lib/netdev-provider.h

   1 /*
   2  * Copyright (c) 2009, 2010, 2011 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 #ifndef NETDEV_PROVIDER_H
  18 #define NETDEV_PROVIDER_H 1
  19
  20 /* Generic interface to network devices. */
  21
  22 #include <assert.h>
  23
  24 #include "netdev.h"
  25 #include "list.h"
  26 #include "shash.h"
  27
  28 #ifdef  __cplusplus
  29 extern "C" {
  30 #endif
  31
  32 /* A network device (e.g. an Ethernet device).
  33  *
  34  * This structure should be treated as opaque by network device
  35  * implementations. */
  36 struct netdev_dev {
  37     char *name;                         /* Name of network device. */
  38     const struct netdev_class *netdev_class; /* Functions to control
  39                                                 this device. */
  40     int ref_cnt;                        /* Times this devices was opened. */
  41     struct shash_node *node;            /* Pointer to element in global map. */
  42     struct shash args;                  /* Argument list from last config. */
  43 };
  44
  45 void netdev_dev_init(struct netdev_dev *, const char *name,
  46                      const struct shash *args,
  47                      const struct netdev_class *);
  48 void netdev_dev_uninit(struct netdev_dev *, bool destroy);
  49 const char *netdev_dev_get_type(const struct netdev_dev *);
  50 const struct netdev_class *netdev_dev_get_class(const struct netdev_dev *);
  51 const char *netdev_dev_get_name(const struct netdev_dev *);
  52 struct netdev_dev *netdev_dev_from_name(const char *name);
  53 void netdev_dev_get_devices(const struct netdev_class *,
  54                             struct shash *device_list);
  55
  56 static inline void netdev_dev_assert_class(const struct netdev_dev *netdev_dev,
  57                                            const struct netdev_class *class_)
  58 {
  59     assert(netdev_dev->netdev_class == class_);
  60 }
  61
  62 /* A instance of an open network device.
  63  *
  64  * This structure should be treated as opaque by network device
  65  * implementations. */
  66 struct netdev {
  67     struct netdev_dev *netdev_dev;   /* Parent netdev_dev. */
  68     struct list node;                /* Element in global list. */
  69
  70     enum netdev_flags save_flags;    /* Initial device flags. */
  71     enum netdev_flags changed_flags; /* Flags that we changed. */
  72 };
  73
  74 void netdev_init(struct netdev *, struct netdev_dev *);
  75 void netdev_uninit(struct netdev *, bool close);
  76 struct netdev_dev *netdev_get_dev(const struct netdev *);
  77
  78 static inline void netdev_assert_class(const struct netdev *netdev,
  79                                        const struct netdev_class *netdev_class)
  80 {
  81     netdev_dev_assert_class(netdev_get_dev(netdev), netdev_class);
  82 }
  83
  84 /* A network device notifier.
  85  *
  86  * Network device implementations should use netdev_notifier_init() to
  87  * initialize this structure, but they may freely read its members after
  88  * initialization. */
  89 struct netdev_notifier {
  90     struct netdev *netdev;
  91     void (*cb)(struct netdev_notifier *);
  92     void *aux;
  93 };
  94 void netdev_notifier_init(struct netdev_notifier *, struct netdev *,
  95                           void (*cb)(struct netdev_notifier *), void *aux);
  96
  97 /* Network device class structure, to be defined by each implementation of a
  98  * network device.
  99  *
 100  * These functions return 0 if successful or a positive errno value on failure,
 101  * except where otherwise noted. */
 102 struct netdev_class {
 103     /* Type of netdevs in this class, e.g. "system", "tap", "gre", etc.
 104      *
 105      * One of the providers should supply a "system" type, since this is
 106      * the type assumed if no type is specified when opening a netdev.
 107      * The "system" type corresponds to an existing network device on
 108      * the system. */
 109     const char *type;
 110
 111     /* Called when the netdev provider is registered, typically at program
 112      * startup.  Returning an error from this function will prevent any network
 113      * device in this class from being opened.
 114      *
 115      * This function may be set to null if a network device class needs no
 116      * initialization at registration time. */
 117     int (*init)(void);
 118
 119     /* Performs periodic work needed by netdevs of this class.  May be null if
 120      * no periodic work is necessary. */
 121     void (*run)(void);
 122
 123     /* Arranges for poll_block() to wake up if the "run" member function needs
 124      * to be called.  May be null if nothing is needed here. */
 125     void (*wait)(void);
 126
 127     /* Attempts to create a network device named 'name' with initial 'args' in
 128      * 'netdev_class'.  On success sets 'netdev_devp' to the newly created
 129      * device. */
 130     int (*create)(const struct netdev_class *netdev_class, const char *name,
 131                   const struct shash *args, struct netdev_dev **netdev_devp);
 132
 133     /* Destroys 'netdev_dev'.
