Network Connection Bridging on Raspberry Pi with Buildroot


This post shows how I add network connection bridging to my custom embedded Linux system for Raspberry Pi. This allows me to experiment with bridging network connections for internet sharing, robustness testing, packet capture, and so on.

Modify Linux kernel configuration

Execute the following in the buildroot folder to get Linux Kernel configuration menu

make linux-menuconfig

Select the 802.1d Ethernet Bridging module shown in the following screenshot

Ethernet Bridging

Modify Buildroot configuration

Execute the following in the buildroot folder to get the configuration menu

make menuconfig

Select the bridge-utils package, shown in the screenshot below. This package contains the brctl utility required to configure bridging.

bridge-utils

Then, just execute make to build the system. Once that is done, copy the new kernel image and root file system over to the SD card.

Perform bridging

These are the sequence of commands I typically use to bring up the bridge manually. I use a regular ethernet interface and a USB CDC ethernet interface for testing.

ifconfig eth0 0.0.0.0 promisc up
ifconfig usb0 0.0.0.0 promisc up
brctl addbr br0
brctl addif br0 eth0 usb0
ifconfig br0 up

If you need the bridge interface to have an IP address, you can assign one manually, or by invoking the DHCP client daemon as shown below. This is useful if you need to have access to your Pi over the network.

dhcpcd br0

To wrap it up, here’s how you can tear everything down.

ifconfig eth0 down
ifconfig usb0 down
ifconfig br0 down
brctl delbr br0

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