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 r, n = (int) size;
  92
  93         assert_return(m, -EINVAL);
  94         assert_return((size_t) n != size, -EINVAL);
  95
  96         if (setsockopt_int(m->sock, SOL_SOCKET, SO_RCVBUF, n) < 0) {
  97                 r = setsockopt_int(m->sock, SOL_SOCKET, SO_RCVBUFFORCE, n);
  98                 if (r < 0)
  99                         return r;
 100         }
 101
 102         return 0;
 103 }
 104
 105 int device_monitor_disconnect(sd_device_monitor *m) {
 106         assert(m);
 107
 108         m->sock = safe_close(m->sock);
 109         return 0;
 110 }
 111
 112 int device_monitor_get_fd(sd_device_monitor *m) {
 113         assert_return(m, -EINVAL);
 114
 115         return m->sock;
 116 }
 117
 118 int device_monitor_new_full(sd_device_monitor **ret, MonitorNetlinkGroup group, int fd) {
 119         _cleanup_(sd_device_monitor_unrefp) sd_device_monitor *m = NULL;
 120         _cleanup_close_ int sock = -1;
 121         int r;
 122
 123         assert_return(ret, -EINVAL);
 124         assert_return(group >= 0 && group < _MONITOR_NETLINK_GROUP_MAX, -EINVAL);
 125
 126         if (group == MONITOR_GROUP_UDEV &&
 127             access("/run/udev/control", F_OK) < 0 &&
 128             dev_is_devtmpfs() <= 0) {
 129
 130                 /*
 131                  * We do not support subscribing to uevents if no instance of
 132                  * udev is running. Uevents would otherwise broadcast the
 133                  * processing data of the host into containers, which is not
 134                  * desired.
 135                  *
 136                  * Containers will currently not get any udev uevents, until
 137                  * a supporting infrastructure is available.
 138                  *
 139                  * We do not set a netlink multicast group here, so the socket
 140                  * will not receive any messages.
 141                  */
 142
 143                 log_debug("The udev service seems not to be active, disabling the monitor");
 144                 group = MONITOR_GROUP_NONE;
 145         }
 146
 147         if (fd < 0) {
 148                 sock = socket(PF_NETLINK, SOCK_RAW|SOCK_CLOEXEC|SOCK_NONBLOCK, NETLINK_KOBJECT_UEVENT);
 149                 if (sock < 0)
 150                         return log_debug_errno(errno, "Failed to create socket: %m");
 151         }
 152
 153         m = new(sd_device_monitor, 1);
 154         if (!m)
 155                 return -ENOMEM;
 156
 157         *m = (sd_device_monitor) {
 158                 .n_ref = 1,
 159                 .sock = fd >= 0 ? fd : TAKE_FD(sock),
 160                 .bound = fd >= 0,
 161                 .snl.nl.nl_family = AF_NETLINK,
 162                 .snl.nl.nl_groups = group,
 163         };
 164
 165         if (fd >= 0) {
 166                 r = monitor_set_nl_address(m);
 167                 if (r < 0)
 168                         return log_debug_errno(r, "Failed to set netlink address: %m");
 169         }
 170
 171         *ret = TAKE_PTR(m);
 172         return 0;
 173 }
 174
 175 _public_ int sd_device_monitor_new(sd_device_monitor **ret) {
 176         return device_monitor_new_full(ret, MONITOR_GROUP_UDEV, -1);
 177 }
 178
 179 _public_ int sd_device_monitor_stop(sd_device_monitor *m) {
 180         assert_return(m, -EINVAL);
 181
 182         m->event_source = sd_event_source_unref(m->event_source);
 183         (void) device_monitor_disconnect(m);
 184
 185         return 0;
 186 }
 187
 188 static int device_monitor_event_handler(sd_event_source *s, int fd, uint32_t revents, void *userdata) {
 189         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 190         sd_device_monitor *m = userdata;
 191
 192         assert(m);
 193
 194         if (device_monitor_receive_device(m, &device) <= 0)
 195                 return 0;
 196
 197         if (m->callback)
 198                 return m->callback(m, device, m->userdata);
 199
 200         return 0;
 201 }
 202
 203 _public_ int sd_device_monitor_start(sd_device_monitor *m, sd_device_monitor_handler_t callback, void *userdata, const char *description) {
