Merge main into fix/db-off-data-plane-469

Brings in main's 8 commits — #470 (backend-agnostic CI guards: BackendStatus
enum, quiet status(), is_backend_available/is_backend_ready, tests/_backend.py
skip_unless_backend) plus firecracker status() readiness checks (kvm/kernel/
dropbear/mke2fs).

Reconciled #470's additions into the reorg'd backend structure:
  * BackendStatus enum + the status(*, quiet=) ABC signature -> backend/base.py
  * is_backend_available / is_backend_ready -> backend/selection.py
  * exposed all three through the lazy backend facade (__init__).
Integration-test conflicts were our control_plane->orchestrator renames vs
main's skip_unless_docker -> skip_unless_backend swap: kept our refactored
import paths + main's guard. Repointed main's new is_backend_* tests to patch
selection._backends (our moved home) instead of the facade.

pyright: 0 errors. Full unit suite green (2272).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

bot_bottle/backend/firecracker/backend.py

@@ -8,7 +8,8 @@ fail-closed nftables egress boundary. Selected by
 
 from __future__ import annotations
 
-from contextlib import contextmanager
+import io
+from contextlib import contextmanager, redirect_stderr
 from pathlib import Path
 from typing import Generator, Sequence
 
@@ -52,8 +53,11 @@ class FirecrackerBottleBackend(
         return _setup.setup()
 
     @classmethod
-    def status(cls) -> int:
+    def status(cls, *, quiet: bool = False) -> int:
         from . import setup as _setup
+        if quiet:
+            with redirect_stderr(io.StringIO()):
+                return _setup.status()
         return _setup.status()
 
     @classmethod

bot_bottle/backend/firecracker/setup.py

@@ -13,6 +13,7 @@ generic `./cli.py backend {setup,status}` command dispatches to.
 
 from __future__ import annotations
 
+import fcntl
 import os
 import shutil
 import subprocess
@@ -22,6 +23,9 @@ from pathlib import Path
 from . import netpool
 from . import util
 
+# KVM_GET_API_VERSION = _IO(KVMIO=0xAE, 0x00): cheapest proof of KVM access.
+_KVM_GET_API_VERSION = 0xAE00
+
 
 _FC_RELEASES = "https://github.com/firecracker-microvm/firecracker/releases"
 _UNIT_PATH = Path("/etc/systemd/system") / netpool.SYSTEMD_UNIT
@@ -219,14 +223,90 @@ def teardown() -> int:
     return 0
 
 
+def _firecracker_binary_ok() -> bool:
+    """True iff the firecracker binary is on PATH and `--version` exits 0."""
+    if shutil.which("firecracker") is None:
+        return False
+    try:
+        return subprocess.run(
+            ["firecracker", "--version"],
+            capture_output=True, check=False, timeout=5,
+        ).returncode == 0
+    except (OSError, subprocess.TimeoutExpired):
+        return False
+
+
+def _kvm_accessible() -> bool:
+    """True iff /dev/kvm can be opened read-write and responds to KVM_GET_API_VERSION.
+
+    VM creation requires write access; opening read-only may satisfy the
+    ioctl but fails at boot time, so O_RDWR is the permission check."""
+    if not os.path.exists(util._KVM_DEVICE):
+        return False
+    try:
+        fd = os.open(util._KVM_DEVICE, os.O_RDWR | os.O_CLOEXEC)
+        try:
+            fcntl.ioctl(fd, _KVM_GET_API_VERSION)
+        finally:
+            os.close(fd)
+        return True
+    except OSError:
+        return False
+
+
 def status() -> int:
-    # Readiness == what the launch preflight hard-requires: the TAP pool
-    # present (unprivileged, authoritative) and no range overlap. Listing
-    # the nft table usually needs root, so — like the preflight — an
-    # unconfirmable table is reported but NOT treated as not-ready; the
-    # post-boot isolation probe is the authoritative check. This keeps an
-    # unprivileged `backend status` usable as a launch gate.
+    # Readiness == what the launch preflight hard-requires: the binary
+    # executable, /dev/kvm accessible, the TAP pool present, and no range
+    # overlap. Listing the nft table usually needs root, so — like the
+    # preflight — an unconfirmable table is reported but NOT treated as
+    # not-ready; the post-boot isolation probe is the authoritative check.
+    # This keeps an unprivileged `backend status` usable as a launch gate.
     ok = True
+    if _firecracker_binary_ok():
+        sys.stderr.write(f"firecracker binary: ok ({shutil.which('firecracker')})\n")
+    else:
+        fc_path = shutil.which("firecracker")
+        if fc_path is None:
+            sys.stderr.write("firecracker binary: NOT found on PATH\n")
+        else:
+            sys.stderr.write(
+                f"firecracker binary: found ({fc_path}) but `--version` failed\n"
+            )
+        ok = False
+    if _kvm_accessible():
+        sys.stderr.write(f"KVM: {util._KVM_DEVICE} accessible\n")
+    else:
+        if not os.path.exists(util._KVM_DEVICE):
+            sys.stderr.write(f"KVM: {util._KVM_DEVICE} not present\n")
+        else:
+            sys.stderr.write(
+                f"KVM: {util._KVM_DEVICE} not accessible (open/ioctl failed)\n"
+            )
+        ok = False
+    kernel = util.kernel_path()
+    if kernel.is_file():
+        sys.stderr.write(f"guest kernel: {kernel}\n")
+    else:
+        sys.stderr.write(
+            f"guest kernel: NOT found at {kernel} "
+            f"(set BOT_BOTTLE_FC_KERNEL or cache a vmlinux there)\n"
+        )
+        ok = False
+    dropbear = util.dropbear_path()
+    if dropbear.is_file():
+        sys.stderr.write(f"dropbear: {dropbear}\n")
+    else:
+        sys.stderr.write(
+            f"dropbear: NOT found at {dropbear} "
+            f"(set BOT_BOTTLE_FC_DROPBEAR or cache a static binary)\n"
+        )
+        ok = False
+    mke2fs = shutil.which("mke2fs")
+    if mke2fs is not None:
+        sys.stderr.write(f"mke2fs: {mke2fs}\n")
+    else:
+        sys.stderr.write("mke2fs: NOT found on PATH (install e2fsprogs)\n")
+        ok = False
     missing = netpool.missing_taps()
     total = netpool.pool_size()
     if missing: