lib/netdev-provider.h

   1 /*
   2  * Copyright (c) 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
   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 "netdev.h"
  23 #include "list.h"
  24 #include "shash.h"
  25 #include "smap.h"
  26
  27 #ifdef  __cplusplus
  28 extern "C" {
  29 #endif
  30
  31 /* A network device (e.g. an Ethernet device).
  32  *
  33  * Network device implementations may read these members but should not modify
  34  * them. */
  35 struct netdev {
  36     /* The following do not change during the lifetime of a struct netdev. */
  37     char *name;                         /* Name of network device. */
  38     const struct netdev_class *netdev_class; /* Functions to control
  39                                                 this device. */
  40
  41     /* The following are protected by 'netdev_mutex' (internal to netdev.c). */
  42     int ref_cnt;                        /* Times this devices was opened. */
  43     struct shash_node *node;            /* Pointer to element in global map. */
  44     struct list saved_flags_list; /* Contains "struct netdev_saved_flags". */
  45 };
  46
  47 const char *netdev_get_type(const struct netdev *);
  48 const struct netdev_class *netdev_get_class(const struct netdev *);
  49 const char *netdev_get_name(const struct netdev *);
  50 struct netdev *netdev_from_name(const char *name);
  51 void netdev_get_devices(const struct netdev_class *,
  52                         struct shash *device_list);
  53
  54 /* A data structure for capturing packets received by a network device.
  55  *
  56  * Network device implementations may read these members but should not modify
  57  * them.
  58  *
  59  * None of these members change during the lifetime of a struct netdev_rx. */
  60 struct netdev_rx {
  61     struct netdev *netdev;      /* Owns a reference to the netdev. */
  62 };
  63
  64 struct netdev *netdev_rx_get_netdev(const struct netdev_rx *);
  65
  66 /* Network device class structure, to be defined by each implementation of a
  67  * network device.
  68  *
  69  * These functions return 0 if successful or a positive errno value on failure,
  70  * except where otherwise noted.
  71  *
  72  *
  73  * Data Structures
  74  * ===============
  75  *
  76  * These functions work primarily with two different kinds of data structures:
  77  *
  78  *   - "struct netdev", which represents a network device.
  79  *
  80  *   - "struct netdev_rx", which represents a handle for capturing packets
  81  *     received on a network device
  82  *
  83  * Each of these data structures contains all of the implementation-independent
  84  * generic state for the respective concept, called the "base" state.  None of
  85  * them contains any extra space for implementations to use.  Instead, each
  86  * implementation is expected to declare its own data structure that contains
  87  * an instance of the generic data structure plus additional
  88  * implementation-specific members, called the "derived" state.  The
  89  * implementation can use casts or (preferably) the CONTAINER_OF macro to
  90  * obtain access to derived state given only a pointer to the embedded generic
  91  * data structure.
  92  *
  93  *
  94  * Life Cycle
  95  * ==========
  96  *
  97  * Four stylized functions accompany each of these data structures:
  98  *
  99  *            "alloc"       "construct"       "destruct"       "dealloc"
 100  *            ------------  ----------------  ---------------  --------------
 101  * netdev     ->alloc       ->construct       ->destruct       ->dealloc
 102  * netdev_rx  ->rx_alloc    ->rx_construct    ->rx_destruct    ->rx_dealloc
 103  *
 104  * Any instance of a given data structure goes through the following life
 105  * cycle:
 106  *
 107  *   1. The client calls the "alloc" function to obtain raw memory.  If "alloc"
 108  *      fails, skip all the other steps.
 109  *
 110  *   2. The client initializes all of the data structure's base state.  If this
 111  *      fails, skip to step 7.
 112  *
 113  *   3. The client calls the "construct" function.  The implementation
 114  *      initializes derived state.  It may refer to the already-initialized
 115  *      base state.  If "construct" fails, skip to step 6.
 116  *
 117  *   4. The data structure is now initialized and in use.
 118  *
 119  *   5. When the data structure is no longer needed, the client calls the
 120  *      "destruct" function.  The implementation uninitializes derived state.
 121  *      The base state has not been uninitialized yet, so the implementation
 122  *      may still refer to it.
 123  *
 124  *   6. The client uninitializes all of the data structure's base state.
 125  *
 126  *   7. The client calls the "dealloc" to free the raw memory.  The
 127  *      implementation must not refer to base or derived state in the data
 128  *      structure, because it has already been uninitialized.