 204         _cleanup_(sd_event_source_unrefp) sd_event_source *s = NULL;
 205         int r;
 206
 207         assert_return(m, -EINVAL);
 208
 209         if (!m->event) {
 210                 r = sd_device_monitor_attach_event(m, NULL, 0);
 211                 if (r < 0)
 212                         return r;
 213         }
 214
 215         r = device_monitor_enable_receiving(m);
 216         if (r < 0)
 217                 return r;
 218
 219         m->callback = callback;
 220         m->userdata = userdata;
 221
 222         r = sd_event_add_io(m->event, &s, m->sock, EPOLLIN, device_monitor_event_handler, m);
 223         if (r < 0)
 224                 return r;
 225
 226         r = sd_event_source_set_priority(s, m->event_priority);
 227         if (r < 0)
 228                 return r;
 229
 230         if (description) {
 231                 r = sd_event_source_set_description(s, description);
 232                 if (r < 0)
 233                         return r;
 234         }
 235
 236         m->event_source = TAKE_PTR(s);
 237
 238         return 0;
 239 }
 240
 241 _public_ int sd_device_monitor_detach_event(sd_device_monitor *m) {
 242         assert_return(m, -EINVAL);
 243
 244         (void) sd_device_monitor_stop(m);
 245         m->event = sd_event_unref(m->event);
 246
 247         return 0;
 248 }
 249
 250 _public_ int sd_device_monitor_attach_event(sd_device_monitor *m, sd_event *event, int64_t priority) {
 251         int r;
 252
 253         assert_return(m, -EINVAL);
 254         assert_return(!m->event, -EBUSY);
 255
 256         if (event)
 257                 m->event = sd_event_ref(event);
 258         else {
 259                 r = sd_event_default(&m->event);
 260                 if (r < 0)
 261                         return 0;
 262         }
 263
 264         m->event_priority = priority;
 265
 266         return 0;
 267 }
 268
 269 _public_ sd_event *sd_device_monitor_get_event(sd_device_monitor *m) {
 270         assert_return(m, NULL);
 271
 272         return m->event;
 273 }
 274
 275 int device_monitor_enable_receiving(sd_device_monitor *m) {
 276         int r;
 277
 278         assert_return(m, -EINVAL);
 279
 280         if (!m->filter_uptodate) {
 281                 r = sd_device_monitor_filter_update(m);
 282                 if (r < 0)
 283                         return log_debug_errno(r, "Failed to update filter: %m");
 284         }
 285
 286         if (!m->bound) {
 287                 if (bind(m->sock, &m->snl.sa, sizeof(struct sockaddr_nl)) < 0)
 288                         return log_debug_errno(errno, "Failed to bind monitoring socket to event source: %m");
 289
 290                 m->bound = true;
 291         }
 292
 293         r = monitor_set_nl_address(m);
 294         if (r < 0)
 295                 return log_debug_errno(r, "Failed to set address: %m");
 296
 297         /* enable receiving of sender credentials */
 298         r = setsockopt_int(m->sock, SOL_SOCKET, SO_PASSCRED, true);
 299         if (r < 0)
 300                 return log_debug_errno(r, "Failed to set socket option SO_PASSCRED: %m");
 301
 302         return 0;
 303 }
 304
 305 static sd_device_monitor *device_monitor_free(sd_device_monitor *m) {
 306         assert(m);
 307
 308         (void) sd_device_monitor_detach_event(m);
 309
 310         hashmap_free_free_free(m->subsystem_filter);
 311         set_free_free(m->tag_filter);
 312
 313         return mfree(m);
 314 }
 315
 316 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_monitor, sd_device_monitor, device_monitor_free);
 317
 318 static int passes_filter(sd_device_monitor *m, sd_device *device) {
 319         const char *tag, *subsystem, *devtype, *s, *d = NULL;
 320         Iterator i;
 321         int r;
 322
 323         assert_return(m, -EINVAL);
 324         assert_return(device, -EINVAL);
 325
 326         if (hashmap_isempty(m->subsystem_filter))
 327                 goto tag;
 328
 329         r = sd_device_get_subsystem(device, &s);
 330         if (r < 0)
 331                 return r;
 332
 333         r = sd_device_get_devtype(device, &d);
 334         if (r < 0 && r != -ENOENT)
 335                 return r;
 336