 134      *
 135      * Netdev devices maintain a reference count that is incremented on
 136      * netdev_open() and decremented on netdev_close().  If 'netdev_dev'
 137      * has a non-zero reference count, then this function will not be
 138      * called. */
 139     void (*destroy)(struct netdev_dev *netdev_dev);
 140
 141     /* Changes the device 'netdev_dev''s configuration to 'args'.
 142      *
 143      * If this netdev class does not support reconfiguring a netdev
 144      * device, this may be a null pointer.
 145      */
 146     int (*set_config)(struct netdev_dev *netdev_dev, const struct shash *args);
 147
 148     /* Attempts to open a network device.  On success, sets 'netdevp'
 149      * to the new network device.
 150      *
 151      * 'ethertype' may be a 16-bit Ethernet protocol value in host byte order
 152      * to capture frames of that type received on the device.  It may also be
 153      * one of the 'enum netdev_pseudo_ethertype' values to receive frames in
 154      * one of those categories. */
 155     int (*open)(struct netdev_dev *netdev_dev, int ethertype,
 156                 struct netdev **netdevp);
 157
 158     /* Closes 'netdev'. */
 159     void (*close)(struct netdev *netdev);
 160
 161     /* Enumerates the names of all network devices of this class.
 162      *
 163      * The caller has already initialized 'all_names' and might already have
 164      * added some names to it.  This function should not disturb any existing
 165      * names in 'all_names'.
 166      *
 167      * If this netdev class does not support enumeration, this may be a null
 168      * pointer. */
 169     int (*enumerate)(struct sset *all_names);
 170
 171     /* Attempts to receive a packet from 'netdev' into the 'size' bytes in
 172      * 'buffer'.  If successful, returns the number of bytes in the received
 173      * packet, otherwise a negative errno value.  Returns -EAGAIN immediately
 174      * if no packet is ready to be received.
 175      *
 176      * May return -EOPNOTSUPP if a network device does not implement packet
 177      * reception through this interface.  This function may be set to null if
 178      * it would always return -EOPNOTSUPP anyhow.  (This will prevent the
 179      * network device from being usefully used by the netdev-based "userspace
 180      * datapath".) */
 181     int (*recv)(struct netdev *netdev, void *buffer, size_t size);
 182
 183     /* Registers with the poll loop to wake up from the next call to
 184      * poll_block() when a packet is ready to be received with netdev_recv() on
 185      * 'netdev'.
 186      *
 187      * May be null if not needed, such as for a network device that does not
 188      * implement packet reception through the 'recv' member function. */
 189     void (*recv_wait)(struct netdev *netdev);
 190
 191     /* Discards all packets waiting to be received from 'netdev'.
 192      *
 193      * May be null if not needed, such as for a network device that does not
 194      * implement packet reception through the 'recv' member function. */
 195     int (*drain)(struct netdev *netdev);
 196
 197     /* Sends the 'size'-byte packet in 'buffer' on 'netdev'.  Returns 0 if
 198      * successful, otherwise a positive errno value.  Returns EAGAIN without
 199      * blocking if the packet cannot be queued immediately.  Returns EMSGSIZE
 200      * if a partial packet was transmitted or if the packet is too big or too
 201      * small to transmit on the device.
 202      *
 203      * The caller retains ownership of 'buffer' in all cases.
 204      *
 205      * The network device is expected to maintain a packet transmission queue,
 206      * so that the caller does not ordinarily have to do additional queuing of
 207      * packets.
 208      *
 209      * May return EOPNOTSUPP if a network device does not implement packet
 210      * transmission through this interface.  This function may be set to null
 211      * if it would always return EOPNOTSUPP anyhow.  (This will prevent the
 212      * network device from being usefully used by the netdev-based "userspace
 213      * datapath".  It will also prevent the OVS implementation of bonding from
 214      * working properly over 'netdev'.) */
 215     int (*send)(struct netdev *netdev, const void *buffer, size_t size);
 216
 217     /* Registers with the poll loop to wake up from the next call to
 218      * poll_block() when the packet transmission queue for 'netdev' has
 219      * sufficient room to transmit a packet with netdev_send().
