TCC8900开发板实现Wi-Fi Tethering + DHCP服务器

来源：互联网发布：mac 日历的其他颜色编辑：程序博客网时间：2024/04/29 02:23

Tethering技术在移动平台上已经运用的越来越广泛了，它可以把移动设备当做一个接入点，其它的设备可以通过Wi-Fi，USB或是Bluetooth等方式连接到此移动设备。

最近在Telechips的TCC8900开发板上调试网络设备，需要在Linux下实现简单的Tethering，通过Wi-Fi的Ad-hoc 模式，将网络连接共享给其它设备。开发板上一个有线网卡(eth1)，一个无线网卡(eth0)，eth1连接到外网，eth0作为AP共享给另一台装了无线网卡的PC，使得PC可以通过开发板连接到外网。(内网的ip地址为192.168.0.*)

分析下来需要实现以下几个简单的功能：
1. Wi-Fi的Master或Ad-hoc模式配置
2. NAT
3. DHCP服务器

Wi-Fi模式设置
随开发板提供的是AR6102，一个SDIO接口的Wi-Fi，从硬件说明上看，这个Wi-Fi只支持Ad-hoc的点对点的模式，而无法支持AP，因此使用iwconfig将它设置成Ad-hoc模式

1iwconfig eth0 mode ad-hoc 
2iwconfig eth0 enc s:12345 
3iwconfig eth0 essid "tcc8900"
4ifconfig eth0 up 
5ifconfig eth0 192.168.0.1

NAT使用iptables实现
iptables可以实现地址翻译，防火墙，端口过滤等功能，这里只用到了最基本的地址翻译，使得PC可以访问外网

1iptables -t nat -A POSTROUTING -o eth1 -s 192.168.0.0/24 -j MASQUERADE 
2echo "1" > /proc/sys/net/ipv4/ip_forward

DHCP服务使用udhcpd搭建
需要新建一个配置文件，默认为/etc/udhcpd.conf，另外需要一个lease（租约）的记录文件，默认为/etc/udhcpd.leases，可以用dumpleases命令来查看已连接的客户端的租约情况。

1touch /etc/udhcpd.leases 
2udhcpd -S /etc/udhcpd.conf

提供一个udhcpd.conf的例子。

01# Sample udhcpd configuration file (/etc/udhcpd.conf) 
02# The start and end of the IP lease block 
03start            192.168.0.2 
04end              192.168.0.100 
05  
06# The interface that udhcpd will use 
07interface        eth0              #default: eth0 
08  
09# The maximim number of leases (includes addressesd reserved 
10# by OFFER's, DECLINE's, and ARP conficts 
11max_leases       20                #default: 254 
12  
13# If remaining is true (default), udhcpd will store the time 
14# remaining for each lease in the udhcpd leases file. This is 
15# for embedded systems that cannot keep time between reboots. 
16# If you set remaining to no, the absolute time that the lease 
17# expires at will be stored in the dhcpd.leases file. 
18remaining        yes               #default: yes 
19  
20# The time period at which udhcpd will write out a dhcpd.leases 
21# file. If this is 0, udhcpd will never automatically write a 
22# lease file. (specified in seconds) 
23auto_time        7200              #default: 7200 (2 hours) 
24  
25# The amount of time that an IP will be reserved (leased) for if a 
26# DHCP decline message is received (seconds). 
27decline_time     3600              #default: 3600 (1 hour) 
28  
29# The amount of time that an IP will be reserved (leased) for if an 
30# ARP conflct occurs. (seconds) 
31conflict_time    3600              #default: 3600 (1 hour) 
32  
33# How long an offered address is reserved (leased) in seconds 
34offer_time       60                #default: 60 (1 minute) 
35  
36# If a lease to be given is below this value, the full lease time is 
37# instead used (seconds). 
38min_lease        60                #defult: 60 
39  
40# The location of the leases file 
41lease_file       /etc/udhcpd.leases 
42  
43# The remainer of options are DHCP options and can be specifed with the 
44# keyword 'opt' or 'option'. If an option can take multiple items, such 
45# as the dns option, they can be listed on the same line, or multiple 
46# lines. The only option with a default is 'lease'. 
47  
48#Examples 
49opt        dns        8.8.8.8 8.8.8.4 
50option     subnet     255.255.255.0 
51opt        router     192.168.0.1