#!/bin/bash

set -euo pipefail

SB_ID="${1:-0}" # Default to 0
TAP_DEV="fc-${SB_ID}-tap0"

# Setup TAP device that uses proxy ARP
MASK_SHORT="/30"
TAP_IP="$(printf '169.254.%s.%s' $(((4 * SB_ID + 2) / 256)) $(((4 * SB_ID + 2) % 256)))"

ip link del "$TAP_DEV" 2> /dev/null || true
ip tuntap add dev "$TAP_DEV" mode tap
sysctl -w net.ipv4.conf."$TAP_DEV".proxy_arp=1 > /dev/null
sysctl -w net.ipv6.conf."$TAP_DEV".disable_ipv6=1 > /dev/null
ip addr add "${TAP_IP}${MASK_SHORT}" dev "$TAP_DEV"
ip link set dev "$TAP_DEV" up

iperf3 -B "$TAP_IP" -s > /dev/null 2>&1 &