ovs-vswitchd.c的main函数最终会进入一个while循环，在这个无限循环中，里面最重要的两个函数是bridge_run()和netdev_run()。

Openvswitch主要管理两种类型的设备，一个是创建的虚拟网桥，一个是连接到虚拟网桥上的设备。

其中bridge_run就是初始化数据库中已经创建的虚拟网桥。

一、虚拟网桥的初始化bridge_run

bridge_run会调用bridge_run__，bridge_run__中最重要的是对于所有的网桥，都调用ofproto_run

static void
bridge_run__(void)
{
……
/* Let each bridge do the work that it needs to do. */
HMAP_FOR_EACH (br, node, &all_bridges) {
ofproto_run(br->ofproto);
}
}

Int ofproto_run(struct ofproto *p)会调用error = p->ofproto_class->run(p);

ofproto_class的定义在ofproto-provider.h中，它的实现定义在ofproto-dpif.c中，这里面的所有的函数，在这个文件中都有定义。

const struct ofproto_class ofproto_dpif_class = {
init,
enumerate_types,
enumerate_names,
del,
port_open_type,
type_run,
type_wait,
alloc,
construct,
destruct,
dealloc,
run,
wait,
NULL, /* get_memory_usage. */
type_get_memory_usage,
flush,
query_tables,
set_tables_version,
port_alloc,
port_construct,
port_destruct,
port_dealloc,
port_modified,
port_reconfigured,
port_query_by_name,
port_add,
port_del,
port_get_stats,
port_dump_start,
port_dump_next,
port_dump_done,
port_poll,
port_poll_wait,
port_is_lacp_current,
port_get_lacp_stats,
NULL, /* rule_choose_table */
rule_alloc,
rule_construct,
rule_insert,
rule_delete,
rule_destruct,
rule_dealloc,
rule_get_stats,
rule_execute,
set_frag_handling,
packet_out,
set_netflow,
get_netflow_ids,
set_sflow,
set_ipfix,
set_cfm,
cfm_status_changed,
get_cfm_status,
set_lldp,
get_lldp_status,
set_aa,
aa_mapping_set,
aa_mapping_unset,
aa_vlan_get_queued,
aa_vlan_get_queue_size,
set_bfd,
bfd_status_changed,
get_bfd_status,
set_stp,
get_stp_status,
set_stp_port,
get_stp_port_status,
get_stp_port_stats,
set_rstp,
get_rstp_status,
set_rstp_port,
get_rstp_port_status,
set_queues,
bundle_set,
bundle_remove,
mirror_set__,
mirror_get_stats__,
set_flood_vlans,
is_mirror_output_bundle,
forward_bpdu_changed,
set_mac_table_config,
set_mcast_snooping,
set_mcast_snooping_port,
set_realdev,
NULL, /* meter_get_features */
NULL, /* meter_set */
NULL, /* meter_get */
NULL, /* meter_del */
group_alloc, /* group_alloc */
group_construct, /* group_construct */
group_destruct, /* group_destruct */
group_dealloc, /* group_dealloc */
group_modify, /* group_modify */
group_get_stats, /* group_get_stats */
get_datapath_version, /* get_datapath_version */
};

在ofproto-provider.h中注释里是这样说的。

这里定义了四类数据结构

Struct ofproto表示一个交换机

Struct ofport表示交换机上的一个端口

Struct rule表示交换机上的一条flow规则

Struct ofgroup表示一个flow规则组

上面说到启动的过程中，会调用ofproto_class->run，也即会调用ofproto-dpif.c中的static int run(struct ofproto *ofproto_)函数。

在这个函数中，会初始化netflow, sflow, ipfix，stp, rstp, mac address learning等一系列操作。

bridge_run还会调用static void bridge_reconfigure(const struct ovsrec_open_vswitch *ovs_cfg)，其中ovs_cfg是从ovsdb-server里面读取出来的配置。

