在新版本的linux中，WIFI使用过nl80211来配置的，但是wext也是保留的，方便其他工具使用。作者最近就在工作中遇到了这个问题，很多配置需要通过iw工具集来实现。那么这里就简单的笔记下wext吧。
PS:作者对于linux网络架构理解的非常浅显，可能有错误，还请大家多多指正。而且有ioctl的数目繁多，这里就简单的笔记下主干分发过程，具体驱动在具体分析吧。
当我们调用socket进行协议调用时，会在文件操作中支持ioctl操作：
/net/socket.c
/*
* Socket files have a set of 'special' operations as well as the generic file ones. These don't appear
* in the operation structures but are done directly via the socketcall() multiplexor.
*/
static const struct file_operations socket_file_ops = {
。。。
.unlocked_ioctl = sock_ioctl,
#ifdef CONFIG_COMPAT
.compat_ioctl = compat_sock_ioctl,
#endif
};
/* 由于socket是通用架构，因此这里不会有具体的ioctl的实现，而是基于每个注册到该协议里的dev的实现 */
static long sock_ioctl(struct file *file, unsigned cmd, unsigned long arg)
{
struct socket *sock;
struct sock *sk;
void __user *argp = (void __user *)arg;
int pid, err;
struct net *net;
sock = file->private_data;
sk = sock->sk;
net = sock_net(sk);
/* 可以看到，只要是cmd符合一定的要求的，全部路由到指定dev中实现 */
if (cmd >= SIOCDEVPRIVATE && cmd <= (SIOCDEVPRIVATE + 15)) {
err = dev_ioctl(net, cmd, argp);
} else
#ifdef CONFIG_WIRELESS_EXT
if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) {
err = dev_ioctl(net, cmd, argp);
} else
#endif /* CONFIG_WIRELESS_EXT */
switch (cmd) {
case FIOSETOWN:
case SIOCSPGRP:
err = -EFAULT;
if (get_user(pid, (int __user *)argp))
break;
err = f_setown(sock->file, pid, 1);
break;
case FIOGETOWN:
case SIOCGPGRP:
err = put_user(f_getown(sock->file),
(int __user *)argp);
break;
case SIOCGIFBR:
case SIOCSIFBR:
case SIOCBRADDBR:
case SIOCBRDELBR:
err = -ENOPKG;
if (!br_ioctl_hook)
request_module("bridge");
mutex_lock(&br_ioctl_mutex);
if (br_ioctl_hook)
err = br_ioctl_hook(net, cmd, argp);
mutex_unlock(&br_ioctl_mutex);
break;
case SIOCGIFVLAN:
case SIOCSIFVLAN:
err = -ENOPKG;
if (!vlan_ioctl_hook)
request_module("8021q");
mutex_lock(&vlan_ioctl_mutex);
if (vlan_ioctl_hook)
err = vlan_ioctl_hook(net, argp);
mutex_unlock(&vlan_ioctl_mutex);
break;
case SIOCADDDLCI:
case SIOCDELDLCI:
err = -ENOPKG;
if (!dlci_ioctl_hook)
request_module("dlci");
mutex_lock(&dlci_ioctl_mutex);
if (dlci_ioctl_hook)
err = dlci_ioctl_hook(cmd, argp);
mutex_unlock(&dlci_ioctl_mutex);
break;
default:
err = sock->ops->ioctl(sock, cmd, arg);
/*
* If this ioctl is unknown try to hand it down
* to the NIC driver.
*/
if (err == -ENOIOCTLCMD)
err = dev_ioctl(net, cmd, argp);
break;
}
return err;
}
/net/core/dev.c
/* 同样，dev也是通用代码，但是在代码的最后会有wext的配置 */
int dev_ioctl(struct net *net, unsigned int cmd, void __user *arg)
{
struct ifreq ifr;
int ret;
char *colon;
/* One special case: SIOCGIFCONF takes ifconf argument
and requires shared lock, because it sleeps writing
to user space.
*/
if (cmd == SIOCGIFCONF) {
rtnl_lock();
ret = dev_ifconf(net, (char __user *) arg);
rtnl_unlock();
return ret;
}
if (cmd == SIOCGIFNAME)
return dev_ifname(net, (struct ifreq __user *)arg);
if (copy_from_user(&ifr, arg, sizeof(struct ifreq)))
return -EFAULT;
ifr.ifr_name[IFNAMSIZ-1] = 0;
colon = strchr(ifr.ifr_name, ':');
if (colon)
*colon = 0;
/*
* See which interface the caller is talking about.
*/
switch (cmd) {
/*
* These ioctl calls:
* - can be done by all.
* - atomic and do not require locking.
