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#####请转贴时保留以下内容######
作者：GTT
请提出宝贵意见Mail:mtloveft@hotmail.com
Linux Version：2.6.33
提示：本文是介绍关于linux 如何实现loopback NIC 驱动！
下面看看Loopback NIC的net_device的注册过程。SourceCode入下。
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/**
* register_netdev - register a network device
* @dev: device to register
*
* Take a completed network device structure and add it to the kernel
* interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier
* chain. 0 is returned on success. A negative errno code is returned
* on a failure to set up the device, or if the name is a duplicate.
*
* This is a wrapper around register_netdevice that takes the rtnl semaphore
* and expands the device name if you passed a format string to
* alloc_netdev.
*/
int register_netdev(struct net_device *dev)
{
int err;
rtnl_lock();
/* If the name is a format string the caller wants us to do a name allocation. */
if (strchr(dev->name, '%')) {
err = dev_alloc_name(dev, dev->name);//对设备名进行设置
if (err < 0) goto out;
}
err = register_netdevice(dev);//把网络设备注册到当前网络空间的网络设备链表中
out:
rtnl_unlock();
return err;
}
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首先判断dev->name是否含有%，如果有%，将重新分配名字。
register_netdevice是具体注册的方法
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/**
* register_netdevice - register a network device
* @dev: device to register
*
* Take a completed network device structure and add it to the kernel
* interfaces. A %NETDEV_REGISTER message is sent to the netdev notifier
* chain. 0 is returned on success. A negative errno code is returned
* on a failure to set up the device, or if the name is a duplicate.
*
* Callers must hold the rtnl semaphore. You may want
* register_netdev() instead of this.
*
* BUGS:
* The locking appears insufficient to guarantee two parallel registers
* will not get the same name.
*/
int register_netdevice(struct net_device *dev)
{
int ret;
struct net *net = dev_net(dev);
BUG_ON(dev_boot_phase);
ASSERT_RTNL();
might_sleep();
/* When net_device's are persistent, this will be fatal. */
BUG_ON(dev->reg_state != NETREG_UNINITIALIZED);
BUG_ON(!net);
//初始化各种锁
spin_lock_init(&dev->addr_list_lock);
netdev_set_addr_lockdep_class(dev);
netdev_init_queue_locks(dev);
dev->iflink = -1;
/* Init, if this function is available */
if (dev->netdev_ops->ndo_init) {
ret = dev->netdev_ops->ndo_init(dev);
if (ret) {
if (ret > 0) ret = -EIO;
goto out;
}
}
//在hash表中检测是否有重复的名字
ret = dev_get_valid_name(net, dev->name, dev->name, 0);
if (ret) goto err_uninit;
dev->ifindex = dev_new_index(net);//给设备分配一个唯一的index
if (dev->iflink == -1) dev->iflink = dev->ifindex;
/* Fix illegal checksum combinations */
if ((dev->features & NETIF_F_HW_CSUM) &&
(dev->features & (NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
printk(KERN_NOTICE "%s: mixed HW and IP checksum settings.\n", dev->name);
dev->features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM);
}
if ((dev->features & NETIF_F_NO_CSUM) &&
(dev->features & (NETIF_F_HW_CSUM|NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM))) {
printk(KERN_NOTICE "%s: mixed no checksumming and other settings.\n", dev->name);
dev->features &= ~(NETIF_F_IP_CSUM|NETIF_F_IPV6_CSUM|NETIF_F_HW_CSUM);
}
dev->features = netdev_fix_features(dev->features, dev->name);
/* Enable software GSO if SG is supported. */
if (dev->features & NETIF_F_SG) dev->features |= NETIF_F_GSO;
netdev_initialize_kobject(dev);//初始化设备驱动的kobject并创建相关的sysfs
ret = call_netdevice_notifiers(NETDEV_POST_INIT, dev);
ret = notifier_to_errno(ret);
if (ret) goto err_uninit;
ret = netdev_register_kobject(dev);
if (ret) goto err_uninit;
dev->reg_state = NETREG_REGISTERED;//设置网络设备为已注册状态
/* Default initial state at registry is that the device is present. */
set_bit(__LINK_STATE_PRESENT, &dev->state);//设置网络设备状态
dev_init_scheduler(dev);//初始化排队规则
dev_hold(dev);
list_netdevice(dev);//将相应的链表插入到网络命名空间的全局的链表中
/* Notify protocols, that a new device appeared. */
ret = call_netdevice_notifiers(NETDEV_REGISTER, dev);//调用netdev_chain通知内核其他子系统。
ret = notifier_to_errno(ret);
if (ret) {
rollback_registered(dev);
dev->reg_state = NETREG_UNREGISTERED;
}
/* Prevent userspace races by waiting until the network
* device is fully setup before sending notifications.
