prog_array_fd, &ind, &prog_fd, BPF_ANY);
 50         if (err < 0) {
 51                 printf("failed to store prog_fd in prog_array\n");
 52                 return -1;
 53         }
 54         return 0;
 55 }
 56 
 57 static int load_and_attach(const char *event, struct bpf_insn *prog, int size)
 58 {
 59         bool is_socket = strncmp(event, "socket", 6) == 0;
 60         bool is_kprobe = strncmp(event, "kprobe/", 7) == 0;
 61         bool is_kretprobe = strncmp(event, "kretprobe/", 10) == 0;
 62         bool is_tracepoint = strncmp(event, "tracepoint/", 11) == 0;
 63         bool is_xdp = strncmp(event, "xdp", 3) == 0;
 64         bool is_perf_event = strncmp(event, "perf_event", 10) == 0;
 65         bool is_cgroup_skb = strncmp(event, "cgroup/skb", 10) == 0;
 66         bool is_cgroup_sk = strncmp(event, "cgroup/sock", 11) == 0;
 67         bool is_sockops = strncmp(event, "sockops", 7) == 0;
 68         size_t insns_cnt = size / sizeof(struct bpf_insn);
 69         enum bpf_prog_type prog_type;
 70         char buf[256];
 71         int fd, efd, err, id;
 72         struct perf_event_attr attr = {};
 73 
 74         attr.type = PERF_TYPE_TRACEPOINT;
 75         attr.sample_type = PERF_SAMPLE_RAW;
 76         attr.sample_period = 1;
 77         attr.wakeup_events = 1;
 78 
 79         if (is_socket) {
 80                 prog_type = BPF_PROG_TYPE_SOCKET_FILTER;
 81         } else if (is_kprobe || is_kretprobe) {
 82                 prog_type = BPF_PROG_TYPE_KPROBE;
 83         } else if (is_tracepoint) {
 84                 prog_type = BPF_PROG_TYPE_TRACEPOINT;
 85         } else if (is_xdp) {
 86                 prog_type = BPF_PROG_TYPE_XDP;
 87         } else if (is_perf_event) {
 88                 prog_type = BPF_PROG_TYPE_PERF_EVENT;
 89         } else if (is_cgroup_skb) {
 90                 prog_type = BPF_PROG_TYPE_CGROUP_SKB;
 91         } else if (is_cgroup_sk) {
 92                 prog_type = BPF_PROG_TYPE_CGROUP_SOCK;
 93         } else if (is_sockops) {
 94                 prog_type = BPF_PROG_TYPE_SOCK_OPS;
 95         } else {
 96                 printf("Unknown event '%s'\n", event);
 97                 return -1;
 98         }
 99 
100         fd = bpf_load_program(prog_type, prog, insns_cnt, license, kern_version,
101                               bpf_log_buf, BPF_LOG_BUF_SIZE);
102         if (fd < 0) {
103                 printf("bpf_load_program() err=%d\n%s", errno, bpf_log_buf);
104                 return -1;
105         }
106 
107         prog_fd[prog_cnt++] = fd;
108 
109         if (is_xdp || is_perf_event || is_cgroup_skb || is_cgroup_sk)
110                 return 0;
111 
112         if (is_socket || is_sockops) {
113                 if (is_socket)
114                         event += 6;
115                 else
116                         event += 7;
117                 if (*event != '/')
118                         return 0;
119                 event++;
120                 if (!isdigit(*event)) {
121                         printf("invalid prog number\n");
122                         return -1;
123                 }
124                 return populate_prog_array(event, fd);
125         }
126 
127         if (is_kprobe || is_kretprobe) {
128                 if (is_kprobe)
129                         event += 7;
130                 else
131                         event += 10;
132 
133                 if (*event == 0) {
134                         printf("event name cannot be empty\n");
135                         return -1;
136                 }
137 
138                 if (isdigit(*event))
139                         return populate_prog_array(event, fd);
140 
141                 snprintf(buf, sizeof(buf),
142                          "echo '%c:%s %s' >> /sys/kernel/debug/tracing/kprobe_events",
143                          is_kprobe ? 'p' : 'r', event, event);
144                 err = system(buf);
145                 if (err < 0) {
146                         printf("failed to create kprobe '%s' error '%s'\n",
147                                event, strerror(errno));
148                         return -1;
149                 }
150 
151                 strcpy(buf, DEBUGFS);
