Linux 中已經包括了點對點協議PPP,其主體是 pppd ,如果你已經使用過 Windows95 或 NT 的撥號網絡,那麼你已經具備了 PPP 的基本經驗了。在 Windows95 的 PPP 在同 ISP 連接後,視 ISP 情況不同,會自動為 Windows 客戶機提供 IP 地址和 DNS 服務器地址,而 Linux 的 PPP 不會自動接收 DNS 地址,這是 Linux 與 Windows 的一點區別,所以,Linux 上的 PPP 在協議連接成功後,要多一步 DNS 的配置。
你的 Linux 系統必須在 kernel 中配置支持 PPP 功能。如果你的 kernel 目前不支持 PPP,你需要重新生成一個支持 PPP 的 kernel。重新編譯 kernel 的方法可看相關 Howto。
我一開始想運行 pppd 來連接撥號網絡,但很快發現這是太麻煩了,因為選項太多。後來我發現,其實在 Linux 上已經提供了幾個 PPP 撥號程序模版,只要對這些模板略作修改,就可輕松聯上 PPP 了。根據我的經驗,如果順利的話,10分鐘就能完成配置。
(1)撥號程序所在的目錄
對於 RedHat 5.0,這幾個撥號程序(Script)在 /usr/doc/ppp-2.2.0f/scripts 下,如果要使用這些腳本,需要把它們拷貝到正確的目錄中,具體如下:
ppp-on: PPP 連接腳本 拷貝到 /usr/sbin
ppp-off: PPP 斷開腳本 拷貝到 /usr/sbin
ppp-on-dialer: PPP 登錄會話腳本 拷貝到 /etc/ppp
ppp-redialer: 可輪循多個電話號碼的登陸腳本 拷貝到 /usr/sbin (本文不用)
對於 Slackware 的用戶,這些腳本已經安裝到正確的目錄了,無需做什麼。
假定你在你的系統上找不到上述文件,可直接在本文後面的附錄中cut。
(2)創建自己的撥號程序
假定現在我們要用 PPP 連接 163 網,我們就可以利用上述腳本來作很簡單的配置。雖然我們可以直接在這些模板上做修改,我還是建議為自己拷貝一份模板,在新的拷貝上作修改比較好。所以,我們先做如下拷貝:
cd /usr/sbin cp ppp-on ppp.163 chmod +x ppp.163 cd /etc/ppp cp ppp-on-dialer dialer.163 chmod +x dialer.163
此外,要保證 ppp-off 也是可執行的
(3)定制自己的撥號程序
首先編輯你的 ppp.163,其中多數內容都不必改動,只要修改以下幾處:
TELEPHONE=163 ACCOUNT=<Your_Login_Name> PASSWORD=<Your_Login_Password> DIALER_SCRIPT=/etc/ppp/dialer.163
另外,在最後的 exec 啟動 pppd 一行裡,注意提供你的 Modem 所在的串口設備文件(通常是 COM1 /dev/cua0 或 /dev/ttyS0,COM2 /dev/cua1 或 /dev/ttyS1),並設置串口的通信速度(缺省是 38400,對於現在的高速 Modem,這個速度太低了,可設置成 57600以上)。完成後的 ppp.163 內容是:
#!/bin/sh # # Script to initiate a ppp connection. This is the first part of the # pair of scripts. This is not a secure pair of scripts as the codes # are visible with the 'ps' command. However, it is simple. # # These are the parameters. Change as needed. TELEPHONE=163 # 撥號號碼 ACCOUNT=YourUserName # 用戶名 PASSWORD=YourPassword # 口令,注意限制其他人讀取本文件! LOCAL_IP=0.0.0.0 # 本地IP地址,0.0.0.0 表示動態分配 REMOTE_IP=0.0.0.0 # 原端IP地址,一般是 0.0.0.0 NETMASK=255.255.255.0 # 子網掩碼 export TELEPHONE ACCOUNT PASSWORD # # This is the location of the script which dials the phone and logs # in. Please use the absolute file name as the $PATH variable is not # used on the connect option. (To do so on a 'root' account would be # a security hole so don't ask.) # DIALER_SCRIPT=/etc/ppp/dialer.163 # 撥號登錄腳本文件名 # # Initiate the connection # # I put most of the common options on this command. Please, don't # forget the 'lock' option or some programs such as mgetty will not # work. The asyncmap and escape will permit the PPP link to work with # a telnet or rlogin connection. You are welcome to make any changes # as desired. Don't use the 'defaultroute' option if you currently # have a default route to an ethernet gateway. # exec /usr/sbin/pppd debug lock modem crtscts /dev/ttycua0 57600 \ asyncmap 20A0000 escape FF kdebug 0 $LOCAL_IP:$REMOTE_IP \ noipdefault netmask $NETMASK defaultroute connect $DIALER_SCRIPT
然後,檢查一下你的登錄會話程序 /etc/ppp/dialer.163,在我所在的 163 ISP,這個從模板拷貝過來的會話程序可直接使用,如果有以下情況,你需要對這個會話程序略作改動:
(1)如果撥號提示輸入用戶名的提示符不是 login:
(2)如果登錄成功後還要用戶再交互打入命令 ,才啟動 ppp 協議
本文後面的附錄三是一個根據上述要求略加修改後的登錄腳本。
建議:假如你有多個 ISP 可連接,就創建多個撥號 PPP 連接腳本和相應的 PPP 登錄腳本。
