feat: cross-compute VXLAN kernel datapath

Cross-compute links can ride kernel VXLAN tunnels instead of the uBridge
UDP relay: each endpoint creates one VXLAN device (uBridge's rtnetlink
vxlan module) enslaved into the same per-link Linux bridge the same-host
datapath uses, so filters, markers, capture and suspend keep running on
the anchor unchanged. Opt-in (Server.enable_vxlan_cross_compute, default
off) because the tunnel caps the usable MTU at the underlay minus the
outer headers; the relay stays the default and the fallback.

The controller derives what the pair must agree on: one VNI per link
(upper VNI space, per-link random salt) and deterministic device names
(gvl{link}{node}) that make crashed-run leftovers claimable
(show -> delete -> create). Same-host compute pairs, switch endpoints
and serial/unix-socket containers stay on the relay.

A VNI the kernel refuses self-heals on every path it can surface:
interactive create retries a fresh salt then degrades to the relay;
project open re-dispatches refused batch entries the same way; node
start recognises the refused device, stops the half-started node,
re-wires both ends on a fresh VNI (or degrades the link) and retries
the start. The device MTU is derived from the lower device (dev=) and
the per-link bridge inherits it - no configuration. The capability
probe (ubridge_vxlan in /capabilities) runs one scratch create/delete
on a scratch port that never equals the configured dstport.

The e2e scenario runs two computes on one machine (a network namespace
joined by a veth pair as the fabric) and needs root.
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YueGuobin 2026-10-11 21:44:23 +08:00
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commit 21b866aeed
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24 changed files with 2107 additions and 59 deletions

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@ -182,6 +182,7 @@ All dozen-plus GNS3 filter types ride these three kernel objects — nine of the
`UDPLink._kernel_datapath_eligible` decides in the controller at NIO prepare time; the compute side only reacts to the NIO type:
* both endpoints on the same compute, both able to anchor — Docker anchors via its veth (any class except unix-socket containers), and QEMU / IOU / Dynamips / Ethernet-switch peers anchor via their own mechanisms, so mixed links take the kernel path too
* cross-compute pairs take the kernel path as a **VXLAN tunnel** when `Server.enable_vxlan_cross_compute` is enabled and both computes can create the device — see [vxlan-cross-compute](vxlan-cross-compute.md); the default there is the relay, because the tunnel caps the usable MTU at the underlay minus 50 bytes
* `Server.enable_kernel_datapath` enabled (default)
Filters never disqualify the kernel path anymore — every type has a kernel equivalent (netem / cls_bpf / eBPF classifier).

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@ -0,0 +1,121 @@
# Cross-compute VXLAN links
## Overview
A link whose endpoints live on two different computes normally flows through the uBridge UDP relay: each end's anchor is attached to a userspace relay bridge and the frames cross the network as plain UDP payloads pumped by uBridge. This feature adds a second, **kernel-native** cross-compute datapath: each end creates a **VXLAN device** (uBridge's `vxlan` module, rtnetlink) and enslaves it into the same per-link kernel bridge the same-host datapath uses, so the kernel encapsulates and decapsulates and no userspace process is on the data path.
It is **opt-in and off by default** (`Server.enable_vxlan_cross_compute`). The reason is MTU: a tunnel can only carry what the underlay carries minus the outer headers, so its sweet spot is a fabric that moves jumbo frames. The relay stays the default cross-compute datapath and the fallback whenever a tunnel cannot be wired — it always works, at the price of a userspace hop.
## Terms
| Term | Meaning |
|---|---|
| Anchor | The host-side interface an adapter owns (a veth host end, a persistent TAP); links attach *to* it, never create it |
| Relay | The default cross-compute datapath: uBridge userspace bridges pumping UDP tunnels between the computes |
| Tunnel device | The per-end VXLAN device (`gvl…`) carrying one link's frames to the peer compute |
| VNI | The VXLAN network identifier — the kernel's demux key for received frames; both ends of a link must use the same one |
| dstport | The UDP port every tunnel of a deployment listens on; the kernel serves one socket per port and demuxes its traffic by VNI |
| Lower device | The underlay interface the route to the peer resolves to; the kernel derives the tunnel's MTU from it |
## Architecture
```mermaid
flowchart LR
subgraph GA["guest A"]
EA["eth0"]
end
subgraph CA["compute A"]
AA["anchor"] --> BA["bridge"]
BA --> VA["tunnel device"]
end
subgraph U["underlay"]
UD["UDP to the peer, demuxed by VNI"]
end
subgraph CB["compute B"]
VB["tunnel device"] --> BB["bridge"]
BB --> AB["anchor"]
end
subgraph GB["guest B"]
EB["eth0"]
end
EA --> AA
VA --> UD
UD --> VB
AB --> EB
```
Everything on the anchor side is shared with the same-host kernel datapath: filters (the full tc surface including the netem extensions the relay cannot run), markers, capture and suspend all run on the anchor, so they behave identically on a tunneled link. The controller picks the VNI and the device names and hands the peer's address to each end; the kernel does the rest. The device names are a pure function of the link id (bridge, `gvl` device) and the endpoint's node id (device), so each machine can recognise its own leftovers without asking anyone.
## Datapath selection
The controller's `UDPLink._kernel_datapath_eligible` decides at NIO prepare time, on every link (re)creation:
| Condition | Outcome |
|---|---|
| Both endpoints on one compute, both able to anchor | Kernel link (per-link bridge, unchanged) |
| Cross-compute, `enable_vxlan_cross_compute` on, both computes report `ubridge_vxlan`, both ends anchorable, addresses on a common subnet and distinct | **VXLAN tunnel** |
| Same-host pair (both computes resolve to one address) | Relay — the kernel keeps one socket per dstport, so a tunnel pair collides with itself on one host |
| Ethernet switch on either end (cross-compute), serial / non-Ethernet ports, unix-socket vendor containers | Relay |
| Capability missing, flag off, or the link was already downgraded | Relay |
On project (re)open every link re-runs the same decision, so flipping the flag upgrades or downgrades links the same way the same-host datapath is chosen.
## Link creation
Each end's compute owns its own machine: it resolves the lower device from the peer address locally (a connected UDP socket picks the route without sending anything), creates the device and enslaves it. The two sides never talk to each other; the controller's VNI is what makes them a pair.
```mermaid
sequenceDiagram
participant C as Controller
participant UA as Compute A uBridge
participant UB as Compute B uBridge
C->>UA: NIO: bridge, VNI, dstport, peer address
C->>UB: NIO: bridge, VNI, dstport, peer address
par compute A
UA->>UA: vxlan show, delete a leftover
UA->>UA: vxlan create with the local lower device
UA->>UA: brctl addif bridge anchor, tunnel
and compute B
UB->>UB: vxlan show, delete a leftover
UB->>UB: vxlan create with the local lower device
UB->>UB: brctl addif bridge anchor, tunnel
end
Note over C: a refused create retries with a fresh VNI, then degrades the link to the relay
```
The `vxlan show` step is the idempotency contract: a device found under the link's deterministic name belongs to this link (a crashed run's leftover, the previous instance of a node restart) and is replaced, never refused. A create that fails with the name free can only be the VNI — the kernel refuses one already registered on the shared socket — so the controller bumps the derivation salt and retries, and after the retries run out it marks the link downgraded and rebuilds it on the relay. The same shape covers project open: a refused entry is reported per link by the batch route, retried on fresh VNIs up to the same candidate count an interactive creation gets, then degraded, so a VNI collision can never make a project unopenable. And a link wired while its nodes were stopped meets its collision only at node start — the controller's `Node.start` recognises the refused device (its name names the link), stops the half-started node, re-wires the link on a fresh VNI or, on a second refusal, degrades it to the relay, and retries: no path can fail permanently over a VNI.
## Interfaces
| Interface | Where | Notes |
|---|---|---|
| `nio_bridge.vxlan` (name, vni, remote, dstport) | Compute API, NIO create/update body | Present only on cross-compute kernel links; ignored by update (the device persists) |
| `ubridge_vxlan` | `GET /capabilities` and `GET /computes/{id}` | Probed with a scratch create/delete on a scratch port; `null` (unknown) keeps links on the relay |
| `kernel_datapath` | Link REST payload | True for tunneled links, like any kernel link |
## Configuration
| Key | Default | Meaning |
|---|---|---|
| `Server.enable_vxlan_cross_compute` | `false` | Wire eligible cross-compute links as VXLAN tunnels |
| `Server.vxlan_dstport` | `14789` | The UDP port all tunnels of the deployment listen on (one kernel socket per port; chosen off the IANA 4789 and the legacy 8472 so other VXLAN software cannot merge demux tables with ours) |
## Known caveats
* **MTU is the whole story.** The kernel derives the tunnel device's MTU from the lower device (`underlay − 50` for the outer headers; `− 70` for an IPv6 underlay) and the per-link bridge, which carries no MTU of its own, reports the minimum of its ports — i.e. the derived value. A frame past it is dropped at the bridge egress **silently** (no ICMP, no log), which is why the datapath is opt-in: on a 1500-byte fabric a tunnel caps guests at 1450 while the relay carries 1500 with no tax. Guests set their own interface MTU, exactly like a VM or container raising eth0 on the same-host datapath.
* **Asymmetric underlays give one-way jumbo.** The derivation is per machine: a 9000-MTU compute paired with a 1500-MTU one forwards large frames in one direction only. Keep the fabric's MTU uniform between computes.
* **The MTU is derived once, at device creation.** Changing the underlay's MTU does not follow; a link delete/re-create (or project reopen) re-derives.
* **VNI collisions self-heal, not never happen.** The VNI is drawn from the upper VNI space (1M–16.7M) but two links of one deployment can still collide on a host. Every path where the kernel's refusal can surface carries its own heal: link creation retries a fresh VNI then degrades to the relay, project open re-dispatches refused entries the same way, and node start (a link wired while its nodes were stopped) stops the half-started node, re-wires the link on a fresh VNI or degrades it on a second refusal, and retries the start. A reopen re-rolls every link's VNI, so an unlucky link is not permanently unlucky.
* **Security is the relay's, unchanged.** VXLAN carries no authentication; the VNI and the shared port are the only demux, and anyone who can reach the port can inject into any VNI. Treat the compute fabric as trusted, exactly as for the relay's UDP tunnels.
* **Same-host compute pairs stay on the relay**, as do switch links, serial ports and unix-socket vendor containers — the tunnel is a per-link-bridge shape, and those cases are not (or would collide with themselves on one host).
## Verification
* Unit: `tests/controller/test_kernel_datapath_link.py` (selection matrix, tunnel spec derivation, VNI retry, downgrade), `tests/utils/test_vxlan.py`, `tests/compute/docker/test_docker_kernel_datapath.py` (device lifecycle, leftover replacement, teardown ordering), `tests/api/routes/compute/test_capabilities.py`.
* Live: `tests/e2e/test_vxlan_cross_compute.py` — two computes on one machine (a network namespace joined to the host by a veth pair as the second "machine"), real containers per compute: VNI/port agreement, bridge membership, the derived MTU and its hard egress drop, dual-stack traffic, a delay filter, leftover replacement, a VNI squatted at node start (both ends re-wired on a fresh VNI, the start succeeding), residue-free delete and a rebuild through the project-open batch path.
## Roadmap
* PMTU probing between computes to pick the datapath (and pin the MTU) per pair instead of a deployment-wide flag.
* Ethernet switch links tunneled through the switch's own bridge (the absorbed-anchor shape) instead of falling back to the relay.
* VNI-space bookkeeping to make collisions impossible by construction rather than self-healing.

