4-Port Managed Switch

An open-source 4-port gigabit managed switch HAT based on a Raspberry Pi with OpenWrt support.

Disclaimer: This is an ongoing project where some features are not working, and some hardware bugs may exist.

Features

• 4 Gigabit Ethernet RJ45 ports
• Supports Raspberry Pi 1–5 (including Raspberry Pi Zero 1–2)
  • Tested with a Raspberry Pi Zero 1
  • Raspberry Pi 5 is not working with OpenWrt due to this issue
• Works with a custom OpenWrt
• Two overlays:
  1. For Linux Distributed Switch Architecture (DSA)
  2. For OpenWrt swconfig
• VLAN support (only on OpenWrt with swconfig)
• Hardware offloading support (only on OpenWrt with swconfig)
• Hardware design in KiCad
• Ready for JLCPCB production
  • Using a much as possible basic parts to lower the assembling costs

Software Status

The hardware works with a modified OpenWrt:
https://github.com/AlbrechtL/rpi-managed-switch-openwrt/tree/rpi_managed_switch

I added the following to OpenWrt:

• Two device tree overlays (for swconfig and DSA)
• Enabled the ENC28J60 driver
• Added a small patch to enable the ENC28J60 for DSA
• Added detection of swconfig or DSA in the first boot scripts so that OpenWrt uses the switch

See the differences:
https://github.com/openwrt/openwrt/compare/main...AlbrechtL:rpi-managed-switch-openwrt:rpi_managed_switch

To communicate with the RTL8367S switch chip, two different Linux drivers are available:

1. OpenWrt swconfig

Driver: drivers/net/phy/rtl8367b.c

• Pros:
  • Full hardware offloading support
  • VLAN support
• Cons:
  • OpenWrt-specific
  • OpenWrt is transitioning from swconfig to DSA

OpenWrt Screenshot

2. Distributed Switch Architecture (DSA)

Driver: drivers/net/dsa/realtek/rtl8365mb.c

• Pros:
  • Integrated into the Linux kernel
  • Mainline RTL8367S support
  • Works on Raspberry Pi OS with a custom Linux kernel
• Cons:
  • No hardware offloading support
  • No VLAN support

There was a discussion on the Linux kernel mailing list about the missing hardware offloading and VLAN support:
https://lkml.iu.edu/hypermail/linux/kernel/2407.0/01589.html

I played a bit with the driver but with no success (details see here https://github.com/AlbrechtL/rtl8365mb-kernel-hacking).

Working DSA Example:

root@OpenWrt:~# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN qlen 1000
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host 
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1508 qdisc fq_codel state UP qlen 1000
    link/ether b8:27:eb:8f:43:df brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ba27:ebff:fe8f:43df/64 scope link 
       valid_lft forever preferred_lft forever
3: lan1@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master switch state UP qlen 1000
    link/ether b8:27:eb:8f:43:df brd ff:ff:ff:ff:ff:ff
4: lan2@eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue master switch state DOWN qlen 1000
    link/ether b8:27:eb:8f:43:e0 brd ff:ff:ff:ff:ff:ff
5: lan3@eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc noqueue master switch state DOWN qlen 1000
    link/ether b8:27:eb:8f:43:e1 brd ff:ff:ff:ff:ff:ff
6: lan4@eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue master switch state UP qlen 1000
    link/ether b8:27:eb:8f:43:e2 brd ff:ff:ff:ff:ff:ff
7: switch: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether b8:27:eb:8f:43:df brd ff:ff:ff:ff:ff:ff
    inet6 fe80::ba27:ebff:fe8f:43df/64 scope link 
       valid_lft forever preferred_lft forever
8: switch.1@switch: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP qlen 1000
    link/ether b8:27:eb:8f:43:df brd ff:ff:ff:ff:ff:ff
    inet 192.168.1.1/24 brd 192.168.1.255 scope global switch.1
       valid_lft forever preferred_lft forever
    inet6 fd8d:3fdb:486f::1/60 scope global noprefixroute 
       valid_lft forever preferred_lft forever
    inet6 fe80::ba27:ebff:fe8f:43df/64 scope link 
       valid_lft forever preferred_lft forever

Hardware Status

I have two assembled PCBs that have basic functionality. See issues for a list of hardware problems.

Raspberry Pi Zero

Raspberry Pi 5

Performance

I don't have detailed performance measurements yet, but here are some bandwidth indications:

• RJ45–RJ45 with OpenWrt swconfig: ~1 Gbit/s (wire speed, full-duplex)
• Raspberry Pi to RJ45 (CPU port): ~5 Mbit/s (half-duplex)
  To support the inexpensive Raspberry Pi Zero, an external SPI Ethernet chip (ENC28J60) is used to connect to the main switch chip (RTL8367S). Due to the slow SPI interface, only ~5 Mbit/s can be achieved. However, for a managed web interface, that's sufficient.
• RJ45–RJ45 with DSA: ~2 Mbit/s
  Currently, the RTL8367S DSA driver doesn't support hardware offloading. As a result, all traffic is routed through the Raspberry Pi and the very slow SPI interface. For a switch, this is not acceptable.

Acknowledgements

I would like to thank the following open-source projects. Without these great works, this open-source switch would not be possible:

• OpenWrt
• RTL8367S Managed Switch
  • Blog post: https://blog.brixit.nl/making-a-linux-managed-network-switch/
  • KiCad: https://github.com/FOSDEM/video/tree/master/hardware/pcbs/switch_board
• ENC28J60 on a Raspberry Pi Zero
  • Hackster: https://www.hackster.io/lightside-instruments/the-ethernet4pizero-ethernet-for-raspberry-pi-zero-shield-dd4316
  • KiCad: https://github.com/lightside-instruments/ethernet4pizero.git
• RPI5-CFE-Hat
• PCIe3_Hub
• RouterPi