 337         HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, i) {
 338                 if (!streq(s, subsystem))
 339                         continue;
 340
 341                 if (!devtype)
 342                         goto tag;
 343
 344                 if (!d)
 345                         continue;
 346
 347                 if (streq(d, devtype))
 348                         goto tag;
 349         }
 350
 351         return 0;
 352
 353 tag:
 354         if (set_isempty(m->tag_filter))
 355                 return 1;
 356
 357         SET_FOREACH(tag, m->tag_filter, i)
 358                 if (sd_device_has_tag(device, tag) > 0)
 359                         return 1;
 360
 361         return 0;
 362 }
 363
 364 int device_monitor_receive_device(sd_device_monitor *m, sd_device **ret) {
 365         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 366         union {
 367                 monitor_netlink_header nlh;
 368                 char raw[8192];
 369         } buf;
 370         struct iovec iov = {
 371                 .iov_base = &buf,
 372                 .iov_len = sizeof(buf)
 373         };
 374         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 375         union sockaddr_union snl;
 376         struct msghdr smsg = {
 377                 .msg_iov = &iov,
 378                 .msg_iovlen = 1,
 379                 .msg_control = cred_msg,
 380                 .msg_controllen = sizeof(cred_msg),
 381                 .msg_name = &snl,
 382                 .msg_namelen = sizeof(snl),
 383         };
 384         struct cmsghdr *cmsg;
 385         struct ucred *cred;
 386         ssize_t buflen, bufpos;
 387         bool is_initialized = false;
 388         int r;
 389
 390         assert(ret);
 391
 392         buflen = recvmsg(m->sock, &smsg, 0);
 393         if (buflen < 0) {
 394                 if (errno != EINTR)
 395                         log_debug_errno(errno, "Failed to receive message: %m");
 396                 return -errno;
 397         }
 398
 399         if (buflen < 32 || (smsg.msg_flags & MSG_TRUNC))
 400                 return log_debug_errno(EINVAL, "Invalid message length.");
 401
 402         if (snl.nl.nl_groups == MONITOR_GROUP_NONE) {
 403                 /* unicast message, check if we trust the sender */
 404                 if (m->snl_trusted_sender.nl.nl_pid == 0 ||
 405                     snl.nl.nl_pid != m->snl_trusted_sender.nl.nl_pid)
 406                         return log_debug_errno(EAGAIN, "Unicast netlink message ignored.");
 407
 408         } else if (snl.nl.nl_groups == MONITOR_GROUP_KERNEL) {
 409                 if (snl.nl.nl_pid > 0)
 410                         return log_debug_errno(EAGAIN, "Multicast kernel netlink message from PID %"PRIu32" ignored.", snl.nl.nl_pid);
 411         }
 412
 413         cmsg = CMSG_FIRSTHDR(&smsg);
 414         if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS)
 415                 return log_debug_errno(EAGAIN, "No sender credentials received, message ignored.");
 416
 417         cred = (struct ucred*) CMSG_DATA(cmsg);
 418         if (cred->uid != 0)
 419                 return log_debug_errno(EAGAIN, "Sender uid="UID_FMT", message ignored.", cred->uid);
 420
 421         if (streq(buf.raw, "libudev")) {
 422                 /* udev message needs proper version magic */
 423                 if (buf.nlh.magic != htobe32(UDEV_MONITOR_MAGIC))
 424                         return log_debug_errno(EAGAIN, "Invalid message signature (%x != %x)",
 425                                                buf.nlh.magic, htobe32(UDEV_MONITOR_MAGIC));
 426
 427                 if (buf.nlh.properties_off+32 > (size_t) buflen)
 428                         return log_debug_errno(EAGAIN, "Invalid message length (%u > %zd)",
 429                                                buf.nlh.properties_off+32, buflen);
 430
 431                 bufpos = buf.nlh.properties_off;
 432
 433                 /* devices received from udev are always initialized */
 434                 is_initialized = true;
 435
 436         } else {
 437                 /* kernel message with header */
 438                 bufpos = strlen(buf.raw) + 1;