152                 strcat(buf, "events/kprobes/");
153                 strcat(buf, event);
154                 strcat(buf, "/id");
155         } else if (is_tracepoint) {
156                 event += 11;
157 
158                 if (*event == 0) {
159                         printf("event name cannot be empty\n");
160                         return -1;
161                 }
162                 strcpy(buf, DEBUGFS);
163                 strcat(buf, "events/");
164                 strcat(buf, event);
165                 strcat(buf, "/id");
166         }
167 
168         efd = open(buf, O_RDONLY, 0);
169         if (efd < 0) {
170                 printf("failed to open event %s\n", event);
171                 return -1;
172         }
173 
174         err = read(efd, buf, sizeof(buf));
175         if (err < 0 || err >= sizeof(buf)) {
176                 printf("read from '%s' failed '%s'\n", event, strerror(errno));
177                 return -1;
178         }
179 
180         close(efd);
181 
182         buf[err] = 0;
183         id = atoi(buf);
184         attr.config = id;
185 
186         efd = sys_perf_event_open(&attr, -1/*pid*/, 0/*cpu*/, -1/*group_fd*/, 0);
187         if (efd < 0) {
188                 printf("event %d fd %d err %s\n", id, efd, strerror(errno));
189                 return -1;
190         }
191         event_fd[prog_cnt - 1] = efd;
192         ioctl(efd, PERF_EVENT_IOC_ENABLE, 0);
193         ioctl(efd, PERF_EVENT_IOC_SET_BPF, fd);
194 
195         return 0;
196 }
197 
198 static int load_maps(struct bpf_map_data *maps, int nr_maps,
199                      fixup_map_cb fixup_map)
200 {
201         int i;
202 
203         for (i = 0; i < nr_maps; i++) {
204                 if (fixup_map) {
205                         fixup_map(&maps[i], i);
206                         /* Allow userspace to assign map FD prior to creation */
207                         if (maps[i].fd != -1) {
208                                 map_fd[i] = maps[i].fd;
209                                 continue;
210                         }
211                 }
212 
213                 if (maps[i].def.type == BPF_MAP_TYPE_ARRAY_OF_MAPS ||
214                     maps[i].def.type == BPF_MAP_TYPE_HASH_OF_MAPS) {
215                         int inner_map_fd = map_fd[maps[i].def.inner_map_idx];
216 
217                         map_fd[i] = bpf_create_map_in_map(maps[i].def.type,
218                                                         maps[i].def.key_size,
219                                                         inner_map_fd,
220                                                         maps[i].def.max_entries,
221                                                         maps[i].def.map_flags);
222                 } else {
223                         map_fd[i] = bpf_create_map(maps[i].def.type,
224                                                    maps[i].def.key_size,
225                                                    maps[i].def.value_size,
226                                                    maps[i].def.max_entries,
227                                                    maps[i].def.map_flags);
228                 }
229                 if (map_fd[i] < 0) {
230                         printf("failed to create a map: %d %s\n",
231                                errno, strerror(errno));
232                         return 1;
233                 }
234                 maps[i].fd = map_fd[i];
235 
236                 if (maps[i].def.type == BPF_MAP_TYPE_PROG_ARRAY)
237                         prog_array_fd = map_fd[i];
238         }
239         return 0;
240 }
241 
242 static int get_sec(Elf *elf, int i, GElf_Ehdr *ehdr, char **shname,
243                    GElf_Shdr *shdr, Elf_Data **data)
244 {
245         Elf_Scn *scn;
246 
247         scn = elf_getscn(elf, i);
248         if (!scn)
249                 return 1;
250 
251         if (gelf_getshdr(scn, shdr) != shdr)
252                 return 2;
253 
254         *shname = elf_strptr(elf, ehdr->e_shstrndx, shdr->sh_name);
255         if (!*shname || !shdr->sh_size)
256                 return 3;
257 
258         *data = elf_getdata(scn, 0);
259         if (!*data || elf_getdata(scn, *data) != NULL)
