Tethering technology has been widely used on mobile platforms. It can use mobile devices as an access point, and other devices can use Wi-Fi, connect to the mobile device using USB or Bluetooth.
Recently, network devices have been debugged on the TCC8900 Development Board of Telechips. You need to implement simple Tethering in Linux and share the network connection with other devices in Wi-Fi Ad-hoc mode. On the Development Board, a wired network adapter (eth1), a wireless network adapter (eth0), eth1 is connected to the Internet, and eth0 is shared as an AP to another PC with a wireless network adapter, this allows the PC to connect to the Internet through the Development Board. (The intranet IP address is 192.168.0 .*)
After analysis, we need to implement the following simple functions:
1. Wi-Fi Master or Ad-hoc mode configuration
2. NAT
3. DHCP server
Wi-Fi Mode settings
The Development Board provides the AR6102, an SDIO interface for Wi-Fi. From the hardware description, This Wi-Fi only supports Ad-hoc point-to-point mode, but does not support AP, therefore, use iwconfig to set it to the Ad-hoc mode.
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iwconfig eth0 mode ad-hoc |
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iwconfig eth0 enc s:12345 |
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iwconfig eth0 essid "tcc8900" |
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ifconfig eth0 192.168.0.1 |
NAT implementation using iptables
Iptables can implement address translation, firewall, port filtering, and other functions. Here we only use the most basic address translation, so that the PC can access the Internet.
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iptables -t nat -A POSTROUTING -o eth1 -s 192.168.0.0/24 -j MASQUERADE |
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echo "1" > /proc/sys/net/ipv4/ip_forward |
Build a DHCP service using udhcpd
You need to create a new configuration file. The default value is/etc/udhcpd. conf, and a lease (lease) record file is required. The default value is/etc/udhcpd. leases, you can use the dumpleases command to view the lease of connected clients.
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touch /etc/udhcpd.leases |
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udhcpd -S /etc/udhcpd.conf |
Provides an example of udhcpd. conf.
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# Sample udhcpd configuration file (/etc/udhcpd.conf) |
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# The start and end of the IP lease block |
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# The interface that udhcpd will use |
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interface eth0 #default: eth0 |
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# The maximim number of leases (includes addressesd reserved |
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# by OFFER's, DECLINE's, and ARP conficts |
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max_leases 20 #default: 254 |
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# If remaining is true (default), udhcpd will store the time |
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# remaining for each lease in the udhcpd leases file. This is |
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# for embedded systems that cannot keep time between reboots. |
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# If you set remaining to no, the absolute time that the lease |
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# expires at will be stored in the dhcpd.leases file. |
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remaining yes #default: yes |
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# The time period at which udhcpd will write out a dhcpd.leases |
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# file. If this is 0, udhcpd will never automatically write a |
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# lease file. (specified in seconds) |
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auto_time 7200 #default: 7200 (2 hours) |
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# The amount of time that an IP will be reserved (leased) for if a |
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# DHCP decline message is received (seconds). |
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decline_time 3600 #default: 3600 (1 hour) |
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# The amount of time that an IP will be reserved (leased) for if an |
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# ARP conflct occurs. (seconds) |
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conflict_time 3600 #default: 3600 (1 hour) |
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# How long an offered address is reserved (leased) in seconds |
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offer_time 60 #default: 60 (1 minute) |
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# If a lease to be given is below this value, the full lease time is |
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# instead used (seconds). |
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min_lease 60 #defult: 60 |
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# The location of the leases file |
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lease_file /etc/udhcpd.leases |
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# The remainer of options are DHCP options and can be specifed with the |
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# keyword 'opt' or 'option'. If an option can take multiple items, such |
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# as the dns option, they can be listed on the same line, or multiple |
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# lines. The only option with a default is 'lease'. |
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opt dns 8.8.8.8 8.8.8.4 |
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option subnet 255.255.255.0 |
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opt router 192.168.0.1 |
