控制面總覽
上圖只是描述了控制面的調用流程，控制面的接口包括如下幾各方面：
1. 虛擬設備的生命週期接口
2. 虛擬設備的業務配置接口
3. 二層基礎協議的運行啓動
4. Openflow協議的運行開啓與流表下發
下面就這幾個層面的分別簡述一下
虛擬設備的生命週期接口
虛擬設備不同於物理設備，除了FCAPS管理之外還需要對其生命週期進行管理，在OVS中，設備類型被分成了很多類（圖中只標註了四類）：Netdev-linux，Netdev-internal，Netdev-bsd，Netdev-tap等，生命週期類的接口採用的是設備文件描述符+ioctl接口，但是ioctl接口只是一個單工的用戶態向內核態通信的接口，而從內核態向用戶態傳遞設備狀態的接口仍然是Netlink接口，這裏Netlink會訂閱NETLINK_ROUTE協議類型的信息。
struct netdev_class {
/* Type of netdevs in this class, e.g. "system", "tap", "gre", etc.
*
* One of the providers should supply a "system" type, since this is
* the type assumed if no type is specified when opening a netdev.
* The "system" type corresponds to an existing network device on
* the system. */
const char *type;
/* If 'true' then this netdev should be polled by PMD threads. */
bool is_pmd;
/* ## ------------------- ## */
/* ## Top-Level Functions ## */
/* ## ------------------- ## */
/* Called when the netdev provider is registered, typically at program
* startup. Returning an error from this function will prevent any network
* device in this class from being opened.
*
* This function may be set to null if a network device class needs no
* initialization at registration time. */
int (*init)(void);
/* Performs periodic work needed by netdevs of this class. May be null if
* no periodic work is necessary.
*
* 'netdev_class' points to the class. It is useful in case the same
* function is used to implement different classes. */
void (*run)(const struct netdev_class *netdev_class);
/* Arranges for poll_block() to wake up if the "run" member function needs
* to be called. Implementations are additionally required to wake
* whenever something changes in any of its netdevs which would cause their
* ->change_seq() function to change its result. May be null if nothing is
* needed here.
*
* 'netdev_class' points to the class. It is useful in case the same
* function is used to implement different classes. */
void (*wait)(const struct netdev_class *netdev_class);
/* ## ---------------- ## */
/* ## netdev Functions ## */
/* ## ---------------- ## */
/* Life-cycle functions for a netdev. See the large comment above on
* struct netdev_class. */
struct netdev *(*alloc)(void);
int (*construct)(struct netdev *);
void (*destruct)(struct netdev *);
void (*dealloc)(struct netdev *);
};除了Netdev的生命週期管理還有內核Datapath的生命週期管理，不過這部分接口是存在於dpif中的，相關代碼如下：
/* Datapath interface class structure, to be defined by each implementation of
* a datapath interface.
*
* These functions return 0 if successful or a positive errno value on failure,
* except where otherwise noted.
*
* These functions are expected to execute synchronously, that is, to block as
* necessary to obtain a result. Thus, they may not return EAGAIN or
* EWOULDBLOCK or EINPROGRESS. We may relax this requirement in the future if
* and when we encounter performance problems. */
struct dpif_class {
/* Type of dpif in this class, e.g. "system", "netdev", etc.
*
* One of the providers should supply a "system" type, since this is
* the type assumed if no type is specified when opening a dpif. */
const char *type;
/* Called when the dpif provider is registered, typically at program
* startup. Returning an error from this function will prevent any
* datapath with this class from being created.
*
* This function may be set to null if a datapath class needs no
* initialization at registration time. */
int (*init)(void);
/* Enumerates the names of all known created datapaths (of class
* 'dpif_class'), if possible, into 'all_dps'. The caller has already
* initialized 'all_dps' and other dpif classes might already have added
* names to it.
*
* This is used by the vswitch at startup, so that it can delete any
* datapaths that are not configured.
*
* Some kinds of datapaths might not be practically enumerable, in which
* case this function may be a null pointer. */
int (*enumerate)(struct sset *all_dps, const struct dpif_class *dpif_class);
/* Returns the type to pass to netdev_open() when a dpif of class
* 'dpif_class' has a port of type 'type', for a few special cases
* when a netdev type differs from a port type. For example, when
* using the userspace datapath, a port of type "internal" needs to
* be opened as "tap".
