Make UML IPv6 setup automatic

[jayapsrivastava]

Why this matters

Most PFS supports IPv6 now. Our UML setup should expose a usable IPv6 address by default so IPv6 NIC discovery/testing is consistent and doesn’t depend on manual setup.

Current manual steps (works, but easy to forget)

We use the private ULA range fd00::/64 to give both sides a global-scope IPv6 address.

Host (tap0)

sudo ip -6 addr add fd00::1/64 dev tap0
sudo ip link set tap0 up

UML guest (vec0)

ip -6 addr add fd00::2/64 dev vec0
ip link set vec0 up

Verify in UML:

ip -6 addr show dev vec0

Expected:

inet6 fd00::2/64 scope global

Connectivity check

From UML:

ping -6 fd00::1

From host:

ping -6 fd00::2%tap0

PFS verify

Inside UML:

umount /mnt/pfs
mount /mnt/pfs
dmesg | grep -i push_nic_address

Expected to see something like:

push_nic_address(..., fd00::2)

Guest: init.sh

Add IPv6 ULA config (and keep it safe to run multiple times):

#!/bin/sh

mount -t proc  proc /proc
mount -t sysfs sys  /sys

ip addr add 192.168.0.253/24 dev vec0
ip -6 addr add fd00::2/64 dev vec0
ip link set vec0 up

# Optional: only if we want full IPv6 routing tests (not needed for PFS detection)
# ip -6 route add default via fd00::1 dev vec0

uname -a
echo "\nWelcome to KDEV-UML (with IPv6 support)\n"
setsid sh -c 'exec /bin/bash </dev/tty0 >/dev/tty0 2>&1'

Host: init-host.sh

Run manually today, but should be hooked into the UML/start scripts:

#!/bin/bash
set -e

ip addr add 192.168.0.1/24 dev tap0 || true
ip -6 addr add fd00::1/64 dev tap0 || true
ip link set tap0 up

echo "Host networking configured: tap0 with IPv4 + IPv6 (ULA)"