 129  *
 130  * Each "alloc" function allocates and returns a new instance of the respective
 131  * data structure.  The "alloc" function is not given any information about the
 132  * use of the new data structure, so it cannot perform much initialization.
 133  * Its purpose is just to ensure that the new data structure has enough room
 134  * for base and derived state.  It may return a null pointer if memory is not
 135  * available, in which case none of the other functions is called.
 136  *
 137  * Each "construct" function initializes derived state in its respective data
 138  * structure.  When "construct" is called, all of the base state has already
 139  * been initialized, so the "construct" function may refer to it.  The
 140  * "construct" function is allowed to fail, in which case the client calls the
 141  * "dealloc" function (but not the "destruct" function).
 142  *
 143  * Each "destruct" function uninitializes and frees derived state in its
 144  * respective data structure.  When "destruct" is called, the base state has
 145  * not yet been uninitialized, so the "destruct" function may refer to it.  The
 146  * "destruct" function is not allowed to fail.
 147  *
 148  * Each "dealloc" function frees raw memory that was allocated by the the
 149  * "alloc" function.  The memory's base and derived members might not have ever
 150  * been initialized (but if "construct" returned successfully, then it has been
 151  * "destruct"ed already).  The "dealloc" function is not allowed to fail.
 152  *
 153  *
 154  * Device Change Notification
 155  * ==========================
 156  *
 157  * Minimally, implementations are required to report changes to netdev flags,
 158  * features, ethernet address or carrier through connectivity_seq. Changes to
 159  * other properties are allowed to cause notification through this interface,
 160  * although implementations should try to avoid this. connectivity_seq_get()
 161  * can be used to acquire a reference to the struct seq. The interface is
 162  * described in detail in seq.h. */
 163 struct netdev_class {
 164     /* Type of netdevs in this class, e.g. "system", "tap", "gre", etc.
 165      *
 166      * One of the providers should supply a "system" type, since this is
 167      * the type assumed if no type is specified when opening a netdev.
 168      * The "system" type corresponds to an existing network device on
 169      * the system. */
 170     const char *type;
 171
 172 /* ## ------------------- ## */
 173 /* ## Top-Level Functions ## */
 174 /* ## ------------------- ## */
 175
 176     /* Called when the netdev provider is registered, typically at program
 177      * startup.  Returning an error from this function will prevent any network
 178      * device in this class from being opened.
 179      *
 180      * This function may be set to null if a network device class needs no
 181      * initialization at registration time. */
 182     int (*init)(void);
 183
 184     /* Performs periodic work needed by netdevs of this class.  May be null if
 185      * no periodic work is necessary. */
 186     void (*run)(void);
 187
 188     /* Arranges for poll_block() to wake up if the "run" member function needs
 189      * to be called.  Implementations are additionally required to wake
 190      * whenever something changes in any of its netdevs which would cause their
 191      * ->change_seq() function to change its result.  May be null if nothing is
 192      * needed here. */
 193     void (*wait)(void);
 194
 195 /* ## ---------------- ## */
 196 /* ## netdev Functions ## */
 197 /* ## ---------------- ## */
 198
 199     /* Life-cycle functions for a netdev.  See the large comment above on
 200      * struct netdev_class. */
 201     struct netdev *(*alloc)(void);
 202     int (*construct)(struct netdev *);
 203     void (*destruct)(struct netdev *);
 204     void (*dealloc)(struct netdev *);
 205
 206     /* Fetches the device 'netdev''s configuration, storing it in 'args'.
 207      * The caller owns 'args' and pre-initializes it to an empty smap.
 208      *
 209      * If this netdev class does not have any configuration options, this may
 210      * be a null pointer. */
 211     int (*get_config)(const struct netdev *netdev, struct smap *args);
 212
 213     /* Changes the device 'netdev''s configuration to 'args'.
 214      *
 215      * If this netdev class does not support configuration, this may be a null
 216      * pointer. */
 217     int (*set_config)(struct netdev *netdev, const struct smap *args);
 218
 219     /* Returns the tunnel configuration of 'netdev'.  If 'netdev' is
 220      * not a tunnel, returns null.
