didericis
39d47b8108
Address the codex review on #398: - P1: inject_guest_boot no longer follows a symlink at bb-init/bb-dropbear. A committed snapshot is guest-controlled and could plant those paths as symlinks aimed at a host file (e.g. bb-init -> ~/.bashrc); write_text / copy2 would then overwrite the target as the host user during resume. Replace any pre-existing entry and create the files with O_EXCL|O_NOFOLLOW so the write stays inside the staging tree. - P2: write the snapshot tar owner-only (0600). It can contain the bottle's private workspace; it was being created world-readable (0644). Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01UoEZHDjv84ChoZbozQERhJ
83 lines
3.4 KiB
Python
83 lines
3.4 KiB
Python
"""FirecrackerFreezer — snapshot a running microVM to a rootfs tar.
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The VM is live and can't be block-copied safely, so — like the macOS
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backend — we stream the guest root filesystem out over the control
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channel (SSH here). Unlike the other backends this needs no Docker: the
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tar *is* the resumable artifact. `resume` extracts it and rebuilds a
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fresh per-bottle ext4 with `mke2fs -d` (see `util.build_committed_rootfs_dir`
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and `launch._build_agent_base`). The bottle keeps running after the
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snapshot.
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"""
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from __future__ import annotations
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import json
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import os
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import subprocess
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from pathlib import Path
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from ...bottle_state import committed_rootfs_path
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from ...log import die, info
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from .. import ActiveAgent
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from ..freeze import Freezer
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from . import util
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class FirecrackerFreezer(Freezer):
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backend_name = "firecracker"
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def _freeze(self, agent: ActiveAgent) -> str:
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run_dir = util.cache_dir() / "run" / agent.slug
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private_key = run_dir / "bottle_id_ed25519"
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guest_ip = _guest_ip_from_config(run_dir / "config.json")
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if not private_key.is_file() or not guest_ip:
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die(f"cannot freeze {agent.slug}: run dir {run_dir} is missing the "
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f"SSH key or VM config (is the bottle still running?)")
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tar_path = committed_rootfs_path(agent.slug)
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_commit_rootfs_via_ssh(private_key, guest_ip, tar_path)
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info(f"committed {agent.slug} -> {tar_path}")
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return str(tar_path)
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def _export_hint(self, slug: str, image_ref: str) -> None:
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info(f"to export for migration: cp {image_ref} {slug}.tar")
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def _guest_ip_from_config(config_path: Path) -> str:
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try:
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cfg = json.loads(config_path.read_text())
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except (OSError, json.JSONDecodeError):
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return ""
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boot_args = cfg.get("boot-source", {}).get("boot_args", "")
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for token in boot_args.split():
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if token.startswith("ip="):
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# ip=<client>::<gw>:<mask>::<dev>:off
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return token[len("ip="):].split(":", 1)[0]
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return ""
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def _commit_rootfs_via_ssh(private_key: Path, guest_ip: str, tar_path: Path) -> None:
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"""Stream the guest rootfs out over SSH into `tar_path`. Excludes the
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virtual/live mounts (proc/sys/dev/run) — resume recreates those empty
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mount points. Written to a `.partial` sibling and renamed on success so
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a failed freeze never leaves a truncated artifact in its place."""
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tar_path.parent.mkdir(parents=True, exist_ok=True)
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partial = tar_path.with_name(tar_path.name + ".partial")
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ssh = util.ssh_base_argv(private_key, guest_ip)
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# The snapshot can contain the bottle's private workspace, so keep it
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# owner-only (0600) — create it that way and re-assert after the rename
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# (os.replace carries the source mode, but be explicit).
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fd = os.open(partial, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
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with os.fdopen(fd, "wb") as tar_out:
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result = subprocess.run(
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[*ssh, "--", "tar", "--create", "--one-file-system",
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"--exclude=./proc", "--exclude=./sys", "--exclude=./dev",
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"--exclude=./run", "--file=-", "--directory=/", "."],
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stdout=tar_out, stderr=subprocess.PIPE, check=False,
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)
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if result.returncode != 0:
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partial.unlink(missing_ok=True)
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die(f"ssh tar for {guest_ip} failed: "
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f"{(result.stderr or b'').decode().strip() or '<no stderr>'}")
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os.replace(partial, tar_path)
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os.chmod(tar_path, 0o600)
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