 220      *
 221      * The network device is expected to maintain a packet transmission queue,
 222      * so that the caller does not ordinarily have to do additional queuing of
 223      * packets.  Thus, this function is unlikely to ever be useful.
 224      *
 225      * May be null if not needed, such as for a network device that does not
 226      * implement packet transmission through the 'send' member function. */
 227     void (*send_wait)(struct netdev *netdev);
 228
 229     /* Sets 'netdev''s Ethernet address to 'mac' */
 230     int (*set_etheraddr)(struct netdev *netdev, const uint8_t mac[6]);
 231
 232     /* Retrieves 'netdev''s Ethernet address into 'mac'. */
 233     int (*get_etheraddr)(const struct netdev *netdev, uint8_t mac[6]);
 234
 235     /* Retrieves 'netdev''s MTU into '*mtup'.
 236      *
 237      * The MTU is the maximum size of transmitted (and received) packets, in
 238      * bytes, not including the hardware header; thus, this is typically 1500
 239      * bytes for Ethernet devices.
 240      *
 241      * If 'netdev' does not have an MTU (e.g. as some tunnels do not), then
 242      * this function should set '*mtup' to INT_MAX. */
 243     int (*get_mtu)(const struct netdev *netdev, int *mtup);
 244
 245     /* Returns the ifindex of 'netdev', if successful, as a positive number.
 246      * On failure, returns a negative errno value.
 247      *
 248      * The desired semantics of the ifindex value are a combination of those
 249      * specified by POSIX for if_nametoindex() and by SNMP for ifIndex.  An
 250      * ifindex value should be unique within a host and remain stable at least
 251      * until reboot.  SNMP says an ifindex "ranges between 1 and the value of
 252      * ifNumber" but many systems do not follow this rule anyhow.
 253      *
 254      * This function may be set to null if it would always return -EOPNOTSUPP.
 255      */
 256     int (*get_ifindex)(const struct netdev *netdev);
 257
 258     /* Sets 'carrier' to true if carrier is active (link light is on) on
 259      * 'netdev'.
 260      *
 261      * May be null if device does not provide carrier status (will be always
 262      * up as long as device is up).
 263      */
 264     int (*get_carrier)(const struct netdev *netdev, bool *carrier);
 265
 266     /* Sets 'miimon' to true if 'netdev' is up according to its MII.  If
 267      * 'netdev' does not support MII, may fall back to another method or return
 268      * EOPNOTSUPP.
 269      *
 270      * This function may be set to null if it would always return EOPNOTSUPP.
 271      */
 272     int (*get_miimon)(const struct netdev *netdev, bool *miimon);
 273
 274     /* Retrieves current device stats for 'netdev' into 'stats'.
 275      *
 276      * A network device that supports some statistics but not others, it should
 277      * set the values of the unsupported statistics to all-1-bits
 278      * (UINT64_MAX). */
 279     int (*get_stats)(const struct netdev *netdev, struct netdev_stats *);
 280
 281     /* Sets the device stats for 'netdev' to 'stats'.
 282      *
 283      * Most network devices won't support this feature and will set this
 284      * function pointer to NULL, which is equivalent to returning EOPNOTSUPP.
 285      *
 286      * Some network devices might only allow setting their stats to 0. */
 287     int (*set_stats)(struct netdev *netdev, const struct netdev_stats *);
 288
 289     /* Stores the features supported by 'netdev' into each of '*current',
 290      * '*advertised', '*supported', and '*peer'.  Each value is a bitmap of
 291      * "enum ofp_port_features" bits, in host byte order.
 292      *
 293      * This function may be set to null if it would always return EOPNOTSUPP.
 294      */
 295     int (*get_features)(const struct netdev *netdev,
 296                         uint32_t *current, uint32_t *advertised,
 297                         uint32_t *supported, uint32_t *peer);
 298
 299     /* Set the features advertised by 'netdev' to 'advertise', which is a
 300      * bitmap of "enum ofp_port_features" bits, in host byte order.
 301      *
 302      * This function may be set to null for a network device that does not
 303      * support configuring advertisements. */
 304     int (*set_advertisements)(struct netdev *netdev, uint32_t advertise);
 305
 306     /* If 'netdev' is a VLAN network device (e.g. one created with vconfig(8)),
 307      * sets '*vlan_vid' to the VLAN VID associated with that device and returns
 308      * 0.
 309      *
 310      * Returns ENOENT if 'netdev' is a network device that is not a
 311      * VLAN device.
