【原创】修改WIFI保持连接脚本

wumai

　　【原创】修改WIFI保持连接脚本
　　项目中用到wifi，由于无线网络的不稳定性，可能会造成wifi的掉线，这就需要在程序中判断网络的是否联通，并且能在断线后继续搜寻无线网络并重新连接。
　　并且因为wifi连接有许多现成的工具，所以在这里就利用shell脚本来实现此功能。
　　本篇博客主要是记录我修改此脚本到当前项目的记录，包含shell脚本的一些用法和wifi连接工具的用法：
　　一、初始化函数init_var



init_var() {
#until [ -d $SYSFS ] ; do sleep 1; done
#find the first useable wifi card
local wifi_dev               #定义局部变量wifi_dev
wifi_dev=$(iwconfig 2>&1  | grep -v "no wireless" ) #查看当前设备有的无线设备，grep -v 指的是去除no wireless这一行
while true; do                #无限循环
if [ -z "$wifi_dev" ]; then #判断wifi_dev字符串是否为空 是空则执行下面的命令
sleep 3
wifi_dev=$(iwconfig 2>&1  | grep -v "no wireless" )
else                   #不为空  获取当前wifi设备名
IFACE=$(iwconfig 2>&1 | grep -v -n "no wireless" | awk '{print $1}' | awk -F: '{print $2}' | grep 0)
break
fi
done
# support only pc run dhclient
which dhclient     #判断 dhclient工具是否存在
if [ $? -ne 0 ]; then
RUN_PC=0
else
RUN_PC=1
fi
if [ "$RUN_PC" = "0" ] ; then
DHCP_CLIENT=udhcpc
DHCP_CLIENT_OPT=" -i "
PING_KEYWORD=round-trip
DHCP_WAIT_TIMES=5
else
DHCP_CLIENT=dhclient
PING_KEYWORD=rtt
DHCP_WAIT_TIMES=5
rm -f /var/lib/dhclient/dhclient.leases
fi
tmpfsloc=$(mount | grep tmpfs | awk '{print $3}' | head -n 1)
loc=${tmpfsloc:-/dev}
WPA_CONFIGFILE=$loc/wpa_supplicant.conf

echo dhcp client app is $DHCP_CLIENT    #打印相关信息
echo ping key words is $PING_KEYWORD
echo ESSID is $CONF_ESSID
echo interface is $IFACE
echo run mode is $RUN_MODE
}

　　
　　二、主循环程序如下



while [ -d $SYSFS ] ; do
network_connect
if [ $? -ne 0 ]; then
echo --INFO--:network is disconnected? try to reconnect
ifconfig $IFACE 0.0.0.0
setup_wifi
fi
sleep $CHECK_PERIOD
done

　　network_connect是一个函数，其主要功能是判断网络是否联通，然后是一个判断语句，如过network_connect不成功（返回的不是0），
　　则执行setup_wifi函数，此函数的主要功能重新设置并连接wifi。如果网络联通则睡眠CHECK_PERIOD秒后再重新判断连接是否正常。
　　三、判断网络是否连接函数network_connect



network_connect() {
#get ip first
ifconfig $IFACE | grep -q "inet addr"  #判断当前是否有IP地址
if [ $? -ne 0 ]; then
echo can\'t find IP
return 1
fi

#get default gateway
route | grep -q default | awk '{print $2}'  #获取当前连接路由的网关地址
if [ $? -ne 0 ]; then
echo can\'t get default gatway
return 1
else
SERVER_IP=$(route | grep default | awk '{print $2}')
fi
if [ -z $SERVER_IP ]; then
echo did not get server ip by route, server_ip=$SERVER_IP
return 1
fi
if ! ping -c $PING_RETRY_COUNT -q $SERVER_IP | grep -q $PING_KEYWORD; then  #利用ping命令查看网络是否联通
echo ping $SERVER_IP failed
return 1
fi
}