#!/bin/sh ################################################################### # # These parameters control the attack dialing sequence. # # Maximum number of attempts to reach the telephone number(s) MAX_ATTEMPTS=10 # Delay between each of the attempts. This is a parameter to sleep # so use "15s" for 15 seconds, "1m" for 1 minute, etc. SLEEP_DELAY=15s ################################################################### # # This is a list of telephone numbers. Add new numbers if you wish # and see the function 'callall' below for the dial process. PHONE1=555-1212 PHONE2=411 ################################################################### # # If you use the ppp-on script, then these are passed to this routine # automatically. There is no need to define them here. If not, then # you will need to set the values. # ACCOUNT=my_account_name PASSWORD=my_password ################################################################### # # Function to initialize the modem and ensure that it is in command # state. This may not be needed, but it doesn't hurt. # function initialize { chat -v TIMEOUT 3 '' AT 'OK-+++\c-OK' return } ################################################################### # # Script to dial a telephone # function callnumber { chat -v \ ABORT '\nBUSY\r' \ ABORT '\nNO ANSWER\r' \ ABORT '\nRINGING\r\n\r\nRINGING\r' \ '' ATDT$1 \ CONNECT '' \ ogin:--ogin: $ACCOUNT \ assword: $PASSWORD # # If the connection was successful then end the whole script with a # success. # if [ "$?" = "0" ]; then exit 0 fi return } ################################################################### # # Script to dial any telephone number # function callall { # echo "dialing attempt number: $1" >/dev/console callnumber $PHONE1 # callnumber $PHONE2 } ################################################################### # # Initialize the modem to ensure that it is in the command state # initialize if [ ! "$?" = "0" ]; then exit 1 fi # # Dial telephone numbers until one answers # attempt=0 while : ; do attempt=`expr $attempt + 1` callall $attempt if [ "$attempt" = "$MAX_ATTEMPTS" ]; then exit 1 fi sleep "$SLEEP_DELAY" done
#!/bin/sh ###################################################################### # # Determine the device to be terminated. # if [ "$1" = "" ]; then DEVICE=ppp0 else DEVICE=$1 fi ###################################################################### # # If the ppp0 pid file is present then the program is running. Stop it. if [ -r /var/run/$DEVICE.pid ]; then kill -INT `cat /var/run/$DEVICE.pid` # # If the kill did not work then there is no process running for this # pid. It may also mean that the lock file will be left. You may wish # to delete the lock file at the same time. if [ ! "$?" = "0" ]; then rm -f /var/run/$DEVICE.pid echo "ERROR: Removed stale pid file" exit 1 fi # # Success. Let pppd clean up its own junk. echo "PPP link to $DEVICE terminated." exit 0 fi # # The ppp process is not running for ppp0 echo "ERROR: PPP link is not active on $DEVICE" exit 1