在这个函数里面，对于每一个网桥，将网卡添加进去

HMAP_FOR_EACH (br, node, &all_bridges) {
bridge_add_ports(br, &br->wanted_ports);
shash_destroy(&br->wanted_ports);
}

static void
bridge_add_ports(struct bridge *br, const struct shash *wanted_ports)
{
/* First add interfaces that request a particular port number. */
bridge_add_ports__(br, wanted_ports, true);
/* Then add interfaces that want automatic port number assignment.
* We add these afterward to avoid accidentally taking a specifically
* requested port number. */
bridge_add_ports__(br, wanted_ports, false);
}

static void bridge_add_ports__(struct bridge *br, const struct shash *wanted_ports, bool with_requested_port)会调用

static bool iface_create(struct bridge *br, const struct ovsrec_interface *iface_cfg, const struct ovsrec_port *port_cfg)会调用

static int iface_do_create(const struct bridge *br, const struct ovsrec_interface *iface_cfg, const struct ovsrec_port *port_cfg, ofp_port_t *ofp_portp, struct netdev **netdevp, char **errp)会调用

int ofproto_port_add(struct ofproto *ofproto, struct netdev *netdev, ofp_port_t *ofp_portp)会调用

error = ofproto->ofproto_class->port_add(ofproto, netdev);

会调用ofproto-dpif.c中的ofproto_dpif_class的static int port_add(struct ofproto *ofproto_, struct netdev *netdev)函数。

会调用int dpif_port_add(struct dpif *dpif, struct netdev *netdev, odp_port_t *port_nop)会调用

error = dpif->dpif_class->port_add(dpif, netdev, &port_no);

会调用dpif_netlink_class的port_add函数，也即dpif_netlink_port_add，也即

static int dpif_netlink_port_add(struct dpif *dpif_, struct netdev *netdev,odp_port_t *port_nop)会调用

static int dpif_netlink_port_add__(struct dpif_netlink *dpif, struct netdev *netdev, odp_port_t *port_nop)

在这个函数里面，会调用netlink的API，命令为OVS_VPORT_CMD_NEW

const char *name = netdev_vport_get_dpif_port(netdev,
namebuf, sizeof namebuf);
struct dpif_netlink_vport request, reply;
struct nl_sock **socksp = NULL;
if (dpif->handlers) {
socksp = vport_create_socksp(dpif, &error);
if (!socksp) {
return error;
}
}
dpif_netlink_vport_init(&request);
request.cmd = OVS_VPORT_CMD_NEW;
request.dp_ifindex = dpif->dp_ifindex;
request.type = netdev_to_ovs_vport_type(netdev);
request.name = name;
upcall_pids = vport_socksp_to_pids(socksp, dpif->n_handlers);
request.n_upcall_pids = socksp ? dpif->n_handlers : 1;
request.upcall_pids = upcall_pids;
error = dpif_netlink_vport_transact(&request, &reply, &buf);

这里会调用内核模块openvswitch.ko，在内核中添加虚拟网卡。这部分详细的过程将在下一节分析。

二、虚拟网卡的初始化netdev_run()

void
netdev_run(void)
OVS_EXCLUDED(netdev_class_mutex, netdev_mutex)
{
struct netdev_registered_class *rc;
netdev_initialize();
ovs_mutex_lock(&netdev_class_mutex);
HMAP_FOR_EACH (rc, hmap_node, &netdev_classes) {
if (rc->class->run) {
rc->class->run();
}
}
ovs_mutex_unlock(&netdev_class_mutex);
}

依次循环调用netdev_classes中的每一个run。

对于不同类型的虚拟网卡，都有对应的netdev_class。

例如对于dpdk的网卡有

static const struct netdev_class dpdk_class =
NETDEV_DPDK_CLASS(
"dpdk",
NULL,
netdev_dpdk_construct,
netdev_dpdk_destruct,
netdev_dpdk_set_multiq,
netdev_dpdk_eth_send,
netdev_dpdk_get_carrier,
netdev_dpdk_get_stats,
netdev_dpdk_get_features,
netdev_dpdk_get_status,
netdev_dpdk_rxq_recv);

