Mirroring traffic on network interfaces in Linux

gistfile1.txt

# create dummy interface for testing
# using iproute2
ip link add dummy0 type dummy
ip link set dummy0 up

# using Network Manager
nmcli connection add type dummy ifname dummy0 ipv4.method disabled ipv6.method disabled

# tc rules below
source_if=eth0
dest_if=dummy0
 
# mirror ingress traffic
tc qdisc add dev $source_if ingress;:
tc filter add dev $source_if parent ffff: \
protocol all \
u32 match u8 0 0 \
action mirred egress mirror dev $dest_if;:
 
# mirror egress traffic
tc qdisc add dev $source_if handle 1: root prio;:
tc filter add dev $source_if parent 1: \
protocol all \
u32 match u8 0 0 \
action mirred egress mirror dev $dest_if;: