diff --git a/entrypoint.sh b/entrypoint.sh deleted file mode 100755 index f760879..0000000 --- a/entrypoint.sh +++ /dev/null @@ -1,8 +0,0 @@ -#!/bin/sh - -qemu-system-x86_64 \ - -vnc 0.0.0.0:0 \ - -m 256 \ - -hda $ROUTEROS_IMAGE \ - -device e1000,netdev=net0 \ - -netdev user,id=net0,hostfwd=tcp::21-:21,hostfwd=tcp::22-:22,hostfwd=tcp::23-:23,hostfwd=tcp::80-:80,hostfwd=tcp::443-:443,hostfwd=tcp::8291-:8291,hostfwd=tcp::8728-:8728,hostfwd=tcp::8729-:8729 diff --git a/scripts/entrypoint.sh b/scripts/entrypoint.sh new file mode 100755 index 0000000..ecf5bf8 --- /dev/null +++ b/scripts/entrypoint.sh @@ -0,0 +1,58 @@ +#!/usr/bin/env bash + +# A bridge of this name will be created to host the TAP interface created for +# the VM +QEMU_BRIDGE='qemubr0' + +# DHCPD must have an IP address to run, but that address doesn't have to +# be valid. This is the dummy address dhcpd is configured to use. +DUMMY_DHCPD_IP='10.0.0.1' + +# These scripts configure/deconfigure the VM interface on the bridge. +QEMU_IFUP='/routeros/qemu-ifup' +QEMU_IFDOWN='/routeros/qemu-ifdown' + +# The name of the dhcpd config file we make +DHCPD_CONF_FILE='/routeros/dhcpd.conf' + +function default_intf() { + ip -json route show | jq -r '.[] | select(.dst == "default") | .dev' +} + +# First step, we run the things that need to happen before we start mucking +# with the interfaces. We start by generating the DHCPD config file based +# on our current address/routes. We "steal" the container's IP, and lease +# it to the VM once it starts up. +/routeros/generate-dhcpd-conf.py $QEMU_BRIDGE > $DHCPD_CONF_FILE +default_dev=`default_intf` + +# Now we start modifying the networking configuration. First we clear out +# the IP address of the default device (will also have the side-effect of +# removing the default route) +ip addr flush dev $default_dev + +# Next, we create our bridge, and add our container interface to it. +ip link add $QEMU_BRIDGE type bridge +ip link set dev $default_dev master $QEMU_BRIDGE + +# Then, we toggle the interface and the bridge to make sure everything is up +# and running. +ip link set dev $default_dev up +ip link set dev $QEMU_BRIDGE up + +# Finally, start our DHCPD server +udhcpd -I $DUMMY_DHCPD_IP -f $DHCPD_CONF_FILE & + +# And run the VM! A brief explanation of the options here: +# -enable-kvm: Use KVM for this VM (much faster for our case). +# -nographic: disable SDL graphics. +# -serial mon:stdio: use "monitored stdio" as our serial output. +# -nic: Use a TAP interface with our custom up/down scripts. +# -drive: The VM image we're booting. +exec qemu-system-x86_64 \ + -enable-kvm -nographic -serial mon:stdio \ + -vnc 0.0.0.0:0 \ + -m 256 \ + -nic tap,id=qemu0,script=$QEMU_IFUP,downscript=$QEMU_IFDOWN \ + "$@" \ + -hda $ROUTEROS_IMAGE diff --git a/entrypoint_with_four_interfaces.sh b/scripts/entrypoint_with_four_interfaces.sh similarity index 100% rename from entrypoint_with_four_interfaces.sh rename to scripts/entrypoint_with_four_interfaces.sh diff --git a/scripts/generate-dhcpd-conf.py b/scripts/generate-dhcpd-conf.py new file mode 100755 index 0000000..a25e5de --- /dev/null +++ b/scripts/generate-dhcpd-conf.py @@ -0,0 +1,73 @@ +#!/usr/bin/env python3 + +import argparse +import ipaddress +import json +import re +import socket +import subprocess + +from typing import List, Iterable + +DEFAULT_ROUTE = 'default' +DEFAULT_DNS_IPS = ('8.8.8.8', '8.8.4.4') + +DHCP_CONF_TEMPLATE = """ +start {host_addr} +end {host_addr} +# avoid dhcpd complaining that we have +# too many addresses +maxleases 1 +interface {dhcp_intf} +option dns {dns} +option router {gateway} +option subnet {subnet} +option hostname {hostname} +""" + +def default_route(routes): + """Returns the host's default route""" + for route in routes: + if route['dst'] == DEFAULT_ROUTE: + return route + raise ValueError('no default route') + +def addr_of(addrs, dev : str) -> ipaddress.IPv4Interface: + """Finds and returns the IP address of `dev`""" + for addr in addrs: + if addr['ifname'] != dev: + continue + info = addr['addr_info'][0] + return ipaddress.IPv4Interface((info['local'], info['prefixlen'])) + raise ValueError('dev {0} not found'.format(dev)) + +def generate_conf(intf_name : str, dns : Iterable[str]) -> str: + """Generates a dhcpd config. `intf_name` is the interface to listen on.""" + with subprocess.Popen(['ip', '-json', 'route'], stdout=subprocess.PIPE) as proc: + routes = json.load(proc.stdout) + with subprocess.Popen(['ip', '-json', 'addr'], stdout=subprocess.PIPE) as proc: + addrs = json.load(proc.stdout) + + droute = default_route(routes) + host_addr = addr_of(addrs, droute['dev']) + + return DHCP_CONF_TEMPLATE.format( + dhcp_intf = intf_name, + dns = ' '.join(dns), + gateway = droute['gateway'], + host_addr = host_addr.ip, + hostname = socket.gethostname(), + subnet = host_addr.network.netmask, + ) + +if __name__ == '__main__': + parser = argparse.ArgumentParser() + parser.add_argument('intf_name') + parser.add_argument('dns_ips', nargs='*') + args = parser.parse_args() + + dns_ips = args.dns_ips + if not dns_ips: + dns_ips = DEFAULT_DNS_IPS + + print(generate_conf(args.intf_name, dns_ips)) diff --git a/scripts/qemu-ifdown b/scripts/qemu-ifdown new file mode 100755 index 0000000..2ffdfa7 --- /dev/null +++ b/scripts/qemu-ifdown @@ -0,0 +1,6 @@ +#!/usr/bin/env bash + +QEMU_BRIDGE='qemubr0' + +ip link set dev $1 nomaster +ip link set dev $1 down diff --git a/scripts/qemu-ifup b/scripts/qemu-ifup new file mode 100755 index 0000000..befeea3 --- /dev/null +++ b/scripts/qemu-ifup @@ -0,0 +1,6 @@ +#!/usr/bin/env bash + +QEMU_BRIDGE='qemubr0' + +ip link set dev $1 up +ip link set dev $1 master $QEMU_BRIDGE