 312      *
 313      * This function should be set to null if it doesn't make any sense for
 314      * your network device (it probably doesn't). */
 315     int (*get_vlan_vid)(const struct netdev *netdev, int *vlan_vid);
 316
 317     /* Attempts to set input rate limiting (policing) policy, such that up to
 318      * 'kbits_rate' kbps of traffic is accepted, with a maximum accumulative
 319      * burst size of 'kbits' kb.
 320      *
 321      * This function may be set to null if policing is not supported. */
 322     int (*set_policing)(struct netdev *netdev, unsigned int kbits_rate,
 323                         unsigned int kbits_burst);
 324
 325     /* Adds to 'types' all of the forms of QoS supported by 'netdev', or leaves
 326      * it empty if 'netdev' does not support QoS.  Any names added to 'types'
 327      * should be documented as valid for the "type" column in the "QoS" table
 328      * in vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 329      *
 330      * Every network device must support disabling QoS with a type of "", but
 331      * this function must not add "" to 'types'.
 332      *
 333      * The caller is responsible for initializing 'types' (e.g. with
 334      * sset_init()) before calling this function.  The caller retains ownership
 335      * of 'types'.
 336      *
 337      * May be NULL if 'netdev' does not support QoS at all. */
 338     int (*get_qos_types)(const struct netdev *netdev, struct sset *types);
 339
 340     /* Queries 'netdev' for its capabilities regarding the specified 'type' of
 341      * QoS.  On success, initializes 'caps' with the QoS capabilities.
 342      *
 343      * Should return EOPNOTSUPP if 'netdev' does not support 'type'.  May be
 344      * NULL if 'netdev' does not support QoS at all. */
 345     int (*get_qos_capabilities)(const struct netdev *netdev,
 346                                 const char *type,
 347                                 struct netdev_qos_capabilities *caps);
 348
 349     /* Queries 'netdev' about its currently configured form of QoS.  If
 350      * successful, stores the name of the current form of QoS into '*typep'
 351      * and any details of configuration as string key-value pairs in
 352      * 'details'.
 353      *
 354      * A '*typep' of "" indicates that QoS is currently disabled on 'netdev'.
 355      *
 356      * The caller initializes 'details' before calling this function.  The
 357      * caller takes ownership of the string key-values pairs added to
 358      * 'details'.
 359      *
 360      * The netdev retains ownership of '*typep'.
 361      *
 362      * '*typep' will be one of the types returned by netdev_get_qos_types() for
 363      * 'netdev'.  The contents of 'details' should be documented as valid for
 364      * '*typep' in the "other_config" column in the "QoS" table in
 365      * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 366      *
 367      * May be NULL if 'netdev' does not support QoS at all. */
 368     int (*get_qos)(const struct netdev *netdev,
 369                    const char **typep, struct shash *details);
 370
 371     /* Attempts to reconfigure QoS on 'netdev', changing the form of QoS to
 372      * 'type' with details of configuration from 'details'.
 373      *
 374      * On error, the previous QoS configuration is retained.
 375      *
 376      * When this function changes the type of QoS (not just 'details'), this
 377      * also resets all queue configuration for 'netdev' to their defaults
 378      * (which depend on the specific type of QoS).  Otherwise, the queue
 379      * configuration for 'netdev' is unchanged.
 380      *
 381      * 'type' should be "" (to disable QoS) or one of the types returned by
 382      * netdev_get_qos_types() for 'netdev'.  The contents of 'details' should
 383      * be documented as valid for the given 'type' in the "other_config" column
 384      * in the "QoS" table in vswitchd/vswitch.xml (which is built as
 385      * ovs-vswitchd.conf.db(8)).
 386      *
 387      * May be NULL if 'netdev' does not support QoS at all. */
 388     int (*set_qos)(struct netdev *netdev,
 389                    const char *type, const struct shash *details);
 390
 391     /* Queries 'netdev' for information about the queue numbered 'queue_id'.
 392      * If successful, adds that information as string key-value pairs to
 393      * 'details'.  Returns 0 if successful, otherwise a positive errno value.
 394      *
 395      * Should return EINVAL if 'queue_id' is greater than or equal to the
 396      * number of supported queues (as reported in the 'n_queues' member of
 397      * struct netdev_qos_capabilities by 'get_qos_capabilities').
 398      *
 399      * The caller initializes 'details' before calling this function.  The
 400      * caller takes ownership of the string key-values pairs added to
 401      * 'details'.
