lib/dpif-linux.c

   1 /*
   2  * Copyright (c) 2008, 2009 Nicira Networks.
   3  *
   4  * Licensed under the Apache License, Version 2.0 (the "License");
   5  * you may not use this file except in compliance with the License.
   6  * You may obtain a copy of the License at:
   7  *
   8  *     http://www.apache.org/licenses/LICENSE-2.0
   9  *
  10  * Unless required by applicable law or agreed to in writing, software
  11  * distributed under the License is distributed on an "AS IS" BASIS,
  12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  13  * See the License for the specific language governing permissions and
  14  * limitations under the License.
  15  */
  16
  17 #include <config.h>
  18 #include "dpif.h"
  19
  20 #include <assert.h>
  21 #include <ctype.h>
  22 #include <errno.h>
  23 #include <fcntl.h>
  24 #include <inttypes.h>
  25 #include <net/if.h>
  26 #include <linux/ethtool.h>
  27 #include <linux/rtnetlink.h>
  28 #include <linux/sockios.h>
  29 #include <stdlib.h>
  30 #include <sys/ioctl.h>
  31 #include <unistd.h>
  32
  33 #include "dpif-provider.h"
  34 #include "ofpbuf.h"
  35 #include "poll-loop.h"
  36 #include "rtnetlink.h"
  37 #include "svec.h"
  38 #include "util.h"
  39
  40 #include "vlog.h"
  41 #define THIS_MODULE VLM_dpif_linux
  42
  43 /* Datapath interface for the openvswitch Linux kernel module. */
  44 struct dpif_linux {
  45     struct dpif dpif;
  46     int fd;
  47
  48     /* Used by dpif_linux_get_all_names(). */
  49     char *local_ifname;
  50     int minor;
  51
  52     /* Change notification. */
  53     int local_ifindex;          /* Ifindex of local port. */
  54     struct svec changed_ports;  /* Ports that have changed. */
  55     struct rtnetlink_notifier port_notifier;
  56     bool change_error;
  57 };
  58
  59 static struct vlog_rate_limit error_rl = VLOG_RATE_LIMIT_INIT(9999, 5);
  60
  61 static int do_ioctl(const struct dpif *, int cmd, const void *arg);
  62 static int lookup_minor(const char *name, int *minor);
  63 static int finish_open(struct dpif *, const char *local_ifname);
  64 static int get_openvswitch_major(void);
  65 static int create_minor(const char *name, int minor, struct dpif **dpifp);
  66 static int open_minor(int minor, struct dpif **dpifp);
  67 static int make_openvswitch_device(int minor, char **fnp);
  68 static void dpif_linux_port_changed(const struct rtnetlink_change *,
  69                                     void *dpif);
  70
  71 static struct dpif_linux *
  72 dpif_linux_cast(const struct dpif *dpif)
  73 {
  74     dpif_assert_class(dpif, &dpif_linux_class);
  75     return CONTAINER_OF(dpif, struct dpif_linux, dpif);
  76 }
  77
  78 static int
  79 dpif_linux_enumerate(struct svec *all_dps)
  80 {
  81     int major;
  82     int error;
  83     int i;
  84
  85     /* Check that the Open vSwitch module is loaded. */
  86     major = get_openvswitch_major();
  87     if (major < 0) {
  88         return -major;
  89     }
  90
  91     error = 0;
  92     for (i = 0; i < ODP_MAX; i++) {
  93         struct dpif *dpif;
  94         char devname[16];
  95         int retval;
  96
  97         sprintf(devname, "dp%d", i);
  98         retval = dpif_open(devname, &dpif);
  99         if (!retval) {
 100             svec_add(all_dps, devname);
 101             dpif_close(dpif);
 102         } else if (retval != ENODEV && !error) {
 103             error = retval;
 104         }
 105     }
 106     return error;
 107 }
 108
 109 static int
 110 dpif_linux_open(const char *name UNUSED, char *suffix, bool create,
 111                 struct dpif **dpifp)
 112 {
 113     int minor;
 114
 115     minor = !strncmp(name, "dp", 2)
 116             && isdigit((unsigned char)name[2]) ? atoi(name + 2) : -1;
 117     if (create) {
 118         if (minor >= 0) {
 119             return create_minor(suffix, minor, dpifp);
 120         } else {
 121             /* Scan for unused minor number. */
 122             for (minor = 0; minor < ODP_MAX; minor++) {