 221      *
 222      * If this function would always return null, it may be null instead. */
 223     const struct netdev_tunnel_config *
 224         (*get_tunnel_config)(const struct netdev *netdev);
 225
 226     /* Sends the 'size'-byte packet in 'buffer' on 'netdev'.  Returns 0 if
 227      * successful, otherwise a positive errno value.  Returns EAGAIN without
 228      * blocking if the packet cannot be queued immediately.  Returns EMSGSIZE
 229      * if a partial packet was transmitted or if the packet is too big or too
 230      * small to transmit on the device.
 231      *
 232      * The caller retains ownership of 'buffer' in all cases.
 233      *
 234      * The network device is expected to maintain a packet transmission queue,
 235      * so that the caller does not ordinarily have to do additional queuing of
 236      * packets.
 237      *
 238      * May return EOPNOTSUPP if a network device does not implement packet
 239      * transmission through this interface.  This function may be set to null
 240      * if it would always return EOPNOTSUPP anyhow.  (This will prevent the
 241      * network device from being usefully used by the netdev-based "userspace
 242      * datapath".  It will also prevent the OVS implementation of bonding from
 243      * working properly over 'netdev'.) */
 244     int (*send)(struct netdev *netdev, const void *buffer, size_t size);
 245
 246     /* Registers with the poll loop to wake up from the next call to
 247      * poll_block() when the packet transmission queue for 'netdev' has
 248      * sufficient room to transmit a packet with netdev_send().
 249      *
 250      * The network device is expected to maintain a packet transmission queue,
 251      * so that the caller does not ordinarily have to do additional queuing of
 252      * packets.  Thus, this function is unlikely to ever be useful.
 253      *
 254      * May be null if not needed, such as for a network device that does not
 255      * implement packet transmission through the 'send' member function. */
 256     void (*send_wait)(struct netdev *netdev);
 257
 258     /* Sets 'netdev''s Ethernet address to 'mac' */
 259     int (*set_etheraddr)(struct netdev *netdev, const uint8_t mac[6]);
 260
 261     /* Retrieves 'netdev''s Ethernet address into 'mac'.
 262      *
 263      * This address will be advertised as 'netdev''s MAC address through the
 264      * OpenFlow protocol, among other uses. */
 265     int (*get_etheraddr)(const struct netdev *netdev, uint8_t mac[6]);
 266
 267     /* Retrieves 'netdev''s MTU into '*mtup'.
 268      *
 269      * The MTU is the maximum size of transmitted (and received) packets, in
 270      * bytes, not including the hardware header; thus, this is typically 1500
 271      * bytes for Ethernet devices.
 272      *
 273      * If 'netdev' does not have an MTU (e.g. as some tunnels do not), then
 274      * this function should return EOPNOTSUPP.  This function may be set to
 275      * null if it would always return EOPNOTSUPP. */
 276     int (*get_mtu)(const struct netdev *netdev, int *mtup);
 277
 278     /* Sets 'netdev''s MTU to 'mtu'.
 279      *
 280      * If 'netdev' does not have an MTU (e.g. as some tunnels do not), then
 281      * this function should return EOPNOTSUPP.  This function may be set to
 282      * null if it would always return EOPNOTSUPP. */
 283     int (*set_mtu)(const struct netdev *netdev, int mtu);
 284
 285     /* Returns the ifindex of 'netdev', if successful, as a positive number.
 286      * On failure, returns a negative errno value.
 287      *
 288      * The desired semantics of the ifindex value are a combination of those
 289      * specified by POSIX for if_nametoindex() and by SNMP for ifIndex.  An
 290      * ifindex value should be unique within a host and remain stable at least
 291      * until reboot.  SNMP says an ifindex "ranges between 1 and the value of
 292      * ifNumber" but many systems do not follow this rule anyhow.
 293      *
 294      * This function may be set to null if it would always return -EOPNOTSUPP.
 295      */
 296     int (*get_ifindex)(const struct netdev *netdev);
 297
 298     /* Sets 'carrier' to true if carrier is active (link light is on) on
 299      * 'netdev'.
 300      *
 301      * May be null if device does not provide carrier status (will be always
 302      * up as long as device is up).
 303      */
 304     int (*get_carrier)(const struct netdev *netdev, bool *carrier);
 305
 306     /* Returns the number of times 'netdev''s carrier has changed since being
 307      * initialized.