 439                 if ((size_t) bufpos < sizeof("a@/d") || bufpos >= buflen)
 440                         return log_debug_errno(EAGAIN, "Invalid message length");
 441
 442                 /* check message header */
 443                 if (!strstr(buf.raw, "@/"))
 444                         return log_debug_errno(EAGAIN, "Invalid message header");
 445         }
 446
 447         r = device_new_from_nulstr(&device, (uint8_t*) &buf.raw[bufpos], buflen - bufpos);
 448         if (r < 0)
 449                 return log_debug_errno(r, "Failed to create device: %m");
 450
 451         if (is_initialized)
 452                 device_set_is_initialized(device);
 453
 454         /* Skip device, if it does not pass the current filter */
 455         r = passes_filter(m, device);
 456         if (r < 0)
 457                 return log_debug_errno(r, "Failed to check received device passing filter: %m");
 458
 459         if (r == 0)
 460                 log_debug("Received device does not pass filter, ignoring");
 461         else
 462                 *ret = TAKE_PTR(device);
 463
 464         return r;
 465 }
 466
 467 static uint32_t string_hash32(const char *str) {
 468         return MurmurHash2(str, strlen(str), 0);
 469 }
 470
 471 /* Get a bunch of bit numbers out of the hash, and set the bits in our bit field */
 472 static uint64_t string_bloom64(const char *str) {
 473         uint64_t bits = 0;
 474         uint32_t hash = string_hash32(str);
 475
 476         bits |= 1LLU << (hash & 63);
 477         bits |= 1LLU << ((hash >> 6) & 63);
 478         bits |= 1LLU << ((hash >> 12) & 63);
 479         bits |= 1LLU << ((hash >> 18) & 63);
 480         return bits;
 481 }
 482
 483 int device_monitor_send_device(
 484                 sd_device_monitor *m,
 485                 sd_device_monitor *destination,
 486                 sd_device *device) {
 487
 488         monitor_netlink_header nlh = {
 489                 .prefix = "libudev",
 490                 .magic = htobe32(UDEV_MONITOR_MAGIC),
 491                 .header_size = sizeof nlh,
 492         };
 493         struct iovec iov[2] = {
 494                 { .iov_base = &nlh, .iov_len = sizeof nlh },
 495         };
 496         struct msghdr smsg = {
 497                 .msg_iov = iov,
 498                 .msg_iovlen = 2,
 499         };
 500         /* default destination for sending */
 501         union sockaddr_union default_destination = {
 502                 .nl.nl_family = AF_NETLINK,
 503                 .nl.nl_groups = MONITOR_GROUP_UDEV,
 504         };
 505         uint64_t tag_bloom_bits;
 506         const char *buf, *val;
 507         ssize_t count;
 508         size_t blen;
 509         int r;
 510
 511         assert(m);
 512         assert(device);
 513
 514         r = device_get_properties_nulstr(device, (const uint8_t **) &buf, &blen);
 515         if (r < 0)
 516                 return log_debug_errno(r, "Failed to get device properties: %m");
 517         if (blen < 32) {
 518                 log_debug("Device buffer is too small to contain a valid device");
 519                 return -EINVAL;
 520         }
 521
 522         /* fill in versioned header */
 523         r = sd_device_get_subsystem(device, &val);
 524         if (r < 0)
 525                 return log_debug_errno(r, "Failed to get device subsystem: %m");
 526         nlh.filter_subsystem_hash = htobe32(string_hash32(val));
 527
 528         if (sd_device_get_devtype(device, &val) >= 0)
 529                 nlh.filter_devtype_hash = htobe32(string_hash32(val));
 530
 531         /* add tag bloom filter */
 532         tag_bloom_bits = 0;
 533         FOREACH_DEVICE_TAG(device, val)
 534                 tag_bloom_bits |= string_bloom64(val);
 535
 536         if (tag_bloom_bits > 0) {
 537                 nlh.filter_tag_bloom_hi = htobe32(tag_bloom_bits >> 32);
 538                 nlh.filter_tag_bloom_lo = htobe32(tag_bloom_bits & 0xffffffff);
 539         }
 540
 541         /* add properties list */
 542         nlh.properties_off = iov[0].iov_len;
 543         nlh.properties_len = blen;
 544         iov[1] = (struct iovec) {
 545                 .iov_base = (char*) buf,