260                 return 4;
261 
262         return 0;
263 }
264 
265 static int parse_relo_and_apply(Elf_Data *data, Elf_Data *symbols,
266                                 GElf_Shdr *shdr, struct bpf_insn *insn,
267                                 struct bpf_map_data *maps, int nr_maps)
268 {
269         int i, nrels;
270 
271         nrels = shdr->sh_size / shdr->sh_entsize;
272 
273         for (i = 0; i < nrels; i++) {
274                 GElf_Sym sym;
275                 GElf_Rel rel;
276                 unsigned int insn_idx;
277                 bool match = false;
278                 int j, map_idx;
279 
280                 gelf_getrel(data, i, &rel);
281 
282                 insn_idx = rel.r_offset / sizeof(struct bpf_insn);
283 
284                 gelf_getsym(symbols, GELF_R_SYM(rel.r_info), &sym);
285 
286                 if (insn[insn_idx].code != (BPF_LD | BPF_IMM | BPF_DW)) {
287                         printf("invalid relo for insn[%d].code 0x%x\n",
288                                insn_idx, insn[insn_idx].code);
289                         return 1;
290                 }
291                 insn[insn_idx].src_reg = BPF_PSEUDO_MAP_FD;
292 
293                 /* Match FD relocation against recorded map_data[] offset */
294                 for (map_idx = 0; map_idx < nr_maps; map_idx++) {
295                         if (maps[map_idx].elf_offset == sym.st_value) {
296                                 match = true;
297                                 break;
298                         }
299                 }
300                 if (match) {
301                         insn[insn_idx].imm = maps[map_idx].fd;
302                 } else {
303                         printf("invalid relo for insn[%d] no map_data match\n",
304                                insn_idx);
305                         return 1;
306                 }
307         }
308 
309         return 0;
310 }
311 
312 static int cmp_symbols(const void *l, const void *r)
313 {
314         const GElf_Sym *lsym = (const GElf_Sym *)l;
315         const GElf_Sym *rsym = (const GElf_Sym *)r;
316 
317         if (lsym->st_value < rsym->st_value)
318                 return -1;
319         else if (lsym->st_value > rsym->st_value)
320                 return 1;
321         else
322                 return 0;
323 }
324 
325 static int load_elf_maps_section(struct bpf_map_data *maps, int maps_shndx,
326                                  Elf *elf, Elf_Data *symbols, int strtabidx)
327 {
328         int map_sz_elf, map_sz_copy;
329         bool validate_zero = false;
330         Elf_Data *data_maps;
331         int i, nr_maps;
332         GElf_Sym *sym;
333         Elf_Scn *scn;
334         int copy_sz;
335 
336         if (maps_shndx < 0)
337                 return -EINVAL;
338         if (!symbols)
339                 return -EINVAL;
340 
341         /* Get data for maps section via elf index */
342         scn = elf_getscn(elf, maps_shndx);
343         if (scn)
344                 data_maps = elf_getdata(scn, NULL);
345         if (!scn || !data_maps) {
346                 printf("Failed to get Elf_Data from maps section %d\n",
347                        maps_shndx);
348                 return -EINVAL;
349         }
350 
351         /* For each map get corrosponding symbol table entry */
352         sym = calloc(MAX_MAPS+1, sizeof(GElf_Sym));
353         for (i = 0, nr_maps = 0; i < symbols->d_size / sizeof(GElf_Sym); i++) {
354                 assert(nr_maps < MAX_MAPS+1);
355                 if (!gelf_getsym(symbols, i, &sym[nr_maps]))
356                         continue;
357                 if (sym[nr_maps].st_shndx != maps_shndx)
358                         continue;
359                 /* Only increment iif maps section */
360                 nr_maps++;
361         }
362 
363         /* Align to map_fd[] order, via sort on offset in sym.st_value */
364         qsort(sym, nr_maps, sizeof(GElf_Sym), cmp_symbols);
365 
366         /* Keeping compatible with ELF maps section changes
367          * ------------------------------------------------
368          * The program size of struct bpf_map_def is known by loader
369          * code, but struct stored in ELF file can be different.