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@ -30,6 +30,7 @@ from gns3server.compute.ubridge.tc_probe import (
probe_iol_tap_support,
probe_tap_support,
probe_tc_capabilities,
probe_vxlan_support,
)
from gns3server.compute.vpcs.vpcs_probe import probe_vpcs_tap
from gns3server.utils.path import get_default_project_directory
@ -75,6 +76,11 @@ async def get_capabilities(request: Request) -> dict:
# kernel link. None = unknown (probe failed or binary missing).
vpcs_tap = await probe_vpcs_tap()
# VXLAN device creation (the vxlan module): the tunnel a cross-compute
# kernel link rides. None = unknown (probe failed, uBridge too old, or
# the kernel refuses vxlan devices here).
ubridge_vxlan = await probe_vxlan_support()
# record the controller hostname or IP address
if request.client:
request.app.state.controller_host = request.client.host
@ -91,4 +97,5 @@ async def get_capabilities(request: Request) -> dict:
"ubridge_iol_tap": ubridge_iol_tap,
"ubridge_bridge_tap": ubridge_bridge_tap,
"vpcs_tap": vpcs_tap,
"ubridge_vxlan": ubridge_vxlan,
}

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@ -35,6 +35,7 @@ from fastapi.encoders import jsonable_encoder
from fastapi.responses import FileResponse
from gns3server import schemas
from gns3server.compute.error import NodeError
from gns3server.compute.project import Project
from gns3server.compute.project_manager import ProjectManager
from gns3server.utils.path import is_safe_path
@ -271,16 +272,35 @@ async def create_batch_nios(
# count (standard == 1, Dynamips == 2) and await the async variant.
sig = inspect.signature(node.manager.create_nio)
dynamips_style = len(sig.parameters) >= 2
failed = []
for entry in entries:
nio_settings = jsonable_encoder(entry.nio, exclude_unset=True)
if dynamips_style:
nio = await node.manager.create_nio(node, nio_settings)
else:
nio = node.manager.create_nio(nio_settings)
await _add_nio_binding(node, entry.adapter_number, entry.port_number, nio)
try:
if dynamips_style:
nio = await node.manager.create_nio(node, nio_settings)
else:
nio = node.manager.create_nio(nio_settings)
await _add_nio_binding(node, entry.adapter_number, entry.port_number, nio)
except NodeError:
# A VXLAN entry that cannot be wired (its VNI already
# registered on the host's shared socket, no route to the
# peer) must not fail the whole project open: report it so
# the controller can degrade that link to the uBridge relay.
# Every other NIO type keeps the fail-the-batch semantics.
if not nio_settings.get("vxlan"):
raise
failed.append(
{
"node_id": entry.node_id,
"adapter_number": entry.adapter_number,
"port_number": entry.port_number,
}
)
return failed
await asyncio.gather(*[_create_one_node(nid, ents) for nid, ents in per_node.items()])
return {"added": len(batch.nios)}
results = await asyncio.gather(*[_create_one_node(nid, ents) for nid, ents in per_node.items()])
failed = [item for node_failed in results for item in node_failed]
return {"added": len(batch.nios) - len(failed), "failed": failed}
@router.put(

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@ -375,7 +375,10 @@ class BaseManager:
nio.markers = nio_settings.get("markers", {})
nio.suspend = nio_settings.get("suspend", False)
elif nio_settings["type"] == "nio_bridge":
nio = NIOBridge(nio_settings["bridge"])
# A vxlan sub-spec marks a cross-compute link: the node creates
# the VXLAN device and enslaves it into the same per-link bridge
# next to its anchor (see KernelDatapathMixin._kernel_attach).
nio = NIOBridge(nio_settings["bridge"], nio_settings.get("vxlan"))
nio.filters = nio_settings.get("filters", {})
# Markers ride the NIO and attach to the veth host interface via
# uBridge's AF_PACKET marker module (marker add_kernel).

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@ -369,7 +369,9 @@ class Dynamips(BaseManager):
# Kernel-datapath NIO: the router binds the port's anchor TAP to
# a hypervisor nio_tap and enslaves it into this per-link bridge
# (Router._attach_kernel_nio). No hypervisor NIO is created here.
nio = NIOBridge(nio_settings["bridge"])
# A vxlan sub-spec (cross-compute link) rides along untouched —
# the router's attach path wires it like any kernel link.
nio = NIOBridge(nio_settings["bridge"], nio_settings.get("vxlan"))
nio.filters = nio_settings.get("filters", {})
nio.markers = nio_settings.get("markers", {})
nio.suspend = nio_settings.get("suspend", False)

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@ -48,6 +48,9 @@ import asyncio
import contextlib
import logging
import os
import socket
import psutil
from gns3server.compute.error import NodeError
from gns3server.compute.ubridge.ubridge_error import UbridgeError
@ -264,6 +267,86 @@ class KernelDatapathMixin:
return not (isinstance(nio, NIOBridge) and nio.bridge is None)
async def _ensure_vxlan_device(self, spec):
"""
Create (or replace) the cross-compute VXLAN device this link end
tunnels through and return the device name. The device name is a
pure function of the link id, so a device found under it belongs to
this link: either a leftover from a run that crashed without
cleanup, or the previous instance of a node restart — deleted and
re-created either way, which makes wiring idempotent. The lower
device is resolved locally from the peer address; the kernel
derives the tunnel MTU from it, which is what keeps the per-link
bridge honest about what the underlay can carry.
A create failure with the name just cleared can only mean the VNI —
the kernel refuses a VNI already registered on the shared dstport
socket (EEXIST) — so it is surfaced as a wiring error and the
controller retries the link with a fresh VNI.
"""
name = spec["name"]
remote = spec["remote"]
try:
await self._ubridge_send(f'vxlan show "{name}"')
except UbridgeError:
# Not present (or uBridge cannot answer): the create below is
# the real gate either way.
pass
else:
await self._ubridge_send(f'vxlan delete "{name}"')
dev = await self._vxlan_lowerdev(remote)
try:
await self._ubridge_send(
f'vxlan create "{name}" {spec["vni"]} remote={remote} dstport={spec["dstport"]} dev={dev}'
)
except UbridgeError as e:
raise self._kernel_error(f"Could not create VXLAN device {name} to {remote} via {dev}: {e}")
return name
async def _vxlan_lowerdev(self, remote):
"""
The local interface the route to *remote* egresses through — the
``dev=`` a cross-compute VXLAN device needs so the kernel can derive
its MTU from the underlay (peer MTU - 50) and pick the outer source
address. A connected UDP socket makes the kernel pick the route
without sending anything; the chosen source address is matched back
to its interface.
"""
try:
info = socket.getaddrinfo(remote, 9, socket.AF_UNSPEC, socket.SOCK_DGRAM)
except socket.gaierror as e:
raise self._kernel_error(f"Cannot resolve VXLAN peer {remote}: {e}")
last_error = None
for af, socktype, proto, _, sa in info:
try:
with socket.socket(af, socktype, proto) as sock:
sock.connect(sa)
local_ip = sock.getsockname()[0]
except OSError as e:
last_error = e
continue
dev = self._interface_with_address(local_ip)
if dev is not None:
return dev
raise self._kernel_error(f"No local interface owns {local_ip}, the route to VXLAN peer {remote}")
raise self._kernel_error(f"No route to VXLAN peer {remote}: {last_error}")
@staticmethod
def _interface_with_address(address):
"""
The name of the interface owning *address* (scope suffix stripped
for link-local IPv6), or None.
"""
plain = address.split("%")[0]
for name, addrs in psutil.net_if_addrs().items():
for addr in addrs:
if addr.address.split("%")[0] == plain:
return name
return None
async def _kernel_attach(self, anchor, nio):
"""
Attach an anchor to the per-link kernel bridge carried by *nio*
@ -276,6 +359,12 @@ class KernelDatapathMixin:
bridge first: an existing bridge is success instead of a create race
failure.
A NIO carrying a ``vxlan`` spec is a cross-compute link: this end's
VXLAN device is (re-)created first and enslaved into the same
bridge next to the anchor, so the kernel encapsulates/decapsulates
the frames while filters, markers, capture and carrier keep running
on the anchor exactly like a same-host kernel link.
A NIO whose ``bridge`` is None means the anchor is bridged
elsewhere — an Ethernet switch absorbed it into the switch's own
bridge — so the membership work is skipped here and only the link
@ -287,6 +376,13 @@ class KernelDatapathMixin:
"""
if nio.bridge is not None:
vxlan_name = None
if nio.vxlan:
# Replace/refresh the device before the bridge work: a
# leftover device may still be enslaved to a leftover bridge
# (its deletion un-enrolls it), and the fresh device must be
# in place when the bridge's MTU auto-adjust runs.
vxlan_name = await self._ensure_vxlan_device(nio.vxlan)
try:
await self._ubridge_send(f'brctl create "{nio.bridge}"')
except UbridgeError:
@ -294,6 +390,8 @@ class KernelDatapathMixin:
await self._ubridge_send(f'brctl show "{nio.bridge}"')
await self._ubridge_send(f'link set "{nio.bridge}" up')
await self._ubridge_send(f'brctl addif "{nio.bridge}" "{anchor}"')
if vxlan_name is not None:
await self._ubridge_send(f'brctl addif "{nio.bridge}" "{vxlan_name}"')
if nio.capturing:
# Restore a capture that was active before a node restart
# (mirrors the relay path's start_capture).
@ -373,6 +471,11 @@ class KernelDatapathMixin:
enslaved fails with EBUSY, so the last endpoint to remove its port
wins the deletion and the loser's failure is expected and suppressed.
A NIO carrying a ``vxlan`` spec is a cross-compute link: this end
also deletes its own tunnel device (the peer deletes its own on its
compute); the kernel's unregister path releases the bridge port, so
it goes before the bridge delete, same as the anchor.
A NIO whose ``bridge`` is None owns no bridge here: the anchor is
bridged by an Ethernet switch, which tears its own membership down
on its side; this end only releases the link state it applied
@ -394,6 +497,9 @@ class KernelDatapathMixin:
with contextlib.suppress(UbridgeError):
await self._ubridge_send(f'brctl delif "{nio.bridge}" "{host_ifc}"')
if nio.bridge is not None:
if nio.vxlan:
with contextlib.suppress(UbridgeError):
await self._ubridge_send(f'vxlan delete "{nio.vxlan["name"]}"')
with contextlib.suppress(UbridgeError):
await self._ubridge_send(f'brctl delete "{nio.bridge}"')
@ -407,6 +513,12 @@ class KernelDatapathMixin:
the same contract as link deletion. A node restart re-creates the
bridge from the NIO in the attach path, so nothing is lost by
deleting it.
A cross-compute NIO's tunnel device is swept with its bridge: each
end owns its own device, and a device left behind would hold its
VNI on the host's shared socket until a reopen's attach path
replaces it by name (which it does — the sweep just frees it
sooner).
"""
if not self.ubridge:
@ -416,6 +528,9 @@ class KernelDatapathMixin:
# bridge None = externally bridged (an Ethernet switch owns
# the bridge); never delete a bridge this node does not own.
if isinstance(nio, NIOBridge) and nio.bridge is not None:
if nio.vxlan:
with contextlib.suppress(UbridgeError):
await self._ubridge_send(f'vxlan delete "{nio.vxlan["name"]}"')
with contextlib.suppress(UbridgeError):
await self._ubridge_send(f'brctl delete "{nio.bridge}"')

