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         if (setsockopt(m->sock, SOL_SOCKET, SO_PASSCRED, &const_int_one, sizeof(const_int_one)) < 0)
 297                 return log_debug_errno(errno, "Failed to set socket option SO_PASSCRED: %m");
 298
 299         return 0;
 300 }
 301
 302 static sd_device_monitor *device_monitor_free(sd_device_monitor *m) {
 303         assert(m);
 304
 305         (void) sd_device_monitor_detach_event(m);
 306
 307         hashmap_free_free_free(m->subsystem_filter);
 308         set_free_free(m->tag_filter);
 309
 310         return mfree(m);
 311 }
 312
 313 DEFINE_PUBLIC_TRIVIAL_REF_UNREF_FUNC(sd_device_monitor, sd_device_monitor, device_monitor_free);
 314
 315 static int passes_filter(sd_device_monitor *m, sd_device *device) {
 316         const char *tag, *subsystem, *devtype, *s, *d = NULL;
 317         Iterator i;
 318         int r;
 319
 320         assert_return(m, -EINVAL);
 321         assert_return(device, -EINVAL);
 322
 323         if (hashmap_isempty(m->subsystem_filter))
 324                 goto tag;
 325
 326         r = sd_device_get_subsystem(device, &s);
 327         if (r < 0)
 328                 return r;
 329
 330         r = sd_device_get_devtype(device, &d);
 331         if (r < 0 && r != -ENOENT)
 332                 return r;
 333
 334         HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, i) {
 335                 if (!streq(s, subsystem))
 336                         continue;
 337
 338                 if (!devtype)
 339                         goto tag;
 340
 341                 if (!d)
 342                         continue;
 343
 344                 if (streq(d, devtype))
 345                         goto tag;
 346         }
 347
 348         return 0;
 349
 350 tag:
 351         if (set_isempty(m->tag_filter))
 352                 return 1;
 353
 354         SET_FOREACH(tag, m->tag_filter, i)
 355                 if (sd_device_has_tag(device, tag) > 0)
 356                         return 1;
 357
 358         return 0;
 359 }
 360
 361 int device_monitor_receive_device(sd_device_monitor *m, sd_device **ret) {
 362         _cleanup_(sd_device_unrefp) sd_device *device = NULL;
 363         union {
 364                 monitor_netlink_header nlh;
 365                 char raw[8192];
 366         } buf;
 367         struct iovec iov = {
 368                 .iov_base = &buf,
 369                 .iov_len = sizeof(buf)
 370         };
 371         char cred_msg[CMSG_SPACE(sizeof(struct ucred))];
 372         union sockaddr_union snl;
 373         struct msghdr smsg = {
 374                 .msg_iov = &iov,
 375                 .msg_iovlen = 1,
 376                 .msg_control = cred_msg,
 377                 .msg_controllen = sizeof(cred_msg),
 378                 .msg_name = &snl,
 379                 .msg_namelen = sizeof(snl),
 380         };
 381         struct cmsghdr *cmsg;
 382         struct ucred *cred;
 383         ssize_t buflen, bufpos;
 384         bool is_initialized = false;
 385         int r;
 386
 387         assert(ret);
 388
 389         buflen = recvmsg(m->sock, &smsg, 0);
 390         if (buflen < 0) {
 391                 if (errno != EINTR)
 392                         log_debug_errno(errno, "Failed to receive message: %m");
 393                 return -errno;
 394         }
 395
 396         if (buflen < 32 || (smsg.msg_flags & MSG_TRUNC))
 397                 return log_debug_errno(EINVAL, "Invalid message length.");
 398
 399         if (snl.nl.nl_groups == MONITOR_GROUP_NONE) {
 400                 /* unicast message, check if we trust the sender */
 401                 if (m->snl_trusted_sender.nl.nl_pid == 0 ||
 402                     snl.nl.nl_pid != m->snl_trusted_sender.nl.nl_pid)
 403                         return log_debug_errno(EAGAIN, "Unicast netlink message ignored.");
 404
 405         } else if (snl.nl.nl_groups == MONITOR_GROUP_KERNEL) {
 406                 if (snl.nl.nl_pid > 0)
 407                         return log_debug_errno(EAGAIN, "Multicast kernel netlink message from PID %"PRIu32" ignored.", snl.nl.nl_pid);
 408         }
 409
 410         cmsg = CMSG_FIRSTHDR(&smsg);
 411         if (!cmsg || cmsg->cmsg_type != SCM_CREDENTIALS)
 412                 return log_debug_errno(EAGAIN, "No sender credentials received, message ignored.");
 413
 414         cred = (struct ucred*) CMSG_DATA(cmsg);
 415         if (cred->uid != 0)
 416                 return log_debug_errno(EAGAIN, "Sender uid="UID_FMT", message ignored.", cred->uid);
 417
 418         if (streq(buf.raw, "libudev")) {
 419                 /* udev message needs proper version magic */
 420                 if (buf.nlh.magic != htobe32(UDEV_MONITOR_MAGIC))
 421                         return log_debug_errno(EAGAIN, "Invalid message signature (%x != %x)",
 422                                                buf.nlh.magic, htobe32(UDEV_MONITOR_MAGIC));