 546                 .iov_len = blen,
 547         };
 548
 549         /*
 550          * Use custom address for target, or the default one.
 551          *
 552          * If we send to a multicast group, we will get
 553          * ECONNREFUSED, which is expected.
 554          */
 555         smsg.msg_name = destination ? &destination->snl : &default_destination;
 556         smsg.msg_namelen = sizeof(struct sockaddr_nl);
 557         count = sendmsg(m->sock, &smsg, 0);
 558         if (count < 0) {
 559                 if (!destination && errno == ECONNREFUSED) {
 560                         log_debug("Passed device to netlink monitor");
 561                         return 0;
 562                 } else
 563                         return log_debug_errno(errno, "Failed to send device to netlink monitor: %m");
 564         }
 565
 566         log_debug("Passed %zi byte device to netlink monitor", count);
 567         return count;
 568 }
 569
 570 static void bpf_stmt(struct sock_filter *ins, unsigned *i,
 571                      unsigned short code, unsigned data) {
 572         ins[(*i)++] = (struct sock_filter) {
 573                 .code = code,
 574                 .k = data,
 575         };
 576 }
 577
 578 static void bpf_jmp(struct sock_filter *ins, unsigned *i,
 579                     unsigned short code, unsigned data,
 580                     unsigned short jt, unsigned short jf) {
 581         ins[(*i)++] = (struct sock_filter) {
 582                 .code = code,
 583                 .jt = jt,
 584                 .jf = jf,
 585                 .k = data,
 586         };
 587 }
 588
 589 _public_ int sd_device_monitor_filter_update(sd_device_monitor *m) {
 590         struct sock_filter ins[512] = {};
 591         struct sock_fprog filter;
 592         const char *subsystem, *devtype, *tag;
 593         unsigned i = 0;
 594         Iterator it;
 595
 596         assert_return(m, -EINVAL);
 597
 598         if (hashmap_isempty(m->subsystem_filter) &&
 599             set_isempty(m->tag_filter)) {
 600                 m->filter_uptodate = true;
 601                 return 0;
 602         }
 603
 604         /* load magic in A */
 605         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, magic));
 606         /* jump if magic matches */
 607         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
 608         /* wrong magic, pass packet */
 609         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 610
 611         if (!set_isempty(m->tag_filter)) {
 612                 int tag_matches = set_size(m->tag_filter);
 613
 614                 /* add all tags matches */
 615                 SET_FOREACH(tag, m->tag_filter, it) {
 616                         uint64_t tag_bloom_bits = string_bloom64(tag);
 617                         uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
 618                         uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
 619
 620                         /* load device bloom bits in A */
 621                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_hi));
 622                         /* clear bits (tag bits & bloom bits) */
 623                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
 624                         /* jump to next tag if it does not match */
 625                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
 626
 627                         /* load device bloom bits in A */
 628                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_lo));
 629                         /* clear bits (tag bits & bloom bits) */
 630                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
 631                         /* jump behind end of tag match block if tag matches */
 632                         tag_matches--;
 633                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
 634                 }
 635
 636                 /* nothing matched, drop packet */
 637                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 638         }
 639
 640         /* add all subsystem matches */
 641         if (!hashmap_isempty(m->subsystem_filter)) {