* - return a value
*/
case SIOCGIFFLAGS:
case SIOCGIFMETRIC:
case SIOCGIFMTU:
case SIOCGIFHWADDR:
case SIOCGIFSLAVE:
case SIOCGIFMAP:
case SIOCGIFINDEX:
case SIOCGIFTXQLEN:
dev_load(net, ifr.ifr_name);
read_lock(&dev_base_lock);
ret = dev_ifsioc_locked(net, &ifr, cmd);
read_unlock(&dev_base_lock);
if (!ret) {
if (colon)
*colon = ':';
if (copy_to_user(arg, &ifr,
sizeof(struct ifreq)))
ret = -EFAULT;
}
return ret;
case SIOCETHTOOL:
dev_load(net, ifr.ifr_name);
rtnl_lock();
ret = dev_ethtool(net, &ifr);
rtnl_unlock();
if (!ret) {
if (colon)
*colon = ':';
if (copy_to_user(arg, &ifr,
sizeof(struct ifreq)))
ret = -EFAULT;
}
return ret;
/*
* These ioctl calls:
* - require superuser power.
* - require strict serialization.
* - return a value
*/
case SIOCGMIIPHY:
case SIOCGMIIREG:
case SIOCSIFNAME:
if (!capable(CAP_NET_ADMIN))
return -EPERM;
dev_load(net, ifr.ifr_name);
rtnl_lock();
ret = dev_ifsioc(net, &ifr, cmd);
rtnl_unlock();
if (!ret) {
if (colon)
*colon = ':';
if (copy_to_user(arg, &ifr,
sizeof(struct ifreq)))
ret = -EFAULT;
}
return ret;
/*
* These ioctl calls:
* - require superuser power.
* - require strict serialization.
* - do not return a value
*/
case SIOCSIFFLAGS:
case SIOCSIFMETRIC:
case SIOCSIFMTU:
case SIOCSIFMAP:
case SIOCSIFHWADDR:
case SIOCSIFSLAVE:
case SIOCADDMULTI:
case SIOCDELMULTI:
case SIOCSIFHWBROADCAST:
case SIOCSIFTXQLEN:
case SIOCSMIIREG:
case SIOCBONDENSLAVE:
case SIOCBONDRELEASE:
case SIOCBONDSETHWADDR:
case SIOCBONDCHANGEACTIVE:
case SIOCBRADDIF:
case SIOCBRDELIF:
case SIOCSHWTSTAMP:
if (!capable(CAP_NET_ADMIN))
return -EPERM;
/* fall through */
case SIOCBONDSLAVEINFOQUERY:
case SIOCBONDINFOQUERY:
dev_load(net, ifr.ifr_name);
rtnl_lock();
ret = dev_ifsioc(net, &ifr, cmd);
rtnl_unlock();
return ret;
case SIOCGIFMEM:
/* Get the per device memory space. We can add this but
* currently do not support it */
case SIOCSIFMEM:
/* Set the per device memory buffer space.
* Not applicable in our case */
case SIOCSIFLINK:
return -EINVAL;
/*
* Unknown or private ioctl.
*/
default:
if (cmd == SIOCWANDEV ||
(cmd >= SIOCDEVPRIVATE &&
cmd <= SIOCDEVPRIVATE + 15)) {
dev_load(net, ifr.ifr_name);
rtnl_lock();
ret = dev_ifsioc(net, &ifr, cmd);
rtnl_unlock();
if (!ret && copy_to_user(arg, &ifr,
sizeof(struct ifreq)))
ret = -EFAULT;
return ret;
}
/* 如果ioctl号码在wext中，那么额外处理 */
/* Take care of Wireless Extensions */
if (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST)
return wext_handle_ioctl(net, &ifr, cmd, arg);
return -EINVAL;
}
}
/net/wireless/wext.c
/* wext针对ioctl的路由主函数 */
int wext_handle_ioctl(struct net *net, struct ifreq *ifr, unsigned int cmd,
void __user *arg)
{
struct iw_request_info info = { .cmd = cmd, .flags = 0 };
int ret;
/* 继续分发 */
ret = wext_ioctl_dispatch(net, ifr, cmd, &info,
ioctl_standard_call,
ioctl_private_call);
if (ret >= 0 &&
IW_IS_GET(cmd) &&
copy_to_user(arg, ifr, sizeof(struct iwreq)))
return -EFAULT;
return ret;
}
/* entry point from dev ioctl */
static int wext_ioctl_dispatch(struct net *net, struct ifreq *ifr,
unsigned int cmd, struct iw_request_info *info,
wext_ioctl_func standard,
wext_ioctl_func private)
{
int ret = wext_permission_check(cmd);
if (ret)
return ret;
dev_load(net, ifr->ifr_name);
rtnl_lock();
/* 继续分发 */
ret = wireless_process_ioctl(net, ifr, cmd, info, standard, private);
rtnl_unlock();
return ret;
}
在分析wireless_process_ioctl之前，先看下standand和private两个函数
/* standand函数实现
这里是wext的标准ioctl的实现