 402      *
 403      * The returned contents of 'details' should be documented as valid for the
 404      * given 'type' in the "other_config" column in the "Queue" table in
 405      * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 406      */
 407     int (*get_queue)(const struct netdev *netdev,
 408                      unsigned int queue_id, struct shash *details);
 409
 410     /* Configures the queue numbered 'queue_id' on 'netdev' with the key-value
 411      * string pairs in 'details'.  The contents of 'details' should be
 412      * documented as valid for the given 'type' in the "other_config" column in
 413      * the "Queue" table in vswitchd/vswitch.xml (which is built as
 414      * ovs-vswitchd.conf.db(8)).  Returns 0 if successful, otherwise a positive
 415      * errno value.  On failure, the given queue's configuration should be
 416      * unmodified.
 417      *
 418      * Should return EINVAL if 'queue_id' is greater than or equal to the
 419      * number of supported queues (as reported in the 'n_queues' member of
 420      * struct netdev_qos_capabilities by 'get_qos_capabilities'), or if
 421      * 'details' is invalid for the type of queue.
 422      *
 423      * This function does not modify 'details', and the caller retains
 424      * ownership of it.
 425      *
 426      * May be NULL if 'netdev' does not support QoS at all. */
 427     int (*set_queue)(struct netdev *netdev,
 428                      unsigned int queue_id, const struct shash *details);
 429
 430     /* Attempts to delete the queue numbered 'queue_id' from 'netdev'.
 431      *
 432      * Should return EINVAL if 'queue_id' is greater than or equal to the
 433      * number of supported queues (as reported in the 'n_queues' member of
 434      * struct netdev_qos_capabilities by 'get_qos_capabilities').  Should
 435      * return EOPNOTSUPP if 'queue_id' is valid but may not be deleted (e.g. if
 436      * 'netdev' has a fixed set of queues with the current QoS mode).
 437      *
 438      * May be NULL if 'netdev' does not support QoS at all, or if all of its
 439      * QoS modes have fixed sets of queues. */
 440     int (*delete_queue)(struct netdev *netdev, unsigned int queue_id);
 441
 442     /* Obtains statistics about 'queue_id' on 'netdev'.  Fills 'stats' with the
 443      * queue's statistics.  May set individual members of 'stats' to all-1-bits
 444      * if the statistic is unavailable.
 445      *
 446      * May be NULL if 'netdev' does not support QoS at all. */
 447     int (*get_queue_stats)(const struct netdev *netdev, unsigned int queue_id,
 448                            struct netdev_queue_stats *stats);
 449
 450     /* Iterates over all of 'netdev''s queues, calling 'cb' with the queue's
 451      * ID, its configuration, and the 'aux' specified by the caller.  The order
 452      * of iteration is unspecified, but (when successful) each queue is visited
 453      * exactly once.
 454      *
 455      * 'cb' will not modify or free the 'details' argument passed in. */
 456     int (*dump_queues)(const struct netdev *netdev,
 457                        void (*cb)(unsigned int queue_id,
 458                                   const struct shash *details,
 459                                   void *aux),
 460                        void *aux);
 461
 462     /* Iterates over all of 'netdev''s queues, calling 'cb' with the queue's
 463      * ID, its statistics, and the 'aux' specified by the caller.  The order of
 464      * iteration is unspecified, but (when successful) each queue must be
 465      * visited exactly once.
 466      *
 467      * 'cb' will not modify or free the statistics passed in. */
 468     int (*dump_queue_stats)(const struct netdev *netdev,
 469                             void (*cb)(unsigned int queue_id,
 470                                        struct netdev_queue_stats *,
 471                                        void *aux),
 472                             void *aux);
 473
 474     /* If 'netdev' has an assigned IPv4 address, sets '*address' to that
 475      * address and '*netmask' to the associated netmask.
 476      *
 477      * The following error values have well-defined meanings:
 478      *
 479      *   - EADDRNOTAVAIL: 'netdev' has no assigned IPv4 address.
 480      *
 481      *   - EOPNOTSUPP: No IPv4 network stack attached to 'netdev'.
 482      *
 483      * This function may be set to null if it would always return EOPNOTSUPP
 484      * anyhow. */
 485     int (*get_in4)(const struct netdev *netdev, struct in_addr *address,
 486                    struct in_addr *netmask);
 487
 488     /* Assigns 'addr' as 'netdev''s IPv4 address and 'mask' as its netmask.  If
 489      * 'addr' is INADDR_ANY, 'netdev''s IPv4 address is cleared.