*
* Returns either 'type' itself or a string literal, which must not
* be freed. */
const char *(*port_open_type)(const struct dpif_class *dpif_class,
const char *type);
/* Attempts to open an existing dpif called 'name', if 'create' is false,
* or to open an existing dpif or create a new one, if 'create' is true.
*
* 'dpif_class' is the class of dpif to open.
*
* If successful, stores a pointer to the new dpif in '*dpifp', which must
* have class 'dpif_class'. On failure there are no requirements on what
* is stored in '*dpifp'. */
int (*open)(const struct dpif_class *dpif_class,
const char *name, bool create, struct dpif **dpifp);
/* Closes 'dpif' and frees associated memory. */
void (*close)(struct dpif *dpif);
/* Attempts to destroy the dpif underlying 'dpif'.
*
* If successful, 'dpif' will not be used again except as an argument for
* the 'close' member function. */
int (*destroy)(struct dpif *dpif);
/* Performs periodic work needed by 'dpif', if any is necessary.
* Returns true if need to revalidate. */
bool (*run)(struct dpif *dpif);
/* Arranges for poll_block() to wake up if the "run" member function needs
* to be called for 'dpif'. */
void (*wait)(struct dpif *dpif);
};虛擬設備的業務配置接口
虛擬設備的業務配置接口也同樣在上數兩個類中，除了設備的直接配置還會有設備的組合配置，比如把Netdev綁定到Datapath中
struct netdev_class {
/* Fetches the device 'netdev''s configuration, storing it in 'args'.
* The caller owns 'args' and pre-initializes it to an empty smap.
*
* If this netdev class does not have any configuration options, this may
* be a null pointer. */
int (*get_config)(const struct netdev *netdev, struct smap *args);
/* Changes the device 'netdev''s configuration to 'args'.
*
* If this netdev class does not support configuration, this may be a null
* pointer.
*
* If the return value is not zero (meaning that an error occurred),
* the provider can allocate a string with an error message in '*errp'.
* The caller has to call free on it. */
int (*set_config)(struct netdev *netdev, const struct smap *args,
char **errp);
/* Returns the tunnel configuration of 'netdev'. If 'netdev' is
* not a tunnel, returns null.
*
* If this function would always return null, it may be null instead. */
const struct netdev_tunnel_config *
(*get_tunnel_config)(const struct netdev *netdev);
/* Build Tunnel header. Ethernet and ip header parameters are passed to
* tunnel implementation to build entire outer header for given flow. */
int (*build_header)(const struct netdev *, struct ovs_action_push_tnl *data,
const struct netdev_tnl_build_header_params *params);
/* build_header() can not build entire header for all packets for given
* flow. Push header is called for packet to build header specific to
* a packet on actual transmit. It uses partial header build by
* build_header() which is passed as data. */
void (*push_header)(struct dp_packet *packet,
const struct ovs_action_push_tnl *data);
/* Pop tunnel header from packet, build tunnel metadata and resize packet
* for further processing.
* Returns NULL in case of error or tunnel implementation queued packet for further
* processing. */
struct dp_packet * (*pop_header)(struct dp_packet *packet);
/* Returns the id of the numa node the 'netdev' is on. If there is no
* such info, returns NETDEV_NUMA_UNSPEC. */
int (*get_numa_id)(const struct netdev *netdev);
/* Configures the number of tx queues of 'netdev'. Returns 0 if successful,
* otherwise a positive errno value.
*
* 'n_txq' specifies the exact number of transmission queues to create.
*
* The caller will call netdev_reconfigure() (if necessary) before using
* netdev_send() on any of the newly configured queues, giving the provider
* a chance to adjust its settings.
*
* On error, the tx queue configuration is unchanged. */
int (*set_tx_multiq)(struct netdev *netdev, unsigned int n_txq);
/* Sends buffers on 'netdev'.
* Returns 0 if successful (for every buffer), otherwise a positive errno
* value. Returns EAGAIN without blocking if one or more packets cannot be
* queued immediately. Returns EMSGSIZE if a partial packet was transmitted
* or if a packet is too big or too small to transmit on the device.
*
* If the function returns a non-zero value, some of the packets might have
* been sent anyway.
*
* If 'may_steal' is false, the caller retains ownership of all the
* packets. If 'may_steal' is true, the caller transfers ownership of all
* the packets to the network device, regardless of success.
