2

I want to configure two containers via docker-compose in a way, so one is OpenVPN client, and another is Squid HTTP proxy, exposing 3128 port to access that tunnel from outside.

Now, the problem is that for some reason requests to Squid take exactly 30 seconds to get inside container.

I started investigating the problem, and it seems that it reproduces only when VPN tunnel is connected, AND the exposed port is located in other container.

Sample web server (simulating Squid) is listening on 8080 port. Now I am timing the request:

$ time { curl http://127.0.0.1:8080; }
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN"><html>
<title>Directory listing for /</title>
<body>
<h2>Directory listing for /</h2>
<hr>
<ul>
</ul>
<hr>
</body>
</html>

real  0m30.066s
user  0m0.005s
sys   0m0.011s

For some reason it takes 30 seconds for packet to arrive inside container. Placing web server inside the same container with OpenVPN resolves the issue. Preventing OpenVPN from connecting "resolves" the issue. This reproduces both on Docker for Mac and on Docker CE installed into Ubuntu virtual machine.

Also there is a similar, but unfortunately unanswered question: How do I make Docker forward a packet from remote when a packet from the dockerhost works?

For your convenience, I am providing full working configuration to reproduce:

docker-compose.yml

version: "3.3"
services:
  vpn:
    build: ./vpn
    cap_add:
      - net_admin
    devices:
      - /dev/net/tun
    restart: unless-stopped
    ports:
      - "8080:8080"

  web:
    image: trinitronx/python-simplehttpserver
    depends_on:
      - vpn
    network_mode: "service:vpn"
    restart: unless-stopped

vpn/Dockerfile

FROM dperson/openvpn-client

COPY vpn.conf /vpn/vpn.conf
COPY creds.txt /vpn/creds.txt

vpn/vpn.conf

client
dev tun
proto tcp
remote 176.126.237.217 443
remote euro217.vpnbook.com 443
resolv-retry infinite
nobind
persist-key
persist-tun
auth-user-pass /vpn/creds.txt
comp-lzo
verb 3
cipher AES-128-CBC
fast-io
pull
route-delay 2
redirect-gateway
<ca>
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
</ca>
<cert>
-----BEGIN CERTIFICATE-----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-----END CERTIFICATE-----
</cert>
<key>
-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
</key>

vpn/creds.txt

vpnbook
5f39ntx
0

After thorough investigation I've tracked it down, and it seems that this is not even a Docker issue.

This is due to weirdly malfunctioning staticpython build from here. Next build from here fixes this problem altogether.

I don't know exact reason, but this behavior only reproduces with the older binary. Updating static binary, or installing Python via package manager removes the delay.

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