370          *
371          * Unfortunately sym[i].st_size is zero.  To calculate the
372          * struct size stored in the ELF file, assume all struct have
373          * the same size, and simply divide with number of map
374          * symbols.
375          */
376         map_sz_elf = data_maps->d_size / nr_maps;
377         map_sz_copy = sizeof(struct bpf_map_def);
378         if (map_sz_elf < map_sz_copy) {
379                 /*
380                  * Backward compat, loading older ELF file with
381                  * smaller struct, keeping remaining bytes zero.
382                  */
383                 map_sz_copy = map_sz_elf;
384         } else if (map_sz_elf > map_sz_copy) {
385                 /*
386                  * Forward compat, loading newer ELF file with larger
387                  * struct with unknown features. Assume zero means
388                  * feature not used.  Thus, validate rest of struct
389                  * data is zero.
390                  */
391                 validate_zero = true;
392         }
393 
394         /* Memcpy relevant part of ELF maps data to loader maps */
395         for (i = 0; i < nr_maps; i++) {
396                 unsigned char *addr, *end;
397                 struct bpf_map_def *def;
398                 const char *map_name;
399                 size_t offset;
400 
401                 map_name = elf_strptr(elf, strtabidx, sym[i].st_name);
402                 maps[i].name = strdup(map_name);
403                 if (!maps[i].name) {
404                         printf("strdup(%s): %s(%d)\n", map_name,
405                                strerror(errno), errno);
406                         free(sym);
407                         return -errno;
408                 }
409 
410                 /* Symbol value is offset into ELF maps section data area */
411                 offset = sym[i].st_value;
412                 def = (struct bpf_map_def *)(data_maps->d_buf + offset);
413                 maps[i].elf_offset = offset;
414                 memset(&maps[i].def, 0, sizeof(struct bpf_map_def));
415                 memcpy(&maps[i].def, def, map_sz_copy);
416 
417                 /* Verify no newer features were requested */
418                 if (validate_zero) {
419                         addr = (unsigned char*) def + map_sz_copy;
420                         end  = (unsigned char*) def + map_sz_elf;
421                         for (; addr < end; addr++) {
422                                 if (*addr != 0) {
423                                         free(sym);
424                                         return -EFBIG;
425                                 }
426                         }
427                 }
428         }
429 
430         free(sym);
431         return nr_maps;
432 }
433 
434 static int do_load_bpf_file(const char *path, fixup_map_cb fixup_map)
435 {
436         int fd, i, ret, maps_shndx = -1, strtabidx = -1;
437         Elf *elf;
438         GElf_Ehdr ehdr;
439         GElf_Shdr shdr, shdr_prog;
440         Elf_Data *data, *data_prog, *data_maps = NULL, *symbols = NULL;
441         char *shname, *shname_prog;
442         int nr_maps = 0;
443 
444         /* reset global variables */
445         kern_version = 0;
446         memset(license, 0, sizeof(license));
447         memset(processed_sec, 0, sizeof(processed_sec));
448 
449         if (elf_version(EV_CURRENT) == EV_NONE)
450                 return 1;
451 
452         fd = open(path, O_RDONLY, 0);
453         if (fd < 0)
454                 return 1;
455 
456         elf = elf_begin(fd, ELF_C_READ, NULL);
457 
458         if (!elf)
459                 return 1;
460 
461         if (gelf_getehdr(elf, &ehdr) != &ehdr)
462                 return 1;
463 
464         /* clear all kprobes */
465         i = system("echo \"\" > /sys/kernel/debug/tracing/kprobe_events");
466 
