网络子系统28_桥接ioctl

//	1.网桥子系统向用户空间提供的接口：
//		1.1 通过socket ioctl创建网桥
//		1.2 通过网桥的特殊设备文件ioctl添加网桥端口

//	桥接在socket ioctl中的衔接处理
//	处理的命令类型：
//		1.获取网桥信息
//		2.设置网桥信息
//		3.添加网桥
//		4.删除网桥
1.1 static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
{
		...
		case SIOCGIFBR:
		case SIOCSIFBR:
		case SIOCBRADDBR:
		case SIOCBRDELBR:
			err = -ENOPKG;
			if (!br_ioctl_hook)//如果钩子函数没有被设置，则加载桥接模块
				request_module("bridge");

			down(&br_ioctl_mutex);//在执行钩子函数的过程中，获取信号量，防止在钩子函数被执行的过程，被设置
			if (br_ioctl_hook) 
				err = br_ioctl_hook(cmd, argp);
			up(&br_ioctl_mutex);
			break;
		...
}
//	网桥的socket ioctl
//		在网桥子系统初始化时，由brioctl_set设置br_ioctl_hook = br_ioctl_deviceless_stub
//	调用路径: sock_ioctl->br_ioctl_hook
1.2 int br_ioctl_deviceless_stub(unsigned int cmd, void __user *uarg)
{
	switch (cmd) {
	case SIOCGIFBR:
	case SIOCSIFBR:
		return old_deviceless(uarg);//老式网桥命令
		
	case SIOCBRADDBR://新网桥命令，添加或删除网桥
	case SIOCBRDELBR:
	{
		char buf[IFNAMSIZ];

		if (!capable(CAP_NET_ADMIN))//当前进程需要admin权限
			return -EPERM;

		if (copy_from_user(buf, uarg, IFNAMSIZ))//uarg提供网桥名字
			return -EFAULT;

		buf[IFNAMSIZ-1] = 0;//c格式字符串
		if (cmd == SIOCBRADDBR)//添加网桥
			return br_add_bridge(buf);

		return br_del_bridge(buf);//删除
	}
	}
	return -EOPNOTSUPP;
}

//	网桥老式ioctl命令处理
//		处理的命令类型为SIOCGIFBR, SIOCSIFBR
//	调用路径:br_ioctl_deviceless_stub->old_deviceless
1.3 static int old_deviceless(void __user *uarg)
{
	unsigned long args[3];

	if (copy_from_user(args, uarg, sizeof(args)))//从用户空间拷贝参数
		return -EFAULT;

	switch (args[0]) {//由uarg[0]提供命令
	case BRCTL_GET_VERSION://获取网桥版本
		return BRCTL_VERSION;

	case BRCTL_GET_BRIDGES://获取网桥接口的index
	{
		int *indices;
		int ret = 0;

		indices = kmalloc(args[2]*sizeof(int), GFP_KERNEL);//uarg[2]指示获取接口数
		if (indices == NULL)
			return -ENOMEM;

		memset(indices, 0, args[2]*sizeof(int));
		args[2] = get_bridge_ifindices(indices, args[2]);//实际获取到的接口数

		ret = copy_to_user((void __user *)args[1], indices, args[2]*sizeof(int))//uarg[1]包含保存返回值的位置
			? -EFAULT : args[2];

		kfree(indices);
		return ret;
	}

	case BRCTL_ADD_BRIDGE://添加或删除网桥，网桥名主机内唯一
	case BRCTL_DEL_BRIDGE:
	{
		char buf[IFNAMSIZ];

		if (!capable(CAP_NET_ADMIN))//当前进程admin权限
			return -EPERM;

		if (copy_from_user(buf, (void __user *)args[1], IFNAMSIZ))//uarg[1]保存网桥名的内存地址
			return -EFAULT;

		buf[IFNAMSIZ-1] = 0;//c风格字符串

		if (args[0] == BRCTL_ADD_BRIDGE)
			return br_add_bridge(buf);//添加网桥

		return br_del_bridge(buf);//删除网桥
	}
	}

	return -EOPNOTSUPP;
}

//	网桥的特殊设备文件ioctl处理
//		通过打开网桥设备文件，ioctl
//	处理的命令：
//		1.老式网桥命令
//		2.新式添加删除网桥端口命令
2.1 int br_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
	struct net_bridge *br = netdev_priv(dev);

	switch(cmd) {
	case SIOCDEVPRIVATE://老式命令
		return old_dev_ioctl(dev, rq, cmd);

	case SIOCBRADDIF://添加删除接口
	case SIOCBRDELIF:
		return add_del_if(br, rq->ifr_ifindex, cmd == SIOCBRADDIF);

