一、配置开发板USB Gadget模式为rndis
1.内核配置：
Device Drivers ---> [*] USB support ---> <*> USB Gadget Support ---> <*> USB Gadget Drivers (USB functions configurable through configfs) ---> [*] Generic serial bulk in/out [*] Abstract Control Model (CDC ACM) [*] Object Exchange Model (CDC OBEX) [ ] Network Control Model (CDC NCM) [ ] Ethernet Control Model (CDC ECM) [ ] Ethernet Control Model (CDC ECM) subset [*] RNDIS [ ] Ethernet Emulation Model (EEM) [*] Mass storage [ ] Loopback and sourcesink function (for testing) [*] Function filesystem (FunctionFS) [ ] MTP gadget [*] Uevent notification of Gadget state [*] Audio Class 1.0 [ ] Audio Class 2.0 [ ] MIDI function [*] HID function [*] USB Webcam function [*] Printer function
2.配置USB Gadget模式为rndis
可以在/etc/init.d目录下添加一个启动脚本：
#!/bin/sh # # Start rndis # export CONFIGFS_HOME=/sys/kernel/config case "$1" in start) echo "Starting usb devices ..." # usb common configs. mount -t configfs none $CONFIGFS_HOME cd $CONFIGFS_HOME/usb_gadget mkdir -p demo/strings/0x409 echo 0x18d1 > demo/idVendor echo 0xd002 > demo/idProduct echo 0x200 > demo/bcdUSB echo 0x100 > demo/bcdDevice echo "xxx" > demo/strings/0x409/manufacturer echo "composite-demo" > demo/strings/0x409/product echo "0123456789ABCDEF" > demo/strings/0x409/serialnumbermkdir -p demo/configs/c.1/strings/0x409 echo "compsite-config" > demo/configs/c.1/strings/0x409/configuration echo 120 > demo/configs/c.1/MaxPower # config device /etc/init.d/usb/rndis $1 # enable UDC. echo 13500000.otg > demo/UDC #13500000.otg根据/sys/class/udc/目录下文件得到 ;; stop) echo "Stop usb devices ..." echo none > demo/UDC /etc/init.d/usb/rndis $1 ;; restart|reload) ;; *) echo "Usage: $0 {start|stop|restart}" exit 1 esac exit $?
/etc/init.d/usb/rndis脚本内容如下：
# cat /etc/init.d/usb/rndis #!/bin/sh # # Start rndis.... # cd $CONFIGFS_HOME/usb_gadget case "$1" in start) echo "Starting usb rndis devices ..." mkdir -p demo/functions/rndis.0 if [ $? != 0 ]; then echo "unable to create function rndis, check kernel config!" exit 1 fi ln -s demo/functions/rndis.0 demo/configs/c.1/ ;; stop) echo "Stop usb rndis devices ..." if [ ! -d demo/configs/c.1/rndis.0 ];then exit 0 fi rm demo/configs/c.1/rndis.0 rm demo/functions/rndis.0 ;; restart|reload) ;; *) echo "Usage: $0 {start|stop|restart}" exit 1 esac exit $?
关于上述配置USB Gadget功能的解释，参见：通过configfs配置的Linux USB gadget 。
二、arm linux开发板网络配置
在/etc/init.d目录下写一个脚本启动dnsmasq服务：
#!/bin/sh [ -f /etc/dnsmasq.conf ] || exit 0 case "$1" in start) printf "Starting dnsmasq: " start-stop-daemon -S -x /usr/sbin/dnsmasq [ $? = 0 ] && echo "OK" || echo "FAIL" ;; stop) printf "Stopping dnsmasq: " start-stop-daemon -K -q -x /usr/sbin/dnsmasq [ $? = 0 ] && echo "OK" || echo "FAIL" ;; restart|reload) $0 stop $0 start ;; *) echo "Usage: $0 {start|stop|restart}" exit 1 esac exit 0
dnsmasq配置文件/etc/dnsmasq.conf内容如下：
dhcp-range=192.168.1.2,192.168.1.25,12h
配置开发板上usb0 IP：
ifconfig usb0 up
ifconfig usb0 192.168.1.1
使能开发板上网络转发功能：
echo "1" > /proc/sys/net/ipv4/ip_forward #echo "net.ipv4.ip_forward = 1" > /etc/sysctl.conf #sysctl -p iptables -F iptables -t nat -F iptables -P INPUT ACCEPT iptables -P FORWARD ACCEPT iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE
通过上面配置 iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE 可以知道使用的是arm开发板上eth0网卡进行转发。
如何配置arm linux开发板kernel层面支持ip_forward，参考：WIFI AP模式通过LAN网线上网 。
三、Linux主机端操作
使用如下命令给usb0分配IP地址：
ifconfig usb0 up udhcpc -i usb0
这时Linux主机端usb0拿到的IP地址理论上在192.168.1.2~25之间。
使用 route -n 或者 netstat -r 查看一下Kernel IP routing table，如果有如下一行，表示路由OK：
root@allen:~# route -n Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 0.0.0.0 192.168.1.1 0.0.0.0 UG 0 0 0 usb0
否则需要手动添加：
route add default gw 192.168.1.1 dev usb0
192.168.1.1为arm linux开发板上面给usb0网卡设置的IP地址。
这时使用 ping www.baidu.com -I usb0 可以看到Linux主机已经可以通过USB使用arm linux开发板的网络去访问公网了。