*
* If 'concurrent_txq' is true, the caller may perform concurrent calls
* to netdev_send() with the same 'qid'. The netdev provider is responsible
* for making sure that these concurrent calls do not create a race
* condition by using locking or other synchronization if required.
*
* The network device is expected to maintain one or more packet
* transmission queues, so that the caller does not ordinarily have to
* do additional queuing of packets. 'qid' specifies the queue to use
* and can be ignored if the implementation does not support multiple
* queues.
*
* May return EOPNOTSUPP if a network device does not implement packet
* transmission through this interface. This function may be set to null
* if it would always return EOPNOTSUPP anyhow. (This will prevent the
* network device from being usefully used by the netdev-based "userspace
* datapath". It will also prevent the OVS implementation of bonding from
* working properly over 'netdev'.) */
int (*send)(struct netdev *netdev, int qid, struct dp_packet_batch *batch,
bool may_steal, bool concurrent_txq);
/* Registers with the poll loop to wake up from the next call to
* poll_block() when the packet transmission queue for 'netdev' has
* sufficient room to transmit a packet with netdev_send().
*
* The network device is expected to maintain one or more packet
* transmission queues, so that the caller does not ordinarily have to
* do additional queuing of packets. 'qid' specifies the queue to use
* and can be ignored if the implementation does not support multiple
* queues.
*
* May be null if not needed, such as for a network device that does not
* implement packet transmission through the 'send' member function. */
void (*send_wait)(struct netdev *netdev, int qid);
/* Sets 'netdev''s Ethernet address to 'mac' */
int (*set_etheraddr)(struct netdev *netdev, const struct eth_addr mac);
/* Retrieves 'netdev''s Ethernet address into 'mac'.
*
* This address will be advertised as 'netdev''s MAC address through the
* OpenFlow protocol, among other uses. */
int (*get_etheraddr)(const struct netdev *netdev, struct eth_addr *mac);
/* Retrieves 'netdev''s MTU into '*mtup'.
*
* The MTU is the maximum size of transmitted (and received) packets, in
* bytes, not including the hardware header; thus, this is typically 1500
* bytes for Ethernet devices.
*
* If 'netdev' does not have an MTU (e.g. as some tunnels do not), then
* this function should return EOPNOTSUPP. This function may be set to
* null if it would always return EOPNOTSUPP. */
int (*get_mtu)(const struct netdev *netdev, int *mtup);
/* Sets 'netdev''s MTU to 'mtu'.
*
* If 'netdev' does not have an MTU (e.g. as some tunnels do not), then
* this function should return EOPNOTSUPP. This function may be set to
* null if it would always return EOPNOTSUPP. */
int (*set_mtu)(struct netdev *netdev, int mtu);
/* Returns the ifindex of 'netdev', if successful, as a positive number.
* On failure, returns a negative errno value.
*
* The desired semantics of the ifindex value are a combination of those
* specified by POSIX for if_nametoindex() and by SNMP for ifIndex. An
* ifindex value should be unique within a host and remain stable at least
* until reboot. SNMP says an ifindex "ranges between 1 and the value of
* ifNumber" but many systems do not follow this rule anyhow.
*
* This function may be set to null if it would always return -EOPNOTSUPP.
*/
int (*get_ifindex)(const struct netdev *netdev);
/* Sets 'carrier' to true if carrier is active (link light is on) on
* 'netdev'.
*
* May be null if device does not provide carrier status (will be always
* up as long as device is up).
*/
int (*get_carrier)(const struct netdev *netdev, bool *carrier);
/* Returns the number of times 'netdev''s carrier has changed since being
* initialized.
*
* If null, callers will assume the number of carrier resets is zero. */
long long int (*get_carrier_resets)(const struct netdev *netdev);
/* Forces ->get_carrier() to poll 'netdev''s MII registers for link status
* instead of checking 'netdev''s carrier. 'netdev''s MII registers will
* be polled once every 'interval' milliseconds. If 'netdev' does not
* support MII, another method may be used as a fallback. If 'interval' is
* less than or equal to zero, reverts ->get_carrier() to its normal
* behavior.
*
* Most network devices won't support this feature and will set this
* function pointer to NULL, which is equivalent to returning EOPNOTSUPP.
*/
int (*set_miimon_interval)(struct netdev *netdev, long long int interval);
/* Retrieves current device stats for 'netdev' into 'stats'.