 308      *
 309      * If null, callers will assume the number of carrier resets is zero. */
 310     long long int (*get_carrier_resets)(const struct netdev *netdev);
 311
 312     /* Forces ->get_carrier() to poll 'netdev''s MII registers for link status
 313      * instead of checking 'netdev''s carrier.  'netdev''s MII registers will
 314      * be polled once ever 'interval' milliseconds.  If 'netdev' does not
 315      * support MII, another method may be used as a fallback.  If 'interval' is
 316      * less than or equal to zero, reverts ->get_carrier() to its normal
 317      * behavior.
 318      *
 319      * Most network devices won't support this feature and will set this
 320      * function pointer to NULL, which is equivalent to returning EOPNOTSUPP.
 321      */
 322     int (*set_miimon_interval)(struct netdev *netdev, long long int interval);
 323
 324     /* Retrieves current device stats for 'netdev' into 'stats'.
 325      *
 326      * A network device that supports some statistics but not others, it should
 327      * set the values of the unsupported statistics to all-1-bits
 328      * (UINT64_MAX). */
 329     int (*get_stats)(const struct netdev *netdev, struct netdev_stats *);
 330
 331     /* Sets the device stats for 'netdev' to 'stats'.
 332      *
 333      * Most network devices won't support this feature and will set this
 334      * function pointer to NULL, which is equivalent to returning EOPNOTSUPP.
 335      *
 336      * Some network devices might only allow setting their stats to 0. */
 337     int (*set_stats)(struct netdev *netdev, const struct netdev_stats *);
 338
 339     /* Stores the features supported by 'netdev' into each of '*current',
 340      * '*advertised', '*supported', and '*peer'.  Each value is a bitmap of
 341      * NETDEV_F_* bits.
 342      *
 343      * This function may be set to null if it would always return EOPNOTSUPP.
 344      */
 345     int (*get_features)(const struct netdev *netdev,
 346                         enum netdev_features *current,
 347                         enum netdev_features *advertised,
 348                         enum netdev_features *supported,
 349                         enum netdev_features *peer);
 350
 351     /* Set the features advertised by 'netdev' to 'advertise', which is a
 352      * set of NETDEV_F_* bits.
 353      *
 354      * This function may be set to null for a network device that does not
 355      * support configuring advertisements. */
 356     int (*set_advertisements)(struct netdev *netdev,
 357                               enum netdev_features advertise);
 358
 359     /* Attempts to set input rate limiting (policing) policy, such that up to
 360      * 'kbits_rate' kbps of traffic is accepted, with a maximum accumulative
 361      * burst size of 'kbits' kb.
 362      *
 363      * This function may be set to null if policing is not supported. */
 364     int (*set_policing)(struct netdev *netdev, unsigned int kbits_rate,
 365                         unsigned int kbits_burst);
 366
 367     /* Adds to 'types' all of the forms of QoS supported by 'netdev', or leaves
 368      * it empty if 'netdev' does not support QoS.  Any names added to 'types'
 369      * should be documented as valid for the "type" column in the "QoS" table
 370      * in vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 371      *
 372      * Every network device must support disabling QoS with a type of "", but
 373      * this function must not add "" to 'types'.
 374      *
 375      * The caller is responsible for initializing 'types' (e.g. with
 376      * sset_init()) before calling this function.  The caller retains ownership
 377      * of 'types'.
 378      *
 379      * May be NULL if 'netdev' does not support QoS at all. */
 380     int (*get_qos_types)(const struct netdev *netdev, struct sset *types);
 381
 382     /* Queries 'netdev' for its capabilities regarding the specified 'type' of
 383      * QoS.  On success, initializes 'caps' with the QoS capabilities.
 384      *
 385      * Should return EOPNOTSUPP if 'netdev' does not support 'type'.  May be
 386      * NULL if 'netdev' does not support QoS at all. */
 387     int (*get_qos_capabilities)(const struct netdev *netdev,
 388                                 const char *type,
 389                                 struct netdev_qos_capabilities *caps);
 390
 391     /* Queries 'netdev' about its currently configured form of QoS.  If
 392      * successful, stores the name of the current form of QoS into '*typep'
 393      * and any details of configuration as string key-value pairs in
 394      * 'details'.
 395      *
 396      * A '*typep' of "" indicates that QoS is currently disabled on 'netdev'.
 397      *
 398      * The caller initializes 'details' before calling this function.  The
 399      * caller takes ownership of the string key-values pairs added to
 400      * 'details'.
 401      *
 402      * The netdev retains ownership of '*typep'.
