Raspberry as Pi Ethernet-WiFi-Bridge
The Challenge
I wanted to set up my Raspberry Pi 3 as Webcam, intranet server, and Ethernet-WiFi-Bridge. In the long run I want to use some kind of QOA/shaping on the Pi to manage my really bad internet connection (yes, 6MBit/s in a country where 82 million people live on 356 thousand square-kilometers (about 230 people per square-km).
Setup
Install additional software
apt get install hostapd bridge-utils dhcp-helper dnsutils traceroute
What do they do?
- hostapd: A daemon that sets up your WiFi as a access point, so anyone can join. Please note, that this means WiFi only. No DHCP, and therefore no DNS.
- bridge-utils: These provide the bridging you need to "connect" the ethernet and WiFi interfaces.
- dhcp-helper: DHCP uses a broadcast to the network (address) to reach the DHCP-server. Since broadcasts stay in the broadcast-domain with a TTL of 1, they won't get bridged. This is where dhcp-helper comes in. It forwards the broadcasts in all other nets (except the one specified with -b, obviously because there is the dhcp-server...).
- dnsutils: Just to do a nslookup from time to time. You can test your DNS-setup as well as lookup with nslookup[1]
- traceroute: Might come in handy if you have networking problems (and you WILL have :) )
Configuration
vi /etc/sysctl.conf
and set
net.ipv4.ip_forward=1 net.ipv6.conf.all.disable_ipv6 = 1
Explanation: Disable IPv6 (to KISS) and enable forwarding for IPv4[2].
vi /etc/default/hostapd
and set:
DAEMON_CONF="/etc/hostapd/hostapd.conf"
Explanation: The hostapd looks in the configfile, where his configfile is. I don't get what this is good for.
vi /etc/hostapd/hostapd.conf
and set something like this:
interface=wlan0 driver=nl80211 bridge=br0 hw_mode=g channel=7 ieee80211n=1 wmm_enabled=1 macaddr_acl=0 auth_algs=1 ignore_broadcast_ssid=0 wpa=2 wpa_key_mgmt=WPA-PSK wpa_pairwise=TKIP rsn_pairwise=CCMP ssid=HeartOfGold wpa_passphrase=42_42_42_42
Explanation: hostapd creates the WiFi-Access Point and creates a bridge-device br0, which he ties (only) wlan0 to[3].
vi /etc/dhcpcd.conf
and set something like this:
nohook wpa_supplicant denyinterfaces wlan0
Explanation: I omit /etc/wpa_supplicant/wpa_supplicant.conf for wlan0. It is essential that there remains only one layer3-active (meaning using IP) interface, and that is br0. Otherwise you get a routing mess. Since br0 and eth0 are not omitted (denied), they get IPAs from the DHCP-Server. That's necessary for br0, and not for eth0 (but when I omitted eth0, the bridge didn't come up. So I removed the IPA later (see below).
vi /etc/network/interfaces
Don't touch this file. dhcpcd gets jealous...
vi /etc/default/dhcp-helper
and set:
DHCPHELPER_OPTS="-b eth0"
Explanation: dhcp-helper will now forward all DHCP-related boradcasts to this interface (and none coming from there to the other interfaces).
vi /etc/avahi/avahi-daemon.conf
and set:
[reflector] enable-reflector=yes
Explanation: Enable mDNS relaying.
As mentioned before, the br0-device is only tied to wlan0, so we must take care of this. You might want to do this with a script in /etc/network/if-up.d/ like (WORK-IN-PROGRESS!): # only do it, if necessary /sbin/brctl show | /bin/grep eth0 && exit 0 /bin/sleep 1 # Remove IPA from eth0 ip addr flush dev eth0
Known issues
- After br0 is set up and this appears in the log:
Feb 5 11:59:10 pi3 kernel: [ 46.256296] br0: port 2(eth0) entered blocking state Feb 5 11:59:10 pi3 kernel: [ 46.256321] br0: port 2(eth0) entered disabled state Feb 5 11:59:10 pi3 kernel: [ 46.257064] device eth0 entered promiscuous mode
Thinking out loud: br0 linkes eth0 and wlan0 on layer 2. Thus can't have an IPA. But br0 can. I hope. :-)
[SOLVED] - The reason was the IPA on eth0, which is no layer3 interface anymore. Removing the IPA did the trick.
Notes
Since you use a DHCP server and you manually set IPAs, you might want to reserve those IPAs in your DHCP-server configuration. This might become handy:
systemd-resolve --status
Displays your DNS-setup
nslookup www.wurst-wasser.net
Displays queried servers and queries (really!)
brctl showstp br0
Shows forwarding state
brctl showmacs br0
Shows all MACs displays something like arp -a does, the MACs of the machines using the bridge.
- Related
- More like this:
- https://unix.stackexchange.com/questions/56092/how-can-i-disable-tcp-ip-for-an-ethernet-adapter
- http://www.microhowto.info/troubleshooting/troubleshooting_ethernet_bridging_on_linux.html
- https://serverfault.com/questions/478453/cannot-ping-from-a-bridged-inteface
- https://unix.stackexchange.com/questions/308086/host-unreachable-after-added-into-linux-bridge
- https://learn.sparkfun.com/tutorials/setting-up-a-raspberry-pi-3-as-an-access-point/all
- http://www.intellamech.com/RaspberryPi-projects/rpi3_simple_wifi_ap.html
- https://nims11.wordpress.com/2012/04/27/hostapd-the-linux-way-to-create-virtual-wifi-access-point/
- https://askubuntu.com/questions/462534/getting-wifi-ap-working-with-hostapd-and-isc-dhcp-server-xubuntu-14-04
- https://thepi.io/how-to-use-your-raspberry-pi-as-a-wireless-access-point/
- https://www.linuxjournal.com/content/wi-fi-command-line
- https://unix.stackexchange.com/questions/119209/hostapd-will-not-start-via-service-but-will-start-directly
- https://raspberrypi.stackexchange.com/questions/33894/i-am-attempting-to-create-a-wifi-gateway
- https://www.raspberrypi.org/forums/viewtopic.php?t=191306
- https://raspberrypi.stackexchange.com/questions/89803/access-point-as-wifi-repeater-optional-with-bridge/89804#89804
- https://raspberrypi.stackexchange.com/questions/88214/setting-up-a-raspberry-pi-as-an-access-point-the-easy-way
- https://github.com/peebles/rpi3-wifi-station-ap-stretch
- https://www.raspberrypi.org/forums/viewtopic.php?t=211305
- http://amadys.blogspot.com/2010/09/dhcp-helper-dhcp-relay-agent-for-linux.html
- https://www.hostinger.com/tutorials/iptables-tutorial#gref
- https://askubuntu.com/questions/907972/route-all-traffic-of-a-machine-through-another-within-a-subnet
- https://wiki.debian.org/BridgeNetworkConnections#Manual_bridge_setup
- https://unix.stackexchange.com/questions/449468/how-to-route-between-interfaces
- Footnotes