*
* A network device that supports some statistics but not others, it should
* set the values of the unsupported statistics to all-1-bits
* (UINT64_MAX). */
int (*get_stats)(const struct netdev *netdev, struct netdev_stats *);
/* Stores the features supported by 'netdev' into each of '*current',
* '*advertised', '*supported', and '*peer'. Each value is a bitmap of
* NETDEV_F_* bits.
*
* This function may be set to null if it would always return EOPNOTSUPP.
*/
int (*get_features)(const struct netdev *netdev,
enum netdev_features *current,
enum netdev_features *advertised,
enum netdev_features *supported,
enum netdev_features *peer);
/* Set the features advertised by 'netdev' to 'advertise', which is a
* set of NETDEV_F_* bits.
*
* This function may be set to null for a network device that does not
* support configuring advertisements. */
int (*set_advertisements)(struct netdev *netdev,
enum netdev_features advertise);
/* Attempts to set input rate limiting (policing) policy, such that up to
* 'kbits_rate' kbps of traffic is accepted, with a maximum accumulative
* burst size of 'kbits' kb.
*
* This function may be set to null if policing is not supported. */
int (*set_policing)(struct netdev *netdev, unsigned int kbits_rate,
unsigned int kbits_burst);
/* Adds to 'types' all of the forms of QoS supported by 'netdev', or leaves
* it empty if 'netdev' does not support QoS. Any names added to 'types'
* should be documented as valid for the "type" column in the "QoS" table
* in vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
*
* Every network device must support disabling QoS with a type of "", but
* this function must not add "" to 'types'.
*
* The caller is responsible for initializing 'types' (e.g. with
* sset_init()) before calling this function. The caller retains ownership
* of 'types'.
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*get_qos_types)(const struct netdev *netdev, struct sset *types);
/* Queries 'netdev' for its capabilities regarding the specified 'type' of
* QoS. On success, initializes 'caps' with the QoS capabilities.
*
* Should return EOPNOTSUPP if 'netdev' does not support 'type'. May be
* NULL if 'netdev' does not support QoS at all. */
int (*get_qos_capabilities)(const struct netdev *netdev,
const char *type,
struct netdev_qos_capabilities *caps);
/* Queries 'netdev' about its currently configured form of QoS. If
* successful, stores the name of the current form of QoS into '*typep'
* and any details of configuration as string key-value pairs in
* 'details'.
*
* A '*typep' of "" indicates that QoS is currently disabled on 'netdev'.
*
* The caller initializes 'details' before calling this function. The
* caller takes ownership of the string key-values pairs added to
* 'details'.
*
* The netdev retains ownership of '*typep'.
*
* '*typep' will be one of the types returned by netdev_get_qos_types() for
* 'netdev'. The contents of 'details' should be documented as valid for
* '*typep' in the "other_config" column in the "QoS" table in
* vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*get_qos)(const struct netdev *netdev,
const char **typep, struct smap *details);
/* Attempts to reconfigure QoS on 'netdev', changing the form of QoS to
* 'type' with details of configuration from 'details'.
*
* On error, the previous QoS configuration is retained.
*
* When this function changes the type of QoS (not just 'details'), this
* also resets all queue configuration for 'netdev' to their defaults
* (which depend on the specific type of QoS). Otherwise, the queue
* configuration for 'netdev' is unchanged.
*
* 'type' should be "" (to disable QoS) or one of the types returned by
* netdev_get_qos_types() for 'netdev'. The contents of 'details' should
* be documented as valid for the given 'type' in the "other_config" column
* in the "QoS" table in vswitchd/vswitch.xml (which is built as
* ovs-vswitchd.conf.db(8)).
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*set_qos)(struct netdev *netdev,
const char *type, const struct smap *details);
/* Queries 'netdev' for information about the queue numbered 'queue_id'.
* If successful, adds that information as string key-value pairs to
* 'details'. Returns 0 if successful, otherwise a positive errno value.
*
* Should return EINVAL if 'queue_id' is greater than or equal to the
* number of supported queues (as reported in the 'n_queues' member of
* struct netdev_qos_capabilities by 'get_qos_capabilities').
*
* The caller initializes 'details' before calling this function. The
* caller takes ownership of the string key-values pairs added to
* 'details'.
