Wanted to run frp’s client frpc with docker to forward the SSH port.

Main issue was binding to a port already open on the host, and one not controlled by a docker thing.

My first attempt led to this: “: Error starting userland proxy: listen tcp4 0.0.0.0:22: bind: address already in use”

After looking around the Internet, found a solution.

Docker’s docker-compose.yml:

services:
  frpc:
    image: chenhw2/frp
    restart: unless-stopped
    environment:
      - ARGS=frpc
    volumes:
      - ./conf/frpc.ini:/frp/frpc.ini
    network_mode: "host"
    ports:
      - "22:22"

The key being the “nertwork_mode” part.

Neither frp server nor client configs needed anything special.

Strangely , I didn’t even need to set any capabilities like I did for dns:

services:
  dns:
    restart: always
    image: strm/dnsmasq
    volumes:
      - ./conf/dnsmasq.conf:/etc/dnsmasq.conf
    ports:
      - "53:53/udp"
    cap_add:
      - NET_ADMIN