467         /* scan over all elf sections to get license and map info */
468         for (i = 1; i < ehdr.e_shnum; i++) {
469 
470                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
471                         continue;
472 
473                 if (0) /* helpful for llvm debugging */
474                         printf("section %d:%s data %p size %zd link %d flags %d\n",
475                                i, shname, data->d_buf, data->d_size,
476                                shdr.sh_link, (int) shdr.sh_flags);
477 
478                 if (strcmp(shname, "license") == 0) {
479                         processed_sec[i] = true;
480                         memcpy(license, data->d_buf, data->d_size);
481                 } else if (strcmp(shname, "version") == 0) {
482                         processed_sec[i] = true;
483                         if (data->d_size != sizeof(int)) {
484                                 printf("invalid size of version section %zd\n",
485                                        data->d_size);
486                                 return 1;
487                         }
488                         memcpy(&kern_version, data->d_buf, sizeof(int));
489                 } else if (strcmp(shname, "maps") == 0) {
490                         int j;
491 
492                         maps_shndx = i;
493                         data_maps = data;
494                         for (j = 0; j < MAX_MAPS; j++)
495                                 map_data[j].fd = -1;
496                 } else if (shdr.sh_type == SHT_SYMTAB) {
497                         strtabidx = shdr.sh_link;
498                         symbols = data;
499                 }
500         }
501 
502         ret = 1;
503 
504         if (!symbols) {
505                 printf("missing SHT_SYMTAB section\n");
506                 goto done;
507         }
508 
509         if (data_maps) {
510                 nr_maps = load_elf_maps_section(map_data, maps_shndx,
511                                                 elf, symbols, strtabidx);
512                 if (nr_maps < 0) {
513                         printf("Error: Failed loading ELF maps (errno:%d):%s\n",
514                                nr_maps, strerror(-nr_maps));
515                         ret = 1;
516                         goto done;
517                 }
518                 if (load_maps(map_data, nr_maps, fixup_map))
519                         goto done;
520                 map_data_count = nr_maps;
521 
522                 processed_sec[maps_shndx] = true;
523         }
524 
525         /* process all relo sections, and rewrite bpf insns for maps */
526         for (i = 1; i < ehdr.e_shnum; i++) {
527                 if (processed_sec[i])
528                         continue;
529 
530                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
531                         continue;
532 
533                 if (shdr.sh_type == SHT_REL) {
534                         struct bpf_insn *insns;
535 
536                         /* locate prog sec that need map fixup (relocations) */
537                         if (get_sec(elf, shdr.sh_info, &ehdr, &shname_prog,
538                                     &shdr_prog, &data_prog))
539                                 continue;
540 
541                         if (shdr_prog.sh_type != SHT_PROGBITS ||
542                             !(shdr_prog.sh_flags & SHF_EXECINSTR))
543                                 continue;
544 
545                         insns = (struct bpf_insn *) data_prog->d_buf;
546                         processed_sec[i] = true; /* relo section */
547 
548                         if (parse_relo_and_apply(data, symbols, &shdr, insns,
549                                                  map_data, nr_maps))
550                                 continue;
551                 }
552         }
553 
554         /* load programs */
