Automatic network start on USB-Netdevice insert

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There are devices connecting the computer to ethernet via USB. It would be nice to raise the network, after the USB netdevice is plugged into the computer

Contents

[edit] Getting the right kernel module

First have a look into the kernel modules, if there is the appropriate module servicing your device. The USB network device modules are located in:

Linux Kernel Configuration: USB network devices 
Device Drivers  --->
  Network device support  --->
    USB Network Adapters  --->
      <select all modules>

There select all devices as modules drivers. Compile and install the modules

make all modules_install

You may find further information in the Gentoo linux kernel guide.

[edit] First Network device start

If you successfully installed the device driver modules, have a look what udev thinks of your device. Today almost all Gentoo installations have udev activated. Have a look in the Gentoo udev guide, if you're not shure.

Now plug in your device. lsusb should list the device and its name and hardware. (This is an example with AX88187 hardware)

Code: lsusb 
Bus 001 Device 016: ID 0b95:1780 ASIX Electronics Corp. AX88178

If you have udev activated and a device driver module, the system logs should list your device, too.

Code: /var/log/messages 
kernel: usb 1-3: new high speed USB device using ehci_hcd and address 16
kernel: usb 1-3: configuration #1 chosen from 1 choice
kernel: eth1: register 'asix' at usb-0000:00:12.2-3, ASIX AX88178 USB 2.0 Ethernet, 00:11:6b:f0:44:b0
Code: dmesg 
usb 1-3: new high speed USB device using ehci_hcd and address 16
usb 1-3: configuration #1 chosen from 1 choice
eth1: register 'asix' at usb-0000:00:12.2-3, ASIX AX88178 USB 2.0 Ethernet, 00:11:6b:f0:44:b0

[edit] Rename the network device

You may leave the network device name to "eth1" and skip this section. I like to rename the device. There are 2 ways to rename it, net config and udev.

[edit] Rename in /etc/conf.d/net

The Gentoo net config file allows to rename a network device. Simply add

Code: /etc/conf.d/net 
rename_eth1="usb0"

Be careful, always use the device eth1 for your USB device. Else you rename a different device, which you won't want to do.

[edit] Rename in /etc/udev/rules.d/70-persistent-net.rules

The other way renames every USB device with a certain hardware ID to "usb0". You have to change the entry in the persistent net rules from udev from "eth1" to "usb0".

Upon your first insert of the USB device, udev has made an entry in the persistent net list. Look for the entry with the same device ID of your USB device (e.g. "USB device 0x0b95:0x1780 (usb)") and change the entry 'NAME=' from "eth1" to "usb0".

If you don't have an entry for your device, check if your device is detected and known to the system. Have a look in the previous section. Also check, that persistent net rules are activated in your system config

Code: /etc/conf.d/udev 
persistent_net_disable="no"

Afterwards it may look like this:

Code: /etc/udev/rules.d/70-persistent-net.rules 
SUBSYSTEM=="net", ACTION=="add", DRIVERS=="?*", ATTR{address}=="00:11:6b:f0:44:b0", ATTR{dev_id}=="0x0", ATTR{type}=="1", KERNEL=="eth*", NAME="usb0"

This however only works for your actual USB device with a certain device ID. You have to redo this step for every USB net device.

[edit] Automatic network start

To have an automatic start of connectivity use sys-apps/ifplugd or sys-apps/netplug. The net example configuration (/etc/conf.d/net.example) lists both. Just
emerge sys-apps/ifplugd
and link the ethernet interface to the network script
ln -s net.lo /etc/init.d/net.usb0


You may add a dhcp entry to the network config. Using dhcp should be default handling if no entry is listed in the config file.

Code: /etc/conf.d/net 
config_usb0=( "dhcp" )

[edit] finish

Now your network connection should appear as net device "usb0" and instantly connect to your network if your net cable is plugged in. "ifconfig" lists your device.

Code: ifconfig 
usb0      Protokoll:Ethernet  Hardware Adresse 00:11:6b:f0:44:b0            
          inet Adresse:192.168.2.171  Bcast:192.168.2.255  Maske:255.255.255.0
          inet6 Adresse: fe80::211:6bff:fef0:44b0/64 Gültigkeitsbereich:Verbindung
          UP BROADCAST RUNNING MULTICAST  MTU:7200  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          Kollisionen:0 Sendewarteschlangenlänge:1000
          RX bytes:0 (0.0 B)  TX bytes:0 (0.0 B)

You may change your MTU of your device, if you own a gigabit net adapter. Add in to the network config file

Code: /etc/conf.d/net 
mtu_usb0="7200"
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