 123                 int error = create_minor(suffix, minor, dpifp);
 124                 if (error != EBUSY) {
 125                     return error;
 126                 }
 127             }
 128
 129             /* All datapath numbers in use. */
 130             return ENOBUFS;
 131         }
 132     } else {
 133         struct dpif_linux *dpif;
 134         struct odp_port port;
 135         int error;
 136
 137         if (minor < 0) {
 138             error = lookup_minor(suffix, &minor);
 139             if (error) {
 140                 return error;
 141             }
 142         }
 143
 144         error = open_minor(minor, dpifp);
 145         if (error) {
 146             return error;
 147         }
 148         dpif = dpif_linux_cast(*dpifp);
 149
 150         /* We need the local port's ifindex for the poll function.  Start by
 151          * getting the local port's name. */
 152         memset(&port, 0, sizeof port);
 153         port.port = ODPP_LOCAL;
 154         if (ioctl(dpif->fd, ODP_PORT_QUERY, &port)) {
 155             error = errno;
 156             if (error != ENODEV) {
 157                 VLOG_WARN("%s: probe returned unexpected error: %s",
 158                           dpif_name(*dpifp), strerror(error));
 159             }
 160             dpif_close(*dpifp);
 161             return error;
 162         }
 163
 164         /* Then use that to finish up opening. */
 165         return finish_open(&dpif->dpif, port.devname);
 166     }
 167 }
 168
 169 static void
 170 dpif_linux_close(struct dpif *dpif_)
 171 {
 172     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 173     rtnetlink_notifier_unregister(&dpif->port_notifier);
 174     svec_destroy(&dpif->changed_ports);
 175     free(dpif->local_ifname);
 176     close(dpif->fd);
 177     free(dpif);
 178 }
 179
 180 static int
 181 dpif_linux_get_all_names(const struct dpif *dpif_, struct svec *all_names)
 182 {
 183     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 184
 185     svec_add_nocopy(all_names, xasprintf("dp%d", dpif->minor));
 186     svec_add(all_names, dpif->local_ifname);
 187     return 0;
 188 }
 189
 190 static int
 191 dpif_linux_delete(struct dpif *dpif_)
 192 {
 193     return do_ioctl(dpif_, ODP_DP_DESTROY, NULL);
 194 }
 195
 196 static int
 197 dpif_linux_get_stats(const struct dpif *dpif_, struct odp_stats *stats)
 198 {
 199     return do_ioctl(dpif_, ODP_DP_STATS, stats);
 200 }
 201
 202 static int
 203 dpif_linux_get_drop_frags(const struct dpif *dpif_, bool *drop_fragsp)
 204 {
 205     int drop_frags;
 206     int error;
 207
 208     error = do_ioctl(dpif_, ODP_GET_DROP_FRAGS, &drop_frags);
 209     if (!error) {
 210         *drop_fragsp = drop_frags & 1;
 211     }
 212     return error;
 213 }
 214
 215 static int
 216 dpif_linux_set_drop_frags(struct dpif *dpif_, bool drop_frags)
 217 {
 218     int drop_frags_int = drop_frags;
 219     return do_ioctl(dpif_, ODP_SET_DROP_FRAGS, &drop_frags_int);
 220 }
 221
 222 static int
 223 dpif_linux_port_add(struct dpif *dpif_, const char *devname, uint16_t flags,
 224                     uint16_t *port_no)
 225 {
 226     struct odp_port port;
 227     int error;
 228
 229     memset(&port, 0, sizeof port);
 230     strncpy(port.devname, devname, sizeof port.devname);
 231     port.flags = flags;
 232     error = do_ioctl(dpif_, ODP_PORT_ADD, &port);
 233     if (!error) {
 234         *port_no = port.port;
 235     }
 236     return error;
 237 }
 238
 239 static int
 240 dpif_linux_port_del(struct dpif *dpif_, uint16_t port_no)
 241 {
 242     int tmp = port_no;
 243     return do_ioctl(dpif_, ODP_PORT_DEL, &tmp);
 244 }
 245
 246 static int
 247 dpif_linux_port_query_by_number(const struct dpif *dpif_, uint16_t port_no,
 248                           struct odp_port *port)
 249 {
 250     memset(port, 0, sizeof *port);
 251     port->port = port_no;
 252     return do_ioctl(dpif_, ODP_PORT_QUERY, port);
 253 }
 254
 255 static int
 256 dpif_linux_port_query_by_name(const struct dpif *dpif_, const char *devname,
