Linux内核中VLAN的实现过程(8)-Netlink控制接口

static const struct nla_policy vlan_policy[IFLA_VLAN_MAX + 1] = {
    // vlan id验证策略：16位无符号整形
	[IFLA_VLAN_ID]		= { .type = NLA_U16 },
    // vlan flags验证策略：长度为sizeof(struct ifla_vlan_flags)
	[IFLA_VLAN_FLAGS]	= { .len = sizeof(struct ifla_vlan_flags) },
    // vlan qos验证策略：嵌套的属性
	[IFLA_VLAN_EGRESS_QOS]	= { .type = NLA_NESTED },
	[IFLA_VLAN_INGRESS_QOS] = { .type = NLA_NESTED },
    // vlan协议验证策略：16位无符号整形
	[IFLA_VLAN_PROTOCOL]	= { .type = NLA_U16 },
};

// vlan netlink接口操作函数定义
struct rtnl_link_ops vlan_link_ops __read_mostly = {
    // 标识符
	.kind		= "vlan",
    // netlink属性最大值
	.maxtype	= IFLA_VLAN_MAX,
    // netlink属性验证策略
	.policy		= vlan_policy,
    // vlan设备私有数据大小
	.priv_size	= sizeof(struct vlan_dev_priv),
    // vlan设备setup函数
	.setup		= vlan_setup,
    // netlink/changelink参数的可选验证函数
	.validate	= vlan_validate,
    // 配置和注册新设备函数
	.newlink	= vlan_newlink,
    // 修改已存在设备参数的函数
	.changelink	= vlan_changelink,
    // 删除设备
	.dellink	= unregister_vlan_dev,
    // 计算dump设备特定网络链接属性所需空间的函数
	.get_size	= vlan_get_size,
    // dump设备特定网络链接属性的函数
	.fill_info	= vlan_fill_info,
    // 获取宿主设备网络命名空间的函数
	.get_link_net	= vlan_get_link_net,
};

// 在vlan模块初始化中调用：vlan_proto_init()->vlan_netlink_init()
int __init vlan_netlink_init(void)
{
    // 注册netlink操作函数集
	return rtnl_link_register(&vlan_link_ops);
}

// 在vlan模块清理中调用：vlan_cleanup_module()->vlan_netlink_fini()
void __exit vlan_netlink_fini(void)
{
    // 注销netlink操作函数集
	rtnl_link_unregister(&vlan_link_ops);
}

// 模块别名（宏展开是rtnl-link-vlan），在Linux内核模块中，可以用MODULE_AUTHOR、MODULE_DESCRIPTION、MODULE_VERSION、MODULE_DEVICE_TABLE、MODULE_ALIAS分别声明模块的作者、描述、版本、设备表和别名
MODULE_ALIAS_RTNL_LINK("vlan");

static int vlan_newlink(struct net *src_net, struct net_device *dev,
			struct nlattr *tb[], struct nlattr *data[],
			struct netlink_ext_ack *extack)
{
    // vlan设备私有数据
	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
	struct net_device *real_dev;
	unsigned int max_mtu;
	__be16 proto;
	int err;

    // 校验netlink属性：vlan id
	if (!data[IFLA_VLAN_ID]) {
		NL_SET_ERR_MSG_MOD(extack, "VLAN id not specified");
		return -EINVAL;
	}

    // 验证是否指定了接口索引
	if (!tb[IFLA_LINK]) {
		NL_SET_ERR_MSG_MOD(extack, "link not specified");
		return -EINVAL;
	}

    // 根据指定的接口索引（nla_get_u32(tb[IFLA_LINK])）查找宿主设备
	real_dev = __dev_get_by_index(src_net, nla_get_u32(tb[IFLA_LINK]));
	if (!real_dev) {
		NL_SET_ERR_MSG_MOD(extack, "link does not exist");
		return -ENODEV;
	}

    // 校验netlink属性：vlan协议
	if (data[IFLA_VLAN_PROTOCOL])
		proto = nla_get_be16(data[IFLA_VLAN_PROTOCOL]);
	else
        // 未指定，则默认802.1q协议
		proto = htons(ETH_P_8021Q);

    // 初始化vlan设备私有数据
	vlan->vlan_proto = proto;
	vlan->vlan_id	 = nla_get_u16(data[IFLA_VLAN_ID]);
	vlan->real_dev	 = real_dev;
	dev->priv_flags |= (real_dev->priv_flags & IFF_XMIT_DST_RELEASE);
	vlan->flags	 = VLAN_FLAG_REORDER_HDR;

