setup-dhcp-tftp-dns-routing.sh

#!/bin/bash
set -e

# Configuration
PXE_INTERFACE="enx00e04c6808b6"
PXE_IP="192.168.201.1"
PXE_SUBNET="192.168.201.0/24"
DHCP_RANGE="192.168.201.100,192.168.201.200"
TFTP_ROOT="/srv/tftp"
LEASE_TIME="24h"

# Check if running as root
if [[ $EUID -ne 0 ]]; then
   echo "Error: This script must be run as root"
   exit 1
fi

# Check if netboot files exist
if [[ ! -d "$TFTP_ROOT/debian-installer" ]]; then
    echo "Error: Debian netboot files not found in $TFTP_ROOT"
    echo "Please extract netboot.tar.gz to $TFTP_ROOT first"
    exit 1
fi

# Check if interface exists
if ! ip link show "$PXE_INTERFACE" &> /dev/null; then
    echo "Error: Interface $PXE_INTERFACE not found"
    exit 1
fi

# Check if interface already has an IP
if ip addr show "$PXE_INTERFACE" | grep -q "inet "; then
    echo "Error: Interface $PXE_INTERFACE already has an IP address configured"
    exit 1
fi

# Check for IP conflicts on the network
if ping -c 1 -W 1 "$PXE_IP" &> /dev/null; then
    echo "Error: IP address $PXE_IP is already in use on the network"
    exit 1
fi

# Detect upstream interface from default route
UPSTREAM_INTERFACE=$(ip route | grep '^default' | awk '{print $5}' | head -n1)
if [[ -z "$UPSTREAM_INTERFACE" ]]; then
    echo "Error: Could not detect upstream interface from default route"
    exit 1
fi
echo "Detected upstream interface: $UPSTREAM_INTERFACE"

# Configure the PXE interface
echo "Configuring interface $PXE_INTERFACE with IP $PXE_IP..."
ip link set "$PXE_INTERFACE" up
ip addr add "$PXE_IP/24" dev "$PXE_INTERFACE"

# Wait for interface to be fully configured
sleep 2

# Verify IP is set
if ! ip addr show "$PXE_INTERFACE" | grep -q "$PXE_IP"; then
    echo "Error: Failed to configure IP address on $PXE_INTERFACE"
    exit 1
fi

# Enable IP forwarding
echo "Enabling IP forwarding..."
echo 1 > /proc/sys/net/ipv4/ip_forward

# Set up iptables masquerading
echo "Setting up iptables NAT/masquerading..."
iptables -t nat -A POSTROUTING -s "$PXE_SUBNET" -o "$UPSTREAM_INTERFACE" -j MASQUERADE
iptables -A FORWARD -i "$PXE_INTERFACE" -o "$UPSTREAM_INTERFACE" -j ACCEPT
iptables -A FORWARD -i "$UPSTREAM_INTERFACE" -o "$PXE_INTERFACE" -m state --state RELATED,ESTABLISHED -j ACCEPT

# Create dnsmasq configuration
DNSMASQ_CONF="/tmp/dnsmasq-pxe.conf"
cat > "$DNSMASQ_CONF" << EOF
# Bind only to PXE interface
interface=$PXE_INTERFACE
bind-interfaces

# DHCP configuration
dhcp-range=$DHCP_RANGE,$LEASE_TIME
dhcp-option=3,$PXE_IP
dhcp-option=6,$PXE_IP

# TFTP configuration
enable-tftp
tftp-root=$TFTP_ROOT

# PXE boot configuration
dhcp-boot=pxelinux.0

# Don't read /etc/hosts
no-hosts

# Log queries for debugging
log-queries
log-dhcp
EOF

# Extract nameservers from /etc/resolv.conf and add to config
if [[ -f /etc/resolv.conf ]]; then
    while read -r line; do
        if [[ $line =~ ^nameserver[[:space:]]+([0-9.]+) ]]; then
            echo "server=${BASH_REMATCH[1]}" >> "$DNSMASQ_CONF"
        fi
    done < /etc/resolv.conf
fi

# If no nameservers found, add fallback
if ! grep -q "^server=" "$DNSMASQ_CONF"; then
    echo "server=8.8.8.8" >> "$DNSMASQ_CONF"
    echo "server=8.8.4.4" >> "$DNSMASQ_CONF"
fi

# Start dnsmasq
echo "Starting dnsmasq..."
dnsmasq -C "$DNSMASQ_CONF" --no-daemon --log-facility=/var/log/dnsmasq-pxe.log &
DNSMASQ_PID=$!

# Give dnsmasq a moment to start
sleep 1

echo ""
echo "PXE boot server started successfully!"
echo "Interface: $PXE_INTERFACE ($PXE_IP)"
echo "DHCP range: $DHCP_RANGE"
echo "Upstream: $UPSTREAM_INTERFACE"
echo "dnsmasq PID: $DNSMASQ_PID"
echo "Log file: /var/log/dnsmasq-pxe.log"
echo ""
echo "Press Ctrl+C to stop the server and clean up..."

# Cleanup function
cleanup() {
    echo ""
    echo "Shutting down PXE server..."
    
    # Kill dnsmasq
    if [[ -n "$DNSMASQ_PID" ]]; then
        kill "$DNSMASQ_PID" 2>/dev/null || true
    fi
    
    # Remove iptables rules
    iptables -t nat -D POSTROUTING -s "$PXE_SUBNET" -o "$UPSTREAM_INTERFACE" -j MASQUERADE 2>/dev/null || true
    iptables -D FORWARD -i "$PXE_INTERFACE" -o "$UPSTREAM_INTERFACE" -j ACCEPT 2>/dev/null || true
    iptables -D FORWARD -i "$UPSTREAM_INTERFACE" -o "$PXE_INTERFACE" -m state --state RELATED,ESTABLISHED -j ACCEPT 2>/dev/null || true
    
    # Remove IP from interface
    ip addr del "$PXE_IP/24" dev "$PXE_INTERFACE" 2>/dev/null || true
    ip link set "$PXE_INTERFACE" down 2>/dev/null || true
    
    # Remove temp config
    rm -f "$DNSMASQ_CONF"
    
    echo "Cleanup complete"
}

trap cleanup EXIT INT TERM

# Wait forever
wait "$DNSMASQ_PID"