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@ -31,6 +31,13 @@ veth host end (marker add_kernel / capture start_kernel).
Ethernet switch absorbed it into the switch's own kernel bridge — and this
node applies only the link state the anchor carries (carrier, markers,
impairments), never bridge membership.
A NIO may additionally carry ``vxlan`` (a BridgeVxlan spec): the link
crosses computes through a VXLAN device this end creates (uBridge's
``vxlan`` module) and enslaves into the same per-link bridge next to the
anchor. The kernel encapsulates/decapsulates the frames; everything else —
filters, markers, capture, carrier, suspend — still runs on the anchor, so
the datapath behaves exactly like a same-host kernel link.
"""
from .nio import NIO
@ -42,12 +49,16 @@ class NIOBridge(NIO):
:param bridge: name of the per-link Linux kernel bridge, or None when
the anchor is bridged by an Ethernet switch (see module docstring)
:param vxlan: cross-compute tunnel spec (dict: name/vni/remote/dstport)
this end creates and enslaves into the bridge, or None for a
same-host kernel link
"""
def __init__(self, bridge):
def __init__(self, bridge, vxlan=None):
super().__init__()
self._bridge = bridge
self._vxlan = vxlan
@property
def bridge(self):
@ -60,6 +71,17 @@ class NIOBridge(NIO):
return self._bridge
@property
def vxlan(self):
"""
Returns the cross-compute VXLAN tunnel spec, or None when the link
is wired on this host alone.
:returns: dict (name/vni/remote/dstport) or None
"""
return self._vxlan
def __str__(self):
return "NIO bridge"
@ -69,6 +91,7 @@ class NIOBridge(NIO):
return {
"type": "nio_bridge",
"bridge": self._bridge,
"vxlan": self._vxlan,
"suspend": self._suspended,
"filters": self._filters,
"markers": self._markers,

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@ -43,6 +43,7 @@ from typing import Optional
from gns3server.config import Config
from gns3server.utils.tc_capabilities import parse_tc_capabilities
from gns3server.utils.vxlan import VXLAN_VNI_MAX, VXLAN_VNI_MIN
from .hypervisor import Hypervisor
from .ubridge_error import UbridgeError
@ -59,6 +60,8 @@ _tap_cache: dict[tuple[str, int, int, int], Optional[bool]] = {}
_iol_tap_cache: dict[tuple[str, int, int, int], Optional[bool]] = {}
# binary identity -> whether the bridge module can release a named TAP NIO (None = unknown)
_bridge_tap_cache: dict[tuple[str, int, int, int], Optional[bool]] = {}
# binary identity -> whether the vxlan module can create a device (None = unknown)
_vxlan_cache: dict[tuple[str, int, int, int], Optional[bool]] = {}
_lock = asyncio.Lock()
@ -358,3 +361,93 @@ async def _probe_bridge_tap(path, config, timeout):
with contextlib.suppress(Exception):
await hypervisor.stop()
shutil.rmtree(working_dir, ignore_errors=True)
async def probe_vxlan_support(timeout: float = 15.0):
"""
Whether this host's uBridge can create a VXLAN device (the ``vxlan``
module) — the carrier a cross-compute kernel link tunnels through.
Probed on a scratch device with a scratch VNI on a scratch dstport
(never the deployment's configured port, so the probe cannot disturb
live tunnels; a device on the port would still be harmless — the kernel
shares one socket — but the probe has no business joining it) and
deleted again, cached by binary identity like the other probes. Any
failure — old build, missing module, no CAP_NET_ADMIN, an unloadable
kernel module — means unknown, reported as None and cached as such;
the controller reads unknown as "keep this link on the relay".
"""
config = Config.instance()
path = shutil.which(config.settings.Server.ubridge_path)
if not path:
return None
try:
stat = os.stat(path)
key = (path, stat.st_mtime_ns, stat.st_size, stat.st_ctime_ns)
except OSError:
return None
async with _lock:
if key in _vxlan_cache:
return _vxlan_cache[key]
supported = await _probe_vxlan(path, config, timeout)
_vxlan_cache[key] = supported
return supported
async def _probe_vxlan(path, config, timeout):
"""
Spawn a throwaway uBridge and run one ``vxlan create``/``delete`` cycle.
The scratch name (uuid suffix) cannot collide with a real link's
deterministic name; the scratch VNI and dstport are drawn from uuids so
two concurrent probes on one host (two servers, one uBridge user) cannot
fight over either. No ``dev=``: this probe answers "can this binary and
kernel create a VXLAN device at all" — resolving the real underlay
interface belongs to the link attach path, where an unroutable peer
means this particular link falls back to the relay, not that the
capability is absent.
"""
working_dir = tempfile.mkdtemp(prefix="gns3-vxlan-probe-")
hypervisor = Hypervisor(
None,
path,
working_dir,
config.settings.Server.ubridge_control_transport,
config.settings.Server.host,
str(uuid.uuid4()),
)
name = f"gvx{uuid.uuid4().hex[:8]}"
# VNI in the deployment's own derived range (utils.vxlan) so the probe
# exercises exactly the kernel path real links use.
vni = VXLAN_VNI_MIN + uuid.uuid4().int % (VXLAN_VNI_MAX - VXLAN_VNI_MIN + 1)
dstport = 20000 + uuid.uuid4().int % 10000
# The scratch socket must never be the configured dstport: on it the
# scratch VNI shares a demux table with the live links' devices, and an
# unlucky draw would make the probe report the capability unknown for
# the process's lifetime (the result is cached).
if dstport == config.settings.Server.vxlan_dstport:
dstport = 20000 if dstport == 29999 else dstport + 1
try:
async def ask():
await hypervisor.start()
await hypervisor.connect()
await hypervisor.send(f"vxlan create {name} {vni} remote=127.0.0.1 dstport={dstport}")
try:
await hypervisor.send(f"vxlan delete {name}")
except UbridgeError as e:
log.warning("Probe VXLAN %s could not be deleted: %s", name, e)
return True
try:
return await asyncio.wait_for(ask(), timeout=timeout)
except (UbridgeError, OSError, asyncio.TimeoutError, ValueError) as e:
# Old build ("Unknown command"), missing module, or no
# CAP_NET_ADMIN: unknown.
log.debug("uBridge vxlan-module probe failed: %s", e)
return None
finally:
with contextlib.suppress(Exception):
await hypervisor.stop()
shutil.rmtree(working_dir, ignore_errors=True)

View File

@ -20,18 +20,33 @@ import copy
import html
import logging
import os
import re
import uuid
from ..config import Config
from ..utils import int_to_macaddress, macaddress_to_int
from ..utils.application_id import is_iol_runner_environment
from ..utils.images import images_directories
from ..utils.vxlan import vxlan_device_name
from .controller_error import ComputeConflictError, ComputeError, ControllerError, ControllerTimeoutError
from .node_types import BUILTIN_NODE_TYPES
from .ports.port_factory import DynamipsPortFactory, PortFactory, StandardPortFactory
log = logging.getLogger(__name__)
# The compute's error when it could not create a VXLAN tunnel device — the
# wording is a same-repo contract with KernelDatapathMixin._kernel_error
# (only computes running this codebase carry VXLAN links: the capability
# gate keeps everything else on the relay), and the captured device name
# identifies the link (a pure function of link id + node id).
_VXLAN_CONFLICT_RE = re.compile(r"Could not create VXLAN device (?P<device>\S+)")
# Node-start self-heal rounds over a refused VXLAN VNI: the first re-wires
# the link on a fresh VNI, the second degrades it to the relay (whose NIOs
# cannot hit the conflict) — a start must not fail permanently because
# another link already registered the VNI on the shared dstport socket.
_VXLAN_START_HEALS = 2
# Image properties of a node, mapped by node type. The value is the image
# "type" used by the image manager (see utils.images). Docker images are not
@ -955,18 +970,32 @@ class Node:
f"Cannot start node '{self._name}': {len(failed_links)} deferred link(s) "
"could not be restored. Please try again."
)
try:
# For IOU: we need to send the licence everytime we start a node
if self.node_type == "iou":
license_check = self._project.controller.iou_license.get("license_check", True)
iourc_content = self._project.controller.iou_license.get("iourc_content", None)
await self.post(
"/start", timeout=240, data={"license_check": license_check, "iourc_content": iourc_content}
for heal in range(_VXLAN_START_HEALS + 1):
try:
await self._start_on_compute(data)
break
except asyncio.TimeoutError:
raise ControllerTimeoutError(f"Timeout when starting {self._name}")
except ComputeError as e:
conflicted = self._vxlan_conflicted_link(e)
if conflicted is None or heal == _VXLAN_START_HEALS:
raise
degrade = heal > 0 # a second conflict takes the relay
log.warning(
"Node '%s': start refused over a VXLAN VNI conflict on link %s — %s and retrying",
self._name,
conflicted.id,
"degrading the link to the uBridge relay" if degrade else "re-wiring the link on a fresh VNI",
)
else:
await self.post("/start", data=data, timeout=240)
except asyncio.TimeoutError:
raise ControllerTimeoutError(f"Timeout when starting {self._name}")
# The refused start leaves the node half-started (the
# emulator process runs, the wiring partial) — stop it
# first: a start on a running container early-returns
# without wiring anything.
await self.stop()
if await self._project._redispatch_vxlan_links([conflicted], downgrade=degrade) and not degrade:
# The fresh VNI was already refused before the start
# could even retry — degrade the pair to the relay now.
await self._project._redispatch_vxlan_links([conflicted], downgrade=True)
self._confirm_status("started")
# A started node may have brought kernel anchors into existence that
# a link needs to finish wiring (the Ethernet-switch fast path joins
@ -974,6 +1003,42 @@ class Node:
for link in self._links:
await link.node_started(self)
async def _start_on_compute(self, data=None):
"""
The compute-side start request (IOU carries its licence along).
"""
# For IOU: we need to send the licence everytime we start a node
if self.node_type == "iou":
license_check = self._project.controller.iou_license.get("license_check", True)
iourc_content = self._project.controller.iou_license.get("iourc_content", None)
await self.post(
"/start", timeout=240, data={"license_check": license_check, "iourc_content": iourc_content}
)
else:
await self.post("/start", data=data, timeout=240)
def _vxlan_conflicted_link(self, error):
"""
The link whose VXLAN device a failed node start could not create,
or None for every other failure.
The compute's error names the device it could not create and the
name is a pure function of (link id, node id), so it identifies the
link with no extra API surface. An unmatched message — another
failure, a future wording change — simply leaves the error to
surface unchanged, which is exactly the behaviour without the heal.
"""
match = _VXLAN_CONFLICT_RE.search(str(error))
if match is None:
return None
device = match.group("device")
for link in self._links:
if vxlan_device_name(link.id, self.id) == device and any(nio.get("vxlan") for nio in link._link_data):
return link
return None
async def stop(self, strict=False):
"""
Stop a node