*
* The returned contents of 'details' should be documented as valid for the
* given 'type' in the "other_config" column in the "Queue" table in
* vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
*/
int (*get_queue)(const struct netdev *netdev,
unsigned int queue_id, struct smap *details);
/* Configures the queue numbered 'queue_id' on 'netdev' with the key-value
* string pairs in 'details'. The contents of 'details' should be
* documented as valid for the given 'type' in the "other_config" column in
* the "Queue" table in vswitchd/vswitch.xml (which is built as
* ovs-vswitchd.conf.db(8)). Returns 0 if successful, otherwise a positive
* errno value. On failure, the given queue's configuration should be
* unmodified.
*
* Should return EINVAL if 'queue_id' is greater than or equal to the
* number of supported queues (as reported in the 'n_queues' member of
* struct netdev_qos_capabilities by 'get_qos_capabilities'), or if
* 'details' is invalid for the type of queue.
*
* This function does not modify 'details', and the caller retains
* ownership of it.
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*set_queue)(struct netdev *netdev,
unsigned int queue_id, const struct smap *details);
/* Attempts to delete the queue numbered 'queue_id' from 'netdev'.
*
* Should return EINVAL if 'queue_id' is greater than or equal to the
* number of supported queues (as reported in the 'n_queues' member of
* struct netdev_qos_capabilities by 'get_qos_capabilities'). Should
* return EOPNOTSUPP if 'queue_id' is valid but may not be deleted (e.g. if
* 'netdev' has a fixed set of queues with the current QoS mode).
*
* May be NULL if 'netdev' does not support QoS at all, or if all of its
* QoS modes have fixed sets of queues. */
int (*delete_queue)(struct netdev *netdev, unsigned int queue_id);
/* Obtains statistics about 'queue_id' on 'netdev'. Fills 'stats' with the
* queue's statistics. May set individual members of 'stats' to all-1-bits
* if the statistic is unavailable.
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*get_queue_stats)(const struct netdev *netdev, unsigned int queue_id,
struct netdev_queue_stats *stats);
/* Attempts to begin dumping the queues in 'netdev'. On success, returns 0
* and initializes '*statep' with any data needed for iteration. On
* failure, returns a positive errno value.
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*queue_dump_start)(const struct netdev *netdev, void **statep);
/* Attempts to retrieve another queue from 'netdev' for 'state', which was
* initialized by a successful call to the 'queue_dump_start' function for
* 'netdev'. On success, stores a queue ID into '*queue_id' and fills
* 'details' with the configuration of the queue with that ID. Returns EOF
* if the last queue has been dumped, or a positive errno value on error.
* This function will not be called again once it returns nonzero once for
* a given iteration (but the 'queue_dump_done' function will be called
* afterward).
*
* The caller initializes and clears 'details' before calling this
* function. The caller takes ownership of the string key-values pairs
* added to 'details'.
*
* The returned contents of 'details' should be documented as valid for the
* given 'type' in the "other_config" column in the "Queue" table in
* vswitchd/vswitch.xml (which is built as ovs-vswitchd.conf.db(8)).
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*queue_dump_next)(const struct netdev *netdev, void *state,
unsigned int *queue_id, struct smap *details);
/* Releases resources from 'netdev' for 'state', which was initialized by a
* successful call to the 'queue_dump_start' function for 'netdev'.
*
* May be NULL if 'netdev' does not support QoS at all. */
int (*queue_dump_done)(const struct netdev *netdev, void *state);
/* Iterates over all of 'netdev''s queues, calling 'cb' with the queue's
* ID, its statistics, and the 'aux' specified by the caller. The order of
* iteration is unspecified, but (when successful) each queue must be
* visited exactly once.
*
* 'cb' will not modify or free the statistics passed in. */
int (*dump_queue_stats)(const struct netdev *netdev,
void (*cb)(unsigned int queue_id,
struct netdev_queue_stats *,
void *aux),
void *aux);
/* Assigns 'addr' as 'netdev''s IPv4 address and 'mask' as its netmask. If
* 'addr' is INADDR_ANY, 'netdev''s IPv4 address is cleared.
*
* This function may be set to null if it would always return EOPNOTSUPP
* anyhow. */
int (*set_in4)(struct netdev *netdev, struct in_addr addr,
struct in_addr mask);
/* Returns all assigned IP address to 'netdev' and returns 0.
* API allocates array of address and masks and set it to
* '*addr' and '*mask'.