 423
 424                 if (buf.nlh.properties_off+32 > (size_t) buflen)
 425                         return log_debug_errno(EAGAIN, "Invalid message length (%u > %zd)",
 426                                                buf.nlh.properties_off+32, buflen);
 427
 428                 bufpos = buf.nlh.properties_off;
 429
 430                 /* devices received from udev are always initialized */
 431                 is_initialized = true;
 432
 433         } else {
 434                 /* kernel message with header */
 435                 bufpos = strlen(buf.raw) + 1;
 436                 if ((size_t) bufpos < sizeof("a@/d") || bufpos >= buflen)
 437                         return log_debug_errno(EAGAIN, "Invalid message length");
 438
 439                 /* check message header */
 440                 if (!strstr(buf.raw, "@/"))
 441                         return log_debug_errno(EAGAIN, "Invalid message header");
 442         }
 443
 444         r = device_new_from_nulstr(&device, (uint8_t*) &buf.raw[bufpos], buflen - bufpos);
 445         if (r < 0)
 446                 return log_debug_errno(r, "Failed to create device: %m");
 447
 448         if (is_initialized)
 449                 device_set_is_initialized(device);
 450
 451         /* Skip device, if it does not pass the current filter */
 452         r = passes_filter(m, device);
 453         if (r < 0)
 454                 return log_debug_errno(r, "Failed to check received device passing filter: %m");
 455
 456         if (r == 0)
 457                 log_debug("Received device does not pass filter, ignoring");
 458         else
 459                 *ret = TAKE_PTR(device);
 460
 461         return r;
 462 }
 463
 464 static uint32_t string_hash32(const char *str) {
 465         return MurmurHash2(str, strlen(str), 0);
 466 }
 467
 468 /* Get a bunch of bit numbers out of the hash, and set the bits in our bit field */
 469 static uint64_t string_bloom64(const char *str) {
 470         uint64_t bits = 0;
 471         uint32_t hash = string_hash32(str);
 472
 473         bits |= 1LLU << (hash & 63);
 474         bits |= 1LLU << ((hash >> 6) & 63);
 475         bits |= 1LLU << ((hash >> 12) & 63);
 476         bits |= 1LLU << ((hash >> 18) & 63);
 477         return bits;
 478 }
 479
 480 int device_monitor_send_device(
 481                 sd_device_monitor *m,
 482                 sd_device_monitor *destination,
 483                 sd_device *device) {
 484
 485         monitor_netlink_header nlh = {
 486                 .prefix = "libudev",
 487                 .magic = htobe32(UDEV_MONITOR_MAGIC),
 488                 .header_size = sizeof nlh,
 489         };
 490         struct iovec iov[2] = {
 491                 { .iov_base = &nlh, .iov_len = sizeof nlh },
 492         };
 493         struct msghdr smsg = {
 494                 .msg_iov = iov,
 495                 .msg_iovlen = 2,
 496         };
 497         /* default destination for sending */
 498         union sockaddr_union default_destination = {
 499                 .nl.nl_family = AF_NETLINK,
 500                 .nl.nl_groups = MONITOR_GROUP_UDEV,
 501         };
 502         uint64_t tag_bloom_bits;
 503         const char *buf, *val;
 504         ssize_t count;
 505         size_t blen;
 506         int r;
 507
 508         assert(m);
 509         assert(device);
 510
 511         r = device_get_properties_nulstr(device, (const uint8_t **) &buf, &blen);
 512         if (r < 0)
 513                 return log_debug_errno(r, "Failed to get device properties: %m");
 514         if (blen < 32) {
 515                 log_debug("Device buffer is too small to contain a valid device");
 516                 return -EINVAL;
 517         }
 518
 519         /* fill in versioned header */
 520         r = sd_device_get_subsystem(device, &val);
 521         if (r < 0)
 522                 return log_debug_errno(r, "Failed to get device subsystem: %m");
 523         nlh.filter_subsystem_hash = htobe32(string_hash32(val));
 524
 525         if (sd_device_get_devtype(device, &val) >= 0 && val)
 526                 nlh.filter_devtype_hash = htobe32(string_hash32(val));
 527
 528         /* add tag bloom filter */
 529         tag_bloom_bits = 0;
 530         FOREACH_DEVICE_TAG(device, val)
 531                 tag_bloom_bits |= string_bloom64(val);
 532
 533         if (tag_bloom_bits > 0) {
 534                 nlh.filter_tag_bloom_hi = htobe32(tag_bloom_bits >> 32);
 535                 nlh.filter_tag_bloom_lo = htobe32(tag_bloom_bits & 0xffffffff);
 536         }
 537
 538         /* add properties list */
 539         nlh.properties_off = iov[0].iov_len;
 540         nlh.properties_len = blen;
 541         iov[1] = (struct iovec) {
 542                 .iov_base = (char*) buf,
 543                 .iov_len = blen,
 544         };
 545
 546         /*
 547          * Use custom address for target, or the default one.
