Rotating IP addresses using Squid and Docker

Great — here’s a low-level, reproducible setup for rotating IPs using Docker and Squid proxy. This is particularly useful for scraping, automation, or anonymization.

We’ll cover:

✅ Architecture Overview
⚙️ Set Up Squid in Docker
🧠 IP Binding: Rotating Different Source IPs
🔄 Proxy Rotation Strategy
🧪 Testing the Setup

✅ 1. Architecture Overview

You’ll set up Squid as a forward proxy, bind it to multiple source IP addresses (eth0:0, eth0:1, …) on the host, then use multiple containers or tools (like proxychains, curl, or requests) to send traffic through Squid, rotating outbound IPs.

Client App → Docker (Squid Proxy) → Outbound Interface [Multiple Source IPs] → Internet

⚙️ 2. Set Up Squid in Docker

Step 1: Add Multiple IPs to Your Host

Replace with real IPs from your VPS provider. Requires you to have multiple public IPs bound.

ip addr add 192.0.2.101/32 dev eth0
ip addr add 192.0.2.102/32 dev eth0

Persist in /etc/network/interfaces or netplan configs depending on your distro.

Step 2: Create Squid Config with Multiple `tcp_outgoing_address`

Here’s a minimal squid.conf:

http_port 3128

acl to_ip_1 myportname 3128
tcp_outgoing_address 192.0.2.101 to_ip_1

acl to_ip_2 myportname 3128
tcp_outgoing_address 192.0.2.102 to_ip_2

# Rotate per connection using round-robin or custom ACL
# You can switch based on client IPs, time, or round-robin with helper scripts

access_log /var/log/squid/access.log
cache deny all

Step 3: Dockerfile for Squid

FROM ubuntu:20.04

RUN apt-get update && \
    DEBIAN_FRONTEND=noninteractive apt-get install -y squid net-tools iproute2 && \
    rm -rf /var/lib/apt/lists/*

COPY squid.conf /etc/squid/squid.conf

CMD ["squid", "-N", "-d1"]

Step 4: Build and Run Docker Container

docker build -t squid-rotator .
docker run -d --name squid-proxy --net=host --cap-add=NET_ADMIN squid-rotator

--net=host allows the container to bind to the host IPs. --cap-add=NET_ADMIN is required if you later want to manipulate routing inside the container.

🧠 3. IP Binding & Source IP Control (Low-level)

Squid uses tcp_outgoing_address to bind to specific source IPs for outbound connections.

Internally, Squid creates the connection socket with an explicit bind() to the source IP (visible in src/client_side.c or comm_openex() logic).

// Simplified pseudo-path
fd = socket(...);
bind(fd, source_ip);  // The IP from tcp_outgoing_address
connect(fd, target_host);

Reference in Squid source:

🔄 4. Proxy Rotation Strategies

✅ Option 1: Manual Proxy Switching

Clients switch between http://proxy:3128 and http://proxy2:3128 mapped to different Squid IPs.

✅ Option 2: Multiple Squid Instances (easiest per-IP bind)

Start multiple Squid containers, each bound to a single IP:

docker run -d --name squid1 --net=host -e OUT_IP=192.0.2.101 squid-rotator
docker run -d --name squid2 --net=host -e OUT_IP=192.0.2.102 squid-rotator

Change squid.conf dynamically with env var replacement.

✅ Option 3: Custom ACL-based Round-Robin

This requires external ACL helpers or rotating NAT rules. More complex, but I can show this if you want to go deep.

🧪 5. Testing the Rotated Proxy

From Client

curl -x http://host-ip:3128 http://ipinfo.io/ip

Or use Python:

import requests

proxies = {
    'http': 'http://host-ip:3128',
    'https': 'http://host-ip:3128',
}

print(requests.get("https://api.ipify.org", proxies=proxies).text)

If setup is correct, the response should change depending on the chosen Squid proxy instance or outbound IP.

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