首先分享一下/sbin/wifi指令碼

#!/bin/sh                                                            
# Copyright (C) 2006 OpenWrt.org                                     

. /lib/functions.sh                                                  
. /usr/share/libubox/jshn.sh                                         

usage() {                                                            
        cat <<EOF                                                    
Usage: $0
 
 [down|detect|reload|status]                                
enables (default), disables or detects a wifi configuration.              
EOF                                                                               
        exit 1                                                       
}                                                                           

ubus_wifi_cmd
 
() {                                                    
        local cmd="$1"                                               
        local dev="$2"                                               

        json_init                                                    
        [ -n "$2" ] && json_add_string device "$2
 
"                   
        ubus call network.wireless "$1" "$(json_dump)"               
}                                                                    

find_net_config() {(                                                 
        local vif="$1"                                               
        local cfg                                                    
        local ifname                                                 

        config_get cfg "$vif" network                                

        [ -z "$cfg" ] && {                                           
                include /lib/network                                    
                scan_interfaces                                         

                config_get ifname "$vif" ifname                                              

                cfg="$(find_config "$ifname")"                               
        }                                                                    
        [ -z "$cfg" ] && return 0                                       
        echo "$cfg"                                                     
)}                                                                                           


bridge_interface() {(                                                                        
        local cfg="$1"                                                                       
        [ -z "$cfg" ] && return 0                                                            

        include /lib/network                                                                 
        scan_interfaces                                                                      

        for cfg in $cfg; do                                                                  
                config_get iftype "$cfg" type                                                
                [ "$iftype" = bridge ] && config_get "$cfg" ifname                           
                prepare_interface_bridge "$cfg"                                              
                return $?                                                                    
        done                                                                                 
)}                                                                                           

prepare_key_wep() {                                                                          
        local key="$1"                                                                       
        local hex=1                                                                          

        echo -n "$key" | grep -qE "[^a-fA-F0-9]" && hex=0                                    
        [ "${#key}" -eq 10 -a $hex -eq 1 ] || \                                              
        [ "${#key}" -eq 26 -a $hex -eq 1 ] || {                                              
                [ "${key:0:2}" = "s:" ] && key="${key#s:}"                   
                key="$(echo -n "$key" | hexdump -ve '1/1 "%02x" ""')"             
        }                                                                         
        echo "$key"                                                               
} 
 wifi_fixup_hwmode() {                                                
        local device="$1"                                            
        local default="$2"                                                
        local hwmode hwmode_11n                                      

        config_get channel "$device" channel                         
        config_get hwmode "$device" hwmode                           
        case "$hwmode" in                                            
                11bg) hwmode=bg;;                                    
                11a) hwmode=a;;                                           
                11b) hwmode=b;;                                                   
                11g) hwmode=g;;                                         
                11n*)                                                       
                        hwmode_11n="${hwmode##11n}"                                          
                        case "$hwmode_11n" in                                                
                                a|g) ;;                                                      
                                default) hwmode_11n="$default"                               
                        esac                                                 
                        config_set "$device" hwmode_11n "$hwmode_11n"        
                ;;                                                   
                *)                                                   
                        hwmode=                                      
                        if [ "${channel:-0}" -gt 0 ]; then                             
                                if [ "${channel:-0}" -gt 14 ]; then     
                                        hwmode=a                     
                                else                                                         
                                        hwmode=g                     
                                fi                                           
                        else                                         
                                hwmode="$default"                    
                        fi                                           
                ;;                                                      
        esac                                                            
        config_set "$device" hwmode "$hwmode"                                                
}                                                                                            

_wifi_updown() {                                                                             
        for device in ${2:-$DEVICES}; do (                                   
                config_get disabled "$device" disabled                       
                [ 1 == "$disabled" ] && {                               
                        echo "'$device' is disabled"                                         
                        set disable                                                          
                }                                                                            
                config_get iftype "$device" type                                             
                if eval "type ${1}_$iftype" 2>/dev/null >/dev/null; then                     
                        eval "scan_$iftype '$device'"                                        
                        eval "${1}_$iftype '$device'" || echo "$device($iftype): ${1} failed"
                elif [ ! -f /lib/netifd/wireless/$iftype.sh ]; then                          
                        echo "$device($iftype): Interface type not supported"                
                fi                                                                           
        ); done                                                                              
}                                                                                            

wifi_updown() {                                                                              
        cmd=down                                                                             
        [ enable = "$1" ] && {                                                               
                _wifi_updown disable "$2"                                                    
                ubus_wifi_cmd "$cmd" "$2"                                                    
                scan_wifi                                                                    
                cmd=up                                                                       
        }                                                                                    
        ubus_wifi_cmd "$cmd" "$2"                                                            
        _wifi_updown "[email protected]"                                                                    
}                                                                                            

wifi_reload_legacy() {                                                       
        _wifi_updown "disable" "$1"                                               
        scan_wifi                                                                 
        _wifi_updown "enable" "$1"                                                
}wifi_reload() {                                                              
        ubus call network reload                                        
        wifi_reload_legacy                                                
}                                                                                            

wifi_detect() {                                                              
        for driver in ${2:-$DRIVERS}; do (                           
                if eval "type detect_$driver" 2>/dev/null >/dev/null; then
                        eval "detect_$driver" || echo "$driver: Detect failed" >&2
                else                                                              
                        echo "$driver: Hardware detection not supported" >&2      
                fi                                                                
        ); done                                                                   
}                                                                                            

start_net() {(                                                                               
        local iface="$1"                                                                     
        local config="$2"                                                         
        local vifmac="$3"                                                         