555         for (i = 1; i < ehdr.e_shnum; i++) {
556 
557                 if (processed_sec[i])
558                         continue;
559 
560                 if (get_sec(elf, i, &ehdr, &shname, &shdr, &data))
561                         continue;
562 
563                 if (memcmp(shname, "kprobe/", 7) == 0 ||
564                     memcmp(shname, "kretprobe/", 10) == 0 ||
565                     memcmp(shname, "tracepoint/", 11) == 0 ||
566                     memcmp(shname, "xdp", 3) == 0 ||
567                     memcmp(shname, "perf_event", 10) == 0 ||
568                     memcmp(shname, "socket", 6) == 0 ||
569                     memcmp(shname, "cgroup/", 7) == 0 ||
570                     memcmp(shname, "sockops", 7) == 0) {
571                         ret = load_and_attach(shname, data->d_buf,
572                                               data->d_size);
573                         if (ret != 0)
574                                 goto done;
575                 }
576         }
577 
578         ret = 0;
579 done:
580         close(fd);
581         return ret;
582 }
583 
584 int load_bpf_file(char *path)
585 {
586         return do_load_bpf_file(path, NULL);
587 }
588 
589 int load_bpf_file_fixup_map(const char *path, fixup_map_cb fixup_map)
590 {
591         return do_load_bpf_file(path, fixup_map);
592 }
593 
594 void read_trace_pipe(void)
595 {
596         int trace_fd;
597 
598         trace_fd = open(DEBUGFS "trace_pipe", O_RDONLY, 0);
599         if (trace_fd < 0)
600                 return;
601 
602         while (1) {
603                 static char buf[4096];
604                 ssize_t sz;
605 
606                 sz = read(trace_fd, buf, sizeof(buf));
607                 if (sz > 0) {
608                         buf[sz] = 0;
609                         puts(buf);
610                 }
611         }
612 }
613 
614 #define MAX_SYMS 300000
615 static struct ksym syms[MAX_SYMS];
616 static int sym_cnt;
617 
618 static int ksym_cmp(const void *p1, const void *p2)
619 {
620         return ((struct ksym *)p1)->addr - ((struct ksym *)p2)->addr;
621 }
622 
623 int load_kallsyms(void)
624 {
625         FILE *f = fopen("/proc/kallsyms", "r");
626         char func[256], buf[256];
627         char symbol;
628         void *addr;
629         int i = 0;
630 
631         if (!f)
632                 return -ENOENT;
633 
634         while (!feof(f)) {
635                 if (!fgets(buf, sizeof(buf), f))
636                         break;
637                 if (sscanf(buf, "%p %c %s", &addr, &symbol, func) != 3)
638                         break;
639                 if (!addr)
640                         continue;
641                 syms[i].addr = (long) addr;
642                 syms[i].name = strdup(func);
643                 i++;
644         }
645         sym_cnt = i;
646         qsort(syms, sym_cnt, sizeof(struct ksym), ksym_cmp);
647         return 0;
648 }
649 
650 struct ksym *ksym_search(long key)
651 {
652         int start = 0, end = sym_cnt;
653         int result;
654 
655         while (start < end) {
656                 size_t mid = start + (end - start) / 2;
657 
658                 result = key - syms[mid].addr;
659                 if (result < 0)
660                         end = mid;
661                 else if (result > 0)
662                         start = mid + 1;
663                 else
664                         return &syms[mid];
665         }
666 
667         if (start >= 1 && syms[start - 1].addr < key &&
668             key < syms[start].addr)
669                 /* valid ksym */
670                 return &syms[start - 1];
671 
672         /* out of range. return _stext */
673         return &syms[0];
674 }
675 
676 int set_link_xdp_fd(int ifindex, int fd, __u32 flags)
677 {
678         struct sockaddr_nl sa;
679         int sock, seq = 0, len, ret = -1;
680         char buf[4096];