 548          *
 549          * If we send to a multicast group, we will get
 550          * ECONNREFUSED, which is expected.
 551          */
 552         smsg.msg_name = destination ? &destination->snl : &default_destination;
 553         smsg.msg_namelen = sizeof(struct sockaddr_nl);
 554         count = sendmsg(m->sock, &smsg, 0);
 555         if (count < 0) {
 556                 if (!destination && errno == ECONNREFUSED) {
 557                         log_debug("Passed device to netlink monitor");
 558                         return 0;
 559                 } else
 560                         return log_debug_errno(errno, "Failed to send device to netlink monitor");
 561         }
 562
 563         log_debug("Passed %zi byte device to netlink monitor", count);
 564         return count;
 565 }
 566
 567 static void bpf_stmt(struct sock_filter *ins, unsigned *i,
 568                      unsigned short code, unsigned data) {
 569         ins[(*i)++] = (struct sock_filter) {
 570                 .code = code,
 571                 .k = data,
 572         };
 573 }
 574
 575 static void bpf_jmp(struct sock_filter *ins, unsigned *i,
 576                     unsigned short code, unsigned data,
 577                     unsigned short jt, unsigned short jf) {
 578         ins[(*i)++] = (struct sock_filter) {
 579                 .code = code,
 580                 .jt = jt,
 581                 .jf = jf,
 582                 .k = data,
 583         };
 584 }
 585
 586 _public_ int sd_device_monitor_filter_update(sd_device_monitor *m) {
 587         struct sock_filter ins[512] = {};
 588         struct sock_fprog filter;
 589         const char *subsystem, *devtype, *tag;
 590         unsigned i = 0;
 591         Iterator it;
 592
 593         assert_return(m, -EINVAL);
 594
 595         if (hashmap_isempty(m->subsystem_filter) &&
 596             set_isempty(m->tag_filter)) {
 597                 m->filter_uptodate = true;
 598                 return 0;
 599         }
 600
 601         /* load magic in A */
 602         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, magic));
 603         /* jump if magic matches */
 604         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, UDEV_MONITOR_MAGIC, 1, 0);
 605         /* wrong magic, pass packet */
 606         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 607
 608         if (!set_isempty(m->tag_filter)) {
 609                 int tag_matches = set_size(m->tag_filter);
 610
 611                 /* add all tags matches */
 612                 SET_FOREACH(tag, m->tag_filter, it) {
 613                         uint64_t tag_bloom_bits = string_bloom64(tag);
 614                         uint32_t tag_bloom_hi = tag_bloom_bits >> 32;
 615                         uint32_t tag_bloom_lo = tag_bloom_bits & 0xffffffff;
 616
 617                         /* load device bloom bits in A */
 618                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_hi));
 619                         /* clear bits (tag bits & bloom bits) */
 620                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_hi);
 621                         /* jump to next tag if it does not match */
 622                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_hi, 0, 3);
 623
 624                         /* load device bloom bits in A */
 625                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_tag_bloom_lo));
 626                         /* clear bits (tag bits & bloom bits) */
 627                         bpf_stmt(ins, &i, BPF_ALU|BPF_AND|BPF_K, tag_bloom_lo);
 628                         /* jump behind end of tag match block if tag matches */
 629                         tag_matches--;
 630                         bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, tag_bloom_lo, 1 + (tag_matches * 6), 0);
 631                 }
 632
 633                 /* nothing matched, drop packet */
 634                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 635         }
 636
 637         /* add all subsystem matches */
 638         if (!hashmap_isempty(m->subsystem_filter)) {
 639                 HASHMAP_FOREACH_KEY(devtype, subsystem, m->subsystem_filter, it) {
