src/libsystemd/sd-device/device-monitor.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <linux/filter.h>
   5 #include <linux/netlink.h>
   6 #include <sys/socket.h>
   7
   8 #include "sd-device.h"
   9 #include "sd-event.h"
  10
  11 #include "MurmurHash2.h"
  12 #include "alloc-util.h"
  13 #include "device-monitor-private.h"
  14 #include "device-private.h"
  15 #include "device-util.h"
  16 #include "fd-util.h"
  17 #include "format-util.h"
  18 #include "hashmap.h"
  19 #include "missing.h"
  20 #include "mount-util.h"
  21 #include "set.h"
  22 #include "socket-util.h"
  23 #include "string-util.h"
  24 #include "strv.h"
  25
  26 struct sd_device_monitor {
  27         unsigned n_ref;
  28
  29         int sock;
  30         union sockaddr_union snl;
  31         union sockaddr_union snl_trusted_sender;
  32         bool bound;
  33
  34         Hashmap *subsystem_filter;
  35         Set *tag_filter;
  36         bool filter_uptodate;
  37
  38         sd_event *event;
  39         sd_event_source *event_source;
  40         int64_t event_priority;
  41         sd_device_monitor_handler_t callback;
  42         void *userdata;
  43 };
  44
  45 #define UDEV_MONITOR_MAGIC                0xfeedcafe
  46
  47 typedef struct monitor_netlink_header {
  48         /* "libudev" prefix to distinguish libudev and kernel messages */
  49         char prefix[8];
  50         /* Magic to protect against daemon <-> Library message format mismatch
  51          * Used in the kernel from socket filter rules; needs to be stored in network order */
  52         unsigned magic;
  53         /* Total length of header structure known to the sender */
  54         unsigned header_size;
  55         /* Properties string buffer */
  56         unsigned properties_off;
  57         unsigned properties_len;
  58         /* Hashes of primary device properties strings, to let libudev subscribers
  59          * use in-kernel socket filters; values need to be stored in network order */
  60         unsigned filter_subsystem_hash;
  61         unsigned filter_devtype_hash;
  62         unsigned filter_tag_bloom_hi;
  63         unsigned filter_tag_bloom_lo;
  64 } monitor_netlink_header;
  65
  66 static int monitor_set_nl_address(sd_device_monitor *m) {
  67         union sockaddr_union snl;
  68         socklen_t addrlen;
  69
  70         assert(m);
  71
  72         /* Get the address the kernel has assigned us.
  73          * It is usually, but not necessarily the pid. */
  74         addrlen = sizeof(struct sockaddr_nl);
  75         if (getsockname(m->sock, &snl.sa, &addrlen) < 0)
  76                 return -errno;
  77
  78         m->snl.nl.nl_pid = snl.nl.nl_pid;
  79         return 0;
  80 }
  81
  82 int device_monitor_allow_unicast_sender(sd_device_monitor *m, sd_device_monitor *sender) {
  83         assert_return(m, -EINVAL);
  84         assert_return(sender, -EINVAL);
  85
  86         m->snl_trusted_sender.nl.nl_pid = sender->snl.nl.nl_pid;
  87         return 0;
  88 }
  89
  90 _public_ int sd_device_monitor_set_receive_buffer_size(sd_device_monitor *m, size_t size) {
  91         int n = (int) size;
  92
  93         assert_return(m, -EINVAL);
  94         assert_return((size_t) n != size, -EINVAL);
  95
  96         if (setsockopt(m->sock, SOL_SOCKET, SO_RCVBUF, &n, sizeof(n)) < 0 &&
  97             setsockopt(m->sock, SOL_SOCKET, SO_RCVBUFFORCE, &n, sizeof(n)) < 0)
  98                 return -errno;
  99
 100         return 0;
 101 }
 102
 103 int device_monitor_disconnect(sd_device_monitor *m) {
 104         assert(m);
 105
 106         m->sock = safe_close(m->sock);
 107         return 0;
 108 }
 109
 110 int device_monitor_get_fd(sd_device_monitor *m) {
 111         assert_return(m, -EINVAL);
 112
 113         return m->sock;
 114 }
 115
 116 int device_monitor_new_full(sd_device_monitor **ret, MonitorNetlinkGroup group, int fd) {
 117         _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *m = NULL;
 118         _cleanup_close_ int sock = -1;
 119         int r;
 120
 121         assert_return(ret, -EINVAL);
 122         assert_return(group >= 0 && group < _MONITOR_NETLINK_GROUP_MAX, -EINVAL);
 123
 124         if (group == MONITOR_GROUP_UDEV &&
 125             access("/run/udev/control", F_OK) < 0 &&
 126             dev_is_devtmpfs() <= 0) {
 127
 128                 /*
 129                  * We do not support subscribing to uevents if no instance of
 130                  * udev is running. Uevents would otherwise broadcast the
 131                  * processing data of the host into containers, which is not
 132                  * desired.