*/
rtmsg_ifinfo(RTM_NEWLINK, dev, ~0U);
out:
return ret;
err_uninit:
if (dev->netdev_ops->ndo_uninit)
dev->netdev_ops->ndo_uninit(dev);
goto out;
}
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dev->netdev_ops->ndo_init是上篇文章里说过的loopback_ops 里定义的方法loopback_dev_init
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static int loopback_dev_init(struct net_device *dev)
{
struct pcpu_lstats *lstats;
lstats = alloc_percpu(struct pcpu_lstats);
if (!lstats) return -ENOMEM;
dev->ml_priv = lstats;
return 0;
}
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这个方法只是分配一个pcpu_lstats结构，用来存送受信的统计信息。作为net_device的私有数据。
即dev->ml_priv。
dev_get_valid_name是检测设备名。
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static int dev_get_valid_name(struct net *net, const char *name, char *buf, bool fmt)
{
if (!dev_valid_name(name)) return -EINVAL;
if (fmt && strchr(name, '%')) return __dev_alloc_name(net, name, buf);
else if (__dev_get_by_name(net, name)) return -EEXIST;
else if (buf != name) strlcpy(buf, name, IFNAMSIZ);
return 0;
}
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dev_valid_name是对网络设备名的Check。
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int dev_valid_name(const char *name)
{
if (*name == '\0') return 0;
if (strlen(name) >= IFNAMSIZ) return 0;
if (!strcmp(name, ".") || !strcmp(name, "..")) return 0;
while (*name) {
if (*name == '/' || isspace(*name)) return 0;
name++;
}
return 1;
}
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名字为空，或者为.和..等都是认为非法的。
__dev_get_by_name是根据名字查找设备，如果设备存在，将不能利用这个名字。
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struct net_device *__dev_get_by_name(struct net *net, const char *name)
{
struct hlist_node *p;
struct net_device *dev;
struct hlist_head *head = dev_name_hash(net, name);
hlist_for_each_entry(dev, p, head, name_hlist)
if (!strncmp(dev->name, name, IFNAMSIZ)) return dev;
return NULL;
}
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netdev_initialize_kobject是在设备文件里增加一个设备，同时在SysFS里增加相应目录等。先不分析这个方法，以后分析。
call_netdevice_notifiers调用netdev_chain通知内核其他子系统。
list_netdevice是把net_device链接到各种链表里。
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/* Device list insertion */
static int list_netdevice(struct net_device *dev)
{
struct net *net = dev_net(dev);
ASSERT_RTNL();
write_lock_bh(&dev_base_lock);
//插入到dev_base_head双向链表
list_add_tail_rcu(&dev->dev_list, &net->dev_base_head);
//根据name插入到name_hlist这个hash表
hlist_add_head_rcu(&dev->name_hlist, dev_name_hash(net, dev->name));
//根据ifindex插入到index_hlist这个hash表
hlist_add_head_rcu(&dev->index_hlist, dev_index_hash(net, dev->ifindex));
write_unlock_bh(&dev_base_lock);
return 0;
}
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各种双向链表和hash表的关系如下
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