Difference between revisions of "Netcfg Tips"

Revision as of 17:09, 12 February 2013

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Enabling WOL

Enabling WOL can be accomplished using a POST_UP statement in the profile.

POST_UP='/usr/sbin/ethtool -s eth0 wol g'

Using jumbo frames

Insert the following line to the network profile(s) which require a non-standard MTU value:

POST_UP='/usr/sbin/ip link set eth0 mtu 4000'

The above example is using a 4k jumbo frame.

Clean logouts for users connected via sshd

Insert the following line to the network profile(s) which will kill all connected sshd sessions upon a network restart/stop:

PRE_DOWN='/usr/bin/pkill sshd'

rfkill (enable/disable radio power)

netcfg can enable/disable radio for wireless cards equipped with software control of radio. For wireless cards with hardware switches, netcfg can detect disabled hardware switches and fail accordingly.

To enable rfkill support, you need to specify what sort of switch the wireless interface has; hardware or software. This can be set within a profile or at the interface level (/etc/network.d/interfaces/$INTERFACE; see #Per-interface configuration).

RFKILL=soft # can be either 'hard' or 'soft'

For some kill switches the rfkill entry in /sys is not linked to the interface and the RFKILL_NAME variable needs to be set to the contents of the matching /sys/class/rfkill/rfkill#/name.

For example, on an Eee PC:

RFKILL=soft
RFKILL_NAME='eeepc-wlan'

On a mid-2011 Thinkpad:

RFKILL=hard
RFKILL_NAME='phy0'

/etc/network.d/interfaces/wlan0

RFKILL=hard
RFKILL_NAME=`cat /sys/class/rfkill/rfkill*/name 2> /dev/null || echo ""`

Execute commands before/after interface up/down

If your interface requires special actions prior/after the establishment/closure of a connection, you may use the PRE_UP, POST_UP, PRE_DOWN, and POST_DOWN variables.

For example, if you want to configure your wireless card to operate in ad-hoc mode but you can only change modes when the interface is down, you could use something like this:

PRE_UP="ip link set wlan0 down; iwconfig wlan0 mode ad-hoc"

Or if you want to mount your network shares after a successful connection, you could use:

POST_UP="sleep 5; mount /mnt/shares/nexus/utorrent 2>/dev/null"

Sometimes you may want to run something from netcfg with another user:

POST_UP="su -c '/you/own/command' username"

Intermittent Connection Failure

Some driver+hardware combinations drop associations sometimes. Use the pre and post commands to add/remove the driver and use a script like the following to fix the current connection:

/usr/local/bin/netcfgd

#!/bin/bash
log() { logger -t "$( basename $0 )" "$*" ; }

main() {
        local host
        while sleep 1; do
                [[ "$( netcfg current )" = "" ]] && continue

                host=$( route -n | awk '/^0.0.0.0/ { print $2 }' )
                ping -c1 -w10 $host && continue

                log "trying to reassociate"
                wpa_cli reassociate
                ping -c1 -w10 $host && continue

                log "reassociate failed, reconfiguring network"
                netcfg -r $( netcfg current )
        done
}

exec 1>/dev/null
[[ $EUID != 0 ]] && { log "must be root"; exit 1; }

for cmd in wpa_cli ping netcfg; do
        ! which $cmd && {
                log "can't find command ${cmd}, exiting..."
                exit 1
        }
done

log 'starting...'
main

Per-interface configuration

Configuration options that apply to all profiles using an interface can be set using /etc/network.d/interfaces/$INTERFACE. For example:

/etc/network.d/interfaces/wlan0

This is useful for wpa_supplicant options, rfkill switch support, pre/post up/down scripts and net-auto-wireless. These options are loaded before profiles so that any profile-based options will take priority.

/etc/network.d/interfaces/$INTERFACE may contain any valid profile option, though you are likely to use PRE_UP/DOWN and POST_UP/DOWN (described in the previous section) or one of the options listed below. Remember that these options are set for all profiles using the interface; you probably do not want to connect to your work VPN here, for instance, as it will try to connect on every wireless network!

WPA_GROUP   - Setting the group of the wpa_ctrl interface
WPA_COUNTRY - Enforces local regulatory limitations and allows use of more channels
WPA_DRIVER  - Defaults to wext, may want nl80211 for mac80211 devices

Output hooks

netcfg has limited support to load hooks that handle output. By default it loads the arch hook which provides the familiar output that you see. A syslog logging hook is also included. These can be found at /usr/lib/network/hooks.

ArchAssistant (GUI)

A Qt-based netcfg front-end called ArchAssistant exists. It proposes to manage and connect/disconnect profiles from a system tray icon. Automatic wireless detection is also available. This tool is particularly useful for laptop users.

Links:

• archassistant^AUR in the AUR
• archassistant on kde-apps.org

There is also a relatively new GUI for netcfg on qt-apps.org that does only network configuration. You can find it here.

