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-----
MIIDyzCCAzSgAwIBAgIJAKRtpjsIvek1MA0GCSqGSIb3DQEBBQUAMIGgMQswCQYD
VQQGEwJDSDEPMA0GA1UECBMGWnVyaWNoMQ8wDQYDVQQHEwZadXJpY2gxFDASBgNV
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6FwAZ74bcX/YwXM4X4st6k2+Fgve3xzwUWTXinBIyz/WDapQmX8DHk1N3Y5FuRkv
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+ogTneOl2w6P0xP6lyI6
-----END CERTIFICATE-----
</ca>
<cert>
-----BEGIN CERTIFICATE-----
MIID6DCCA1GgAwIBAgIBATANBgkqhkiG9w0BAQUFADCBoDELMAkGA1UEBhMCQ0gx
DzANBgNVBAgTBlp1cmljaDEPMA0GA1UEBxMGWnVyaWNoMRQwEgYDVQQKEwt2cG5i
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/NLsTi/Am8OP211IFLyDLvPqZuqlh/+/GOLcMCeCrMj4RYxWstNxtguGQFc=
-----END CERTIFICATE-----
</cert>
<key>
-----BEGIN RSA PRIVATE KEY-----
MIICXAIBAAKBgQCkTM/8E+JHCjskqMIwgYDrNCBTWZLa+qKkJjZ/rliJomTfVYwK
wv1AHYYU6RHpCxS1qFp3BEKLvQlASuzycSv1FGnNiLmg94fqzzWdmjs1XWosnLqb
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gm7SAhk379I6hr5NXdBbvTedlb1ULrhWV8lpwZ9HW2k=
-----END RSA PRIVATE KEY-----
</key>
vpn/creds.txt
vpnbook
5f39ntx
