在ARM+LINUX上使用pppd拔號上網(GPRS)流程

1.修改2.6.30內核選項，
make menuconfig
Device drivers -> Networking device support -> PPP(point to point protocol) support
我選了以下模塊(以M方式即module方式)
PPP support for async serial ports
PPP support for sync tty ports
PPP Deflate compression
PPP BSD-Compress compression
SLIP(serial line) support
之后編譯：make && make install && make modules && make modules_install
得到了幾個ko形式的內核庫文件，拷貝它們到ARM目標板上，并在/etc/init.d/rcS中動態加載：
insmod /etc/ppp/slhc.ko
insmod /etc/ppp/ppp_generic.ko
insmod /etc/ppp/ppp_async.ko
insmod /etc/ppp/ppp_synctty.ko
insmod /etc/ppp/ppp_deflate.ko
insmod /etc/ppp/bsd_comp.ko
insmod /etc/ppp/slip.ko
注意加載順序，我記得好象必須把slhc.ko先加載

2. 移植ppp與連接網絡過程,
1) ppp2.4.4 源碼編譯過程

#./configure

#make CC=arm-linux-gcc 注意指定arm-linux-gcc的路徑，或是直接用絕對路徑指定

需要拷貝到ARM目標板的文件有：
pppd
pppdump
pppstatus
chat
2 ) 腳本準備
有4個腳本需要準備，一個是規則文件/etc/ppp/gprs-connect-chat，一個是參數文件/etc/ppp/peers/gprs, 還有認證文件：pap-secret和chap-secret。（其實我這里只用到了pap-secret, 至于chap-secret 沒有有到。anyhow，把它們全創建上）
(1) 腳本 #gprs-connect-chat:
TIMEOUT 15
ABORT nBUSYr
ABORT nNO ANSWERr
ABORT nRINGINGrnrnRINGINGr
# AT
#OK-+++c-OK ATH0
TIMEOUT 40
rAT
OK AT+FLO=0#這個是GC864-DUAL-V2特別要設置的，就是要關閉流控
OK ATS0=0
OK ATE0V1
OK AT+CGDCONT=1,"IP","CMNET" #連接中國移動cmnet網
OK ATDT*99*1#
CONNECT
(2) 腳本gprsoptions
#/etc/ppp/peers/gprsoptions
# Usage: root>pppd call gprsoptions
/dev/ttyS4
115200
nocrtscts
modem
#noauth
#auth
#-pap
#+chap
lock
debug
nodetach
#hide-password
usepeerdns
noipdefault
defaultroute
user cmnet
#user smsong
0.0.0.0:0.0.0.0
ipcp-accept-local
#ipcp-accept-remote
#lcp-echo-failure 12
#lcp-echo-interval 3
noccp
#novj
#novjccomp
persist
connect /etc/ppp/chat -s -v -f /etc/ppp/gprs-connect-chat
(3) 認證文件pap-secrets根據需要來改
/etc/ppp # cat pap-secrets
# Secrets for authentication using PAP
# client server secret IP addresses
cmnet * cmnet *
(4) 認證文件 chap-secrets 根據需要來修改，現在暫時沒用到
/etc/ppp # cat chap-secrets
# Secrets for authentication using CHAP
# client server secret IP addresses
* *

3） 調用過程
ifconfig eth0 down //先關閉有線網卡，以免與拔號初始化沖突
/etc/ppp/pppd call gprs& //啟動/etc/ppp/peers/gprs腳本
ifconfig eth0 up //重新開有線網卡
來看連接的顯示日志內容：
/etc/ppp # ./pppd call gprs&
/etc/ppp # timeout set to 15 seconds
abort on (nBUSYr)
abort on (nNO ANSWERr)
abort on (nRINGINGrnrnRINGINGr)
timeout set to 40 seconds
send (^MAT^M)
expect (OK)
AT^M^M
OK
-- got it

send (AT+FLO=0^M)
expect (OK)
^M
AT+FLO=0^M^M
OK
-- got it

send (ATS0=0^M)
expect (OK)
^M
ATS0=0^M^M
OK
-- got it

send (ATE0V1^M)
expect (OK)
^M
ATE0V1^M^M
OK
-- got it

send (AT+CGDCONT=1,"IP","CMNET"^M)
expect (OK)
^M
^M
OK
-- got it

send (ATDT*99*1#^M)
expect (CONNECT)
^M
^M
CONNECT
-- got it

send (^M)
Serial connection established.
using channel 1
Using interface ppp0
Connect: ppp0 <--> /dev/ttyS4
Warning - secret file /etc/ppp/pap-secrets has world and/or group access
sent [LCP ConfReq id=0x1 ]
rcvd [LCP ConfAck id=0x1 ]
rcvd [LCP ConfReq id=0x1 ]
sent [LCP ConfAck id=0x1 ]
Warning - secret file /etc/ppp/pap-secrets has world and/or group access
sent [PAP AuthReq id=0x1 user="cmnet" password=]
rcvd [PAP AuthAck id=0x1 "Welcome!"]
Remote message: Welcome!
PAP authentication succeeded
sent [IPCP ConfReq id=0x1 ]
rcvd [IPCP ConfReq id=0x1 ]
sent [IPCP ConfAck id=0x1 ]
rcvd [IPCP ConfRej id=0x1 ]
sent [IPCP ConfReq id=0x2 ]
rcvd [IPCP ConfNak id=0x2 ]
sent [IPCP ConfReq id=0x3 ]
rcvd [IPCP ConfAck id=0x3 ]
local IP address 10.176.120.186
remote IP address 192.168.202.0
primary DNS address 218.201.96.130
secondary DNS address 211.137.191.26