* Otherwise, returns a positive errno value and sets '*addr', '*mask
* and '*n_addr' to NULL.
*
* The following error values have well-defined meanings:
*
* - EADDRNOTAVAIL: 'netdev' has no assigned IPv6 address.
*
* - EOPNOTSUPP: No IPv6 network stack attached to 'netdev'.
*
* 'addr' may be null, in which case the address itself is not reported. */
int (*get_addr_list)(const struct netdev *netdev, struct in6_addr **in,
struct in6_addr **mask, int *n_in6);
/* Adds 'router' as a default IP gateway for the TCP/IP stack that
* corresponds to 'netdev'.
*
* This function may be set to null if it would always return EOPNOTSUPP
* anyhow. */
int (*add_router)(struct netdev *netdev, struct in_addr router);
/* Looks up the next hop for 'host' in the host's routing table. If
* successful, stores the next hop gateway's address (0 if 'host' is on a
* directly connected network) in '*next_hop' and a copy of the name of the
* device to reach 'host' in '*netdev_name', and returns 0. The caller is
* responsible for freeing '*netdev_name' (by calling free()).
*
* This function may be set to null if it would always return EOPNOTSUPP
* anyhow. */
int (*get_next_hop)(const struct in_addr *host, struct in_addr *next_hop,
char **netdev_name);
/* Retrieves driver information of the device.
*
* Populates 'smap' with key-value pairs representing the status of the
* device. 'smap' is a set of key-value string pairs representing netdev
* type specific information. For more information see
* ovs-vswitchd.conf.db(5).
*
* The caller is responsible for destroying 'smap' and its data.
*
* This function may be set to null if it would always return EOPNOTSUPP
* anyhow. */
int (*get_status)(const struct netdev *netdev, struct smap *smap);
/* Looks up the ARP table entry for 'ip' on 'netdev' and stores the
* corresponding MAC address in 'mac'. A return value of ENXIO, in
* particular, indicates that there is no ARP table entry for 'ip' on
* 'netdev'.
*
* This function may be set to null if it would always return EOPNOTSUPP
* anyhow. */
int (*arp_lookup)(const struct netdev *netdev, ovs_be32 ip,
struct eth_addr *mac);
/* Retrieves the current set of flags on 'netdev' into '*old_flags'. Then,
* turns off the flags that are set to 1 in 'off' and turns on the flags
* that are set to 1 in 'on'. (No bit will be set to 1 in both 'off' and
* 'on'; that is, off & on == 0.)
*
* This function may be invoked from a signal handler. Therefore, it
* should not do anything that is not signal-safe (such as logging). */
int (*update_flags)(struct netdev *netdev, enum netdev_flags off,
enum netdev_flags on, enum netdev_flags *old_flags);
/* If the provider called netdev_request_reconfigure(), the upper layer
* will eventually call this. The provider can update the device
* configuration knowing that the upper layer will not call rxq_recv() or
* send() until this function returns.
*
* On error, the configuration is indeterminant and the device cannot be
* used to send and receive packets until a successful configuration is
* applied. */
int (*reconfigure)(struct netdev *netdev);
/* ## -------------------- ## */
/* ## netdev_rxq Functions ## */
/* ## -------------------- ## */
/* If a particular netdev class does not support receiving packets, all these
* function pointers must be NULL. */
/* Life-cycle functions for a netdev_rxq. See the large comment above on
* struct netdev_class. */
struct netdev_rxq *(*rxq_alloc)(void);
int (*rxq_construct)(struct netdev_rxq *);
void (*rxq_destruct)(struct netdev_rxq *);
void (*rxq_dealloc)(struct netdev_rxq *);
/* Attempts to receive a batch of packets from 'rx'. In 'batch', the
* caller supplies 'packets' as the pointer to the beginning of an array
* of NETDEV_MAX_BURST pointers to dp_packet. If successful, the
* implementation stores pointers to up to NETDEV_MAX_BURST dp_packets into
* the array, transferring ownership of the packets to the caller, stores
* the number of received packets into 'count', and returns 0.
*
* The implementation does not necessarily initialize any non-data members
* of 'packets' in 'batch'. That is, the caller must initialize layer
* pointers and metadata itself, if desired, e.g. with pkt_metadata_init()
* and miniflow_extract().
*
* Implementations should allocate buffers with DP_NETDEV_HEADROOM bytes of
* headroom.