 403      *
 404      * '*typep' will be one of the types returned by netdev_get_qos_types() for
 405      * 'netdev'.  The contents of 'details' should be documented as valid for
 406      * '*typep' in the "other_config" column in the "QoS" table in
 407      * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 408      *
 409      * May be NULL if 'netdev' does not support QoS at all. */
 410     int (*get_qos)(const struct netdev *netdev,
 411                    const char **typep, struct smap *details);
 412
 413     /* Attempts to reconfigure QoS on 'netdev', changing the form of QoS to
 414      * 'type' with details of configuration from 'details'.
 415      *
 416      * On error, the previous QoS configuration is retained.
 417      *
 418      * When this function changes the type of QoS (not just 'details'), this
 419      * also resets all queue configuration for 'netdev' to their defaults
 420      * (which depend on the specific type of QoS).  Otherwise, the queue
 421      * configuration for 'netdev' is unchanged.
 422      *
 423      * 'type' should be "" (to disable QoS) or one of the types returned by
 424      * netdev_get_qos_types() for 'netdev'.  The contents of 'details' should
 425      * be documented as valid for the given 'type' in the "other_config" column
 426      * in the "QoS" table in vswitchd/vswitch.xml (which is built as
 427      * ovs-vswitchd.conf.db(8)).
 428      *
 429      * May be NULL if 'netdev' does not support QoS at all. */
 430     int (*set_qos)(struct netdev *netdev,
 431                    const char *type, const struct smap *details);
 432
 433     /* Queries 'netdev' for information about the queue numbered 'queue_id'.
 434      * If successful, adds that information as string key-value pairs to
 435      * 'details'.  Returns 0 if successful, otherwise a positive errno value.
 436      *
 437      * Should return EINVAL if 'queue_id' is greater than or equal to the
 438      * number of supported queues (as reported in the 'n_queues' member of
 439      * struct netdev_qos_capabilities by 'get_qos_capabilities').
 440      *
 441      * The caller initializes 'details' before calling this function.  The
 442      * caller takes ownership of the string key-values pairs added to
 443      * 'details'.
 444      *
 445      * The returned contents of 'details' should be documented as valid for the
 446      * given 'type' in the "other_config" column in the "Queue" table in
 447      * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 448      */
 449     int (*get_queue)(const struct netdev *netdev,
 450                      unsigned int queue_id, struct smap *details);
 451
 452     /* Configures the queue numbered 'queue_id' on 'netdev' with the key-value
 453      * string pairs in 'details'.  The contents of 'details' should be
 454      * documented as valid for the given 'type' in the "other_config" column in
 455      * the "Queue" table in vswitchd/vswitch.xml (which is built as
 456      * ovs-vswitchd.conf.db(8)).  Returns 0 if successful, otherwise a positive
 457      * errno value.  On failure, the given queue's configuration should be
 458      * unmodified.
 459      *
 460      * Should return EINVAL if 'queue_id' is greater than or equal to the
 461      * number of supported queues (as reported in the 'n_queues' member of
 462      * struct netdev_qos_capabilities by 'get_qos_capabilities'), or if
 463      * 'details' is invalid for the type of queue.
 464      *
 465      * This function does not modify 'details', and the caller retains
 466      * ownership of it.
 467      *
 468      * May be NULL if 'netdev' does not support QoS at all. */
 469     int (*set_queue)(struct netdev *netdev,
 470                      unsigned int queue_id, const struct smap *details);
 471
 472     /* Attempts to delete the queue numbered 'queue_id' from 'netdev'.
 473      *
 474      * Should return EINVAL if 'queue_id' is greater than or equal to the
 475      * number of supported queues (as reported in the 'n_queues' member of
 476      * struct netdev_qos_capabilities by 'get_qos_capabilities').  Should
 477      * return EOPNOTSUPP if 'queue_id' is valid but may not be deleted (e.g. if
 478      * 'netdev' has a fixed set of queues with the current QoS mode).
 479      *
 480      * May be NULL if 'netdev' does not support QoS at all, or if all of its
 481      * QoS modes have fixed sets of queues. */
 482     int (*delete_queue)(struct netdev *netdev, unsigned int queue_id);
 483
 484     /* Obtains statistics about 'queue_id' on 'netdev'.  Fills 'stats' with the
 485      * queue's statistics.  May set individual members of 'stats' to all-1-bits
 486      * if the statistic is unavailable.