 133                  *
 134                  * Containers will currently not get any udev uevents, until
 135                  * a supporting infrastructure is available.
 136                  *
 137                  * We do not set a netlink multicast group here, so the socket
 138                  * will not receive any messages.
 139                  */
 140
 141                 log_debug("The udev service seems not to be active, disabling the monitor");
 142                 group = MONITOR_GROUP_NONE;
 143         }
 144
 145         if (fd < 0) {
 146                 sock = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
 147                 if (sock < 0)
 148                         return log_debug_errno(errno, "Failed to create socket: %m");
 149         }
 150
 151         m = new(sd_device_monitor, 1);
 152         if (!m)
 153                 return -ENOMEM;
 154
 155         *m = (sd_device_monitor) {
 156                 .n_ref = 1,
 157                 .sock = fd >= 0 ? fd : TAKE_FD(sock),
 158                 .bound = fd >= 0,
 159                 .snl.nl.nl_family = AF_NETLINK,
 160                 .snl.nl.nl_groups = group,
 161         };
 162
 163         if (fd >= 0) {
 164                 r = monitor_set_nl_address(m);
 165                 if (r < 0)
 166                         return log_debug_errno(r, "Failed to set netlink address: %m");
 167         }
 168
 169         *ret = TAKE_PTR(m);
 170         return 0;
 171 }
 172
 173 _public_ int sd_device_monitor_new(sd_device_monitor **ret) {
 174         return device_monitor_new_full(ret, MONITOR_GROUP_UDEV, -1);
 175 }
 176
 177 _public_ int sd_device_monitor_stop(sd_device_monitor *m) {
 178         assert_return(m, -EINVAL);
 179
 180         m->event_source = sd_event_source_unref(m->event_source);
 181         (void) device_monitor_disconnect(m);
 182
 183         return 0;
 184 }
 185
 186 static int device_monitor_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 187         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 188         sd_device_monitor *m = userdata;
 189
 190         assert(m);
 191
 192         if (device_monitor_receive_device(m, &device) <= 0)
 193                 return 0;
 194
 195         if (m->callback)
 196                 return m->callback(m, device, m->userdata);
 197
 198         return 0;
 199 }
 200
 201 _public_ int sd_device_monitor_start(sd_device_monitor *m, sd_device_monitor_handler_t callback, void *userdata, const char *description) {
 202         _cleanup_(sd_event_source_unrefp) sd_event_source *s = NULL;
 203         int r;
 204
 205         assert_return(m, -EINVAL);
 206
 207         if (!m->event) {
 208                 r = sd_device_monitor_attach_event(m, NULL, 0);
 209                 if (r < 0)
 210                         return r;
 211         }
 212
 213         r = device_monitor_enable_receiving(m);
 214         if (r < 0)
 215                 return r;
 216
 217         m->callback = callback;
 218         m->userdata = userdata;
 219
 220         r = sd_event_add_io(m->event, &s, m->sock, EPOLLIN, device_monitor_event_handler, m);
 221         if (r < 0)
 222                 return r;
 223
 224         r = sd_event_source_set_priority(s, m->event_priority);
 225         if (r < 0)
 226                 return r;
 227
 228         if (description) {
 229                 r = sd_event_source_set_description(s, description);
 230                 if (r < 0)
 231                         return r;
 232         }
 233
 234         m->event_source = TAKE_PTR(s);
 235
 236         return 0;
 237 }
 238
 239 _public_ int sd_device_monitor_detach_event(sd_device_monitor *m) {
 240         assert_return(m, -EINVAL);
 241
 242         (void) sd_device_monitor_stop(m);
 243         m->event = sd_event_unref(m->event);
 244
 245         return 0;
 246 }
 247
 248 _public_ int sd_device_monitor_attach_event(sd_device_monitor *m, sd_event *event, int64_t priority) {
 249         int r;
 250
 251         assert_return(m, -EINVAL);
 252         assert_return(!m->event, -EBUSY);
 253
 254         if (event)
 255                 m->event = sd_event_ref(event);
 256         else {
 257                 r = sd_event_default(&m->event);
 258                 if (r < 0)
 259                         return 0;
 260         }
 261
 262         m->event_priority = priority;
 263
 264         return 0;
 265 }
 266
 267 _public_ sd_event *sd_device_monitor_get_event(sd_device_monitor *m) {
 268         assert_return(m, NULL);
 269
 270         return m->event;
 271 }
 272
 273 int device_monitor_enable_receiving(sd_device_monitor *m) {
 274         int r;
 275
 276         assert_return(m, -EINVAL);