*
* Returns EAGAIN immediately if no packet is ready to be received or
* another positive errno value if an error was encountered. */
int (*rxq_recv)(struct netdev_rxq *rx, struct dp_packet_batch *batch);
/* Registers with the poll loop to wake up from the next call to
* poll_block() when a packet is ready to be received with
* netdev_rxq_recv() on 'rx'. */
void (*rxq_wait)(struct netdev_rxq *rx);
/* Discards all packets waiting to be received from 'rx'. */
int (*rxq_drain)(struct netdev_rxq *rx);
};在Netdev側的配置完成之後通常還會配套在Datapath側做配置，下面以端口綁定流程爲例講解。
具體綁定的接口在Dpif.h中，Dpif模塊本身就是Datapath對外暴露的接口，同時也起到協調設備和datapath協同工作的作用。
/* Attempts to add 'netdev' as a port on 'dpif'. If 'port_nop' is
* non-null and its value is not ODPP_NONE, then attempts to use the
* value as the port number.
*
* If successful, returns 0 and sets '*port_nop' to the new port's port
* number (if 'port_nop' is non-null). On failure, returns a positive
* errno value and sets '*port_nop' to ODPP_NONE (if 'port_nop' is
* non-null). */
int
dpif_port_add(struct dpif *dpif, struct netdev *netdev, odp_port_t *port_nop)
{
const char *netdev_name = netdev_get_name(netdev);
odp_port_t port_no = ODPP_NONE;
int error;
COVERAGE_INC(dpif_port_add);
if (port_nop) {
port_no = *port_nop;
}
error = dpif->dpif_class->port_add(dpif, netdev, &port_no);
if (!error) {
VLOG_DBG_RL(&dpmsg_rl, "%s: added %s as port %"PRIu32,
dpif_name(dpif), netdev_name, port_no);
} else {
VLOG_WARN_RL(&error_rl, "%s: failed to add %s as port: %s",
dpif_name(dpif), netdev_name, ovs_strerror(error));
port_no = ODPP_NONE;
}
if (port_nop) {
*port_nop = port_no;
}
return error;
}在上述代碼在Datapath上創建一個指向netdev的vport，同時其端口號爲port_no，這涉及到用戶進程和內核進程的交互，用戶態使用Netlink發送創建端口的消息給內核datapath進程，在內核態收到對應的消息類型後分別調用對應的方法進行處理，這裏會調用ovs_vport_cmd_new方法進行處理
static struct genl_ops dp_vport_genl_ops[] = {
{ .cmd = OVS_VPORT_CMD_NEW,
.flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
.policy = vport_policy,
.doit = ovs_vport_cmd_new
},
{ .cmd = OVS_VPORT_CMD_DEL,
.flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
.policy = vport_policy,
.doit = ovs_vport_cmd_del
},
{ .cmd = OVS_VPORT_CMD_GET,
.flags = 0, /* OK for unprivileged users. */
.policy = vport_policy,
.doit = ovs_vport_cmd_get,
.dumpit = ovs_vport_cmd_dump
},
{ .cmd = OVS_VPORT_CMD_SET,
.flags = GENL_UNS_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */
.policy = vport_policy,
.doit = ovs_vport_cmd_set,
},
};函數ovs_vport_cmd_new會調用static struct vport *new_vport(const struct vport_parms *parms)會繼續調用到struct vport *ovs_vport_add(const struct vport_parms *parms)裏面會調用vport = ops->create(parms);
ops是什麼呢？在dp_init函數中會調用ovs_netdev_init，它會調用ovs_vport_ops_register(&ovs_netdev_vport_ops);
所以ops->create會調用netdev_create，它會調用ovs_netdev_link，其中有下面的代碼：
vport->dev = dev_get_by_name(ovs_dp_get_net(vport->dp), name);
err = netdev_rx_handler_register(vport->dev, netdev_frame_hook,
vport);netdev_rx_handler_register會註冊一個方法叫做netdev_frame_hook到對應的Netdev中，每當網卡收到包的時候，就調用這個方法。
在後面講數據面的章節中，我們會從這個函數開始，解析整個網絡包的處理過程。
另外要說一點，內核是通過用戶進程傳遞的netdev_name在內核對應的namespace中尋找到對應的設備的，namespace可以起到網絡設備隔離的作用。