View File

@ -49,7 +49,7 @@ from .link import _UNSET
from .node import Node
from .snapshot import Snapshot
from .topology import load_topology, project_to_topology
from .udp_link import UDPLink
from .udp_link import _VXLAN_ATTEMPTS, UDPLink
log = logging.getLogger(__name__)
@ -1021,6 +1021,84 @@ class Project:
entries = await link._prepare()
return (link, entries)
async def _dispatch_nio_batch(self, compute, nio_entries):
"""
POST one compute's NIO batch for this project, returning the entries
it refused (VXLAN entries a compute could not wire — see the batch
route; other NIO types fail the whole request).
"""
response = await compute.post(
f"/projects/{self._id}/nios/batch",
data={"nios": nio_entries},
timeout=300,
)
return response.json.get("failed") or []
async def _redispatch_vxlan_links(self, links, downgrade):
"""
Re-prepare *links* and dispatch their NIOs in a second per-compute
batch, returning the links the computes still refused.
With ``downgrade=False`` each link's VNI salt is bumped first — a
fresh VNI, since the refused one was already registered on the
host's shared dstport socket. With ``downgrade=True`` the links are
marked degraded to the uBridge relay (whose UDP NIOs cannot fail
this way) before re-preparing.
"""
for link in links:
if downgrade:
log.warning(
"Project '%s' [%s]: VXLAN wiring failed for link %s — falling back to the uBridge relay datapath",
self._name,
self._id,
link.id,
)
link._vxlan_downgraded = True
else:
link._vxlan_salt += 1
per_compute = {}
by_key = {}
for link in links:
for node, adapter_number, port_number, nio_data in await link._prepare():
by_key[(str(node.id), adapter_number, port_number)] = link
per_compute.setdefault(node.compute, []).append(
{
"node_id": node.id,
"adapter_number": adapter_number,
"port_number": port_number,
"nio": nio_data,
}
)
if not per_compute:
return []
results = await asyncio.gather(
*[self._dispatch_nio_batch(compute, entries) for compute, entries in per_compute.items()]
)
failed = []
for item in (i for sub in results for i in sub):
link = by_key.get((str(item["node_id"]), item["adapter_number"], item["port_number"]))
if link is not None and link not in failed:
failed.append(link)
return failed
async def _heal_refused_vxlan_links(self, pending):
"""
Drive the links a compute refused at open onto a working datapath:
fresh-VNI rounds first — the same candidate count an interactive
link creation tries — then, for whatever still fails, the
degradation to the uBridge relay (whose UDP NIOs cannot hit this
refusal).
"""
for _ in range(_VXLAN_ATTEMPTS - 1):
if not pending:
return
pending = await self._redispatch_vxlan_links(pending, downgrade=False)
if pending:
await self._redispatch_vxlan_links(pending, downgrade=True)
async def restore_deferred_links(self, node):
"""
Create on the computes the NIOs of the links that were deferred while
@ -1994,15 +2072,30 @@ class Project:
}
)
async def _dispatch_batch(compute, nio_entries):
await compute.post(
f"/projects/{self._id}/nios/batch",
data={"nios": nio_entries},
timeout=300,
)
if per_compute:
await asyncio.gather(*[_dispatch_batch(c, n) for c, n in per_compute.items()])
results = await asyncio.gather(
*[self._dispatch_nio_batch(compute, entries) for compute, entries in per_compute.items()]
)
failed = [item for sub in results for item in sub]
else:
failed = []
# A VXLAN entry a compute refused (its VNI already registered on
# the host's shared socket, no route to the peer) must not fail
# the whole open: the refused links are healed onto a working
# datapath (fresh VNIs, then the relay) — see
# _heal_refused_vxlan_links.
if failed:
by_key = {}
for link, entries in valid:
for node, adapter_number, port_number, nio_data in entries:
if nio_data.get("vxlan"):
by_key[(str(node.id), adapter_number, port_number)] = link
pending = []
for item in failed:
link = by_key.get((str(item["node_id"]), item["adapter_number"], item["port_number"]))
if link is not None and link not in pending:
pending.append(link)
await self._heal_refused_vxlan_links(pending)
# Finalise every link: wire node/port back-references, mark created,
# notify clients, and apply project-level marker definitions.

View File

@ -18,6 +18,7 @@
import asyncio
import logging
import uuid
from gns3server.config import Config
from gns3server.utils.application_id import is_iol_runner_environment
@ -26,6 +27,7 @@ from gns3server.utils.packet_filter_validation import (
split_kernel_only_features,
validate_bpf_syntax,
)
from gns3server.utils.vxlan import derive_vni, vxlan_device_name
from .compute import ComputeError
from .controller_error import ControllerError, ControllerNotFoundError
@ -52,6 +54,10 @@ _MARKER_CAPABLE_TYPES = frozenset(
log = logging.getLogger(__name__)
# VXLAN wiring attempts per link creation (the first plus the salt-bumped
# retries) before the link degrades to the uBridge relay.
_VXLAN_ATTEMPTS = 3
def _is_unix_socket_docker(node):
"""
@ -92,6 +98,15 @@ class UDPLink(Link):
# of its endpoints has a missing image. The NIO creation is retried
# once the image is resolved.
self._deferred = False
# Cross-compute VXLAN wiring state: the salt is this link object's
# starting point in the VNI space — random per object, so a project
# reopen re-rolls every link's VNI and a link whose VNI collided
# with an unrelated device on a host is not permanently unlucky
# (the device *name*, which cleanup keys on, stays deterministic).
# _commit_vxlan bumps it for an in-flight retry; the downgrade flag
# marks a link degraded to the UDP relay for this object's lifetime.
self._vxlan_salt = uuid.uuid4().int
self._vxlan_downgraded = False
@property
def debug_link_data(self):
@ -206,9 +221,13 @@ class UDPLink(Link):
Every adapter owns an anchor, so the datapath is a runtime decision —
links attach to running nodes too: the compute side enslaves the
anchor (brctl) or attaches the relay to it (add_nio_ethernet) without
touching the interfaces the node itself uses. Both endpoints must be
on the same compute (there is no kernel link across hosts) and both
must be able to anchor: Docker adapters are born as veth pairs, and
touching the interfaces the node itself uses. Both endpoints must sit
on computes that can carry their end: on one compute the ends meet in
a per-link Linux bridge; across computes each end additionally rides
its own VXLAN device (opt-in via enable_vxlan_cross_compute, uBridge's
vxlan module) enslaved into the same per-link bridge, so everything
below the bridge — filters, markers, capture, carrier — is identical
either way. Both must be able to anchor: Docker adapters are born as veth pairs, and
IOL runner containers — whose guest leg is unix sockets, not a veth —
anchor on persistent TAPs reached through the bridge module's
swappable TAP leg (its own capability pair, see
@ -232,8 +251,21 @@ class UDPLink(Link):
if not Config.instance().settings.Server.enable_kernel_datapath:
return False
if node1.compute.id != node2.compute.id:
return False
cross_compute = node1.compute.id != node2.compute.id
if cross_compute:
# Cross-compute kernel links tunnel: each endpoint rides a VXLAN
# device into the same per-link bridge the same-host datapath
# uses. Opt-in (the tunnel caps the usable MTU at the underlay
# minus the outer headers, so it pays off on jumbo fabrics) and
# gated on both computes' uBridge being able to create the
# device; a link that cannot tunnel stays on the relay, where it
# always works. The downgrade flag is the runtime fallback: after
# the kernel kept refusing this link's VNI, the link stays on the
# relay for this object's lifetime.
if not Config.instance().settings.Server.enable_vxlan_cross_compute:
return False
if self._vxlan_downgraded:
return False
if _is_unix_socket_docker(node1) or _is_unix_socket_docker(node2):
return False
for side in self._nodes:
@ -249,10 +281,17 @@ class UDPLink(Link):
# pair is the only shape a bridge-to-bridge cable can take).
switch = self._switch_endpoint()
if switch is not None:
if cross_compute:
# The fast path is a one-host shape (the peer's anchor is
# absorbed into the switch's bridge); a switch link across
# computes stays on the relay.
return False
if node1.node_type == "ethernet_switch" and node2.node_type == "ethernet_switch":
return True
peer = node2 if switch[0] == 0 else node1
return self._kernel_endpoint_ready(peer)
if cross_compute:
return self._vxlan_endpoint_ready(node1) and self._vxlan_endpoint_ready(node2)
return self._kernel_endpoint_ready(node1) and self._kernel_endpoint_ready(node2)
def _switch_endpoint(self):
@ -305,6 +344,23 @@ class UDPLink(Link):
return capabilities.get("ubridge_tap") is True and capabilities.get("vpcs_tap") is True
return False
@staticmethod
def _vxlan_endpoint_ready(node):
"""
Whether a node can carry its end of a cross-compute VXLAN link: it
must be able to anchor (the same per-node-type capability the
same-host kernel datapath needs — its end of the tunnel is enslaved
into a per-link bridge like any kernel link's) and its compute's
uBridge must be able to create the VXLAN device the tunnel rides.
Strict True on both, like the other capability gates: an unreported
or failed probe keeps the link on the relay, where it always works.
"""
if not UDPLink._kernel_endpoint_ready(node):
return False
capabilities = node.compute.capabilities or {}
return capabilities.get("ubridge_vxlan") is True
async def _prepare(self):
"""
Local-only link setup: resolve peer addresses, reserve UDP ports and
@ -330,10 +386,77 @@ class UDPLink(Link):
adapter_number2 = self._nodes[1]["adapter_number"]
port_number2 = self._nodes[1]["port_number"]
if self._kernel_datapath_eligible(node1, node2):
cross_compute = node1.compute.id != node2.compute.id
# A cross-compute link needs the compute pair's addresses on both
# datapaths (the VXLAN tunnel's outer endpoints, the relay's UDP
# peers): resolve once, and let the no-common-subnet failure stay a
# ControllerError either way — it is a deployment error, not a
# datapath decision. Equal addresses mean both computes share one
# host: the kernel shares one VXLAN socket per dstport, so a tunnel
# pair cannot live there, and such links keep the relay, where the
# two ends are told apart by their UDP ports.
hosts = None
if cross_compute:
try:
hosts = await node1.compute.get_ip_on_same_subnet(node2.compute)
except ValueError as e:
raise ControllerError(f"Cannot get an IP address on same subnet: {e}")
same_host = hosts is not None and hosts[0] == hosts[1]
if self._kernel_datapath_eligible(node1, node2) and not same_host:
node1_filters, node2_filters = self._get_node_filters(node1, node2, kernel=True)
node1_markers, node2_markers = self._get_node_markers(node1, node2)
switch = self._switch_endpoint()
if hosts is not None:
# Cross-compute VXLAN: each end gets one VXLAN device
# carrying the link's VNI, enslaved into the per-link kernel
# bridge next to the node's anchor (see _kernel_attach on
# the compute side). The controller derives name and VNI —
# both ends must agree on the VNI and neither can ask the
# other — and the compute resolves the underlay interface
# locally from the peer address, so the kernel derives the
# device MTU (underlay - 50) and the bridge reports the
# honest "what this fabric can carry" value. A VNI the
# kernel refuses as already registered on the shared
# dstport socket surfaces as a commit failure; create()
# retries with a bumped salt and degrades to the relay when
# the retries run out.
node1_host, node2_host = hosts
dstport = Config.instance().settings.Server.vxlan_dstport
vni = derive_vni(self._id, self._vxlan_salt)
bridge_name = "gns3" + self._id.replace("-", "")[:11]
self._link_data = [
{
"type": "nio_bridge",
"bridge": bridge_name,
"vxlan": {
"name": vxlan_device_name(self._id, node1.id),
"vni": vni,
"remote": node2_host,
"dstport": dstport,
},
"filters": node1_filters,
"markers": node1_markers,
"suspend": self._suspended,
},
{
"type": "nio_bridge",
"bridge": bridge_name,
"vxlan": {
"name": vxlan_device_name(self._id, node2.id),
"vni": vni,
"remote": node1_host,
"dstport": dstport,
},
"filters": node2_filters,
"markers": node2_markers,
"suspend": self._suspended,
},
]
return [
(node1, adapter_number1, port_number1, self._link_data[0]),
(node2, adapter_number2, port_number2, self._link_data[1]),
]
if switch is not None:
if node1.node_type == "ethernet_switch" and node2.node_type == "ethernet_switch":
# Switch-to-switch cascade: one veth pair joins the two
@ -449,11 +572,16 @@ class UDPLink(Link):
(node2, adapter_number2, port_number2, self._link_data[1]),
]
# Get an IP allowing communication between both host
try:
(node1_host, node2_host) = await node1.compute.get_ip_on_same_subnet(node2.compute)
except ValueError as e:
raise ControllerError(f"Cannot get an IP address on same subnet: {e}")
# Relay datapath: UDP tunnels between the computes' addresses —
# already resolved for a cross-compute pair, resolved here otherwise
# (a same-compute relay pair resolves to the host's own address on
# both sides, distinguished by their UDP ports).
if hosts is None:
try:
hosts = await node1.compute.get_ip_on_same_subnet(node2.compute)
except ValueError as e:
raise ControllerError(f"Cannot get an IP address on same subnet: {e}")
node1_host, node2_host = hosts
# Reserve a UDP port on both sides in parallel. Pre-allocated ports
# (used during batch project loading) are popped from memory; otherwise
@ -537,17 +665,70 @@ class UDPLink(Link):
raise errors[0]
self._created = True
@staticmethod
def _has_vxlan(entries):
"""
Whether any prepared NIO spec of this link carries a VXLAN tunnel.
"""
return any(nio_data.get("vxlan") for _, _, _, nio_data in entries)
async def create(self):
"""
Create the link on the nodes (interactive path: prepare + commit).
"""
entries = await self._prepare()
await self._commit_nios(entries)
if self._has_vxlan(entries):
await self._commit_vxlan(entries)
else:
await self._commit_nios(entries)
# New links automatically inherit every active project-level marker
# definition so the user doesn't have to reconfigure.
await self._project.apply_defs_to_new_link(self)
async def _commit_vxlan(self, entries):
"""
Commit a cross-compute VXLAN link, retrying with a bumped VNI salt
on failure and degrading the link to the UDP relay when the retries
run out.
The kernel refuses a VNI already registered on the shared dstport
socket at device creation (EEXIST) — the one conflict a freshly
created, deterministically named device can hit: the other end's
device lives on another host, and a leftover under this end's name
is replaced by the attach path, not refused. Any other commit
failure (a stopped node, a missing underlay route) is retried too,
harmlessly — it fails the same way every attempt, and the final
relay attempt surfaces the real error if the link genuinely cannot
be created. VXLAN is opt-in and the relay always works, so a tunnel
that cannot be wired degrades instead of failing the link; the
degradation lasts for this link object's lifetime (a project reopen
retries VXLAN from a clean state).
"""
last_error = None
for attempt in range(_VXLAN_ATTEMPTS):
if attempt:
self._vxlan_salt += 1
entries = await self._prepare()
if not self._has_vxlan(entries):
# Eligibility changed under us (a capability disappeared):
# commit the relay entries as prepared.
await self._commit_nios(entries)
return
try:
await self._commit_nios(entries)
return
except (ComputeError, ControllerError) as e:
last_error = e
log.warning(
"Link %s: VXLAN wiring failed (%s) — falling back to the uBridge relay datapath", self._id, last_error
)
self._vxlan_downgraded = True
entries = await self._prepare()
await self._commit_nios(entries)
async def update(self):
"""
Update the link on the nodes