681         struct nlattr *nla, *nla_xdp;
682         struct {
683                 struct nlmsghdr  nh;
684                 struct ifinfomsg ifinfo;
685                 char             attrbuf[64];
686         } req;
687         struct nlmsghdr *nh;
688         struct nlmsgerr *err;
689 
690         memset(&sa, 0, sizeof(sa));
691         sa.nl_family = AF_NETLINK;
692 
693         sock = socket(AF_NETLINK, SOCK_RAW, NETLINK_ROUTE);
694         if (sock < 0) {
695                 printf("open netlink socket: %s\n", strerror(errno));
696                 return -1;
697         }
698 
699         if (bind(sock, (struct sockaddr *)&sa, sizeof(sa)) < 0) {
700                 printf("bind to netlink: %s\n", strerror(errno));
701                 goto cleanup;
702         }
703 
704         memset(&req, 0, sizeof(req));
705         req.nh.nlmsg_len = NLMSG_LENGTH(sizeof(struct ifinfomsg));
706         req.nh.nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
707         req.nh.nlmsg_type = RTM_SETLINK;
708         req.nh.nlmsg_pid = 0;
709         req.nh.nlmsg_seq = ++seq;
710         req.ifinfo.ifi_family = AF_UNSPEC;
711         req.ifinfo.ifi_index = ifindex;
712 
713         /* started nested attribute for XDP */
714         nla = (struct nlattr *)(((char *)&req)
715                                 + NLMSG_ALIGN(req.nh.nlmsg_len));
716         nla->nla_type = NLA_F_NESTED | 43/*IFLA_XDP*/;
717         nla->nla_len = NLA_HDRLEN;
718 
719         /* add XDP fd */
720         nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
721         nla_xdp->nla_type = 1/*IFLA_XDP_FD*/;
722         nla_xdp->nla_len = NLA_HDRLEN + sizeof(int);
723         memcpy((char *)nla_xdp + NLA_HDRLEN, &fd, sizeof(fd));
724         nla->nla_len += nla_xdp->nla_len;
725 
726         /* if user passed in any flags, add those too */
727         if (flags) {
728                 nla_xdp = (struct nlattr *)((char *)nla + nla->nla_len);
729                 nla_xdp->nla_type = 3/*IFLA_XDP_FLAGS*/;
730                 nla_xdp->nla_len = NLA_HDRLEN + sizeof(flags);
731                 memcpy((char *)nla_xdp + NLA_HDRLEN, &flags, sizeof(flags));
732                 nla->nla_len += nla_xdp->nla_len;
733         }
734 
735         req.nh.nlmsg_len += NLA_ALIGN(nla->nla_len);
736 
737         if (send(sock, &req, req.nh.nlmsg_len, 0) < 0) {
738                 printf("send to netlink: %s\n", strerror(errno));
739                 goto cleanup;
740         }
741 
742         len = recv(sock, buf, sizeof(buf), 0);
743         if (len < 0) {
744                 printf("recv from netlink: %s\n", strerror(errno));
745                 goto cleanup;
746         }
747 
748         for (nh = (struct nlmsghdr *)buf; NLMSG_OK(nh, len);
749              nh = NLMSG_NEXT(nh, len)) {
750                 if (nh->nlmsg_pid != getpid()) {
751                         printf("Wrong pid %d, expected %d\n",
752                                nh->nlmsg_pid, getpid());
753                         goto cleanup;
754                 }
755                 if (nh->nlmsg_seq != seq) {
756                         printf("Wrong seq %d, expected %d\n",
757                                nh->nlmsg_seq, seq);
758                         goto cleanup;
759                 }
760                 switch (nh->nlmsg_type) {
761                 case NLMSG_ERROR:
762                         err = (struct nlmsgerr *)NLMSG_DATA(nh);
763                         if (!err->error)
764                                 continue;
765                         printf("nlmsg error %s\n", strerror(-err->error));
766                         goto cleanup;
767                 case NLMSG_DONE:
768                         break;
769                 }
770         }
771 
772         ret = 0;
773 
774 cleanup:
775         close(sock);
776         return ret;
777 }
778 

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