busybox：启动阶段的静态 IP 配置过程

文章目录

[1. 前言](#1. 前言)
[2. 启动阶段 busybox 配置静态 IP 过程](#2. 启动阶段 busybox 配置静态 IP 过程)

1. 前言

限于作者能力水平，本文可能存在谬误，因此而给读者带来的损失，作者不做任何承诺。

2. 启动阶段 busybox 配置静态 IP 过程

编辑 /etc/network/interfaces 文件内容如下：

bash 复制代码

auto lo
iface lo inet loopback

auto eth0
iface eth0 inet static
address 192.168.1.188
netmask 255.255.255.0
gateway 192.168.1.1

启动时用命令 /sbin/ifup eth0 配置网络，该命令调用 busybox/networking/ifupdown.c 中的函数 ifupdown_main() 解析 /etc/network/interfaces 对网络进行配置：

c 复制代码

/* busybox/networking/ifupdown.c */

ifupdown_main()
	...
	static_up()

static int FAST_FUNC static_up(struct interface_defn_t *ifd, execfn *exec)
{
	int result;
# if ENABLE_FEATURE_IFUPDOWN_IP
	result = execute("ip addr add %address%/%bnmask%[[ broadcast %broadcast%]] "
			"dev %iface%[[ peer %pointopoint%]][[ label %label%]]", ifd, exec);
	result += execute("ip link set[[ mtu %mtu%]][[ addr %hwaddress%]] %iface% up", ifd, exec);
	result += execute("[[ip route add default via %gateway% dev %iface%[[ metric %metric%]]]]", ifd, exec);
	return ((result == 3) ? 3 : 0);
# else
	/* ifconfig said to set iface up before it processes hw %hwaddress%,
	 * which then of course fails. Thus we run two separate ifconfig */
	result = execute("ifconfig %iface%[[ hw %hwaddress%]][[ media %media%]][[ mtu %mtu%]] up",
				ifd, exec);
	result += execute("ifconfig %iface% %address% netmask %netmask%"
				"[[ broadcast %broadcast%]][[ pointopoint %pointopoint%]]",
				ifd, exec);
	result += execute("[[route add default gw %gateway%[[ metric %metric%]] %iface%]]", ifd, exec);
	return ((result == 3) ? 3 : 0);
# endif
}