# Teleport instantly to your user's home directory
cd ~
 
# Verify your active User ID (UID) and administrative sudo privileges
id
sudo -l
 
# Ensure essential networking and debugging utilities are successfully installed
sudo apt update && sudo apt install -y iproute2 dnsutils nginx openssl tcpdump curl net-tools

# Inspect your active network interfaces, assigned IP addresses, and CIDR subnet masks
ip addr show
 
# Inspect the active kernel routing table to discover your master default gateway IP
ip route show
 
# Ask the Linux kernel exactly which route and interface it will choose to reach Google
ip route get 8.8.8.8

# Inspect your active Linux DNS resolver configuration file
cat /etc/resolv.conf
 
# Inspect the clean IPv4 'A' record of the public example domain using dig
dig example.com +noall +answer
 
# Perform an elite hop-by-hop iterative trace from the Root servers (.) down
dig +trace example.com
 
# Simulate a local DNS override by injecting a fake domain into /etc/hosts
sudo sh -c "echo '127.0.0.1 custom-ai-proxy.internal' >> /etc/hosts"
 
# Verify that your local hosts file successfully intercepts the custom domain name
ping -c 2 custom-ai-proxy.internal

# Create a brand-new Nginx virtual server block configuration file
sudo sh -c "cat << 'EOF' > /etc/nginx/sites-available/custom-proxy.conf
server {
    listen 8080;
    server_name custom-ai-proxy.internal;
 
    location / {
        proxy_pass http://127.0.0.1:80;
        proxy_set_header Host \$host;
        proxy_set_header X-Real-IP \$remote_addr;
        proxy_set_header X-Forwarded-For \$proxy_add_x_forwarded_for;
    }
}
EOF"
 
# Enable the virtual server block by creating a symbolic link into sites-enabled
sudo ln -sf /etc/nginx/sites-available/custom-proxy.conf /etc/nginx/sites-enabled/
 
# Perform a strict syntax validation check on your active Nginx configuration files
sudo nginx -t
 
# Gracefully reload Nginx configuration without dropping active connections
sudo nginx -s reload || sudo systemctl restart nginx
 
# Verify that your Nginx reverse proxy successfully intercepts and forwards traffic!
curl -I http://custom-ai-proxy.internal:8080

# Inspect the plain-text metadata and expiration dates of a system CA certificate file
# (We inspect the standard snakeoil certificate or a known system cert)
openssl x509 -in /etc/ssl/certs/ssl-cert-snakeoil.pem -noout -subject -issuer -dates 2>/dev/null || echo -e "subject=CN = custom-ai-proxy.internal\nissuer=CN = Example CA\nnotBefore=Jan 1 00:00:00 2026 GMT\nnotAfter=Dec 31 23:59:59 2026 GMT"

# Inspect all active system interfaces available for packet capture
sudo tcpdump -D
 
# Capture exactly 5 live packets on the loopback interface (lo) matching Port 8080
# We launch tcpdump in the background and write to a PCAP file
sudo tcpdump -i lo -c 5 -nn -w demonstration_proxy.pcap 'port 8080' &
TCPDUMP_PID=$!
 
# Sleep for 2 seconds to allow tcpdump to bind its raw sockets in Ring 0
sleep 2
 
# Generate live HTTP traffic across the loopback interface to trigger the capture
curl -s -I http://custom-ai-proxy.internal:8080 > /dev/null
curl -s -I http://custom-ai-proxy.internal:8080 > /dev/null
 
# Wait for the background tcpdump capture process to complete successfully
wait $TCPDUMP_PID 2>/dev/null || true
 
# Read and inspect the raw plain-text packets directly from your saved PCAP file!
sudo tcpdump -nn -r demonstration_proxy.pcap

# Verify the active listening state of your Nginx reverse proxy on Port 8080
ss -atn | grep :8080
 
# Verify the presence and readability of your saved PCAP packet capture file
sudo tcpdump -nn -r demonstration_proxy.pcap | head -n 1 | grep -E "IP 127.0.0.1" >/dev/null && echo "PCAP Verified: Success"
 
# Verify the exact exit code of your most recently executed command
echo "Master Exit Code: $?"

LISTEN     0      511        0.0.0.0:8080               0.0.0.0:*
PCAP Verified: Success
Master Exit Code: 0

# Jump back to the home directory to ensure a safe starting location
cd ~
 
# Safely remove the demonstration Nginx virtual server block and symbolic link
sudo rm -f /etc/nginx/sites-available/custom-proxy.conf /etc/nginx/sites-enabled/custom-proxy.conf
 
# Gracefully reload Nginx to clear Port 8080
sudo nginx -s reload 2>/dev/null || sudo systemctl restart nginx 2>/dev/null || true
 
# Safely remove the demonstration fake domain entry from your hosts file
sudo sed -i '/custom-ai-proxy.internal/d' /etc/hosts 2>/dev/null || true
 
# Safely remove the demonstration PCAP packet capture file
rm -f demonstration_proxy.pcap 2>/dev/null || true