box/drill/RUNS.md
claude-hdb 6899fc3626 fix(drill): the NIC inside a VM is enp5s0, not eth0 — read by subnet instead
A3, the one probe the whole audit exists for, has never fired in six
runs. It was never the network: the profile names the DEVICE eth0, but
inside a VM guest predictable naming renames it enp5s0, so every address
lookup — first the '(eth0)' CSV match, then 'ip addr show dev eth0' —
was hunting an interface that does not exist. I fixed that symptom twice
without ever questioning the assumption underneath it.

Read the address from inside the box and select by SUBNET (10.87.x, what
claudenet hands out) rather than by interface name. docker0's 172.17.x
is the decoy; the NIC's name is the guest's business, not ours.

A3 also gains a guard it should have had from the start: if the peer and
the source hold the SAME address, refuse to probe. That is not
hypothetical — clones were inheriting their source's machine-id, hence
its DHCP lease, hence its address, so 'archive → peer' was archive
probing itself and would have reported a cheerful 'reachable' as an
isolation failure.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
2026-07-13 23:32:22 +00:00

8.2 KiB

Drill run log

What the drill has actually found, what has broken in the drill itself, and how to diagnose the next stall without starting from zero. Append a section per run; keep the traps table current — it is the part that saves time.

The audit this feeds is #15.

Where the audit stands

Probe Answer Run
A1/A5 egress + gateway DNS PASS 2, 3, 4
A2 box → host dropped 2, 3, 4
A2 box → RFC1918 dropped 2, 3, 4
A3 sibling isolation still unanswered — blocked by a drill bug in every run so far
A4 DNS enumeration LEAKS — a box resolves its sibling by name (as #12 predicted) 2, 3, 4
A6 IPv6 off none 2, 3, 4
A7 inbound host → box dropped 3, 4
B1 @internal on a bridge ACL REJECTEDUnsupported nftables subject ⇒ #16 derives the subnet 2, 3
B2 incus copy preserves user.* YES ⇒ #17's metadata design holds 2, 3, 4
B3 dns.mode=none closes the leak; egress verdict FLIPPED between runs (see below) 2, 3
B4 config get on unset key empty + exit 0 ⇒ #17 must use ${var:-}, never || 2, 3, 4
B5 L2 filtering box networking intact; in-box docker unverified 2, 3

A3 is the whole point and it has never fired. It is the one claim #12 could not verify from a code reading. Until it is answered, #16 does not know whether it is writing a formalization or a fix.

Findings in claudebox (not in the drill)

Finding Status
setup-host.sh called nft but a stock Debian 13 cloud image ships neither nftables nor UFW — host setup died on a fresh cloud host fixed (setup-host installs it)
claudebox exec box -- claude … — the help's own example — failed: the binary is in ~/.local/bin, but cloud-init exported PATH only in .bashrc/.zshrc, which the non-interactive shell behind exec never reads (login shell is zsh, so even sudo -i misses both) fixed (symlink into /usr/local/bin)
Cold mint takes ~95s, not the ~10 min the docs claim — consistently. Either the host is fast, or cloud-init status --wait returns before runcmd finishes (which would hand over boxes whose installs are still running) open — worth its own issue if run 6 shows cloud-init mid-flight

Traps this script has already fallen into

Read this before adding a probe. Every one of these cost a run.

