Let a project's container run a VPN client #27

Merged

jknapp merged 2 commits from feat/vpn-support into main 2026-08-14 15:30:04 +00:00

Conversation 1 Commits 2 Files Changed 8

+427 -2

2 Commits

Author	SHA1	Message	Date
shadow-testandClaude Opus 5	2b35aa8c16	Explain a missing tun device where the failure actually happens ... Review caught that the device guard was wired to the wrong call. The daemon does not resolve `--device` at create: verified against Docker 29.7, `docker create --device /dev/does-not-exist` succeeds and prints an id, and runc only resolves the device — and validates sysctls — when it builds the container. So on a host with no tun module the create returns fine and `start` fails, which means the explanation never ran and the user saw the raw daemon string naming a path they would go looking for on the wrong machine. The unit tests fed the create-side string straight in, so they confirmed a function no real failure could reach. Move the guard onto `start_container`, covering create as well in case a future daemon checks earlier. It no longer takes `vpn_support_enabled` — `start_container` has a container id and no project, and nothing else in Triple-C ever requests a device, so an error naming /dev/net/tun is unambiguous on its own. The test now uses the daemon's verbatim message via bollard's real Display format. Also from review: * Soften the security claim. Docker does not enable user-namespace remapping by default, so this is a real CAP_NET_ADMIN in the initial user namespace with only the network namespace confining it. It cannot touch host interfaces, but "confers no authority outside the container" was too strong: within its namespace it can set promiscuous mode and add addresses, routes and NAT on the shared docker0 segment, which puts sibling containers — the LiteLLM gateway among them — within ARP-spoofing reach, and it can flush netfilter rules sandbox mode may rely on. Said plainly in the code, CLAUDE.md and HOW-TO-USE. * Drop Tailscale from the list of clients needing this. Its --tun=userspace-networking mode needs neither the capability nor the device, and listing it invites granting NET_ADMIN for nothing. * Say in the toggle's own hint that changing it recreates the container, matching how every other recreation-triggering setting is labelled. The tab's generic "stop the container first" chip does not tell the user what is about to happen. * Add RuntimeSection tests: saves on, saves off explicitly rather than dropping the key, reflects state, is disabled while running, and carries the recreation warning. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-08-14 08:15:05 -07:00
shadow-testandClaude Opus 5	65a3d4eb29	Let a project's container run a VPN client ... A VPN client installed in a container today starts, runs, and then hangs until its connection times out. Nothing reports an error: a default container has no /dev/net/tun to open and no CAP_NET_ADMIN to add an interface or a route with, and clients surface that as a generic timeout rather than a permissions failure. Add an opt-in per-project "VPN support" switch granting the three things a tunnel needs. They are useless individually, which is why vpn_host_config() defines the set in one place and the tests assert all of it: * CAP_NET_ADMIN — Docker's default bounding set has net_raw but not net_admin, so a client can ping but never connect. * /dev/net/tun — passed through from the host so the kernel's tun module backs it, rather than mknod-ed inside. * net.ipv4.conf.all.src_valid_mark — WireGuard's wg-quick sets this and cannot from inside a container, /proc/sys being read-only, so its handshakes are dropped by reverse-path filtering. Off by default and deliberately opt-in: NET_ADMIN lets anything in the container reconfigure that container's network stack. It is namespaced — no authority over the host's interfaces or any other container. Capabilities and devices are fixed when a container is created, so this is container state and takes the label-and-compare treatment. triple-c.vpn-support is written unconditionally, false included, for the usual docker commit reason: a true stamped once would ride the snapshot image into every future container and make the switch impossible to turn back off. A missing label reads as false and off is byte-identical to today, so no existing project is churned. Requesting the device fails at creation when the host kernel has no tun module, which would otherwise surface as a project that simply refuses to start. explain_create_failure() rewrites that one error to name the switch and the Docker-Desktop-VM-versus-your-machine distinction, and leaves every other failure untouched. Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>	2026-08-14 08:06:39 -07:00