 487      *
 488      * May be NULL if 'netdev' does not support QoS at all. */
 489     int (*get_queue_stats)(const struct netdev *netdev, unsigned int queue_id,
 490                            struct netdev_queue_stats *stats);
 491
 492     /* Attempts to begin dumping the queues in 'netdev'.  On success, returns 0
 493      * and initializes '*statep' with any data needed for iteration.  On
 494      * failure, returns a positive errno value.
 495      *
 496      * May be NULL if 'netdev' does not support QoS at all. */
 497     int (*queue_dump_start)(const struct netdev *netdev, void **statep);
 498
 499     /* Attempts to retrieve another queue from 'netdev' for 'state', which was
 500      * initialized by a successful call to the 'queue_dump_start' function for
 501      * 'netdev'.  On success, stores a queue ID into '*queue_id' and fills
 502      * 'details' with the configuration of the queue with that ID.  Returns EOF
 503      * if the last queue has been dumped, or a positive errno value on error.
 504      * This function will not be called again once it returns nonzero once for
 505      * a given iteration (but the 'queue_dump_done' function will be called
 506      * afterward).
 507      *
 508      * The caller initializes and clears 'details' before calling this
 509      * function.  The caller takes ownership of the string key-values pairs
 510      * added to 'details'.
 511      *
 512      * The returned contents of 'details' should be documented as valid for the
 513      * given 'type' in the "other_config" column in the "Queue" table in
 514      * vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
 515      *
 516      * May be NULL if 'netdev' does not support QoS at all. */
 517     int (*queue_dump_next)(const struct netdev *netdev, void *state,
 518                            unsigned int *queue_id, struct smap *details);
 519
 520     /* Releases resources from 'netdev' for 'state', which was initialized by a
 521      * successful call to the 'queue_dump_start' function for 'netdev'.
 522      *
 523      * May be NULL if 'netdev' does not support QoS at all. */
 524     int (*queue_dump_done)(const struct netdev *netdev, void *state);
 525
 526     /* Iterates over all of 'netdev''s queues, calling 'cb' with the queue's
 527      * ID, its statistics, and the 'aux' specified by the caller.  The order of
 528      * iteration is unspecified, but (when successful) each queue must be
 529      * visited exactly once.
 530      *
 531      * 'cb' will not modify or free the statistics passed in. */
 532     int (*dump_queue_stats)(const struct netdev *netdev,
 533                             void (*cb)(unsigned int queue_id,
 534                                        struct netdev_queue_stats *,
 535                                        void *aux),
 536                             void *aux);
 537
 538     /* If 'netdev' has an assigned IPv4 address, sets '*address' to that
 539      * address and '*netmask' to the associated netmask.
 540      *
 541      * The following error values have well-defined meanings:
 542      *
 543      *   - EADDRNOTAVAIL: 'netdev' has no assigned IPv4 address.
 544      *
 545      *   - EOPNOTSUPP: No IPv4 network stack attached to 'netdev'.
 546      *
 547      * This function may be set to null if it would always return EOPNOTSUPP
 548      * anyhow. */
 549     int (*get_in4)(const struct netdev *netdev, struct in_addr *address,
 550                    struct in_addr *netmask);
 551
 552     /* Assigns 'addr' as 'netdev''s IPv4 address and 'mask' as its netmask.  If
 553      * 'addr' is INADDR_ANY, 'netdev''s IPv4 address is cleared.
 554      *
 555      * This function may be set to null if it would always return EOPNOTSUPP
 556      * anyhow. */
 557     int (*set_in4)(struct netdev *netdev, struct in_addr addr,
 558                    struct in_addr mask);
 559
 560     /* If 'netdev' has an assigned IPv6 address, sets '*in6' to that address.
 561      *
 562      * The following error values have well-defined meanings:
 563      *
 564      *   - EADDRNOTAVAIL: 'netdev' has no assigned IPv6 address.
 565      *
 566      *   - EOPNOTSUPP: No IPv6 network stack attached to 'netdev'.
 567      *
 568      * This function may be set to null if it would always return EOPNOTSUPP
 569      * anyhow. */
 570     int (*get_in6)(const struct netdev *netdev, struct in6_addr *in6);
 571
 572     /* Adds 'router' as a default IP gateway for the TCP/IP stack that
 573      * corresponds to 'netdev'.