 640                         uint32_t hash = string_hash32(subsystem);
 641
 642                         /* load device subsystem value in A */
 643                         bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_subsystem_hash));
 644                         if (!devtype) {
 645                                 /* jump if subsystem does not match */
 646                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 647                         } else {
 648                                 hash = string_hash32(devtype);
 649
 650                                 /* jump if subsystem does not match */
 651                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 3);
 652                                 /* load device devtype value in A */
 653                                 bpf_stmt(ins, &i, BPF_LD|BPF_W|BPF_ABS, offsetof(monitor_netlink_header, filter_devtype_hash));
 654                                 /* jump if value does not match */
 655                                 bpf_jmp(ins, &i, BPF_JMP|BPF_JEQ|BPF_K, hash, 0, 1);
 656                         }
 657
 658                         /* matched, pass packet */
 659                         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 660
 661                         if (i+1 >= ELEMENTSOF(ins))
 662                                 return -E2BIG;
 663                 }
 664
 665                 /* nothing matched, drop packet */
 666                 bpf_stmt(ins, &i, BPF_RET|BPF_K, 0);
 667         }
 668
 669         /* matched, pass packet */
 670         bpf_stmt(ins, &i, BPF_RET|BPF_K, 0xffffffff);
 671
 672         /* install filter */
 673         filter = (struct sock_fprog) {
 674                 .len = i,
 675                 .filter = ins,
 676         };
 677         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 678                 return -errno;
 679
 680         m->filter_uptodate = true;
 681         return 0;
 682 }
 683
 684 _public_ int sd_device_monitor_filter_add_match_subsystem_devtype(sd_device_monitor *m, const char *subsystem, const char *devtype) {
 685         _cleanup_free_ char *s = NULL, *d = NULL;
 686         int r;
 687
 688         assert_return(m, -EINVAL);
 689         assert_return(subsystem, -EINVAL);
 690
 691         s = strdup(subsystem);
 692         if (!s)
 693                 return -ENOMEM;
 694
 695         if (devtype) {
 696                 d = strdup(devtype);
 697                 if (!d)
 698                         return -ENOMEM;
 699         }
 700
 701         r = hashmap_ensure_allocated(&m->subsystem_filter, NULL);
 702         if (r < 0)
 703                 return r;
 704
 705         r = hashmap_put(m->subsystem_filter, s, d);
 706         if (r < 0)
 707                 return r;
 708
 709         s = d = NULL;
 710         m->filter_uptodate = false;
 711
 712         return 0;
 713 }
 714
 715 _public_ int sd_device_monitor_filter_add_match_tag(sd_device_monitor *m, const char *tag) {
 716         _cleanup_free_ char *t = NULL;
 717         int r;
 718
 719         assert_return(m, -EINVAL);
 720         assert_return(tag, -EINVAL);
 721
 722         t = strdup(tag);
 723         if (!t)
 724                 return -ENOMEM;
 725
 726         r = set_ensure_allocated(&m->tag_filter, &string_hash_ops);
 727         if (r < 0)
 728                 return r;
 729
 730         r = set_put(m->tag_filter, t);
 731         if (r == -EEXIST)
 732                 return 0;
 733         if (r < 0)
 734                 return r;
 735
 736         TAKE_PTR(t);
 737         m->filter_uptodate = false;
 738
 739         return 0;
 740 }
 741
 742 _public_ int sd_device_monitor_filter_remove(sd_device_monitor *m) {
 743         static const struct sock_fprog filter = { 0, NULL };
 744
 745         assert_return(m, -EINVAL);
 746
 747         m->subsystem_filter = hashmap_free_free_free(m->subsystem_filter);
 748         m->tag_filter = set_free_free(m->tag_filter);
 749
 750         if (setsockopt(m->sock, SOL_SOCKET, SO_ATTACH_FILTER, &filter, sizeof(filter)) < 0)
 751                 return -errno;
 752
 753         m->filter_uptodate = true;
 754         return 0;
 755 }