由于wext已经不再开发，只是维护，因此这里代码会尽可能的转到nl80211上去，（wireless_send_event 会通过构建nlmsg发到内核netlink队列里，然后同nl80211进行实现），不过也有可能WIFI驱动定义了自己的
标准的IOCTL的实现函数，这里不再分析。
*/
static int ioctl_standard_call(struct net_device * dev,
struct iwreq *iwr,
unsigned int cmd,
struct iw_request_info *info,
iw_handler handler)
{
const struct iw_ioctl_description * descr;
int ret = -EINVAL;
/* Get the description of the IOCTL */
if ((cmd - SIOCIWFIRST) >= standard_ioctl_num)
return -EOPNOTSUPP;
descr = &(standard_ioctl[cmd - SIOCIWFIRST]);
/* Check if we have a pointer to user space data or not */
if (descr->header_type != IW_HEADER_TYPE_POINT) {
/* No extra arguments. Trivial to handle */
ret = handler(dev, info, &(iwr->u), NULL);
/* Generate an event to notify listeners of the change */
if ((descr->flags & IW_DESCR_FLAG_EVENT) &&
((ret == 0) || (ret == -EIWCOMMIT)))
wireless_send_event(dev, cmd, &(iwr->u), NULL);
} else {
ret = ioctl_standard_iw_point(&iwr->u.data, cmd, descr,
handler, dev, info);
}
/* Call commit handler if needed and defined */
if (ret == -EIWCOMMIT)
ret = call_commit_handler(dev);
/* Here, we will generate the appropriate event if needed */
return ret;
}
/*
private函数实现
由于这里的ioctl都不是标准的，因此只能通过驱动中自定义的ioctl来实现
*/
static int ioctl_private_call(struct net_device *dev, struct iwreq *iwr,
unsigned int cmd, struct iw_request_info *info,
iw_handler handler)
{
int extra_size = 0, ret = -EINVAL;
const struct iw_priv_args *descr;
extra_size = get_priv_descr_and_size(dev, cmd, &descr);
/* Check if we have a pointer to user space data or not. */
if (extra_size == 0) {
/* No extra arguments. Trivial to handle */
ret = handler(dev, info, &(iwr->u), (char *) &(iwr->u));
} else {
ret = ioctl_private_iw_point(&iwr->u.data, cmd, descr,
handler, dev, info, extra_size);
}
/* Call commit handler if needed and defined */
if (ret == -EIWCOMMIT)
ret = call_commit_handler(dev);
return ret;
}
最后在来分析wireless_process_ioctl函数
/* ioctl分发实现函数 */
static int wireless_process_ioctl(struct net *net, struct ifreq *ifr,
unsigned int cmd,
struct iw_request_info *info,
wext_ioctl_func standard,
wext_ioctl_func private)
{
struct iwreq *iwr = (struct iwreq *) ifr;
struct net_device *dev;
iw_handler handler;
/* Permissions are already checked in dev_ioctl() before calling us.
* The copy_to/from_user() of ifr is also dealt with in there */
/* Make sure the device exist */
if ((dev = __dev_get_by_name(net, ifr->ifr_name)) == NULL)
return -ENODEV;
/* 调用标准实现 */
/* A bunch of special cases, then the generic case...
* Note that 'cmd' is already filtered in dev_ioctl() with
* (cmd >= SIOCIWFIRST && cmd <= SIOCIWLAST) */
if (cmd == SIOCGIWSTATS)
return standard(dev, iwr, cmd, info,
&iw_handler_get_iwstats);
if (cmd == SIOCGIWPRIV && dev->wireless_handlers)
return standard(dev, iwr, cmd, info,
&iw_handler_get_private);
/* Basic check */
if (!netif_device_present(dev))
return -ENODEV;
/* 如果WIFI驱动定义了自己的ioctl的实现函数，那么这里就可以处理 */
/* New driver API : try to find the handler */
handler = get_handler(dev, cmd);
if (handler) {
/* Standard and private are not the same */
if (cmd < SIOCIWFIRSTPRIV)
return standard(dev, iwr, cmd, info, handler);
else
return private(dev, iwr, cmd, info, handler);
}
/* 如果WIFI驱动没有定义自己的ioctl实现，但是定义了ndo_do_ioctl函数，也可以调用该函数进行实现 */
/* Old driver API : call driver ioctl handler */
if (dev->netdev_ops->ndo_do_ioctl)
return dev->netdev_ops->ndo_do_ioctl(dev, ifr, cmd);
return -EOPNOTSUPP;
}
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