Netcfg Easy Wireless LAN (newlan)

newlan is a mono console application that starts a user-friendly wizard to create netcfg profiles; it also supports wired connections.

Install the newlan^AUR package from the AUR.

newlan must be run with root privileges:

# newlan -n mynewprofile

wifi-select

There is a console tool for selecting wireless networks in "real-time" (in NetworkManager fashion) called wifi-select. The tool is convenient for use in Internet cafés or other places you are visiting for the first (and maybe the last) time. With this tool, you do not need to create a profile for a new network, just run wifi-select wlan0 as root and choose the desired network.

The tool is currently packaged as wifi-select and is available in the official repositories.

wifi-select does the following:

• parses iwlist scan results and presents a list of networks along with their security settings (WPA/WEP/none) using dialog
• if user selects network with existing profile -- just use this profile to connect with netcfg
• if user selects a new network (for example, a Wi-Fi hotspot), wifi-select automatically generates a new profile with corresponding $SECURITY and asks for the key (if needed). It uses DHCP as $IP by default
• then, if the connection succeeds, the profile is saved for later usage
• if the connection fails, the user is asked if he or she wants to keep generated profile for further usage (for example to change $IP to static or adjust some additional options)

Links:

• Forum thread related to development of wifi-select
• wifi-select on GitHub

Passing arguments to dhcpcd

For example, add this to the desired profile:

DHCP_OPTIONS='-C resolv.conf -G'

The above example prevents dhcpcd from writing to /etc/resolv.conf and setting any default routes.

Speed up DHCP with dhcpcd

By default, dhcpcd confirms that the assigned IP address is not already taken via ARP. If you are confident that it will not be, e.g. in your home network, you can speed up the connection process by about 5 seconds by adding --noarp to DHCP_OPTIONS:

DHCP_OPTIONS="--noarp"

If you never want dhcpcd to perform this check for any connection, you can globally configure this by adding the following line to /etc/dhcpcd.conf:

noarp

Using dhclient instead of dhcpcd

To use dhclient instead of dhcpcd, simply add DHCLIENT=yes to the desired profile.

Configuring a bridge for use with virtual machines (VMs)

To configure a bridge named br0 with a static IP:

/etc/network.d/br0

INTERFACE="br0"
CONNECTION="bridge"
DESCRIPTION="bridge br0 static"
BRIDGE_INTERFACES="eth0"
IP='static'
ADDR='10.0.0.10'
GATEWAY='10.0.0.1'
DNS='10.0.0.1'

To configure a bridge named br0 with a dhcp IP:

/etc/network.d/br0

INTERFACE="br0"
CONNECTION="bridge"
DESCRIPTION="bridge br0 dhcp"
BRIDGE_INTERFACES="eth0"
IP='dhcp'

Then add the corresponding bridge name to your NETWORKS=(...) in /etc/conf.d/netcfg.

It can be brought up by calling it directly, or by restarting net-profiles.

netcfg br0

rc.d restart net-profiles

Adding multiple IP addresses to one interface

If you want to assign multiple IP addresses to 1 specific interface, this can be done by issuing the relevant ip command in a POST_UP statement (which as the name suggests will be executed after the interface has been brought up). Multiple statements can be separated with a ;. So if you for example would want to assign both 10.0.0.1 and 10.0.0.2 to interface eth0; the config would look something among the lines of:

/etc/network.d/multiple_ip

INTERFACE="eth0"
CONNECTION="ethernet"
IP='static'
ADDR='10.0.0.1'
POST_UP='ip addr add 10.0.0.2/24 dev eth0'

Adding static routes

When wanting to configure static routes, this can be done by issuing the relevant ip command in a POSTUP statement (which as the name suggests will be executed after the interface has been brought up). Optionally, a PRE_DOWN statement can be added to remove said routes when the interface is brought down. Multiple statements can be separated with a ;. In the below example we'll route 10.0.1.0/24 over interface eth1 and then remove the route when the interface is brought down.

/etc/network.d/static_routes

INTERFACE="eth1"
CONNECTION="ethernet"
IP='static'
POST_UP='ip route add 10.0.1.0/24 dev eth1'
PRE_DOWN='ip route del 10.0.1.0/24 dev eth1'

Bluetooth tethering with pand

You can create a netcfg profile for easy tethering with your Bluetooth enabled device by using the regular "ethernet" connection and managing the pand connection in the PRE_UP and POST_DOWN hooks. Assuming an already paired device with address 00:00:DE:AD:BE:EF:

/etc/network.d/tether

CONNECTION="ethernet"
DESCRIPTION="Ethernet via pand tethering to Bluetooth device"
INTERFACE="bnep0"
BTADDR="00:00:DE:AD:BE:EF"
PRE_UP="pand -E -S -c ${BTADDR} -e ${INTERFACE} -n 2>/dev/null"
POST_DOWN="pand -k ${BTADDR}"
IP="dhcp"

Then, either as root or using sudo, execute:

# netcfg tether

To bring the interface down and un-tether:

# netcfg down tether