 257                               struct odp_port *port)
 258 {
 259     memset(port, 0, sizeof *port);
 260     strncpy(port->devname, devname, sizeof port->devname);
 261     return do_ioctl(dpif_, ODP_PORT_QUERY, port);
 262 }
 263
 264 static int
 265 dpif_linux_flow_flush(struct dpif *dpif_)
 266 {
 267     return do_ioctl(dpif_, ODP_FLOW_FLUSH, NULL);
 268 }
 269
 270 static int
 271 dpif_linux_port_list(const struct dpif *dpif_, struct odp_port *ports, int n)
 272 {
 273     struct odp_portvec pv;
 274     int error;
 275
 276     pv.ports = ports;
 277     pv.n_ports = n;
 278     error = do_ioctl(dpif_, ODP_PORT_LIST, &pv);
 279     return error ? -error : pv.n_ports;
 280 }
 281
 282 static int
 283 dpif_linux_port_poll(const struct dpif *dpif_, char **devnamep)
 284 {
 285     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 286
 287     if (dpif->change_error) {
 288         dpif->change_error = false;
 289         svec_clear(&dpif->changed_ports);
 290         return ENOBUFS;
 291     } else if (dpif->changed_ports.n) {
 292         *devnamep = dpif->changed_ports.names[--dpif->changed_ports.n];
 293         return 0;
 294     } else {
 295         return EAGAIN;
 296     }
 297 }
 298
 299 static void
 300 dpif_linux_port_poll_wait(const struct dpif *dpif_)
 301 {
 302     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 303     if (dpif->changed_ports.n || dpif->change_error) {
 304         poll_immediate_wake();
 305     } else {
 306         rtnetlink_notifier_wait();
 307     }
 308 }
 309
 310 static int
 311 dpif_linux_port_group_get(const struct dpif *dpif_, int group,
 312                           uint16_t ports[], int n)
 313 {
 314     struct odp_port_group pg;
 315     int error;
 316
 317     assert(n <= UINT16_MAX);
 318     pg.group = group;
 319     pg.ports = ports;
 320     pg.n_ports = n;
 321     error = do_ioctl(dpif_, ODP_PORT_GROUP_GET, &pg);
 322     return error ? -error : pg.n_ports;
 323 }
 324
 325 static int
 326 dpif_linux_port_group_set(struct dpif *dpif_, int group,
 327                           const uint16_t ports[], int n)
 328 {
 329     struct odp_port_group pg;
 330
 331     assert(n <= UINT16_MAX);
 332     pg.group = group;
 333     pg.ports = (uint16_t *) ports;
 334     pg.n_ports = n;
 335     return do_ioctl(dpif_, ODP_PORT_GROUP_SET, &pg);
 336 }
 337
 338 static int
 339 dpif_linux_flow_get(const struct dpif *dpif_, struct odp_flow flows[], int n)
 340 {
 341     struct odp_flowvec fv;
 342     fv.flows = flows;
 343     fv.n_flows = n;
 344     return do_ioctl(dpif_, ODP_FLOW_GET, &fv);
 345 }
 346
 347 static int
 348 dpif_linux_flow_put(struct dpif *dpif_, struct odp_flow_put *put)
 349 {
 350     return do_ioctl(dpif_, ODP_FLOW_PUT, put);
 351 }
 352
 353 static int
 354 dpif_linux_flow_del(struct dpif *dpif_, struct odp_flow *flow)
 355 {
 356     return do_ioctl(dpif_, ODP_FLOW_DEL, flow);
 357 }
 358
 359 static int
 360 dpif_linux_flow_list(const struct dpif *dpif_, struct odp_flow flows[], int n)
 361 {
 362     struct odp_flowvec fv;
 363     int error;
 364
 365     fv.flows = flows;
 366     fv.n_flows = n;
 367     error = do_ioctl(dpif_, ODP_FLOW_LIST, &fv);
 368     return error ? -error : fv.n_flows;
 369 }
 370
 371 static int
 372 dpif_linux_execute(struct dpif *dpif_, uint16_t in_port,
 373                    const union odp_action actions[], int n_actions,
 374                    const struct ofpbuf *buf)
 375 {
 376     struct odp_execute execute;
 377     memset(&execute, 0, sizeof execute);
 378     execute.in_port = in_port;
 379     execute.actions = (union odp_action *) actions;
 380     execute.n_actions = n_actions;
 381     execute.data = buf->data;
 382     execute.length = buf->size;
 383     return do_ioctl(dpif_, ODP_EXECUTE, &execute);
 384 }
 385
 386 static int
 387 dpif_linux_recv_get_mask(const struct dpif *dpif_, int *listen_mask)
 388 {
 389     return do_ioctl(dpif_, ODP_GET_LISTEN_MASK, listen_mask);
 390 }
 391
 392 static int