  1. set -o pipefail breaks refusal checks. Half the drill is claudebox <refusal> 2>&1 | grep -q 'text'. The refusal exits 1/2 by design, and grep -q SIGPIPEs the left side when it matches early. Under pipefail both become false FAILs. The pipeline's verdict must be grep's alone — hence set -u and no pipefail.
  2. $( ) waits for stdout to CLOSE, not for the command to exit. A grandchild inheriting an incus exec session's stdout holds the substitution open forever, and timeout does not save you: it kills the wrapper, not the process holding the pipe. Use in_box/box_curl, which talk to incus exec directly, pin stdin to /dev/null, and land output in a file rather than a pipe.
  3. Never start a background process inside a box. Same mechanism as (2), and it is why the drill now runs no listener anywhere. It does not need one: curl exit 7 (refused) means the packet arrived, 28 (timeout) means it was dropped. A closed port answers the question.
  4. The box's address is hard to read, and every way of getting it wrong was tried. (a) incus list name filters are not regexesincus list "^peer$" silently matches nothing. (b) Its CSV quotes a multi-address box across lines. (c) The interface is not eth0. The profile names the device eth0, but inside a VM guest predictable naming renames it enp5s0 — so ip addr show dev eth0 finds nothing either. That is the real reason A3 went unprobed for six runs, through two "fixes" of mine that never questioned the interface name. Read it from inside the box and select by subnet (10.87.x), not by interface name: docker0 (172.17.x) is the decoy, and the NIC's name is the guest's business. Lesson: when the same probe fails three different ways, stop patching the probe and go look at the thing itself.
  5. incus delete -f a b c aborts at the first MISSING name. One interrupted run then poisons the next: stale boxes survive cleanup and cascade into half a dozen unrelated FAILs. Delete one name at a time.
  6. apt-get -qq … >/dev/null hides both a sudo prompt and the apt lock. apt-daily/unattended-upgrades hold the lock on a cloud image and apt waits in complete silence. Pre-authorize sudo, set DPkg::Lock::Timeout, and narrate.
  7. claudebox exec is sudo -u claude -i — a login zsh with oh-my-zsh. Fine for a human, needless machinery for a probe, and one more thing that can hold an fd. Probes use incus exec directly.
  8. Clean before you set up, not after. setup-host.sh reconfigures the network's ACLs, and a previous run's boxes are still attached to that network — incus network set then has to push the change onto every live NIC. An aborted run also leaves the D-phase mutations (dns.mode=none, NIC filtering) in place, so setup converges against a moving target. Delete the boxes and revert the mutations first.

Diagnosing a stall

The drill narrates every long step. If it goes quiet, open a second terminal:

# what is actually running / blocked?
ps -eo pid,etimes,stat,args | grep -Ev grep | grep -E 'apt|dpkg|incus|setup-host|sudo|curl'

# apt lock held by a background upgrade? (the classic silent stall)
sudo fuser -v /var/lib/dpkg/lock-frontend
systemctl status unattended-upgrades apt-daily.service

# incus itself wedged?
incus list
journalctl -u incus --no-pager -n 30

Running one probe by hand

Nothing in the audit requires the whole drill. To answer A3 on a host that already has two boxes up (archive and peer):

PEER_IP=$(timeout 20 incus exec peer -- ip -4 -o addr show dev eth0 \
          | awk '{split($4,a,"/"); print a[1]}')
timeout 30 incus exec archive -- curl -sS -m 5 -o /dev/null "http://$PEER_IP:8088"
echo "curl exit: $?"    # 28 = dropped (isolated) · 7 = refused (it ARRIVED) · 0 = connected
timeout 30 incus exec archive -- ping -c1 -W2 "$PEER_IP"
echo "ping exit: $?"    # 0 = ICMP replies — isolation is partial at best

No listener is needed, and none should be started: see trap 3.

Run history

Run Result What it cost
1 hung at C7; ~9 false FAILs traps 1, 2, 4 — pipefail, the exec-pty hang, the DHCP race
2 42/49 trap 5 — an interrupted run 1 left boxes behind, cascading 5 FAILs. Found the claude-on-PATH bug. Phase D delivered B1 (@internal rejected) and a B3 reading of broken
3 48/49 trap 4 — eth0_ip never matched, so A3 again unprobed. B3 now read intact, contradicting run 2
4 hung at C4 trap 2 again, this time via claudebox exec in a command substitution
5 stalled in host setup trap 6 — silence through apt/sudo
6 stalled in setup-host.sh trap 8 — cleanup ran after setup, so setup reconfigured claudenet's ACLs while run 4's boxes were still attached to it

The instrument has been less reliable than the thing it measures. Four of five runs died on drill plumbing, not on claudebox. That is worth stating plainly: if a probe can be answered by hand (see above), answer it by hand and move on rather than paying for another full run.

The B3 flip — a lesson worth keeping

Run 2 said dns.mode=none broke egress; run 3 said it was intact. Both probed ~2s after setting the key, and setting dns.mode restarts the network's dnsmasq — so run 2 caught the restart window and run 3 missed it. A design veto was posted to #16 on the strength of run 2, then retracted.

A verdict drawn from one observation of a system with restart semantics is not a verdict. The probe now distinguishes transient (recovers within 30s) from broken (does not), and any test #16 ships must tolerate that window rather than race it.