在datapath/datapath.c中会调用module_init(dp_init);来初始化内核模块。
static int __init dp_init(void)
{ int err; BUILD_BUG_ON(sizeof(struct ovs_skb_cb) > FIELD_SIZEOF(struct sk_buff, cb)); pr_info("Open vSwitch switching datapath %s\n", VERSION); err = compat_init(); if (err) goto error; err = action_fifos_init(); if (err) goto error_compat_exit; err = ovs_internal_dev_rtnl_link_register(); if (err) goto error_action_fifos_exit; err = ovs_flow_init(); if (err) goto error_unreg_rtnl_link; err = ovs_vport_init(); if (err) goto error_flow_exit; err = register_pernet_device(&ovs_net_ops); if (err) goto error_vport_exit; err = register_netdevice_notifier(&ovs_dp_device_notifier); if (err) goto error_netns_exit; err = ovs_netdev_init(); if (err) goto error_unreg_notifier; err = dp_register_genl(); if (err < 0) goto error_unreg_netdev; return 0; error_unreg_netdev: ovs_netdev_exit();error_unreg_notifier: unregister_netdevice_notifier(&ovs_dp_device_notifier);error_netns_exit: unregister_pernet_device(&ovs_net_ops);error_vport_exit: ovs_vport_exit();error_flow_exit: ovs_flow_exit();error_unreg_rtnl_link: ovs_internal_dev_rtnl_link_unregister();error_action_fifos_exit: action_fifos_exit();error_compat_exit: compat_exit();error: return err;}其中比较重要的是调用了dp_register_genl()，这个就是注册netlink函数，从而ovs-vswitchd可以通过netlink调用内核。
static int dp_register_genl(void)
{ int err; int i; for (i = 0; i < ARRAY_SIZE(dp_genl_families); i++) { err = genl_register_family(dp_genl_families[i]); if (err) goto error; } return 0; error: dp_unregister_genl(i); return err;}这里dp_genl_families由四个netlink的family组成
static struct genl_family *dp_genl_families[] = {
&dp_datapath_genl_family, &dp_vport_genl_family, &dp_flow_genl_family, &dp_packet_genl_family,};其中分别定义了以下的操作：
Family名称
.name
.ops
dp_datapath_genl_family
static struct genl_family dp_datapath_genl_family = {
.id = GENL_ID_GENERATE, .hdrsize = sizeof(struct ovs_header), .name = OVS_DATAPATH_FAMILY, .version = OVS_DATAPATH_VERSION, .maxattr = OVS_DP_ATTR_MAX, .netnsok = true, .parallel_ops = true, .ops = dp_datapath_genl_ops, .n_ops = ARRAY_SIZE(dp_datapath_genl_ops), .mcgrps = &ovs_dp_datapath_multicast_group, .n_mcgrps = 1,};static struct genl_ops dp_datapath_genl_ops[] = { { .cmd = OVS_DP_CMD_NEW, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = datapath_policy, .doit = ovs_dp_cmd_new }, { .cmd = OVS_DP_CMD_DEL, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = datapath_policy, .doit = ovs_dp_cmd_del }, { .cmd = OVS_DP_CMD_GET, .flags = 0, /* OK for unprivileged users. */ .policy = datapath_policy, .doit = ovs_dp_cmd_get, .dumpit = ovs_dp_cmd_dump }, { .cmd = OVS_DP_CMD_SET, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = datapath_policy, .doit = ovs_dp_cmd_set, },};dp_vport_genl_familystruct genl_family dp_vport_genl_family = {
.id = GENL_ID_GENERATE, .hdrsize = sizeof(struct ovs_header), .name = OVS_VPORT_FAMILY, .version = OVS_VPORT_VERSION, .maxattr = OVS_VPORT_ATTR_MAX, .netnsok = true, .parallel_ops = true, .ops = dp_vport_genl_ops, .n_ops = ARRAY_SIZE(dp_vport_genl_ops), .mcgrps = &ovs_dp_vport_multicast_group, .n_mcgrps = 1,};static struct genl_ops dp_vport_genl_ops[] = { { .cmd = OVS_VPORT_CMD_NEW, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = vport_policy, .doit = ovs_vport_cmd_new }, { .cmd = OVS_VPORT_CMD_DEL, .flags = GENL_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_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = vport_policy, .doit = ovs_vport_cmd_set, },};dp_flow_genl_familystatic struct genl_family dp_flow_genl_family = {
.id = GENL_ID_GENERATE, .hdrsize = sizeof(struct ovs_header), .name = OVS_FLOW_FAMILY, .version = OVS_FLOW_VERSION, .maxattr = OVS_FLOW_ATTR_MAX, .netnsok = true, .parallel_ops = true, .ops = dp_flow_genl_ops, .n_ops = ARRAY_SIZE(dp_flow_genl_ops), .mcgrps = &ovs_dp_flow_multicast_group, .n_mcgrps = 1,};static struct genl_ops dp_flow_genl_ops[] = { { .cmd = OVS_FLOW_CMD_NEW, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = flow_policy, .doit = ovs_flow_cmd_new }, { .cmd = OVS_FLOW_CMD_DEL, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = flow_policy, .doit = ovs_flow_cmd_del }, { .cmd = OVS_FLOW_CMD_GET, .flags = 0, /* OK for unprivileged users. */ .policy = flow_policy, .doit = ovs_flow_cmd_get, .dumpit = ovs_flow_cmd_dump }, { .cmd = OVS_FLOW_CMD_SET, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = flow_policy, .doit = ovs_flow_cmd_set, },};dp_packet_genl_familystatic struct genl_family dp_packet_genl_family = {
.id = GENL_ID_GENERATE, .hdrsize = sizeof(struct ovs_header), .name = OVS_PACKET_FAMILY, .version = OVS_PACKET_VERSION, .maxattr = OVS_PACKET_ATTR_MAX, .netnsok = true, .parallel_ops = true, .ops = dp_packet_genl_ops, .n_ops = ARRAY_SIZE(dp_packet_genl_ops),};static struct genl_ops dp_packet_genl_ops[] = { { .cmd = OVS_PACKET_CMD_EXECUTE, .flags = GENL_ADMIN_PERM, /* Requires CAP_NET_ADMIN privilege. */ .policy = packet_policy, .doit = ovs_packet_cmd_execute }};如上一节中，ovs-vswitchd启动的时候，将虚拟网卡添加到虚拟交换机上的时候，会调用netlink的OVS_VPORT_CMD_NEW命令，因而会调用函数ovs_vport_cmd_new。
会调用static struct vport *new_vport(const struct vport_parms *parms)
会调用struct vport *ovs_vport_add(const struct vport_parms *parms)里面会调用vport = ops->create(parms);
ops是什么呢？在dp_init函数中会调用ovs_netdev_init，它会调用ovs_vport_ops_register(&ovs_netdev_vport_ops);
static struct vport_ops ovs_netdev_vport_ops = {
.type = OVS_VPORT_TYPE_NETDEV, .create = netdev_create, .destroy = netdev_destroy, .send = dev_queue_xmit,};所以ops->create会调用netdev_create，它会调用ovs_netdev_link，其中有下面的代码：
err = netdev_rx_handler_register(vport->dev, netdev_frame_hook,
vport);注册一个方法叫做netdev_frame_hook，每当网卡收到包的时候，就调用这个方法。