 393 dpif_linux_recv_set_mask(struct dpif *dpif_, int listen_mask)
 394 {
 395     return do_ioctl(dpif_, ODP_SET_LISTEN_MASK, &listen_mask);
 396 }
 397
 398 static int
 399 dpif_linux_recv(struct dpif *dpif_, struct ofpbuf **bufp)
 400 {
 401     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 402     struct ofpbuf *buf;
 403     int retval;
 404     int error;
 405
 406     buf = ofpbuf_new(65536);
 407     retval = read(dpif->fd, ofpbuf_tail(buf), ofpbuf_tailroom(buf));
 408     if (retval < 0) {
 409         error = errno;
 410         if (error != EAGAIN) {
 411             VLOG_WARN_RL(&error_rl, "%s: read failed: %s",
 412                          dpif_name(dpif_), strerror(error));
 413         }
 414     } else if (retval >= sizeof(struct odp_msg)) {
 415         struct odp_msg *msg = buf->data;
 416         if (msg->length <= retval) {
 417             buf->size += retval;
 418             *bufp = buf;
 419             return 0;
 420         } else {
 421             VLOG_WARN_RL(&error_rl, "%s: discarding message truncated "
 422                          "from %"PRIu32" bytes to %d",
 423                          dpif_name(dpif_), msg->length, retval);
 424             error = ERANGE;
 425         }
 426     } else if (!retval) {
 427         VLOG_WARN_RL(&error_rl, "%s: unexpected end of file", dpif_name(dpif_));
 428         error = EPROTO;
 429     } else {
 430         VLOG_WARN_RL(&error_rl,
 431                      "%s: discarding too-short message (%d bytes)",
 432                      dpif_name(dpif_), retval);
 433         error = ERANGE;
 434     }
 435
 436     *bufp = NULL;
 437     ofpbuf_delete(buf);
 438     return error;
 439 }
 440
 441 static void
 442 dpif_linux_recv_wait(struct dpif *dpif_)
 443 {
 444     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 445     poll_fd_wait(dpif->fd, POLLIN);
 446 }
 447
 448 const struct dpif_class dpif_linux_class = {
 449     "",                         /* This is the default class. */
 450     "linux",
 451     NULL,
 452     NULL,
 453     dpif_linux_enumerate,
 454     dpif_linux_open,
 455     dpif_linux_close,
 456     dpif_linux_get_all_names,
 457     dpif_linux_delete,
 458     dpif_linux_get_stats,
 459     dpif_linux_get_drop_frags,
 460     dpif_linux_set_drop_frags,
 461     dpif_linux_port_add,
 462     dpif_linux_port_del,
 463     dpif_linux_port_query_by_number,
 464     dpif_linux_port_query_by_name,
 465     dpif_linux_port_list,
 466     dpif_linux_port_poll,
 467     dpif_linux_port_poll_wait,
 468     dpif_linux_port_group_get,
 469     dpif_linux_port_group_set,
 470     dpif_linux_flow_get,
 471     dpif_linux_flow_put,
 472     dpif_linux_flow_del,
 473     dpif_linux_flow_flush,
 474     dpif_linux_flow_list,
 475     dpif_linux_execute,
 476     dpif_linux_recv_get_mask,
 477     dpif_linux_recv_set_mask,
 478     dpif_linux_recv,
 479     dpif_linux_recv_wait,
 480 };
 481 \f
 482 static int get_openvswitch_major(void);
 483 static int get_major(const char *target);
 484
 485 static int
 486 do_ioctl(const struct dpif *dpif_, int cmd, const void *arg)
 487 {
 488     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 489     return ioctl(dpif->fd, cmd, arg) ? errno : 0;
 490 }
 491
 492 static int
 493 lookup_minor(const char *name, int *minorp)
 494 {
 495     struct ethtool_drvinfo drvinfo;
 496     int minor, port_no;
 497     struct ifreq ifr;
 498     int error;
 499     int sock;
 500
 501     sock = socket(AF_INET, SOCK_DGRAM, 0);
 502     if (sock < 0) {
 503         VLOG_WARN("socket(AF_INET) failed: %s", strerror(errno));
 504         error = errno;
 505         goto error;
 506     }
 507
 508     memset(&ifr, 0, sizeof ifr);
 509     strncpy(ifr.ifr_name, name, sizeof ifr.ifr_name);
 510     ifr.ifr_data = (caddr_t) &drvinfo;
 511
 512     memset(&drvinfo, 0, sizeof drvinfo);
 513     drvinfo.cmd = ETHTOOL_GDRVINFO;
 514     if (ioctl(sock, SIOCETHTOOL, &ifr)) {
 515         VLOG_WARN("ioctl(SIOCETHTOOL) failed: %s", strerror(errno));
 516         error = errno;