 574      *
 575      * This function may be set to null if it would always return EOPNOTSUPP
 576      * anyhow. */
 577     int (*add_router)(struct netdev *netdev, struct in_addr router);
 578
 579     /* Looks up the next hop for 'host'.  If successful, stores the next hop
 580      * gateway's address (0 if 'host' is on a directly connected network) in
 581      * '*next_hop' and a copy of the name of the device to reach 'host' in
 582      * '*netdev_name', and returns 0.  The caller is responsible for freeing
 583      * '*netdev_name' (by calling free()).
 584      *
 585      * This function may be set to null if it would always return EOPNOTSUPP
 586      * anyhow. */
 587     int (*get_next_hop)(const struct in_addr *host, struct in_addr *next_hop,
 588                         char **netdev_name);
 589
 590     /* Retrieves driver information of the device.
 591      *
 592      * Populates 'smap' with key-value pairs representing the status of the
 593      * device.  'smap' is a set of key-value string pairs representing netdev
 594      * type specific information.  For more information see
 595      * ovs-vswitchd.conf.db(5).
 596      *
 597      * The caller is responsible for destroying 'smap' and its data.
 598      *
 599      * This function may be set to null if it would always return EOPNOTSUPP
 600      * anyhow. */
 601     int (*get_status)(const struct netdev *netdev, struct smap *smap);
 602
 603     /* Looks up the ARP table entry for 'ip' on 'netdev' and stores the
 604      * corresponding MAC address in 'mac'.  A return value of ENXIO, in
 605      * particular, indicates that there is no ARP table entry for 'ip' on
 606      * 'netdev'.
 607      *
 608      * This function may be set to null if it would always return EOPNOTSUPP
 609      * anyhow. */
 610     int (*arp_lookup)(const struct netdev *netdev, ovs_be32 ip,
 611                       uint8_t mac[6]);
 612
 613     /* Retrieves the current set of flags on 'netdev' into '*old_flags'.  Then,
 614      * turns off the flags that are set to 1 in 'off' and turns on the flags
 615      * that are set to 1 in 'on'.  (No bit will be set to 1 in both 'off' and
 616      * 'on'; that is, off & on == 0.)
 617      *
 618      * This function may be invoked from a signal handler.  Therefore, it
 619      * should not do anything that is not signal-safe (such as logging). */
 620     int (*update_flags)(struct netdev *netdev, enum netdev_flags off,
 621                         enum netdev_flags on, enum netdev_flags *old_flags);
 622
 623 /* ## ------------------- ## */
 624 /* ## netdev_rx Functions ## */
 625 /* ## ------------------- ## */
 626
 627 /* If a particular netdev class does not support receiving packets, all these
 628  * function pointers must be NULL. */
 629
 630     /* Life-cycle functions for a netdev_rx.  See the large comment above on
 631      * struct netdev_class. */
 632     struct netdev_rx *(*rx_alloc)(void);
 633     int (*rx_construct)(struct netdev_rx *);
 634     void (*rx_destruct)(struct netdev_rx *);
 635     void (*rx_dealloc)(struct netdev_rx *);
 636
 637     /* Attempts to receive a packet from 'rx' into the 'size' bytes in
 638      * 'buffer'.  If successful, returns the number of bytes in the received
 639      * packet, otherwise a negative errno value.  Returns -EAGAIN immediately
 640      * if no packet is ready to be received.
 641      *
 642      * Must return -EMSGSIZE, and discard the packet, if the received packet
 643      * is longer than 'size' bytes.
 644      *
 645      * Specify NULL if this */
 646     int (*rx_recv)(struct netdev_rx *rx, void *buffer, size_t size);
 647
 648     /* Registers with the poll loop to wake up from the next call to
 649      * poll_block() when a packet is ready to be received with netdev_rx_recv()
 650      * on 'rx'. */
 651     void (*rx_wait)(struct netdev_rx *rx);
 652
 653     /* Discards all packets waiting to be received from 'rx'. */
 654     int (*rx_drain)(struct netdev_rx *rx);
 655 };
 656
 657 int netdev_register_provider(const struct netdev_class *);
 658 int netdev_unregister_provider(const char *type);
 659
 660 extern const struct netdev_class netdev_linux_class;
 661 extern const struct netdev_class netdev_internal_class;
 662 extern const struct netdev_class netdev_tap_class;
 663 #if defined(__FreeBSD__) || defined(__NetBSD__)
 664 extern const struct netdev_class netdev_bsd_class;
 665 #endif
 666
 667 #ifdef  __cplusplus
 668 }
 669 #endif
 670
 671 #endif /* netdev.h */