网络子系统28_桥接ioctl

转：http://blog.csdn.net/nerdx/article/details/12223489

//  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;
}