        [ -f "/var/run/$iface.pid" ] && kill "$(cat /var/run/${iface}.pid)" 2>/dev/null
        [ -z "$config" ] || {                                                          
                include /lib/network                                                   
                scan_interfaces                                                        
                for config in $config; do                                                    
                        setup_interface "$iface" "$config" "" "$vifmac"                      
                done                                                                   
        }                                                                              
)}                                                                                     

set_wifi_up() {                                                                        
        local cfg="$1"                                                                 
        local ifname="$2"                                                              
        uci_set_state wireless "$cfg" up 1                                                   
        uci_set_state wireless "$cfg" ifname "$ifname"                                       
}                                                                                            

set_wifi_down() {                                                                      
        local cfg="$1"                                                                 
        local vifs vif vifstr                                                          

        [ -f "/var/run/wifi-${cfg}.pid" ] &&                                                 
                kill "$(cat "/var/run/wifi-${cfg}.pid")" 2>/dev/null                         
        uci_revert_state wireless "$cfg"                                                     
        config_get vifs "$cfg" vifs                                                          
        for vif in $vifs; do                                                                 
                uci_revert_state wireless "$vif"                                             
        done                                                                                 
}                                                                                            

scan_wifi() {                                                                                
        local cfgfile="$1"                                                                   
        DEVICES=                                                                             
        config_cb() {                                                                        
                local type="$1"                                                              
                local section="$2"                                                           

                # section start                                                              
                case "$type" in                                                              
                        wifi-device)                                                         
                                append DEVICES "$section"                                    
                                config_set "$section" vifs ""                                
                                config_set "$section" ht_capab ""                            
                        ;;                                                                   
                esac                                                                         

                # section end                                                     
                config_get TYPE "$CONFIG_SECTION" TYPE                            
                case "$TYPE" in                            
                        wifi-device)                                                         
                                append DEVICES "$section"                              
                                config_set "$section" vifs ""                          
                                config_set "$section" ht_capab ""                      
                        ;;                                                                   
                esac                                                                         

                # section end                                                                
                config_get TYPE "$CONFIG_SECTION" TYPE                                       
                case "$TYPE" in                                                              
                        wifi-iface)                                                          
                                config_get device "$CONFIG_SECTION" device                   
                                config_get vifs "$device" vifs                               
                                append vifs "$CONFIG_SECTION"                                
                                config_set "$device" vifs "$vifs"                            
                        ;;                                                                   
                esac                                                                         
        }                                                                                    
        config_load "${cfgfile:-wireless}"                                                   
}                                                                                            

DEVICES=                                                                                     
DRIVERS=                                                                                     
include /lib/wifi                                                                            
scan_wifi                                                                                    

case "$1" in                                                                                 
        down) wifi_updown "disable" "$2";;                                                   
        detect) wifi_detect "$2";;                                                           
        status) ubus_wifi_cmd "status" "$2";;                                
        reload) wifi_reload "$2";;                                                
        reload_legacy) wifi_reload_legacy "$2";;                                  
        --help|help) usage;;                                                      
        *) ubus call network reload; wifi_updown "enable" "$2";;                             
esac                                         

前面定義了函式，後面實際執行
wifi up
wifi down
wifi detect
wifi status
wifi reload
wifi reload_legacy
wifi –help
wifi **
不同的命令調動不同的函式

這裡只分析wifi up
wifi up = wifi
執行 ubus call network reload
對network進行了reload
wifi_updown “enable” “2”進入函數wifiupdown參數enable2
$2為網路裝置

wifi_updown() {                                                              
        cmd=down                                                                             
        [ enable = "$1" ] && {                                                               
                _wifi_updown disable "$2"                                                    
                ubus_wifi_cmd "$cmd" "$2"                                                    
                scan_wifi                                                                    
                cmd=up                                                                       
        }                                                                                    
        ubus_wifi_cmd "$cmd" "$2"                                                            
        _wifi_updown "[email protected]"                                                                    
}                               

進入函式enable
ubus_wifi_cmd

ubus_wifi_cmd() {                                                                 
        local cmd="$1"                                                            
        local dev="$2"                                                            

        json_init                                                                            
        [ -n "$2" ] && json_add_string device "$2"                                           
        ubus call network.wireless "$1" "$(json_dump)"                                       
}