 277
 278         if (!m->filter_uptodate) {
 279                 r = sd_device_monitor_filter_update(m);
 280                 if (r < 0)
 281                         return log_debug_errno(r, "Failed to update filter: %m");
 282         }
 283
 284         if (!m->bound) {
 285                 if (bind(m->sock, &m->snl.sa, sizeof(struct sockaddr_nl)) < 0)
 286                         return log_debug_errno(errno, "Failed to bind monitoring socket to event source: %m");
 287
 288                 m->bound = true;
 289         }
 290
 291         r = monitor_set_nl_address(m);
 292         if (r < 0)
 293                 return log_debug_errno(r, "Failed to set address: %m");
 294
 295         /* enable receiving of sender credentials */
 296         r = setsockopt_int(m->sock, SOL_SOCKET, SO_PASSCRED, true);
 297         if (r < 0)
 298                 return log_debug_errno(r, "Failed to set socket option SO_PASSCRED: %m");
 299
 300         return 0;
 301 }
 302
 303 static sd_device_monitor *device_monitor_free(sd_device_monitor *m) {
 304         assert(m);
 305
 306         (void) sd_device_monitor_detach_event(m);
 307
 308         hashmap_free_free_free(m->subsystem_filter);
 309         set_free_free(m->tag_filter);
 310
 311         return mfree(m);
 312 }
 313
 314 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_monitor, sd_device_monitor, device_monitor_free);
 315
 316 static int passes_filter(sd_device_monitor *m, sd_device *device) {
 317         const char *tag, *subsystem, *devtype, *s, *d = NULL;
 318         Iterator i;
 319         int r;
 320
 321         assert_return(m, -EINVAL);
 322         assert_return(device, -EINVAL);
 323
 324         if (hashmap_isempty(m->subsystem_filter))
 325                 goto tag;
 326
 327         r = sd_device_get_subsystem(device, &s);
 328         if (r < 0)
 329                 return r;
 330
 331         r = sd_device_get_devtype(device, &d);
 332         if (r < 0 && r != -ENOENT)
 333                 return r;
 334
 335         HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, i) {
 336                 if (!streq(s, subsystem))
 337                         continue;
 338
 339                 if (!devtype)
 340                         goto tag;
 341
 342                 if (!d)
 343                         continue;
 344
 345                 if (streq(d, devtype))
 346                         goto tag;
 347         }
 348
 349         return 0;
 350
 351 tag:
 352         if (set_isempty(m->tag_filter))
 353                 return 1;
 354
 355         SET_FOREACH(tag, m->tag_filter, i)
 356                 if (sd_device_has_tag(device, tag) > 0)
 357                         return 1;
 358
 359         return 0;
 360 }
 361
 362 int device_monitor_receive_device(sd_device_monitor *m, sd_device **ret) {
 363         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 364         union {
 365                 monitor_netlink_header nlh;
 366                 char raw[8192];
 367         } buf;
 368         struct iovec iov = {
 369                 .iov_base = &buf,
 370                 .iov_len = sizeof(buf)
 371         };
 372         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 373         union sockaddr_union snl;
 374         struct msghdr smsg = {
 375                 .msg_iov = &iov,
 376                 .msg_iovlen = 1,
 377                 .msg_control = cred_msg,
 378                 .msg_controllen = sizeof(cred_msg),
 379                 .msg_name = &snl,
 380                 .msg_namelen = sizeof(snl),
 381         };
 382         struct cmsghdr *cmsg;
 383         struct ucred *cred;
 384         ssize_t buflen, bufpos;
 385         bool is_initialized = false;
 386         int r;
 387
 388         assert(ret);
 389
 390         buflen = recvmsg(m->sock, &smsg, 0);
 391         if (buflen < 0) {
 392                 if (errno != EINTR)
 393                         log_debug_errno(errno, "Failed to receive message: %m");
 394                 return -errno;
 395         }
 396
 397         if (buflen < 32 || (smsg.msg_flags & MSG_TRUNC))
 398                 return log_debug_errno(EINVAL, "Invalid message length.");
 399
 400         if (snl.nl.nl_groups == MONITOR_GROUP_NONE) {
 401                 /* unicast message, check if we trust the sender */
 402                 if (m->snl_trusted_sender.nl.nl_pid == 0 ||
 403                     snl.nl.nl_pid != m->snl_trusted_sender.nl.nl_pid)
 404                         return log_debug_errno(EAGAIN, "Unicast netlink message ignored.");
 405
 406         } else if (snl.nl.nl_groups == MONITOR_GROUP_KERNEL) {
 407                 if (snl.nl.nl_pid > 0)