 517         goto error_close_sock;
 518     }
 519
 520     if (strcmp(drvinfo.driver, "openvswitch")) {
 521         VLOG_WARN("%s is not an openvswitch device", name);
 522         error = EOPNOTSUPP;
 523         goto error_close_sock;
 524     }
 525
 526     if (sscanf(drvinfo.bus_info, "%d.%d", &minor, &port_no) != 2) {
 527         VLOG_WARN("%s ethtool bus_info has unexpected format", name);
 528         error = EPROTOTYPE;
 529         goto error_close_sock;
 530     } else if (port_no != ODPP_LOCAL) {
 531         /* This is an Open vSwitch device but not the local port.  We
 532          * intentionally support only using the name of the local port as the
 533          * name of a datapath; otherwise, it would be too difficult to
 534          * enumerate all the names of a datapath. */
 535         error = EOPNOTSUPP;
 536         goto error_close_sock;
 537     }
 538
 539     *minorp = minor;
 540     close(sock);
 541     return 0;
 542
 543 error_close_sock:
 544     close(sock);
 545 error:
 546     return error;
 547 }
 548
 549 static int
 550 make_openvswitch_device(int minor, char **fnp)
 551 {
 552     const char dirname[] = "/dev/net";
 553     int major;
 554     dev_t dev;
 555     struct stat s;
 556     char fn[128];
 557
 558     major = get_openvswitch_major();
 559     if (major < 0) {
 560         return -major;
 561     }
 562     dev = makedev(major, minor);
 563
 564     *fnp = NULL;
 565     sprintf(fn, "%s/dp%d", dirname, minor);
 566     if (!stat(fn, &s)) {
 567         if (!S_ISCHR(s.st_mode)) {
 568             VLOG_WARN_RL(&error_rl, "%s is not a character device, fixing",
 569                          fn);
 570         } else if (s.st_rdev != dev) {
 571             VLOG_WARN_RL(&error_rl,
 572                          "%s is device %u:%u but should be %u:%u, fixing",
 573                          fn, major(s.st_rdev), minor(s.st_rdev),
 574                          major(dev), minor(dev));
 575         } else {
 576             goto success;
 577         }
 578         if (unlink(fn)) {
 579             VLOG_WARN_RL(&error_rl, "%s: unlink failed (%s)",
 580                          fn, strerror(errno));
 581             return errno;
 582         }
 583     } else if (errno == ENOENT) {
 584         if (stat(dirname, &s)) {
 585             if (errno == ENOENT) {
 586                 if (mkdir(dirname, 0755)) {
 587                     VLOG_WARN_RL(&error_rl, "%s: mkdir failed (%s)",
 588                                  dirname, strerror(errno));
 589                     return errno;
 590                 }
 591             } else {
 592                 VLOG_WARN_RL(&error_rl, "%s: stat failed (%s)",
 593                              dirname, strerror(errno));
 594                 return errno;
 595             }
 596         }
 597     } else {
 598         VLOG_WARN_RL(&error_rl, "%s: stat failed (%s)", fn, strerror(errno));
 599         return errno;
 600     }
 601
 602     /* The device needs to be created. */
 603     if (mknod(fn, S_IFCHR | 0700, dev)) {
 604         VLOG_WARN_RL(&error_rl,
 605                      "%s: creating character device %u:%u failed (%s)",
 606                      fn, major(dev), minor(dev), strerror(errno));
 607         return errno;
 608     }
 609
 610 success:
 611     *fnp = xstrdup(fn);
 612     return 0;
 613 }
 614
 615 /* Return the major device number of the Open vSwitch device.  If it
 616  * cannot be determined, a negative errno is returned. */
 617 static int
 618 get_openvswitch_major(void)
 619 {
 620     static int openvswitch_major = -1;
 621     if (openvswitch_major < 0) {
 622         openvswitch_major = get_major("openvswitch");
 623     }
 624     return openvswitch_major;
 625 }
 626
 627 static int
 628 get_major(const char *target)
 629 {
 630     const char fn[] = "/proc/devices";
 631     char line[128];
 632     FILE *file;
 633     int ln;
 634
 635     file = fopen(fn, "r");
 636     if (!file) {
 637         VLOG_ERR("opening %s failed (%s)", fn, strerror(errno));
