[Solved] Share internet from (laptop) wifi to (RaspberryPi) ethernet

Question

Hi,
I've been attempting to share the internet from my laptop wifi connection to a raspberry pi (with arch) connected via an ethernet port.
For some reason, the Rpi doesn't connect. I've closely followed the instructions at:
https://wiki.archlinux.org/index.php/Internet_sharing
Yet the following script doesn't seem to work. The Rpi recognizes the the Ethernet connection but dhcpcd isn't dishing out an IP address. When I plug the Rpi into an ethernet port on my router it connects fine so as far as i'm understanding it should 'just work'.
#!/bin/bash
DEVICE="enp0s25"
ip link set $DEVICE down
ip link set $DEVICE up
ip addr add 192.168.123.1/24 dev $DEVICE
sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -o internet0 -j MASQUERADE
iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i $DEVICE -o internet0 -j ACCEPT
dhcpcd $DEVICE
Any tips for getting to the bottom of the issue?
Tom
Last edited by anthillsocial (2015-04-08 12:03:14)

Answer 1

Success!! I'd mistakenly thought that dhcpcd acted as both client and server so that's where I went wrong. The following script now works using dhcpd. As a reference for others, here's my setup:
#!/bin/bash
DEVICE="enp0s25"
ROUTERIP=139.96.30.1 # 192.168.123.1
ip link set $DEVICE down
ip link set $DEVICE up
ip addr add $ROUTERIP/24 dev $DEVICE # arbitrary address
sysctl net.ipv4.ip_forward=1
iptables -t nat -A POSTROUTING -o internet0 -j MASQUERADE
iptables -A FORWARD -m conntrack --ctstate RELATED,ESTABLISHED -j ACCEPT
iptables -A FORWARD -i $DEVICE -o internet0 -j ACCEPT
#Config file: /etc/dhcpd.conf
#Database file: /var/lib/dhcp/dhcpd.leases # cat this to see if a device has been asigned a lease
#PID file: /var/run/dhcpd.pid
dhcpd $DEVICE
And /etc/dhcpd.conf contains:
option domain-name-servers 8.8.8.8, 8.8.4.4;
option subnet-mask 255.255.255.0;
option routers 139.96.30.100;
subnet 139.96.30.0 netmask 255.255.255.0 {
range 139.96.30.150 139.96.30.250;
Then to find out the IP address assigned to the Rpi, simply
cat /var/lib/dhcp/dhcpd.leases
Thanks for the help