 408                         return log_debug_errno(EAGAIN, "Multicast kernel netlink message from PID %"PRIu32" ignored.", snl.nl.nl_pid);
 409         }
 410
 411         cmsg = CMSG_FIRSTHDR(&smsg);
 412         if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS)
 413                 return log_debug_errno(EAGAIN, "No sender credentials received, message ignored.");
 414
 415         cred = (struct ucred*) CMSG_DATA(cmsg);
 416         if (cred->uid != 0)
 417                 return log_debug_errno(EAGAIN, "Sender uid="UID_FMT", message ignored.", cred->uid);
 418
 419         if (streq(buf.raw, "libudev")) {
 420                 /* udev message needs proper version magic */
 421                 if (buf.nlh.magic != htobe32(UDEV_MONITOR_MAGIC))
 422                         return log_debug_errno(EAGAIN, "Invalid message signature (%x != %x)",
 423                                                buf.nlh.magic, htobe32(UDEV_MONITOR_MAGIC));
 424
 425                 if (buf.nlh.properties_off+32 > (size_t) buflen)
 426                         return log_debug_errno(EAGAIN, "Invalid message length (%u > %zd)",
 427                                                buf.nlh.properties_off+32, buflen);
 428
 429                 bufpos = buf.nlh.properties_off;
 430
 431                 /* devices received from udev are always initialized */
 432                 is_initialized = true;
 433
 434         } else {
 435                 /* kernel message with header */
 436                 bufpos = strlen(buf.raw) + 1;
 437                 if ((size_t) bufpos < sizeof("a@/d") || bufpos >= buflen)
 438                         return log_debug_errno(EAGAIN, "Invalid message length");
 439
 440                 /* check message header */
 441                 if (!strstr(buf.raw, "@/"))
 442                         return log_debug_errno(EAGAIN, "Invalid message header");
 443         }
 444
 445         r = device_new_from_nulstr(&device, (uint8_t*) &buf.raw[bufpos], buflen - bufpos);
 446         if (r < 0)
 447                 return log_debug_errno(r, "Failed to create device: %m");
 448
 449         if (is_initialized)
 450                 device_set_is_initialized(device);
 451
 452         /* Skip device, if it does not pass the current filter */
 453         r = passes_filter(m, device);
 454         if (r < 0)
 455                 return log_debug_errno(r, "Failed to check received device passing filter: %m");
 456
 457         if (r == 0)
 458                 log_debug("Received device does not pass filter, ignoring");
 459         else
 460                 *ret = TAKE_PTR(device);
 461
 462         return r;
 463 }
 464
 465 static uint32_t string_hash32(const char *str) {
 466         return MurmurHash2(str, strlen(str), 0);
 467 }
 468
 469 /* Get a bunch of bit numbers out of the hash, and set the bits in our bit field */
 470 static uint64_t string_bloom64(const char *str) {
 471         uint64_t bits = 0;
 472         uint32_t hash = string_hash32(str);
 473
 474         bits |= 1LLU << (hash & 63);
 475         bits |= 1LLU << ((hash >> 6) & 63);
 476         bits |= 1LLU << ((hash >> 12) & 63);
 477         bits |= 1LLU << ((hash >> 18) & 63);
 478         return bits;
 479 }
 480
 481 int device_monitor_send_device(
 482                 sd_device_monitor *m,
 483                 sd_device_monitor *destination,
 484                 sd_device *device) {
 485
 486         monitor_netlink_header nlh = {
 487                 .prefix = "libudev",
 488                 .magic = htobe32(UDEV_MONITOR_MAGIC),
 489                 .header_size = sizeof nlh,
 490         };
 491         struct iovec iov[2] = {
 492                 { .iov_base = &nlh, .iov_len = sizeof nlh },
 493         };
 494         struct msghdr smsg = {
 495                 .msg_iov = iov,
 496                 .msg_iovlen = 2,
 497         };
 498         /* default destination for sending */
 499         union sockaddr_union default_destination = {
 500                 .nl.nl_family = AF_NETLINK,
 501                 .nl.nl_groups = MONITOR_GROUP_UDEV,
 502         };
 503         uint64_t tag_bloom_bits;
 504         const char *buf, *val;
 505         ssize_t count;
 506         size_t blen;
 507         int r;
 508
 509         assert(m);
 510         assert(device);
 511
 512         r = device_get_properties_nulstr(device, (const uint8_t **) &buf, &blen);
 513         if (r < 0)
 514                 return log_debug_errno(r, "Failed to get device properties: %m");
 515         if (blen < 32) {
 516                 log_debug("Device buffer is too small to contain a valid device");
 517                 return -EINVAL;
 518         }
 519
 520         /* fill in versioned header */
