samples/bpf/bpf_load.c

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