深入追踪openwrt下的hostapd之后,发现openwrt无线管理机制格外的复杂,几乎所以的触发与回调均离不开ubus,关于ubus这里不作解释,先大概了解其用途即可(出门左转:https://wiki.openwrt.org/doc/techref/ubus)。咱们先来了解openwrt下无线启动,我们首先查看系统启动脚本:/etc/preinit,发现该脚本主要是系统的检验与初始化,然后我们进入/etc/init.d/:
root@openwrt:/etc/init.d# ls
cron done firewall log odhcpd rpcd sysfixtime system uhttpd
boot dropbear led network protectx sysctl sysntpd telnet umount
通过查看与网络相关的启动脚本,最后发现network文件里面,出现:
start_service() {
init_switch
procd_open_instance
procd_set_param command /sbin/netifd
procd_set_param respawn
procd_set_param watch network.interface
[ -e /proc/sys/kernel/core_pattern ] && {
procd_set_param limits core="unlimited"
echo '/tmp/%e.%p.%s.%t.core' > /proc/sys/kernel/core_pattern
}
procd_close_instance
}
通过查阅相关资料发现netifd大有文章(https://wiki.openwrt.org/doc/techref/netifd), 简单的来说,netifd是老版本openwrt脚本初始化与配置网络的替代品,主要底层构建在netlink之上。netifd可以监视/etc/config/network配置文件,这样一来可能通过/etc/init.d/network reload
重新加载网络,而
不用每次重启全部的网络组件,netifd主要的组成有:
openwrt编译目录为:package/network/config/netifd
1. Shell脚本:
/sbin/ifup,
/sbin/ifdown(link to ifup),
/sbin/ifstatus,
/sbin/devstatus
2. init.d脚本:
/etc/init.d/network
3. hotplug2脚本:
/etc/hotplug.d/iface/00-netstate,
/etc/hotplug.d/iface/10-sysctl
4. udhcpc脚本:
/usr/share/udhcpc/default.script
5. netifd守护进程binary:
/sbin/netifd
其它相关:
hostapd(hostapd.sh)
dhcp
等等
netifd在启动时候会调用网络相关组件进行初始化:
void netifd_init_script_handlers(int dir_fd, script_dump_cb cb)
{
glob_t g;
int i, prev_fd;
prev_fd = netifd_dir_push(dir_fd);
glob("./*.sh", 0, NULL, &g);
for (i = 0; i < g.gl_pathc; i++)
netifd_parse_script_handler(g.gl_pathv[i], cb);
netifd_dir_pop(prev_fd);
}
上述函数中即调用了hostapd的启动脚本:
lib/netifd/wireless/mac80211.sh
向ubus注册了网络接口处理函数
int
netifd_ubus_init(const char *path)
{
uloop_init();
ubus_path = path;
ubus_ctx = ubus_connect(path);
if (!ubus_ctx)
return -EIO;
DPRINTF("connected as %08x
", ubus_ctx->local_id);
ubus_ctx->connection_lost = netifd_ubus_connection_lost;
netifd_ubus_add_fd();
netifd_add_object(&main_object);
netifd_add_object(&dev_object);
netifd_add_object(&wireless_object);
netifd_add_iface_object();
return 0;
}