DF-3376 environment / guest facts
==================================
uname -a (baseline & controls):
DragonFly dfbsd 6.5-DEVELOPMENT DragonFly 6.5-DEVELOPMENT #0: Thu Jul  2 06:02:54 UTC 2026  root@dfbsd:/usr/obj/usr/src/sys/X86_64_GENERIC  x86_64

hw.ncpu: 6
net.inet6.ip6.forwarding: 0
net.inet6.ip6.accept_rtadv: 0        (global; per-if ND6_IFF_ACCEPT_RTADV set on gif0 by rig)
net.inet6.icmp6.nd6_prune: 1         (expiry sweep every 1 s)

rig interface:
gif0: flags=808051<UP,POINTOPOINT,RUNNING,MULTICAST,PROXY> metric 0 mtu 1280
    tunnel inet6 ::1 --> ::1
    inet6 fe80::8c70:4df9:fc70:9151%gif0 prefixlen 64 scopeid 0x3
    groups: gif
ND flags on gif0: ACCEPT_RTADV | AUTO_LINKLOCAL (via SIOCSIFINFO_FLAGS)

compiler (in-guest): CCVER=gcc80, cc (GCC) 8.x
injection: raw IPPROTO_IPV6 (proto-41) socket -> ::1 -> gif0 decap ->
ip6_input -> icmp6_input -> nd6_ra_input  (rig inherited from DF-3331)