View File

@ -73,6 +73,26 @@ class BridgeNIOType(str, Enum):
bridge = "nio_bridge"
class BridgeVxlan(BaseModel):
"""
VXLAN tunnel spec carried by a cross-compute BridgeNIO. Each endpoint
creates one VXLAN device (uBridge ``vxlan create``) and enslaves it into
the link's per-link kernel bridge next to the node's anchor; the kernel
encapsulates/decapsulates the frames. The controller derives the name
and VNI (utils.vxlan) and resolves the peer address, so both endpoints
agree on the VNI without ever talking to each other.
The device's MTU is derived by the kernel from the underlay interface
the route to ``remote`` picks (MTU - 50 for the outer headers), which is
what the link's bridge then reports as "what this fabric can carry".
"""
name: str = Field(..., max_length=15, description="VXLAN device name on this endpoint's host (IFNAMSIZ-1)")
vni: int = Field(..., ge=1, le=16777215, description="VXLAN network identifier, identical on both endpoints")
remote: str = Field(..., description="Peer compute's address (unicast tunnel endpoint)")
dstport: int = Field(..., ge=1, le=65535, description="UDP destination port, identical on both endpoints")
class BridgeNIO(BaseModel):
"""
Kernel-datapath bridge Network Input/Output properties. The NIO tells the
@ -99,6 +119,11 @@ class BridgeNIO(BaseModel):
description="Kernel bridge name e.g. gns3a1b2c3d4e5; None when an Ethernet switch "
"owns the anchor's bridge membership (absorbed link)",
)
vxlan: Optional[BridgeVxlan] = Field(
None,
description="Cross-compute tunnel: the VXLAN device this end creates and enslaves into the bridge "
"next to the anchor; absent for same-host kernel links",
)
suspend: Optional[bool] = Field(None, description="Suspend the NIO")
filters: Optional[dict] = Field(
None,

View File

@ -192,6 +192,24 @@ class ServerSettings(BaseModel):
"or QEMU when the compute's uBridge supports persistent TAPs) through kernel interfaces instead "
"of the uBridge UDP relay",
)
enable_vxlan_cross_compute: bool = Field(
False,
description="Wire eligible cross-compute links through kernel VXLAN tunnels (one device per endpoint, "
"uBridge's vxlan module) instead of the uBridge UDP relay. The kernel encapsulates/decapsulates, so "
"no user-space forwarding is involved; the price is MTU: a tunnel can only carry the underlay MTU "
"minus 50 bytes of outer headers, so enable this where the fabric between computes carries jumbo "
"frames. The relay stays the default and the fallback when a tunnel cannot be wired",
)
vxlan_dstport: int = Field(
14789,
ge=1,
le=65535,
description="UDP destination port every cross-compute VXLAN tunnel listens on. The kernel shares one "
"socket per port across all VXLAN devices, so all links of a deployment ride this one port — chosen "
"off the IANA 4789 and the legacy 8472 (other VXLAN software's ports: sharing a socket would merge "
"their demux table with ours) and above the ephemeral range. Change it only when it collides with "
"a service already listening on the computes",
)
auto_discover_images: bool = Field(True, description="Automatically discover images in the images directory")
image_sync_interval: int = Field(900, ge=10, description="Seconds between automatic image inventory scans")
report_errors: bool = Field(True, description="Automatically send crash reports to the GNS3 team")

View File

@ -73,3 +73,8 @@ class Capabilities(BaseModel):
"keeps the guest from auto-configuring the host side of the anchor TAP); absent when the "
"probe failed",
)
ubridge_vxlan: Optional[bool] = Field(
None,
description="Whether uBridge can create VXLAN devices (the vxlan module, kernel support included) — "
"the tunnel a cross-compute kernel link rides; absent when the probe failed",
)

86
gns3server/utils/vxlan.py Normal file
View File

@ -0,0 +1,86 @@
#
# Copyright (C) 2026 GNS3 Technologies Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Identity of a cross-compute VXLAN link: the device name and VNI the
controller derives and ships in both endpoints' NIOs.
A cross-compute kernel link is carried by one VXLAN device per endpoint
(uBridge's ``vxlan`` module, rtnetlink), enslaved into the link's per-link
kernel bridge next to the node's anchor. Each device is local to its own
host, but the VNI is the kernel's demux key for received frames on the
deployment-wide shared dstport socket — both ends must agree on it while
neither can ask the other, so the controller is the single source for both
values.
* the device name is a pure function of the link id plus the endpoint's
node id: unique per (link, endpoint), within IFNAMSIZ, and outside the
``gns3``/anchor name spaces (``gvl`` prefix). Determinism is what makes
a crashed run's leftover device recognisable — the compute deletes a
device it finds under the name before re-creating it;
* the VNI is a pure function of the link id and a controller-side salt —
a random base per link object, bumped when a retry needs a fresh VNI —
drawn from the upper half of the VNI space so it cannot collide with the
low well-known VNIs other software uses (Flannel's 1, Docker overlay
networks from 256, ...).
The kernel refuses a second device registering a VNI already taken on the
same (dstport, socket) pair with EEXIST — a check that doubles as the
collision detector: the controller retries with a bumped salt and falls
back to the UDP relay when the space stays occupied (the relay needs no
VNI at all).
"""
import hashlib
# The VNI range derived links draw from: at or above 0x100000 (1M) to stay
# clear of the low VNIs other VXLAN software commonly registers, at or below
# 0xFFFFFE so every derived value is valid for the module's 1..16777215
# (0xFFFFFF) check with one value of headroom.
VXLAN_VNI_MIN = 0x100000
VXLAN_VNI_MAX = 0xFFFFFE
# IFNAMSIZ (16) - 1 for the terminator: "gvl" (3) + 8 (link) + 4 (node) = 15.
VXLAN_NAME_PREFIX = "gvl"
def derive_vni(link_id, salt=0):
"""
The VNI both endpoints of *link_id* tunnel through.
:param link_id: link UUID (or str)
:param salt: controller-side retry counter — bumped when the kernel
refuses the previous VNI as already registered on the shared
dstport socket; 0 for the first attempt
:returns: VNI in [VXLAN_VNI_MIN, VXLAN_VNI_MAX]
"""
digest = hashlib.sha256(f"{link_id}:{salt}".encode()).digest()
span = VXLAN_VNI_MAX - VXLAN_VNI_MIN + 1
return VXLAN_VNI_MIN + int.from_bytes(digest[:8], "big") % span
def vxlan_device_name(link_id, node_id):
"""
The VXLAN device name one endpoint of *link_id* creates on its own host,
deterministic from the link id plus the endpoint's node id (the pair
normally lives on two hosts, but a forced same-host pair must not name
both its devices identically).
"""
link = str(link_id).replace("-", "")[:8]
node = str(node_id).replace("-", "")[:4]
return f"{VXLAN_NAME_PREFIX}{link}{node}"