 521         r = sd_device_get_subsystem(device, &val);
 522         if (r < 0)
 523                 return log_debug_errno(r, "Failed to get device subsystem: %m");
 524         nlh.filter_subsystem_hash = htobe32(string_hash32(val));
 525
 526         if (sd_device_get_devtype(device, &val) >= 0)
 527                 nlh.filter_devtype_hash = htobe32(string_hash32(val));
 528
 529         /* add tag bloom filter */
 530         tag_bloom_bits = 0;
 531         FOREACH_DEVICE_TAG(device, val)
 532                 tag_bloom_bits |= string_bloom64(val);
 533
 534         if (tag_bloom_bits > 0) {
 535                 nlh.filter_tag_bloom_hi = htobe32(tag_bloom_bits >> 32);
 536                 nlh.filter_tag_bloom_lo = htobe32(tag_bloom_bits & 0xffffffff);
 537         }
 538
 539         /* add properties list */
 540         nlh.properties_off = iov[0].iov_len;
 541         nlh.properties_len = blen;
 542         iov[1] = (struct iovec) {
 543                 .iov_base = (char*) buf,
 544                 .iov_len = blen,
 545         };
 546
 547         /*
 548          * Use custom address for target, or the default one.
 549          *
 550          * If we send to a multicast group, we will get
 551          * ECONNREFUSED, which is expected.
 552          */
 553         smsg.msg_name = destination ? &destination->snl : &default_destination;
 554         smsg.msg_namelen = sizeof(struct sockaddr_nl);
 555         count = sendmsg(m->sock, &smsg, 0);
 556         if (count < 0) {
 557                 if (!destination && errno == ECONNREFUSED) {
 558                         log_debug("Passed device to netlink monitor");
 559                         return 0;
 560                 } else
 561                         return log_debug_errno(errno, "Failed to send device to netlink monitor");
 562         }
 563
 564         log_debug("Passed %zi byte device to netlink monitor", count);
 565         return count;
 566 }
 567
 568 static void bpf_stmt(struct sock_filter *ins, unsigned *i,
 569                      unsigned short code, unsigned data) {
 570         ins[(*i)++] = (struct sock_filter) {
 571                 .code = code,
 572                 .k = data,
 573         };
 574 }
 575
 576 static void bpf_jmp(struct sock_filter *ins, unsigned *i,
 577                     unsigned short code, unsigned data,
 578                     unsigned short jt, unsigned short jf) {
 579         ins[(*i)++] = (struct sock_filter) {
 580                 .code = code,
 581                 .jt = jt,
 582                 .jf = jf,
 583                 .k = data,
 584         };
 585 }
 586
 587 _public_ int sd_device_monitor_filter_update(sd_device_monitor *m) {
 588         struct sock_filter ins[512] = {};
 589         struct sock_fprog filter;
 590         const char *subsystem, *devtype, *tag;
 591         unsigned i = 0;
 592         Iterator it;
 593
 594         assert_return(m, -EINVAL);
 595
 596         if (hashmap_isempty(m->subsystem_filter) &&
 597             set_isempty(m->tag_filter)) {
 598                 m->filter_uptodate = true;
 599                 return 0;
 600         }
 601
 602         /* load magic in A */
 603         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, magic));
 604         /* jump if magic matches */
 605         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
 606         /* wrong magic, pass packet */
 607         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 608
 609         if (!set_isempty(m->tag_filter)) {
 610                 int tag_matches = set_size(m->tag_filter);
 611
 612                 /* add all tags matches */
 613                 SET_FOREACH(tag, m->tag_filter, it) {
 614                         uint64_t tag_bloom_bits = string_bloom64(tag);
 615                         uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
 616                         uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
 617
 618                         /* load device bloom bits in A */
 619                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_hi));
 620                         /* clear bits (tag bits & bloom bits) */
 621                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
 622                         /* jump to next tag if it does not match */
 623                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
 624
 625                         /* load device bloom bits in A */
 626                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_lo));
 627                         /* clear bits (tag bits & bloom bits) */
 628                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