　　
　　四、加入路由函数setup_wifi



setup_wifi() {
ifconfig $IFACE down
ifconfig $IFACE up        #将无线网卡重启
echo start wireless scanning
local count=0
until [ $count -ge 3 ]  ;
do
get_auth_mode          #获取AP加密方式等信息，如果未找到指定AP，将会返回1
if [ $? -ne 0 ]; then
echo "AP $CONF_ESSID not found, sleeping...";
sleep 5;
let 'count=count+1';              
else
break                         #找到后返回
fi
done
#scan ok
if [ $count -lt 3 ] ; then
if [ "$RUN_MODE" = "debug" ] ; then
set_wifi_mode
return 0
fi
fi
local index
if [ $count -lt 3 ] ; then
echo APs list: ${mac_ary

}  #打印获取后的同名AP列表
echo signal list: ${siglevel_ary

}
echo sort index: ${sort_ary

}
for(( i = 1; i <= $AP_COUNT; i++)) #下面的功能是找到最大信号的那个AP  并加入到其中，如果加入不成功，依次加次强的那个
do
index=${sort_ary} #the first is most signal
bssid=${mac_ary[index]}
echo try AP: ${ssid_name_ary[index]}  $bssid
set_wifi_mode                      #该函数是设置wifi模式，并调用WPA_CONFIGFILE工具，连接AP
if [ $? -ne 0 ]; then
echo association with $bssid failed
else
echo association with $bssid OK
break
fi
done
fi
}

　　五、搜寻指定AP，并获得AP加密方式函数get_auth_mode



get_auth_mode() {
local grep_expr found
local ad_hoc_grep
iwlist_log=$(iwlist $IFACE scanning)  #扫描所有AP信息
grep_expr="ESSID:\"$CONF_ESSID\""
ad_hoc_grep="Mode:$ADHOC_MODE"

local start_line
start_line=$(printf "%s \n" "$iwlist_log" | grep -n $grep_expr | awk -F: '{print $1}')#找到符合指定AP名的行
AP_COUNT=$(echo $start_line | wc -w)   #判断有几行
echo total ap number is $AP_COUNT　　　　#有几行就说明有几个同名AP
# if AP_COUNT > 0
if [ $AP_COUNT -gt 0 ]; then   #如果大于0就说明找到指定AP
found=true
else
return 1
fi
start_line=$(printf "%s \n" "$iwlist_log" | grep  $grep_expr -B 2 | grep Cell | awk '{print $2}') #获得全部指定AP名的Cell
local i cell
for((i = 1; i <= $AP_COUNT; i++ )) #将每个同名AP分离出来  并存到数组内
do
cell=$(echo $start_line | awk '{print $('$i')}')
get_ssid_str $cell  $i                   #根据Cell编号，获取每个同名AP的加密信息
done
#suppose all APs used the same encryption settings, for supporting roaming
ssid_str=${ssid_str_ary[1]}   #数组内第一个AP就是同名AP中信号最强的
Encryption=$(printf "%s \n" "$ssid_str" | grep Encryption | awk -F: '{print $2}')#下面是获取其加密类型
Auth_Suite=$(printf "%s \n" "$ssid_str" | grep "Authentication Suites" | awk '{print $5}')
Group_cipher=$(printf "%s \n" "$ssid_str" | grep "Group Cipher" | head -n 1 | awk '{print $4}')
echo --INFO--:Group_cipher=$Group_cipher
#Pair_ciper=$(printf "%s \n" "$ssid_str" | grep "Pairwise Ciphers" | awk '{print $5}')
if [ "$Auth_Suite" = "802.1X" ]; then #转化为wpa_supplicant对应的加密类型
#Auth_Suite is PSK or 802.1X
echo didn\'t support WPA Enterprise, Authentication Suites is $Auth_Suite
return 1
fi
if [ "$Group_cipher" = "CCMP" -o "$Group_cipher" = "TKIP" ]; then
EncrypType=$Group_cipher
fi
AuthMode=WEP
if [ "$Encryption" = "off"  ]; then
AuthMode=
return 0
fi
if  echo $ssid_str | grep -q "802.11i/WPA2"  ; then
AuthMode=WPA2
return 0
fi
if  echo $ssid_str | grep -q "WPA Version" ; then
AuthMode=WPA
return 0
fi
return 0
}

