C( o . o ) ╯ brnana - the minimal bridge with extra potassium!🍌
A lightweight Linux kernel module that implements a custom Ethernet bridge with basic port enslaving and forwarding support.
brnana is developed and tested on:
- Linux kernel 6.8.0-60-generic
$ make
$ sudo insmod brnana.ko num_bridge=1
Check if it is loaded:
$ lsmod | grep "brnana"
Check the Interface
$ ip addr
3: brnana0: <BROADCAST,MULTICAST,UP,LOWER_UP> ...
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
# Bring the interface down (required before changing MAC)
sudo ip link set brnana0 down
# Set a new MAC address
sudo ip link set brnana0 address 02:11:22:33:44:55
# Bring the interface up
sudo ip link set brnana0 up- Note: brnana will reject invalid MAC addresses (e.g., multicast or all-zero).
Check MAC Address
$ ip link show brnana0
13: brnana0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN mode DEFAULT group default qlen 1000
link/ether 02:11:22:33:44:55 brd ff:ff:ff:ff:ff:ff
When a MAC address is set via ip, the kernel module logs it:
[ 5076.512850] C( o . o ) ╯ brnana: bridge 0 set mac : 02:11:22:33:44:55
# Load the dummy network driver (if not already loaded)
sudo modprobe dummy
# Create a dummy network interface named dummy0
sudo ip link add dummy0 type dummy
# Bring the dummy interface up
sudo ip link set dummy0 up
# Enslave dummy0 to the brnana bridge (e.g., brnana0)
sudo ip link set dummy0 master brnana0
# Detach dummy0 from the brnana bridge
sudo ip link set dummy0 nomaster
# Delete the dummy interface
sudo ip link delete dummy0$ ip addr
3: brnana0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UNKNOWN group default qlen 1000
link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff
4: dummy0: <BROADCAST,NOARP,UP,LOWER_UP> mtu 1500 qdisc noqueue master brnana0 state UNKNOWN group default qlen 1000
link/ether 02:36:dd:b5:2d:e9 brd ff:ff:ff:ff:ff:ff
inet6 fe80::36:ddff:feb5:2de9/64 scope link
valid_lft forever preferred_lft forever
$ sudo dmesg
[ 107.502301] C( o . o ) ╯ brnana: 1 bridge loaded
[ 107.502345] C( o . o ) ╯ brnana: bridge 0 init
[ 107.502724] C( o . o ) ╯ brnana: New BR 0
[ 107.534732] C( o . o ) ╯ brnana: bridge 0 open
[ 150.731318] C( o . o ) ╯ brnana: enslaved dummy0 to brnana0
[ 280.721538] C( o . o ) ╯ brnana: removing port dummy0 from brnana0
[ 327.221292] C( o . o ) ╯ brnana: 1 bridge unloaded
[ 327.221752] C( o . o ) ╯ brnana: bridge 0 stop
[ 327.222751] C( o . o ) ╯ brnana: bridge 0 uninit
$ sudo rmmod brnana.ko