# Openwrt 修改默认ip脚本分析

## /etc/board.json生成

1. `etc/init.d/boot`

   ```bash
   boot() {
   	/bin/config_generate
   }
   ```

   

2. `/bin/config_generate`

   ```bash
   #!/bin/sh
   
   CFG=/etc/board.json
   
   . /usr/share/libubox/jshn.sh
   
   # /etc/board.json文件存在不存在或者为空，则调用 board_detect 生成该文件，否则往下进行
   # 第一次启动肯定不会存在该文件，所以肯定执行 board_detect
   [ -s $CFG ] || /bin/board_detect || exit 1
   [ -s /etc/config/network -a -s /etc/config/system ] && exit 0
   ```

   

3. `/bin/board_detect`

   ```bash
   #!/bin/sh
   
   CFG=$1
   
   [ -n "$CFG" ] || CFG=/etc/board.json
   
   # 如果/etc/board.d/是个目录，且 /etc/board.json 文件存在不存在或者为空
   # 变量/etc/board.d/下面的脚本，然后执行
   [ -d "/etc/board.d/" -a ! -s "$CFG" ] && {
   	for a in $(ls /etc/board.d/*); do
   		[ -x $a ] || continue;
   		$(. $a)
   	done
   }
   
   [ -s "$CFG" ] || return 1
   ```

   

4. 在`/etc/board.d/`目录下脚本如下：

   - 02_network：来源 target/linux/mpc85xx/base-files/etc/board.d/02_network    

     ```bash
     #!/bin/sh
     # Copyright (C) 2014-2015 OpenWrt.org
     
     . /lib/functions/uci-defaults.sh
     . /lib/functions.sh
     . /lib/functions/system.sh
     
     board_config_update
     # board=fsl,P2020RDB 来源dts compatible = "fsl,P2020RDB";
     board=$(board_name)
     
     case "$board" in
     fsl,P2020RDB)
     	# 这里把eth0 eth1 都设置为lan口
     	ucidef_set_interface_lan "eth0 eth1"
     	;;
     *)
     	# 这里把eth0设置为lan口，把eth1 设置为wan口
     	ucidef_set_interfaces_lan_wan "eth0" "eth1"
     	;;
     esac
     
     board_config_flush
     
     exit 0
     ```

     **注意**：ucidef_set_interface_lan和ucidef_set_interfaces_lan_wan函数会生成`/etc/board.json`文件。这两个函数存放位置：`package/base-files/files/lib/functions/uci-defaults.sh`

     - `ucidef_set_interface_lan`函数

       ```bash
       ucidef_set_interface_lan() {
       	ucidef_set_interface "lan" device "$1" protocol "${2:-static}"
       }
       ```

       

     - `ucidef_set_interfaces_lan_wan`函数

       ```bash
       ucidef_set_interfaces_lan_wan() {
       	local lan_if="$1"
       	local wan_if="$2"
       
       	ucidef_set_interface_lan "$lan_if"
       	ucidef_set_interface_wan "$wan_if"
       }
       ```

     - `ucidef_set_interface`函数

       ```
       以ucidef_set_interface_lan "eth0 eth1" 为例说明该函数功能：
       
       - ucidef_set_interface "lan" device "eth0 eth1" protocol "${2:-static}"
         - $1 = lan
         - $2 = device 
         - $3 = "eth0 eth1"
         - $4 = protocol 
         - $5 = static
       ```

       

       下面分析代码

       ```bash
       ucidef_set_interface() {
       	# network=lan
       	local network=$1; shift
       	# 选中/etc/board.json 里面的 network下的lan节点
       	json_select_object network
       	json_select_object "$network"
       	# 此时$1=device
       	while [ -n "$1" ]; do
       		local opt=$1; shift # opt=device
       		local val=$1; shift # val = "eth0 eth1"
       
       		[ -n "$opt" -a -n "$val" ] || break
       		# 如果 val是列表，会添加json数组
       		# 大概是这个样子 "ports": ["eth0", "eth1"],
       		[ "$opt" = "device" -a "$val" != "${val/ //}" ] && {
       			# 这里处理device 多个网口 桥接到lan
       			json_select_array "ports"
       			for e in $val; do json_add_string "" "$e"; done
       			json_close_array
       		} || {
       			# lan下的"protocol"节点
       			json_add_string "$opt" "$val"
       		}
       	done
       	
       	# 下面如果 没有protocol 设置默认的值，
       	if ! json_is_a protocol string; then
       		case "$network" in
       			lan) json_add_string protocol static ;;
       			wan) json_add_string protocol dhcp ;;
       			*) json_add_string protocol none ;;
       		esac
       	fi
       
       	json_select ..
       	json_select ..
       }
       ```

       经过上面的代码后，就会生成`/etc/board.json` 

       ```
       {
               "model": {
                       "id": "fsl,P2020RDB",
                       "name": "Freescale P2020RDB"
               },
               "network": {
                       "lan": {
                               "ports": [
                                       "eth0",
                                       "eth1"
                               ],
                               "protocol": "static"
                       }
               }
       }
       ```

       

     

   - 99-default_network：来源 package/base-files/files/etc/board.d/99-default_network

     ```bash
     #!/bin/sh
     #
     # Copyright (C) 2013-2015 OpenWrt.org
     #
     
     . /lib/functions/uci-defaults.sh
     
     board_config_update
     # 判断/etc/board.json里面是否有 network 节点，如果有直接退出，没有的话往下
     json_is_a network object && exit 0
     