 638         return -errno;
 639     }
 640
 641     for (ln = 1; fgets(line, sizeof line, file); ln++) {
 642         char name[64];
 643         int major;
 644
 645         if (!strncmp(line, "Character", 9) || line[0] == '\0') {
 646             /* Nothing to do. */
 647         } else if (!strncmp(line, "Block", 5)) {
 648             /* We only want character devices, so skip the rest of the file. */
 649             break;
 650         } else if (sscanf(line, "%d %63s", &major, name)) {
 651             if (!strcmp(name, target)) {
 652                 fclose(file);
 653                 return major;
 654             }
 655         } else {
 656             static bool warned;
 657             if (!warned) {
 658                 VLOG_WARN("%s:%d: syntax error", fn, ln);
 659             }
 660             warned = true;
 661         }
 662     }
 663
 664     VLOG_ERR("%s: %s major not found (is the module loaded?)", fn, target);
 665     return -ENODEV;
 666 }
 667
 668 static int
 669 finish_open(struct dpif *dpif_, const char *local_ifname)
 670 {
 671     struct dpif_linux *dpif = dpif_linux_cast(dpif_);
 672     dpif->local_ifname = strdup(local_ifname);
 673     dpif->local_ifindex = if_nametoindex(local_ifname);
 674     if (!dpif->local_ifindex) {
 675         int error = errno;
 676         dpif_close(dpif_);
 677         VLOG_WARN("could not get ifindex of %s device: %s",
 678                   local_ifname, strerror(errno));
 679         return error;
 680     }
 681     return 0;
 682 }
 683
 684 static int
 685 create_minor(const char *name, int minor, struct dpif **dpifp)
 686 {
 687     int error = open_minor(minor, dpifp);
 688     if (!error) {
 689         error = do_ioctl(*dpifp, ODP_DP_CREATE, name);
 690         if (!error) {
 691             error = finish_open(*dpifp, name);
 692         } else {
 693             dpif_close(*dpifp);
 694         }
 695     }
 696     return error;
 697 }
 698
 699 static int
 700 open_minor(int minor, struct dpif **dpifp)
 701 {
 702     int error;
 703     char *fn;
 704     int fd;
 705
 706     error = make_openvswitch_device(minor, &fn);
 707     if (error) {
 708         return error;
 709     }
 710
 711     fd = open(fn, O_RDONLY | O_NONBLOCK);
 712     if (fd >= 0) {
 713         struct dpif_linux *dpif = xmalloc(sizeof *dpif);
 714         error = rtnetlink_notifier_register(&dpif->port_notifier,
 715                                            dpif_linux_port_changed, dpif);
 716         if (!error) {
 717             char *name;
 718
 719             name = xasprintf("dp%d", minor);
 720             dpif_init(&dpif->dpif, &dpif_linux_class, name, minor, minor);
 721             free(name);
 722
 723             dpif->fd = fd;
 724             dpif->local_ifname = NULL;
 725             dpif->minor = minor;
 726             dpif->local_ifindex = 0;
 727             svec_init(&dpif->changed_ports);
 728             dpif->change_error = false;
 729             *dpifp = &dpif->dpif;
 730         } else {
 731             free(dpif);
 732         }
 733     } else {
 734         error = errno;
 735         VLOG_WARN("%s: open failed (%s)", fn, strerror(error));
 736     }
 737     free(fn);
 738
 739     return error;
 740 }
 741
 742 static void
 743 dpif_linux_port_changed(const struct rtnetlink_change *change, void *dpif_)
 744 {
 745     struct dpif_linux *dpif = dpif_;
 746
 747     if (change) {
 748         if (change->master_ifindex == dpif->local_ifindex
 749             && (change->nlmsg_type == RTM_NEWLINK
 750                 || change->nlmsg_type == RTM_DELLINK))
 751         {
 752             /* Our datapath changed, either adding a new port or deleting an
 753              * existing one. */
 754             if (!svec_contains(&dpif->changed_ports, change->ifname)) {
 755                 svec_add(&dpif->changed_ports, change->ifname);
 756                 svec_sort(&dpif->changed_ports);
 757             }
 758         }
 759     } else {
 760         dpif->change_error = true;
 761     }
 762 }