Openvswitch原理与代码分析(3): openvswitch内核模块的加载

 

上一节我们讲了ovs-vswitchd，其中虚拟网桥初始化的时候，对调用内核模块来添加虚拟网卡。

 

我们从openvswitch内核模块的加载过程，来看这个过程。

 

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_family	struct 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_family	static 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_family	static 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。

 

在下面的章节中，我们会从这个函数开始，解析整个网络包的处理过程。