I am running docker desktop on windows. I’m running a homemade emulator that emulates on device inside a container. It is meant to communicate with an NMS server (in a different container) on a docker LAN segment (mylan). Our emulator is connected to a tap device which connects to the docker LAN via a bridge device (see setup script below). When the emulator is run inside its container (myemu), it comes up and sends an arp request to mynms. Running tcpdump on mynms, I see the expected ARP request and reply pair. Running tcpdump on myemu, I see the ARP request and reply pair on eth0. But when I run tcpdump on the tap device used by the emulator to connect to mylan, I only see the ARP requests. It appears as if the bridge device “consumes” the ARP reply and doesn’t forward it across the bridge to the tap device.
If I run this exact same setup on an ubuntu workstation (without Docker desktop), this setup works flawlessly. Below are snippets from my config files. Any suggestions are greatly appreciated.
I have created a container network using docker-compose. The relevant entries in the docker-compose.yml file are as follows:
networks:
mylan:
driver: bridge
ipam:
driver:default
config:
subnet: 10.1.2.0/24
gateway: 10.1.2.254
services:
myemu:
...
networks:
mylan:
ipv4_address: 10.1.2.103
privileged: true
mynms:
networks:
mylan:
ipv4_address: 10.1.2.100
...
myemu runs a bash script on startup to set up a bridge from eth0 (mylan) to the emulator which connects to the tap device (myemutap0):
set -eux
ip tuntap add mode tap myemutap0
ip addr flush dev myemutap0
ip addr flush dev eth0
ip link add name ifbr0 type bridge
ip link set dev ifbr0 up
ip link set dev myemutap0 up
ip link set myemutap0 master ifbr0
ip link set eth0 master ifbr0