    // 从宿主设备vlan组中查找符合vlan协议和vlan id的设备，并校验，extract是为ack的error消息
	err = vlan_check_real_dev(real_dev, vlan->vlan_proto, vlan->vlan_id,
				  extack);
	if (err < 0)
		return err;

    // 计算最大mtu
	max_mtu = netif_reduces_vlan_mtu(real_dev) ? real_dev->mtu - VLAN_HLEN :
						     real_dev->mtu;
    // 没有指定mtu，则使用上面计算的mtu
	if (!tb[IFLA_MTU])
		dev->mtu = max_mtu;
    // 校验：vlan设备mtu不可能大于宿主设备的最大mtu
	else if (dev->mtu > max_mtu)
		return -EINVAL;

    // 修vlan设备参数
	err = vlan_changelink(dev, tb, data, extack);
	if (err)
		return err;
    // 注册vlan设备
	err = register_vlan_dev(dev, extack);
	if (err)
		vlan_dev_free_egress_priority(dev);
	return err;
}

static int vlan_changelink(struct net_device *dev, struct nlattr *tb[],
			   struct nlattr *data[],
			   struct netlink_ext_ack *extack)
{
	struct ifla_vlan_flags *flags;
	struct ifla_vlan_qos_mapping *m;
	struct nlattr *attr;
	int rem, err;

    // 判断vlan flags是否设置
	if (data[IFLA_VLAN_FLAGS]) {
        // 获取vlan flags
		flags = nla_data(data[IFLA_VLAN_FLAGS]);
        // 修改vlan flags
		err = vlan_dev_change_flags(dev, flags->flags, flags->mask);
		if (err)
			return err;
	}
    // 判断入口qos是否设置
	if (data[IFLA_VLAN_INGRESS_QOS]) {
        // 遍历嵌套的qos属性
		nla_for_each_nested(attr, data[IFLA_VLAN_INGRESS_QOS], rem) {
            // 属性payload
			m = nla_data(attr);
            // 设置入口优先级
			vlan_dev_set_ingress_priority(dev, m->to, m->from);
		}
	}
    // 判断出口qos是否设置
	if (data[IFLA_VLAN_EGRESS_QOS]) {
        // 遍历嵌套的qos属性
		nla_for_each_nested(attr, data[IFLA_VLAN_EGRESS_QOS], rem) {
            // 属性payload
			m = nla_data(attr);
            // 设置出口优先级
			err = vlan_dev_set_egress_priority(dev, m->from, m->to);
			if (err)
				return err;
		}
	}
	return 0;
}

void unregister_vlan_dev(struct net_device *dev, struct list_head *head)
{
	struct vlan_dev_priv *vlan = vlan_dev_priv(dev);
	struct net_device *real_dev = vlan->real_dev;
	struct vlan_info *vlan_info;
	struct vlan_group *grp;
	u16 vlan_id = vlan->vlan_id;

	ASSERT_RTNL();

    // 获取vlan设备信息
	vlan_info = rtnl_dereference(real_dev->vlan_info);
	BUG_ON(!vlan_info);

    // 获取设备上的vlan组
	grp = &vlan_info->grp;
    // vlan个数减1
	grp->nr_vlan_devs--;

    // 注销garp vlan协议和multiple vlan协议
	if (vlan->flags & VLAN_FLAG_MVRP)
		vlan_mvrp_request_leave(dev);
	if (vlan->flags & VLAN_FLAG_GVRP)
		vlan_gvrp_request_leave(dev);

    // 从vlan组中移除该vlan设备
	vlan_group_set_device(grp, vlan->vlan_proto, vlan_id, NULL);

    // 从宿主设备上删除指向vlan设备的链接，调用者必须持有RTNL锁
	netdev_upper_dev_unlink(real_dev, dev);
    // 此函数关闭设备接口并将其从内核表中删除。 如果head不为NULL，则设备将排队等待稍后取消注册。调用者必须持有rtnl信号量。
	/* Because unregister_netdevice_queue() makes sure at least one rcu
	 * grace period is respected before device freeing,
	 * we dont need to call synchronize_net() here.
	 */
	unregister_netdevice_queue(dev, head);

    // vlan个数为0
	if (grp->nr_vlan_devs == 0) {
        // 注销宿主设备上的garp vlan和multiple vlan协议应用
		vlan_mvrp_uninit_applicant(real_dev);
		vlan_gvrp_uninit_applicant(real_dev);
	}

    // 删除宿主设备上记录的该vlan id设备
	vlan_vid_del(real_dev, vlan->vlan_proto, vlan_id);
}