 642                 HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, it) {
 643                         uint32_t hash = string_hash32(subsystem);
 644
 645                         /* load device subsystem value in A */
 646                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_subsystem_hash));
 647                         if (!devtype) {
 648                                 /* jump if subsystem does not match */
 649                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 650                         } else {
 651                                 hash = string_hash32(devtype);
 652
 653                                 /* jump if subsystem does not match */
 654                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
 655                                 /* load device devtype value in A */
 656                                 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_devtype_hash));
 657                                 /* jump if value does not match */
 658                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 659                         }
 660
 661                         /* matched, pass packet */
 662                         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 663
 664                         if (i+1 >= ELEMENTSOF(ins))
 665                                 return -E2BIG;
 666                 }
 667
 668                 /* nothing matched, drop packet */
 669                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 670         }
 671
 672         /* matched, pass packet */
 673         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 674
 675         /* install filter */
 676         filter = (struct sock_fprog) {
 677                 .len = i,
 678                 .filter = ins,
 679         };
 680         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 681                 return -errno;
 682
 683         m->filter_uptodate = true;
 684         return 0;
 685 }
 686
 687 _public_ int sd_device_monitor_filter_add_match_subsystem_devtype(sd_device_monitor *m, const char *subsystem, const char *devtype) {
 688         _cleanup_free_ char *s = NULL, *d = NULL;
 689         int r;
 690
 691         assert_return(m, -EINVAL);
 692         assert_return(subsystem, -EINVAL);
 693
 694         s = strdup(subsystem);
 695         if (!s)
 696                 return -ENOMEM;
 697
 698         if (devtype) {
 699                 d = strdup(devtype);
 700                 if (!d)
 701                         return -ENOMEM;
 702         }
 703
 704         r = hashmap_ensure_allocated(&m->subsystem_filter, NULL);
 705         if (r < 0)
 706                 return r;
 707
 708         r = hashmap_put(m->subsystem_filter, s, d);
 709         if (r < 0)
 710                 return r;
 711
 712         s = d = NULL;
 713         m->filter_uptodate = false;
 714
 715         return 0;
 716 }
 717
 718 _public_ int sd_device_monitor_filter_add_match_tag(sd_device_monitor *m, const char *tag) {
 719         _cleanup_free_ char *t = NULL;
 720         int r;
 721
 722         assert_return(m, -EINVAL);
 723         assert_return(tag, -EINVAL);
 724
 725         t = strdup(tag);
 726         if (!t)
 727                 return -ENOMEM;
 728
 729         r = set_ensure_allocated(&m->tag_filter, &string_hash_ops);
 730         if (r < 0)
 731                 return r;
 732
 733         r = set_put(m->tag_filter, t);
 734         if (r == -EEXIST)
 735                 return 0;
 736         if (r < 0)
 737                 return r;
 738
 739         TAKE_PTR(t);
 740         m->filter_uptodate = false;
 741
 742         return 0;
 743 }
 744
 745 _public_ int sd_device_monitor_filter_remove(sd_device_monitor *m) {
 746         static const struct sock_fprog filter = { 0, NULL };
 747
 748         assert_return(m, -EINVAL);
 749
 750         m->subsystem_filter = hashmap_free_free_free(m->subsystem_filter);
 751         m->tag_filter = set_free_free(m->tag_filter);
 752
 753         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 754                 return -errno;
 755
 756         m->filter_uptodate = true;
 757         return 0;
 758 }