	}

	pr_debug("Bridge does not support ioctl 0x%x\n", cmd);
	return -EOPNOTSUPP;
}

//	遗留的老式设备文件ioctl
//		通过cmd=SIOCDEVPRIVATE调用
//	调用路径：br_dev_ioctl->old_dev_ioctl
2.2 static int old_dev_ioctl(struct net_device *dev, struct ifreq *rq, int cmd)
{
	struct net_bridge *br = netdev_priv(dev);
	unsigned long args[4];
	
	if (copy_from_user(args, rq->ifr_data, sizeof(args)))
		return -EFAULT;

	switch (args[0]) {//删除添加接口
	case BRCTL_ADD_IF:
	case BRCTL_DEL_IF:
		return add_del_if(br, args[1], args[0] == BRCTL_ADD_IF);

	case BRCTL_GET_BRIDGE_INFO:
	{
		struct __bridge_info b;
		//获取网桥设备信息
		...

		if (copy_to_user((void __user *)args[1], &b, sizeof(b)))
			return -EFAULT;

		return 0;
	}

	case BRCTL_GET_PORT_LIST://获取网桥端口链表
	{
		int num, *indices;
		...
		//返回网桥端口的index
		get_port_ifindices(br, indices, num);
		if (copy_to_user((void __user *)args[1], indices, num*sizeof(int)))
			num =  -EFAULT;
		kfree(indices);
		return num;
	}

	case BRCTL_SET_BRIDGE_FORWARD_DELAY://设置状态转移时间间隔
		if (!capable(CAP_NET_ADMIN))//当前进程需要admin权限
			return -EPERM;

		spin_lock_bh(&br->lock);
		br->bridge_forward_delay = clock_t_to_jiffies(args[1]);
		if (br_is_root_bridge(br))
			br->forward_delay = br->bridge_forward_delay;
		spin_unlock_bh(&br->lock);
		return 0;

	case BRCTL_SET_BRIDGE_HELLO_TIME://设置hello时间间隔
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		spin_lock_bh(&br->lock);
		br->bridge_hello_time = clock_t_to_jiffies(args[1]);
		if (br_is_root_bridge(br))
			br->hello_time = br->bridge_hello_time;
		spin_unlock_bh(&br->lock);
		return 0;

	case BRCTL_SET_BRIDGE_MAX_AGE://BPDU信息的生存期
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		spin_lock_bh(&br->lock);
		br->bridge_max_age = clock_t_to_jiffies(args[1]);
		if (br_is_root_bridge(br))
			br->max_age = br->bridge_max_age;
		spin_unlock_bh(&br->lock);
		return 0;

	case BRCTL_SET_AGEING_TIME://转发项的老化时间
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		br->ageing_time = clock_t_to_jiffies(args[1]);
		return 0;

	case BRCTL_GET_PORT_INFO://端口信息
	{
		struct __port_info p;
		struct net_bridge_port *pt;

		rcu_read_lock();
		if ((pt = br_get_port(br, args[2])) == NULL) {
			rcu_read_unlock();
			return -EINVAL;
		}
		....
		rcu_read_unlock();

		if (copy_to_user((void __user *)args[1], &p, sizeof(p)))
			return -EFAULT;

		return 0;
	}

	case BRCTL_SET_BRIDGE_STP_STATE://启动或关闭stp
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		br->stp_enabled = args[1]?1:0;
		return 0;

	case BRCTL_SET_BRIDGE_PRIORITY://设置网桥的优先级
		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		spin_lock_bh(&br->lock);
		br_stp_set_bridge_priority(br, args[1]);
		spin_unlock_bh(&br->lock);
		return 0;

	case BRCTL_SET_PORT_PRIORITY://设置端口的优先级
	{
		struct net_bridge_port *p;
		int ret = 0;

		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		if (args[2] >= (1<<(16-BR_PORT_BITS)))//2字节中，端口号使用的位数
			return -ERANGE;

		spin_lock_bh(&br->lock);
		if ((p = br_get_port(br, args[1])) == NULL) 
			ret = -EINVAL;
		else
			br_stp_set_port_priority(p, args[2]);
		spin_unlock_bh(&br->lock);
		return ret;
	}

	case BRCTL_SET_PATH_COST://设置路径开销
	{
		struct net_bridge_port *p;
		int ret = 0;

		if (!capable(CAP_NET_ADMIN))
			return -EPERM;

		spin_lock_bh(&br->lock);
		if ((p = br_get_port(br, args[1])) == NULL)
			ret = -EINVAL;
		else
			br_stp_set_path_cost(p, args[2]);
		spin_unlock_bh(&br->lock);
		return ret;
	}

	case BRCTL_GET_FDB_ENTRIES://获取转发项的个数
		return get_fdb_entries(br, (void __user *)args[1], 
				       args[2], args[3]);
	}

	return -EOPNOTSUPP;
}