entrypoints root was changed, additional scripts added

entrypoint.sh

@@ -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

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

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))

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

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