 629                         /* jump behind end of tag match block if tag matches */
 630                         tag_matches--;
 631                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
 632                 }
 633
 634                 /* nothing matched, drop packet */
 635                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 636         }
 637
 638         /* add all subsystem matches */
 639         if (!hashmap_isempty(m->subsystem_filter)) {
 640                 HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, it) {
 641                         uint32_t hash = string_hash32(subsystem);
 642
 643                         /* load device subsystem value in A */
 644                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_subsystem_hash));
 645                         if (!devtype) {
 646                                 /* jump if subsystem does not match */
 647                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 648                         } else {
 649                                 hash = string_hash32(devtype);
 650
 651                                 /* jump if subsystem does not match */
 652                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
 653                                 /* load device devtype value in A */
 654                                 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_devtype_hash));
 655                                 /* jump if value does not match */
 656                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 657                         }
 658
 659                         /* matched, pass packet */
 660                         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 661
 662                         if (i+1 >= ELEMENTSOF(ins))
 663                                 return -E2BIG;
 664                 }
 665
 666                 /* nothing matched, drop packet */
 667                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 668         }
 669
 670         /* matched, pass packet */
 671         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 672
 673         /* install filter */
 674         filter = (struct sock_fprog) {
 675                 .len = i,
 676                 .filter = ins,
 677         };
 678         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 679                 return -errno;
 680
 681         m->filter_uptodate = true;
 682         return 0;
 683 }
 684
 685 _public_ int sd_device_monitor_filter_add_match_subsystem_devtype(sd_device_monitor *m, const char *subsystem, const char *devtype) {
 686         _cleanup_free_ char *s = NULL, *d = NULL;
 687         int r;
 688
 689         assert_return(m, -EINVAL);
 690         assert_return(subsystem, -EINVAL);
 691
 692         s = strdup(subsystem);
 693         if (!s)
 694                 return -ENOMEM;
 695
 696         if (devtype) {
 697                 d = strdup(devtype);
 698                 if (!d)
 699                         return -ENOMEM;
 700         }
 701
 702         r = hashmap_ensure_allocated(&m->subsystem_filter, NULL);
 703         if (r < 0)
 704                 return r;
 705
 706         r = hashmap_put(m->subsystem_filter, s, d);
 707         if (r < 0)
 708                 return r;
 709
 710         s = d = NULL;
 711         m->filter_uptodate = false;
 712
 713         return 0;
 714 }
 715
 716 _public_ int sd_device_monitor_filter_add_match_tag(sd_device_monitor *m, const char *tag) {
 717         _cleanup_free_ char *t = NULL;
 718         int r;
 719
 720         assert_return(m, -EINVAL);
 721         assert_return(tag, -EINVAL);
 722
 723         t = strdup(tag);
 724         if (!t)
 725                 return -ENOMEM;
 726
 727         r = set_ensure_allocated(&m->tag_filter, &string_hash_ops);
 728         if (r < 0)
 729                 return r;
 730
 731         r = set_put(m->tag_filter, t);
 732         if (r == -EEXIST)
 733                 return 0;
 734         if (r < 0)
 735                 return r;
 736
 737         TAKE_PTR(t);
 738         m->filter_uptodate = false;
 739
 740         return 0;
 741 }
 742
 743 _public_ int sd_device_monitor_filter_remove(sd_device_monitor *m) {
 744         static const struct sock_fprog filter = { 0, NULL };
 745
 746         assert_return(m, -EINVAL);
 747
 748         m->subsystem_filter = hashmap_free_free_free(m->subsystem_filter);
 749         m->tag_filter = set_free_free(m->tag_filter);
 750
 751         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 752                 return -errno;
 753
 754         m->filter_uptodate = true;
 755         return 0;
 756 }