View File

@ -45,6 +45,7 @@ class TestCapabilitiesRoutes:
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_iol_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_bridge_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vpcs_tap", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vxlan_support", _no_tap_probe)
response = await compute_client.get(app.url_path_for("compute:get_capabilities"))
assert response.status_code == status.HTTP_200_OK
assert response.json() == {
@ -73,6 +74,7 @@ class TestCapabilitiesRoutes:
"ubridge_iol_tap": None,
"ubridge_bridge_tap": None,
"vpcs_tap": None,
"ubridge_vxlan": None,
}
async def test_get_on_gns3vm(self, app: FastAPI, compute_client: AsyncClient, on_gns3vm, monkeypatch) -> None:
@ -85,6 +87,7 @@ class TestCapabilitiesRoutes:
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_iol_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_bridge_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vpcs_tap", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vxlan_support", _no_tap_probe)
response = await compute_client.get(app.url_path_for("compute:get_capabilities"))
assert response.status_code == status.HTTP_200_OK
assert response.json() == {
@ -113,6 +116,7 @@ class TestCapabilitiesRoutes:
"ubridge_iol_tap": None,
"ubridge_bridge_tap": None,
"vpcs_tap": None,
"ubridge_vxlan": None,
}
async def test_get_reports_ubridge_tc(self, app: FastAPI, compute_client: AsyncClient, monkeypatch) -> None:
@ -199,6 +203,25 @@ class TestCapabilitiesRoutes:
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_iol_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_bridge_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vxlan_support", _no_tap_probe)
response = await compute_client.get(app.url_path_for("compute:get_capabilities"))
assert response.status_code == status.HTTP_200_OK
assert response.json()["vpcs_tap"] is True
async def test_get_reports_ubridge_vxlan(self, app: FastAPI, compute_client: AsyncClient, monkeypatch) -> None:
"""
The vxlan capability is what makes a cross-compute link tunnel-
eligible, so it travels with the other compute capabilities.
"""
async def fake_vxlan_probe():
return True
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vxlan_support", fake_vxlan_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_iol_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_bridge_tap_support", _no_tap_probe)
monkeypatch.setattr("gns3server.api.routes.compute.capabilities.probe_vpcs_tap", _no_tap_probe)
response = await compute_client.get(app.url_path_for("compute:get_capabilities"))
assert response.status_code == status.HTTP_200_OK
assert response.json()["ubridge_vxlan"] is True

View File

@ -22,6 +22,7 @@ fallback and cleanup.
"""
import os
import socket
import uuid
from unittest.mock import MagicMock, call, patch
@ -32,6 +33,7 @@ from gns3server.compute.compute_error import ComputeError
from gns3server.compute.docker import Docker
from gns3server.compute.docker.docker_error import DockerError, DockerHttp404Error
from gns3server.compute.docker.docker_vm import DockerVM
from gns3server.compute.error import NodeError
from gns3server.compute.nios.nio_bridge import NIOBridge
from gns3server.compute.ubridge.ubridge_error import UbridgeError, UbridgeNamespaceError
from tests.utils import AsyncioMagicMock
@ -1468,3 +1470,147 @@ async def test_stop_clears_relay_bridge_registry(vm):
await vm.stop()
assert vm._bridges == set()
assert vm._ubridge_tc_caps is None
# ---------------------------------------------------------------------------
# Cross-compute VXLAN tunnel
# ---------------------------------------------------------------------------
VXLAN_SPEC = {"name": "gvl01234567abcd", "vni": 1048577, "remote": "192.168.1.2", "dstport": 14789}
def test_create_nio_bridge_carries_vxlan_spec(vm):
"""
The vxlan sub-spec of a cross-compute NIO survives the factory and the
asdict round-trip (the node replays the NIO from asdict on restart).
"""
nio = vm.manager.create_nio({"type": "nio_bridge", "bridge": BRIDGE, "vxlan": dict(VXLAN_SPEC)})
assert isinstance(nio, NIOBridge)
assert nio.vxlan == VXLAN_SPEC
assert nio.asdict()["vxlan"] == VXLAN_SPEC
@pytest.mark.asyncio
async def test_add_ubridge_kernel_connection_with_vxlan(vm):
"""
A vxlan-carrying NIO creates this end's tunnel device (lower device
resolved locally from the peer address) and enslaves it into the link's
kernel bridge next to the anchor.
"""
async def send(command):
if command.startswith("vxlan show"):
raise UbridgeError("VXLAN does not exist")
vm._ubridge_hypervisor = MagicMock()
vm._ubridge_hypervisor.send = AsyncioMagicMock(side_effect=send)
vm._namespace = 42
nio = vm.manager.create_nio({"type": "nio_bridge", "bridge": BRIDGE, "vxlan": dict(VXLAN_SPEC)})
with patch.object(DockerVM, "_vxlan_lowerdev", return_value="eth0"):
await vm._add_ubridge_connection(nio, 0)
host_ifc, _ = vm._veth_names(0, 0)
sends = [c.args[0] for c in vm._ubridge_hypervisor.send.call_args_list]
show = f'vxlan show "{VXLAN_SPEC["name"]}"'
create = (
f'vxlan create "{VXLAN_SPEC["name"]}" {VXLAN_SPEC["vni"]} '
f"remote={VXLAN_SPEC['remote']} dstport={VXLAN_SPEC['dstport']} dev=eth0"
)
assert sends.index(show) < sends.index(create)
# The tunnel device is enslaved after the node's anchor, and the anchor
# still goes up.
assert sends.index(f'brctl addif "{BRIDGE}" "{host_ifc}"') < sends.index(
f'brctl addif "{BRIDGE}" "{VXLAN_SPEC["name"]}"'
)
assert f'link set "{host_ifc}" up' in sends
# A failed show (device absent) must not trigger a delete.
assert f'vxlan delete "{VXLAN_SPEC["name"]}"' not in sends
@pytest.mark.asyncio
async def test_add_ubridge_kernel_connection_replaces_vxlan_leftover(vm):
"""
A device found under this link's deterministic name is this link's own
leftover (a crashed run, a node restart): deleted and re-created, which
makes wiring idempotent.
"""
vm._ubridge_hypervisor = MagicMock()
vm._namespace = 42
nio = vm.manager.create_nio({"type": "nio_bridge", "bridge": BRIDGE, "vxlan": dict(VXLAN_SPEC)})
with patch.object(DockerVM, "_vxlan_lowerdev", return_value="eth0"):
await vm._add_ubridge_connection(nio, 0)
sends = [c.args[0] for c in vm._ubridge_hypervisor.send.call_args_list]
show = f'vxlan show "{VXLAN_SPEC["name"]}"'
delete = f'vxlan delete "{VXLAN_SPEC["name"]}"'
create = (
f'vxlan create "{VXLAN_SPEC["name"]}" {VXLAN_SPEC["vni"]} '
f"remote={VXLAN_SPEC['remote']} dstport={VXLAN_SPEC['dstport']} dev=eth0"
)
assert sends.index(show) < sends.index(delete) < sends.index(create)
@pytest.mark.asyncio
async def test_remove_kernel_nio_deletes_vxlan_device(vm):
"""
Link teardown deletes this end's tunnel device (the kernel un-enrolls it
from the bridge on unregister) before the bridge delete.
"""
vm._ubridge_hypervisor = MagicMock()
vm._ubridge_send = AsyncioMagicMock()
vm.status = "started"
host_ifc, _ = vm._veth_names(0, 0)
vm._kernel_veths[(0, 0)] = host_ifc
vm._ethernet_adapters[0].add_nio(
0, vm.manager.create_nio({"type": "nio_bridge", "bridge": BRIDGE, "vxlan": dict(VXLAN_SPEC)})
)
await vm.adapter_remove_nio_binding(0)
vm._ubridge_send.assert_has_calls(
[
call(f'brctl delif "{BRIDGE}" "{host_ifc}"'),
call(f'vxlan delete "{VXLAN_SPEC["name"]}"'),
call(f'brctl delete "{BRIDGE}"'),
],
any_order=False,
)
@pytest.mark.asyncio
async def test_vxlan_lowerdev_unresolvable_peer_raises(vm):
"""
A peer that cannot be resolved (or routed to) is a wiring error of this
link — the controller retries and then degrades it to the relay.
"""
with patch("gns3server.compute.kernel_datapath.socket.getaddrinfo", side_effect=socket.gaierror("nope")):
with pytest.raises(NodeError):
await vm._vxlan_lowerdev("192.0.2.1")
def test_interface_with_address_matches_the_owning_interface():
"""
The route's chosen source address is matched back to its interface,
scope suffixes stripped (link-local IPv6).
"""
class _Addr:
def __init__(self, address):
self.address = address
with patch(
"gns3server.compute.kernel_datapath.psutil.net_if_addrs",
return_value={
"eth0": [_Addr("192.168.1.1")],
"eth1": [_Addr("fe80::1%eth1")],
},
):
assert DockerVM._interface_with_address("192.168.1.1") == "eth0"
assert DockerVM._interface_with_address("fe80::1%eth1") == "eth1"
assert DockerVM._interface_with_address("10.0.0.1") is None