     # 理论上不会到这，因为在 02_network 中肯定生成了 /etc/board.json中的network节点
     # 能跑到这说明没有network 节点，这里会设置节点，
     #
     ucidef_set_interface_lan 'eth0'
     [ -d /sys/class/net/eth1 ] && ucidef_set_interface_wan 'eth1'
     
     board_config_flush
     
     exit 0
     ```



## config_generate继续分析

在上个章节第2步骤，通过`[ -s $CFG ] || /bin/board_detect || exit 1` 会生成默认的/etc/board.json文件，接下来会继续根据给json文件生成`/etc/config/network`，下面继续分析。

`/bin/config_generate`文件下面的内容：

```bash
# 加载/etc/board.json文件到shell
json_init
json_load "$(cat ${CFG})"

umask 077

# 如果network不存在或者为空
if [ ! -s /etc/config/network ]; then
	bridge_name=""
	# 创建该文件
	touch /etc/config/network
	# 生成config interface 'loopback'和config globals 'globals'节点
	generate_static_network

	# 获取json中的bridge 这里是空的，json里面没有bridge
	json_get_vars bridge
	[ -n "$bridge" ] && {
		# 由于是空的，所以不会到这里，但是如果不是空的
		json_select bridge
		json_get_vars name macaddr
		generate_bridge "$name" "$macaddr"
		json_select ..
		bridge_name=$name
	}
	# 按照上面提到的json文件，这里keys=lan
	# 所以执行的是 bridge_name=""
	# generate_network lan $bridge_name
	json_get_keys keys network
	for key in $keys; do generate_network $key $bridge_name; done

	json_get_keys keys switch
	for key in $keys; do generate_switch $key; done
fi
```

 

`generate_network`代码如下：

```bash
addr_offset=2
generate_network() {
	local ports device macaddr protocol type ipaddr netmask vlan
	local bridge=$2

	json_select network
		json_select "$1"
			json_get_vars device macaddr metric protocol ipaddr netmask vlan
			json_get_values ports ports
		json_select ..
	json_select ..

	[ -n "$device" -o -n "$ports" ] || return

	# Force bridge for "lan" as it may have other devices (e.g. wireless)
	# bridged
	[ "$1" = "lan" -a -z "$ports" ] && {
		ports="$device"
	}

	[ -n "$ports" -a -z "$bridge" ] && {
		uci -q batch <<-EOF
			add network device
			set network.@device[-1].name='br-$1'
			set network.@device[-1].type='bridge'
		EOF
		for port in $ports; do uci add_list network.@device[-1].ports="$port"; done
		[ -n "$macaddr" ] && {
			for port in $ports; do
				uci -q batch <<-EOF
					add network device
					set network.@device[-1].name='$port'
					set network.@device[-1].macaddr='$macaddr'
				EOF
			done
		}
		device=br-$1
		type=
		macaddr=""
	}

	[ -n "$bridge" ] && {
		[ -z "$ports" ] && ports="$device"
		if [ -z "$vlan" ]; then
			bridge_vlan_id=$((bridge_vlan_id + 1))
			vlan=$bridge_vlan_id
		fi
		generate_bridge_vlan $1 $bridge "$ports" $vlan
		device=$bridge.$vlan
		type=""
	}

	if [ -n "$macaddr" ]; then
		uci -q batch <<-EOF
			add network device
			set network.@device[-1].name='$device'
			set network.@device[-1].macaddr='$macaddr'
		EOF
	fi

	uci -q batch <<-EOF
		delete network.$1
		set network.$1='interface'
		set network.$1.type='$type'
		set network.$1.device='$device'
		set network.$1.metric='$metric'
		set network.$1.proto='none'
	EOF

	case "$protocol" in
		static)
			local ipad
			case "$1" in
				lan) ipad=${ipaddr:-"192.168.10.1"} ;;
				*) ipad=${ipaddr:-"192.168.$((addr_offset++)).1"} ;;
			esac

			netm=${netmask:-"255.255.255.0"}

			uci -q batch <<-EOF
				set network.$1.proto='static'
				set network.$1.ipaddr='$ipad'
				set network.$1.netmask='$netm'
			EOF
			[ -e /proc/sys/net/ipv6 ] && uci set network.$1.ip6assign='60'
		;;

		dhcp)
			# fixup IPv6 slave interface if parent is a bridge
			[ "$type" = "bridge" ] && device="br-$1"

			uci set network.$1.proto='dhcp'
			[ -e /proc/sys/net/ipv6 ] && {
				uci -q batch <<-EOF
					delete network.${1}6
					set network.${1}6='interface'
					set network.${1}6.device='$device'
					set network.${1}6.proto='dhcpv6'
				EOF
			}
		;;

		pppoe)
			uci -q batch <<-EOF
				set network.$1.proto='pppoe'
				set network.$1.username='username'
				set network.$1.password='password'
			EOF
			[ -e /proc/sys/net/ipv6 ] && {
				uci -q batch <<-EOF
					set network.$1.ipv6='1'
					delete network.${1}6
					set network.${1}6='interface'
					set network.${1}6.device='@${1}'
					set network.${1}6.proto='dhcpv6'
				EOF
			}
		;;
	esac
}
```