 490      *
 491      * This function may be set to null if it would always return EOPNOTSUPP
 492      * anyhow. */
 493     int (*set_in4)(struct netdev *netdev, struct in_addr addr,
 494                    struct in_addr mask);
 495
 496     /* If 'netdev' has an assigned IPv6 address, sets '*in6' to that address.
 497      *
 498      * The following error values have well-defined meanings:
 499      *
 500      *   - EADDRNOTAVAIL: 'netdev' has no assigned IPv6 address.
 501      *
 502      *   - EOPNOTSUPP: No IPv6 network stack attached to 'netdev'.
 503      *
 504      * This function may be set to null if it would always return EOPNOTSUPP
 505      * anyhow. */
 506     int (*get_in6)(const struct netdev *netdev, struct in6_addr *in6);
 507
 508     /* Adds 'router' as a default IP gateway for the TCP/IP stack that
 509      * corresponds to 'netdev'.
 510      *
 511      * This function may be set to null if it would always return EOPNOTSUPP
 512      * anyhow. */
 513     int (*add_router)(struct netdev *netdev, struct in_addr router);
 514
 515     /* Looks up the next hop for 'host'.  If succesful, stores the next hop
 516      * gateway's address (0 if 'host' is on a directly connected network) in
 517      * '*next_hop' and a copy of the name of the device to reach 'host' in
 518      * '*netdev_name', and returns 0.  The caller is responsible for freeing
 519      * '*netdev_name' (by calling free()).
 520      *
 521      * This function may be set to null if it would always return EOPNOTSUPP
 522      * anyhow. */
 523     int (*get_next_hop)(const struct in_addr *host, struct in_addr *next_hop,
 524                         char **netdev_name);
 525
 526     /* Retrieves the status of the device.
 527      *
 528      * Populates 'sh' with key-value pairs representing the status of the
 529      * device.  A device's status is a set of key-value string pairs
 530      * representing netdev type specific information.  For more information see
 531      * ovs-vswitchd.conf.db(5).
 532      *
 533      * The data of 'sh' are heap allocated strings which the caller is
 534      * responsible for deallocating.
 535      *
 536      * This function may be set to null if it would always return EOPNOTSUPP
 537      * anyhow. */
 538     int (*get_status)(const struct netdev *netdev, struct shash *sh);
 539
 540     /* Looks up the ARP table entry for 'ip' on 'netdev' and stores the
 541      * corresponding MAC address in 'mac'.  A return value of ENXIO, in
 542      * particular, indicates that there is no ARP table entry for 'ip' on
 543      * 'netdev'.
 544      *
 545      * This function may be set to null if it would always return EOPNOTSUPP
 546      * anyhow. */
 547     int (*arp_lookup)(const struct netdev *netdev, uint32_t ip, uint8_t mac[6]);
 548
 549     /* Retrieves the current set of flags on 'netdev' into '*old_flags'.
 550      * Then, turns off the flags that are set to 1 in 'off' and turns on the
 551      * flags that are set to 1 in 'on'.  (No bit will be set to 1 in both 'off'
 552      * and 'on'; that is, off & on == 0.)
 553      *
 554      * This function may be invoked from a signal handler.  Therefore, it
 555      * should not do anything that is not signal-safe (such as logging). */
 556     int (*update_flags)(struct netdev *netdev, enum netdev_flags off,
 557                         enum netdev_flags on, enum netdev_flags *old_flags);
 558
 559     /* Arranges for 'cb' to be called whenever one of the attributes of
 560      * 'netdev' changes and sets '*notifierp' to a newly created
 561      * netdev_notifier that represents this arrangement.  The created notifier
 562      * will have its 'netdev', 'cb', and 'aux' members set to the values of the
 563      * corresponding parameters. */
 564     int (*poll_add)(struct netdev *netdev,
 565                     void (*cb)(struct netdev_notifier *notifier), void *aux,
 566                     struct netdev_notifier **notifierp);
 567
 568     /* Cancels poll notification for 'notifier'. */
 569     void (*poll_remove)(struct netdev_notifier *notifier);
 570 };
 571
 572 int netdev_register_provider(const struct netdev_class *);
 573 int netdev_unregister_provider(const char *type);
 574 const struct netdev_class *netdev_lookup_provider(const char *type);
 575
 576 extern const struct netdev_class netdev_linux_class;
 577 extern const struct netdev_class netdev_internal_class;
 578 extern const struct netdev_class netdev_tap_class;
 579
 580 #ifdef  __cplusplus
 581 }
 582 #endif
 583
 584 #endif /* netdev.h */