View File

@ -29,8 +29,10 @@ from gns3server.compute.ubridge.tc_probe import (
probe_iol_tap_support,
probe_tap_support,
probe_tc_capabilities,
probe_vxlan_support,
)
from gns3server.compute.ubridge.ubridge_error import UbridgeError
from gns3server.config import Config
pytestmark = pytest.mark.asyncio
@ -92,6 +94,7 @@ def probe_env(monkeypatch, tmp_path):
tc_probe._tap_cache.clear()
tc_probe._iol_tap_cache.clear()
tc_probe._bridge_tap_cache.clear()
tc_probe._vxlan_cache.clear()
FakeHypervisor.last = None
# a real file on disk: the cache is keyed on its (path, mtime, size,
# ctime)
@ -275,3 +278,51 @@ async def test_probe_bridge_tap_support_missing_binary(monkeypatch):
monkeypatch.setattr(tc_probe.shutil, "which", lambda name: None)
assert await probe_bridge_tap_support() is None
assert FakeHypervisor.spawned == 0
class _FixedUuid:
"""A uuid4 stand-in whose .int/.hex pin the probe's random draws."""
def __init__(self, value):
self.int = value
self.hex = f"{value:032x}"
def _probe_create_port():
"""The dstport of the one `vxlan create` the probe issued."""
create = next(c for c in FakeHypervisor.last.commands if c.startswith("vxlan create "))
return int(create.rsplit("dstport=", 1)[1])
async def test_probe_vxlan_avoids_the_configured_dstport(monkeypatch, probe_env):
"""
A scratch draw landing exactly on the configured dstport must move: on
that port the scratch VNI shares a demux table with the live links'
devices, and an unlucky VNI draw would make the probe report the
capability unknown for the process's lifetime (the result is cached).
"""
# int % 10000 == 9999 -> the scratch window draws its very last value
monkeypatch.setattr(tc_probe.uuid, "uuid4", lambda: _FixedUuid(29999))
settings = Config.instance().settings.Server
monkeypatch.setattr(settings, "vxlan_dstport", 29999)
assert await probe_vxlan_support() is True
assert _probe_create_port() == 20000
async def test_probe_vxlan_scratch_port_stays_off_the_configured_one(monkeypatch, probe_env):
"""
Whatever the configured dstport, the probe's socket never lands on it
and stays inside its scratch window.
"""
settings = Config.instance().settings.Server
for configured in (14789, 20000, 25000, 29999):
monkeypatch.setattr(settings, "vxlan_dstport", configured)
tc_probe._vxlan_cache.clear()
assert await probe_vxlan_support() is True
port = _probe_create_port()
assert 20000 <= port <= 29999, port
assert port != configured, (port, configured)

View File

@ -20,18 +20,21 @@ Controller-side kernel-datapath link selection: eligibility of Docker-to-
Docker links, NIO emission and the filters/markers guards.
"""
from contextlib import contextmanager
from unittest.mock import MagicMock, patch
import pytest
from gns3server.config import Config
from gns3server.controller.controller_error import ControllerError
from gns3server.controller.compute import ComputeError
from gns3server.controller.controller_error import ComputeConflictError, ControllerError
from gns3server.controller.link import FILTERS
from gns3server.controller.node import Node
from gns3server.controller.ports.ethernet_port import EthernetPort
from gns3server.controller.ports.serial_port import SerialPort
from gns3server.controller.udp_link import UDPLink
from gns3server.utils.kernel_anchor import kernel_anchor_name, kernel_cascade_names
from gns3server.utils.vxlan import vxlan_device_name
from tests.utils import AsyncioMagicMock
@ -1174,3 +1177,350 @@ async def test_node_started_repushes_both_cascade_ends(project):
sw1.put.assert_called_once_with("/adapters/0/ports/0/nio", data=entries[0][3], timeout=120)
sw2.put.assert_called_once_with("/adapters/0/ports/0/nio", data=entries[1][3], timeout=120)
# ---------------------------------------------------------------------------
# Cross-compute VXLAN links
# ---------------------------------------------------------------------------
@contextmanager
def _cross_compute_enabled():
settings = Config.instance().settings.Server
original = settings.enable_vxlan_cross_compute
settings.enable_vxlan_cross_compute = True
try:
yield settings
finally:
settings.enable_vxlan_cross_compute = original
def _vxlan_compute(compute_id, vxlan=True):
compute = MagicMock()
compute.id = compute_id
compute.capabilities = {"ubridge_vxlan": vxlan}
return compute
async def _cross_compute_link(project, vxlan1=True, vxlan2=True, same_host=False):
"""A docker↔docker link whose endpoints live on two computes, with the
peer resolution (and the relay fallback's port reservation) mocked."""
compute1 = _vxlan_compute("compute-1", vxlan1)
compute2 = _vxlan_compute("compute-2", vxlan2)
async def subnet_callback(other):
return ("192.168.1.1", "192.168.1.1" if same_host else "192.168.1.2")
compute1.get_ip_on_same_subnet.side_effect = subnet_callback
async def post_callback(path, data=None, **kwargs):
response = MagicMock()
response.json = {"udp_port": 1024}
return response
compute1.post.side_effect = post_callback
compute2.post.side_effect = post_callback
node1 = _node(project, compute1, "docker1")
node2 = _node(project, compute2, "docker2")
link = UDPLink(project)
await link.add_node(node1, 0, 0, batch=True, dump=False)
await link.add_node(node2, 0, 0, batch=True, dump=False)
return link, node1, node2
@pytest.mark.asyncio
async def test_vxlan_cross_compute_disabled_by_config(project):
"""
Cross-compute links stay on the relay until the deployment opts in —
the VXLAN tunnel caps the usable MTU at the underlay minus the outer
headers, so it is opt-in.
"""
link, node1, node2 = await _cross_compute_link(project)
assert link._kernel_datapath_eligible(node1, node2) is False
with _cross_compute_enabled():
assert link._kernel_datapath_eligible(node1, node2) is True
@pytest.mark.asyncio
async def test_vxlan_cross_compute_requires_the_vxlan_capability(project):
"""
Both computes' uBridge must be able to create the tunnel device; an
unreported/failed probe (None) or an old build (False) keeps the link
on the relay, exactly like the other capability gates.
"""
with _cross_compute_enabled():
for vxlan1, vxlan2 in ((False, True), (True, False), (True, None), (None, None)):
link, node1, node2 = await _cross_compute_link(project, vxlan1=vxlan1, vxlan2=vxlan2)
assert link._kernel_datapath_eligible(node1, node2) is False
@pytest.mark.asyncio
async def test_vxlan_cross_compute_switch_stays_on_relay(project):
"""
The switch fast path absorbs the peer's anchor into the switch's own
bridge — a one-host shape; a switch link across computes keeps the
relay.
"""
switch = _node(project, _vxlan_compute("compute-1"), "switch1", node_type="ethernet_switch")
peer = _node(project, _vxlan_compute("compute-2"), "docker2")
link = await _link(project, switch, peer)
with _cross_compute_enabled():
assert link._kernel_datapath_eligible(switch, peer) is False
@pytest.mark.asyncio
async def test_prepare_vxlan_link_emits_tunnel_specs(project):
"""
Both ends get one nio_bridge sharing the per-link bridge name, each
carrying the same VNI/dstport (the pair must agree, and neither end can
ask the other) and the peer's address, with per-endpoint deterministic
device names.
"""
with _cross_compute_enabled():
link, node1, node2 = await _cross_compute_link(project)
entries = await link._prepare()
assert len(entries) == 2
expected_bridge = "gns3" + link.id.replace("-", "")[:11]
dstport = Config.instance().settings.Server.vxlan_dstport
specs = [entry[3] for entry in entries]
assert all(spec["type"] == "nio_bridge" for spec in specs)
assert all(spec["bridge"] == expected_bridge for spec in specs)
vxlan1, vxlan2 = specs[0]["vxlan"], specs[1]["vxlan"]
assert vxlan1["vni"] == vxlan2["vni"]
assert vxlan1["dstport"] == vxlan2["dstport"] == dstport
assert vxlan1["remote"] == "192.168.1.2"
assert vxlan2["remote"] == "192.168.1.1"
assert vxlan1["name"] == vxlan_device_name(link.id, node1.id)
assert vxlan2["name"] == vxlan_device_name(link.id, node2.id)
assert vxlan1["name"] != vxlan2["name"]
@pytest.mark.asyncio
async def test_prepare_vxlan_same_host_pair_falls_back_to_relay(project):
"""
Equal resolved addresses mean both computes share one host: the kernel
shares one VXLAN socket per dstport, so a tunnel pair cannot live there
— such links keep the relay, where the ends differ by UDP port.
"""
with _cross_compute_enabled():
link, node1, node2 = await _cross_compute_link(project, same_host=True)
entries = await link._prepare()
assert all(entry[3]["type"] == "nio_udp" for entry in entries)
@pytest.mark.asyncio
async def test_commit_vxlan_retries_with_a_fresh_vni(project):
"""
A refused commit (reactively: the VNI was already registered on the
host's shared socket) re-prepares the link with a bumped salt — a fresh
VNI, identical on both ends — and recommits.
"""
with _cross_compute_enabled():
link, node1, node2 = await _cross_compute_link(project)
vnis = []
async def commit(entries):
vnis.append(entries[0][3]["vxlan"]["vni"])
if len(vnis) == 1:
raise ComputeError("Could not create vxlan gvl...: File exists")
with patch.object(link, "_commit_nios", commit):
await link.create()
assert len(vnis) == 2
assert vnis[0] != vnis[1]
assert link._vxlan_downgraded is False
@pytest.mark.asyncio
async def test_commit_vxlan_degrades_to_relay_after_retries(project):
"""
When every VXLAN attempt fails, the link degrades to the UDP relay —
the opt-in datapath must never make a link uncreatable.
"""
with _cross_compute_enabled():
link, node1, node2 = await _cross_compute_link(project)
commits = []
async def commit(entries):
commits.append(entries)
if any(entry[3].get("vxlan") for entry in entries):
raise ComputeError("Could not create vxlan gvl...: File exists")
with patch.object(link, "_commit_nios", commit):
await link.create()
assert link._vxlan_downgraded is True
assert len(commits) == 4 # the three VXLAN attempts, then the relay
assert all(entry[3].get("vxlan") for entry in commits[0])
assert all(entry[3]["type"] == "nio_udp" for entry in commits[-1])
async def _prepared_vxlan_link(project):
"""A cross-compute link with its tunnel NIOs prepared (the shape a node
start replays) — call inside ``_cross_compute_enabled`` so the heal's
re-preparation stays on the tunnel too. _bind_members mirrors the
project-open finalize (the node's link back-reference is what lets the
heal find the conflicted link)."""
link, node1, node2 = await _cross_compute_link(project)
await link._prepare()
link._bind_members()
link._created = True
return link, node1, node2
def _vni_conflict(node, link):
"""The compute's 409 when the kernel refuses the link's VNI on the
shared dstport socket — the wording KernelDatapathMixin emits."""
device = vxlan_device_name(link.id, node.id)
return ComputeConflictError(
"http://compute", {"message": f"Could not create VXLAN device {device} to 192.168.1.2 via eth0: File exists"}
)
@pytest.mark.asyncio
async def test_node_start_self_heals_a_vni_conflict(project):
"""
A link wired while its nodes were stopped hits its VNI collision at
node start (the kernel's refusal is the first time anyone asks). The
start stops the half-started node, re-wires the link on a fresh VNI —
both ends, through the per-compute batch — and retries.
"""
with _cross_compute_enabled():
link, node1, node2 = await _prepared_vxlan_link(project)
salt = link._vxlan_salt
starts = []
async def post_callback(path, data=None, **kwargs):
if path.endswith("/start"):
starts.append(path)
if len(starts) == 1:
raise _vni_conflict(node1, link)
response = MagicMock()
response.json = {"udp_port": 1024}
return response
node1.compute.post.side_effect = post_callback
await node1.start()
assert len(starts) == 2
assert link._vxlan_downgraded is False
assert link._vxlan_salt == salt + 1
# the half-started node was stopped before the retry (a start on a
# running container early-returns without wiring)
assert any(call.args[0].endswith("/stop") for call in node1.compute.post.call_args_list)
# the fresh-VNI NIOs were re-dispatched to both computes
for compute in (node1.compute, node2.compute):
batches = [c for c in compute.post.call_args_list if str(c.args[0]).endswith("/nios/batch")]
assert len(batches) == 1
@pytest.mark.asyncio
async def test_node_start_degrades_the_link_after_a_second_conflict(project):
"""
A conflict that survives the fresh VNI degrades the link to the relay
— the start must succeed no later than that round, the same guarantee
create() and the project-open batch path give.
"""
with _cross_compute_enabled():
link, node1, node2 = await _prepared_vxlan_link(project)
starts = []
async def post_callback(path, data=None, **kwargs):
if path.endswith("/start"):
starts.append(path)
if len(starts) <= 2:
raise _vni_conflict(node1, link)
response = MagicMock()
response.json = {"udp_port": 1024}
return response
node1.compute.post.side_effect = post_callback
await node1.start()
assert len(starts) == 3
assert link._vxlan_downgraded is True
assert all(nio["type"] == "nio_udp" for nio in link._link_data)
@pytest.mark.asyncio
async def test_node_start_does_not_retry_other_failures(project):
"""
Only the VXLAN device conflict heals: any other start failure surfaces
unchanged, with a single attempt and no stop/redispatch side effects.
"""
with _cross_compute_enabled():
link, node1, node2 = await _prepared_vxlan_link(project)
salt = link._vxlan_salt
async def post_callback(path, data=None, **kwargs):
if path.endswith("/start"):
raise ComputeError("DockerError: image not found")
response = MagicMock()
response.json = {}
return response
node1.compute.post.side_effect = post_callback
with pytest.raises(ComputeError):
await node1.start()
starts = [c for c in node1.compute.post.call_args_list if str(c.args[0]).endswith("/start")]
assert len(starts) == 1
assert not any(call.args[0].endswith("/stop") for call in node1.compute.post.call_args_list)
assert link._vxlan_salt == salt
assert link._vxlan_downgraded is False
@pytest.mark.asyncio
async def test_open_heal_tries_the_full_vni_candidate_count(project):
"""
The project-open heal gives a refused link the same VNI candidate count
an interactive creation gets (fresh-salt rounds), degrading to the
relay only after they run out.
"""
link, node1, node2 = await _cross_compute_link(project)
rounds = []
async def redispatch(links, downgrade):
rounds.append(downgrade)
return links if not downgrade else []
with patch.object(project, "_redispatch_vxlan_links", redispatch):
await project._heal_refused_vxlan_links([link])
assert rounds == [False, False, True]
@pytest.mark.asyncio
async def test_open_heal_stops_at_the_first_successful_vni(project):
"""
A link healed by the first fresh-VNI round needs no further rounds —
no pointless second redispatch, no relay degradation.
"""
link, node1, node2 = await _cross_compute_link(project)
rounds = []
async def redispatch(links, downgrade):
rounds.append(downgrade)
return []
with patch.object(project, "_redispatch_vxlan_links", redispatch):
await project._heal_refused_vxlan_links([link])
assert rounds == [False]