　　六、加入AP函数set_wifi_mode



set_wifi_mode() {
echo auth mode is $AuthMode
if [ "$RUN_MODE" = "debug" ] ; then
killall $DHCP_CLIENT
killall wpa_supplicant
sleep 5
ifconfig $IFACE up
sleep 2
#iwconfig $IFACE key off
iwconfig $IFACE mode $ADHOC_MODE
sleep 2
iwconfig $IFACE essid "$DEBUG_CONF_ESSID"
ifconfig $IFACE $DEBUG_FIX_IP
return
fi
if [ "$AuthMode" = "WEP" ] ; then #判断加密类型  生成wpa_supplicant所需的.conf文件
local pref
if [ "$WEP_KEY_TYPE" = "char" ] ; then
pref="s:"
fi
iwconfig $IFACE key open $pref$PASSWORD  [$WEP_KEYINDEX]
iwconfig $IFACE essid "$CONF_ESSID"
echo try "open" Authentication mode
sleep 5
name=$(iwconfig $IFACE | head -1 | awk -F\" '{print $2}')
if [ "$name" != "$CONF_ESSID" ];then
echo "open" Authentication mode failed, try shard mode
iwconfig $IFACE key restricted $pref$PASSWORD  [$WEP_KEYINDEX]
iwconfig $IFACE essid "$CONF_ESSID"
fi
elif [ "$AuthMode" = "WPA2" -o "$AuthMode" = "WPA" ] ; then
killall wpa_supplicant
write_wpa_config                       #此函数生产.conf文件
sleep 2
ifconfig $IFACE up
sleep 2
wpa_supplicant -i $IFACE -B -c $WPA_CONFIGFILE  #利用wpa_supplicant工具加AP
#wait wpa config, associ
sleep 10
else
iwconfig $IFACE key off
iwconfig $IFACE essid "$CONF_ESSID"
fi
if [ "$AuthMode" != "WPA2" -a "$AuthMode" != "WPA" ]; then
if [ "$SET_MODE" = "yes" ] ; then
if [ "$RUN_MODE" = "debug" ] ; then
killall $DHCP_CLIENT
killall wpa_supplicant
sleep 2
ifconfig $IFACE up
sleep 2
fi
iwconfig $IFACE mode $ADHOC_MODE
else
iwconfig $IFACE mode $DEFAULT_MODE
fi
fi
#check if successed  #判断是否加入成功
ssidname=$(iwconfig $IFACE | grep $IFACE | awk -F: '{print $2}' | awk '{print $1}')
cur_bssid=$(iwconfig $IFACE | grep "Access Point:" | awk  '{print $6}')
cur_mode=$(iwconfig $IFACE | grep Mode | awk -F: '{print $2}' | awk '{print $1}')
echo $ssidname $cur_bssid $cur_mode
if [ "$ssidname" != "\"$CONF_ESSID\"" -o "$bssid" != "$cur_bssid" \
-o "$cur_mode" != "$DEFAULT_MODE" ]; then
#fail
return 1
fi
if [ -z $FIX_IP ] ; then
dhcp_pc
dhcp_ok=$(ifconfig $IFACE  | grep "inet addr" | awk '{print $1}')
if [ -z $dhcp_ok ]; then
return 1
fi
else
ifconfig $IFACE $FIX_IP
fi
if [ "$RUN_MODE" != "debug" ] ; then
route add default gateway $SERVER_IP $IFACE
fi
return 0
}

　　七、生产wpa_supplicant所需.conf文件函数



write_wpa_config() {
#init wpa_supplicant.conf file
if [ -f $WPA_CONFIGFILE ]; then
rm -f $WPA_CONFIGFILE
fi
cat >$WPA_CONFIGFILE<<-EOF
ctrl_interface=/var/run/wpa_supplicant
network={
ssid="$CONF_ESSID"
bssid=$bssid
scan_ssid=1
key_mgmt=WPA-PSK
proto=$AuthMode
pairwise=$EncrypType
group=$EncrypType
psk="$PASSWORD"
}
EOF
}

　　至此，此脚本全部结束，这个脚本的最好处在于支持wifi信号的漫游。