4) 查看網絡設置與ping實驗
/etc/ppp # ifconfig
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

ppp0 Link encap:Point-to-Point Protocol
inet addr:10.176.120.186 P-t-P:192.168.202.0 Mask:255.255.255.255
UP POINTOPOINT RUNNING NOARP MULTICAST MTU:1500 Metric:1
RX packets:4 errors:0 dropped:0 overruns:0 frame:0
TX packets:4 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:3
RX bytes:64 (64.0 B) TX bytes:82 (82.0 B)
來ping 一下看看
/etc/ppp # ping www.163.com -c 3
PING www.163.com (221.204.240.161): 56 data bytes
64 bytes from 221.204.240.161: seq=0 ttl=46 time=466.873 ms
64 bytes from 221.204.240.161: seq=1 ttl=46 time=435.762 ms
64 bytes from 221.204.240.161: seq=2 ttl=46 time=414.000 ms

--- www.163.com ping statistics ---
3 packets transmitted, 3 packets received, 0% packet loss
round-trip min/avg/max = 414.000/438.878/466.873 ms

3.其它問題

1 ) 設置DNS地址
/etc/ppp 下會由拔號自動產生resolv.conf 文件， 但它和 /etc/resolv.conf 并不是同一個文件，所以有的時候不能解析DNS。
一個好辦法是，首先保證存在/etc/resolv.conf, 然后在/etc/ppp下創建軟鏈接ln -s /etc/ppp/resolv.conf /etc/resolv.conf
這樣在拔號成功后，在/etc/resolv.conf中會有類似以下內容：
nameserver 218.201.96.130
nameserver 211.137.191.26
2） 只能ping IP地址，不能ping域名的現象
在busybox的命令幫助頁面有這樣一段話：
引用:
LIBC NSS
When used with glibc, the BusyBox networking applets will similarly require that you install at least some of the glibc NSS stuff (in particular, /etc/nsswitch.conf, /lib/libnss_dns*, /lib/libnss_files*, and /lib/libresolv*).
于是把arm-linux工具鏈的lib目錄下的 libnss_dns* , libnss_files* , libresolv* 拷貝到ARM目標板的/lib下?？梢詐ing域名啦
/etc/ppp # ping www.163.com
PING www.163.com (221.204.240.161): 56 data bytes
64 bytes from 221.204.240.161: seq=0 ttl=46 time=641.269 ms
64 bytes from 221.204.240.161: seq=1 ttl=46 time=435.801 ms
64 bytes from 221.204.240.161: seq=2 ttl=46 time=446.776 ms
64 bytes from 221.204.240.161: seq=3 ttl=46 time=381.381 ms
64 bytes from 221.204.240.161: seq=4 ttl=46 time=468.495 ms

--- www.163.com ping statistics ---
5 packets transmitted, 5 packets received, 0% packet loss
round-trip min/avg/max = 381.381/474.744/641.269 ms


3） 如何實現拔號與中國聯通的3G 聯網？
換用TELIT公司的UC864-E， 使用USB連接方式。指定串口為ttyUSB0
對于ppp方面，只需要更改4個腳本中的少量內容
a. 更改options腳本
把gprsoptions更名為g3options, 把里面的這一行參數/dev/ttyS4 更改為/dev/ttyUSB0，
把connect /etc/ppp/chat -s -v -f /etc/ppp/gprs-connect-chat
更改為connect /etc/ppp/chat -s -v -f/etc/ppp/g3-connect-chat
b. 更改chat腳本
TIMEOUT 15
ABORT nBUSYr
ABORT nNO ANSWERr
ABORT nRINGINGrnrnRINGINGr
# AT
#OK-+++c-OK ATH0
TIMEOUT 40
rAT
OK AT+FLO=0
OK ATS0=0
OK ATE0V1
OK AT+CGDCONT=1,"IP","UNINET"#UNINET是代表中國聯通網的意思
#OK AT+CGDCONT=1,"IP","CMNET"
OK ATDT*99*1#
CONNECT
c. 更改pap-secrets
# Secrets for authentication using PAP
# client server secret IP addresses
#cmnet * cmnet * #如果是中國移動GPRS就用cmnet
uninet * uninet * #如果是中國聯通3G就用uninet

d. 更改chap-secrets
同上pap-secrets