对于物理网卡，也需要有相应的netdev_class

const struct netdev_class netdev_linux_class =
NETDEV_LINUX_CLASS(
"system",
netdev_linux_construct,
netdev_linux_get_stats,
netdev_linux_get_features,
netdev_linux_get_status);

对于连接到KVM的tap网卡

const struct netdev_class netdev_tap_class =
NETDEV_LINUX_CLASS(
"tap",
netdev_linux_construct_tap,
netdev_tap_get_stats,
netdev_linux_get_features,
netdev_linux_get_status);

对于虚拟的软网卡，比如veth pair

const struct netdev_class netdev_internal_class =
NETDEV_LINUX_CLASS(
"internal",
netdev_linux_construct,
netdev_internal_get_stats,
NULL, /* get_features */
netdev_internal_get_status);

其中NETDEV_LINUX_CLASS是一个宏，不是所有的参数都需要全部填写。

#define NETDEV_LINUX_CLASS(NAME, CONSTRUCT, GET_STATS, \
GET_FEATURES, GET_STATUS) \
{ \
NAME, \
\
NULL, \
netdev_linux_run, \
netdev_linux_wait, \
\
netdev_linux_alloc, \
CONSTRUCT, \
netdev_linux_destruct, \
netdev_linux_dealloc, \
NULL, /* get_config */ \
NULL, /* set_config */ \
NULL, /* get_tunnel_config */ \
NULL, /* build header */ \
NULL, /* push header */ \
NULL, /* pop header */ \
NULL, /* get_numa_id */ \
NULL, /* set_multiq */ \
\
netdev_linux_send, \
netdev_linux_send_wait, \
\
netdev_linux_set_etheraddr, \
netdev_linux_get_etheraddr, \
netdev_linux_get_mtu, \
netdev_linux_set_mtu, \
netdev_linux_get_ifindex, \
netdev_linux_get_carrier, \
netdev_linux_get_carrier_resets, \
netdev_linux_set_miimon_interval, \
GET_STATS, \
\
GET_FEATURES, \
netdev_linux_set_advertisements, \
\
netdev_linux_set_policing, \
netdev_linux_get_qos_types, \
netdev_linux_get_qos_capabilities, \
netdev_linux_get_qos, \
netdev_linux_set_qos, \
netdev_linux_get_queue, \
netdev_linux_set_queue, \
netdev_linux_delete_queue, \
netdev_linux_get_queue_stats, \
netdev_linux_queue_dump_start, \
netdev_linux_queue_dump_next, \
netdev_linux_queue_dump_done, \
netdev_linux_dump_queue_stats, \
\
netdev_linux_get_in4, \
netdev_linux_set_in4, \
netdev_linux_get_in6, \
netdev_linux_add_router, \
netdev_linux_get_next_hop, \
GET_STATUS, \
netdev_linux_arp_lookup, \
\
netdev_linux_update_flags, \
\
netdev_linux_rxq_alloc, \
netdev_linux_rxq_construct, \
netdev_linux_rxq_destruct, \
netdev_linux_rxq_dealloc, \
netdev_linux_rxq_recv, \
netdev_linux_rxq_wait, \
netdev_linux_rxq_drain, \
}

rc->class->run()调用的是netdev-linux.c下的netdev_linux_run

netdev_linux_run会调用netlink的sock得到虚拟网卡的状态，并且更新状态。

error = nl_sock_recv(sock, &buf, false);
if (!error) {
struct rtnetlink_change change;
if (rtnetlink_parse(&buf, &change)) {
struct netdev *netdev_ = netdev_from_name(change.ifname);
if (netdev_ && is_netdev_linux_class(netdev_->netdev_class)) {
struct netdev_linux *netdev = netdev_linux_cast(netdev_);
ovs_mutex_lock(&netdev->mutex);
netdev_linux_update(netdev, &change);
ovs_mutex_unlock(&netdev->mutex);
}
netdev_close(netdev_);
}
}