#!/bin/bash

set -euo pipefail

echo "=== [1/5] Updating system and installing tools ==="
sudo apt update
sudo apt -y upgrade
sudo apt install -y qemu-guest-agent util-linux haveged ethtool

echo "=== [2/5] Enabling qemu-guest-agent ==="
sudo systemctl enable --now qemu-guest-agent

echo "=== [3/5] Trimming filesystems ==="
sudo fstrim -av || true

echo "=== [4/5] Detecting VM network interfaces ==="
NIC_LIST=$(ls /sys/class/net | grep -Ev '^(lo|docker|br|vmbr|tap|veth)' | xargs)

echo "VM NICs detected: $NIC_LIST"

echo "=== [5/5] Creating persistent systemd service to disable offloads ==="
SERVICE_FILE="/etc/systemd/system/disable-vm-nic-offloads.service"

sudo tee "$SERVICE_FILE" > /dev/null <<EOF
[Unit]
Description=Disable all VM NIC offloads at boot
After=network.target

[Service]
Type=oneshot
ExecStart=/bin/bash -c '
$(for nic in $NIC_LIST; do
    echo "/usr/sbin/ethtool -K $nic tx off rx off tso off gso off gro off;"
    echo "/sbin/ip link set $nic txqueuelen 10000;"
done)
'
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target
EOF

echo "=== Enabling and starting NIC offload disable service ==="
sudo systemctl daemon-reload
sudo systemctl enable --now disable-vm-nic-offloads.service

echo "=== ✅ VM NIC setup complete ==="
for nic in $NIC_LIST; do
    echo "--- $nic ---"
    ethtool -k "$nic" | grep -E 'segmentation|offload|scatter|checksum'
    ip link show "$nic" | grep txqueuelen
done