View File

@ -27,6 +27,7 @@ Beyond a Linux kernel with the datapath features (bridges, veth/TAP devices, tc
* **`tc` (iproute2)** for the filter scenarios: their qdisc and classifier assertions read it from `PATH`. Without it those assertions cannot run.
* **A Docker daemon** for the Docker scenarios (the harness's own guest driver talks to the same daemon as the server; socket override: `GNS3_E2E_DOCKER_SOCKET`).
* **A C compiler that can link statically** (`cc -static`) for the raw-frame probe of the link-local scenario; without it that probe skips.
* **Root (or passwordless sudo) for the cross-compute scenario** — a second network stack on one machine is a network namespace, and Linux confines creating and entering one to CAP_SYS_ADMIN (uBridge's file capabilities do not help there). The scenario skips with the exact run command otherwise; it also writes the second compute's node files, which the harness's passwordless-sudo path cannot do as the test user.
* **Emulator images** — see the matrix below.
## Test images
@ -93,3 +94,5 @@ Every kernel scenario also asserts the L2-anchor spec's server-side guarantees (
* `GNS3_E2E_DOCKER_SOCKET` — the Docker daemon socket the harness's guest driver talks to (default `/var/run/docker.sock` — the same daemon the server uses).
* `GNS3_E2E_IDLEPC` — skip idle-PC detection for the Dynamips scenarios and use the given value.
* `GNS3_E2E_DEBUG=1` — run the isolated instance with debug logging (the uBridge command stream lands in its `server.log`).
* `test_vxlan_cross_compute.py` — the cross-compute VXLAN datapath, with two computes on one machine: the isolated instance on the host and a second isolated instance inside a network namespace joined to the host by a veth pair (`harness.cross_compute_fabric` — two computes cannot tunnel from the host namespace, since the kernel keeps one VXLAN socket per (namespace, dstport) and the pair must share one VNI on it). One real Alpine container per compute, linked across the tunnel: both ends agree on the VNI and the shared dstport, each per-link bridge enslaves exactly `[anchor, tunnel]`, the tunnel device's MTU is the underlay minus 50 with the bridges inheriting it (a frame at it crosses, one past it is dropped at the bridge egress), dual-stack ICMP crosses, a `delay 100` filter shapes both directions, a stale device squatting on the link's deterministic name is replaced on node restart, a device squatting the link's VNI at node start self-heals (both ends re-wired on a fresh VNI, the start succeeding), link delete leaves nothing behind on either machine, and a project close/reopen rebuilds the tunnel through the batch path. **Needs root** (see host requirements) — run it with `sudo env GNS3_E2E_IMAGES=$HOME/GNS3/images pytest -m e2e tests/e2e/test_vxlan_cross_compute.py -s`.

View File

@ -67,6 +67,7 @@ import time
import urllib.error
import urllib.parse
import urllib.request
import uuid
import pytest
from websockets.sync.client import connect as ws_connect
@ -145,14 +146,15 @@ class Compute:
{"compute_id": "local", "name": name, "node_type": "dynamips", "properties": properties},
)
def create_docker_node(self, project_id, name, image, adapters=1):
def create_docker_node(self, project_id, name, image, adapters=1, compute_id="local"):
"""A standard Docker node (the veth datapath): the scenario addresses
its eth0 from the host and pings through it."""
its eth0 from the host and pings through it. *compute_id* places it
on a remote compute (the cross-compute VXLAN scenario's peer)."""
return self.call(
"POST",
f"/projects/{project_id}/nodes",
{
"compute_id": "local",
"compute_id": compute_id,
"name": name,
"node_type": "docker",
"properties": {"image": image, "adapters": adapters, "console_type": "telnet"},
@ -295,10 +297,11 @@ default_admin_username = admin
default_admin_password = admin
[Server]
host = 127.0.0.1
host = {host}
port = {port}
ubridge_path = {ubridge}
enable_kernel_datapath = {kernel}
enable_vxlan_cross_compute = {vxlan}
report_errors = False
projects_path = {tmp}/projects
configs_path = {tmp}/configs
@ -330,10 +333,14 @@ class Server:
instance (own config dir — the controller DB and every path follow it —
under a temporary directory removed on stop)."""
def __init__(self, compute, process=None, tmpdir=None):
def __init__(self, compute, process=None, tmpdir=None, privilege=()):
self.compute = compute
self.process = process
self.tmpdir = tmpdir
# Command prefix for cleaning up the temp directory when the process
# ran privileged (a compute spawned inside a netns as root writes
# root-owned files the test user cannot remove itself).
self.privilege = privilege
@property
def isolated(self):
@ -361,6 +368,11 @@ class Server:
self._stop_process()
if self.tmpdir:
shutil.rmtree(self.tmpdir, ignore_errors=True)
if self.privilege and os.path.exists(self.tmpdir):
# S603: fixed argv (the privilege prefix is sudo -n or empty)
subprocess.run( # noqa: S603
[*self.privilege, "rm", "-rf", self.tmpdir], capture_output=True, check=False
)
def restart(self, kernel=True):
"""Restart an isolated instance in place: stop the process — the
@ -376,10 +388,15 @@ class Server:
return self
def _spawn_isolated(tmpdir, kernel):
def _spawn_isolated(tmpdir, kernel, host="127.0.0.1", vxlan=False, netns=None, privilege=()):
"""Start one isolated instance inside *tmpdir* (its config is written
there; a fresh free port each boot) and return ``(process, compute)``,
logged in. Shared by the first boot and by ``Server.restart``."""
logged in. Shared by the first boot and by ``Server.restart``.
With *netns* the instance is spawned inside that network namespace
(through *privilege*, e.g. ``sudo -n``) and binds *host* — the pattern
the cross-compute VXLAN scenario uses for its second "machine".
"""
ubridge = shutil.which("ubridge")
dynamips = shutil.which("dynamips")
if not ubridge:
@ -402,7 +419,15 @@ def _spawn_isolated(tmpdir, kernel):
fork_build = os.path.expanduser("~/myCode/GNS3/vpcs/src/vpcs")
vpcs = fork_build if os.path.isfile(fork_build) else (shutil.which("vpcs") or "vpcs")
config = ISOLATED_CONFIG.format(
port=port, ubridge=ubridge, dynamips=dynamips, images=images, tmp=tmpdir, kernel=kernel, vpcs=vpcs
port=port,
ubridge=ubridge,
dynamips=dynamips,
images=images,
tmp=tmpdir,
kernel=kernel,
vpcs=vpcs,
vxlan=vxlan,
host=host,
)
config_path = os.path.join(tmpdir, "gns3_server.conf")
with open(config_path, "w") as f:
@ -410,7 +435,15 @@ def _spawn_isolated(tmpdir, kernel):
log = open(os.path.join(tmpdir, "server.log"), "a")
# S603: fixed argv, this interpreter, no shell involvement
argv = [sys.executable, "-m", "gns3server", "--config", config_path]
argv = [
*privilege,
*(["ip", "netns", "exec", netns] if netns else []),
sys.executable,
"-m",
"gns3server",
"--config",
config_path,
]
if os.environ.get("GNS3_E2E_DEBUG"):
argv.append("-d") # debug logging — the uBridge command stream lands in server.log
process = subprocess.Popen( # noqa: S603
@ -420,13 +453,13 @@ def _spawn_isolated(tmpdir, kernel):
stderr=subprocess.STDOUT,
)
process.log = log # keep the file object alive with the process handle
compute = Compute(f"http://127.0.0.1:{port}/v3")
compute = Compute(f"http://{host}:{port}/v3")
deadline = time.time() + 60
while time.time() < deadline:
try:
# S310: the port is ours, the host loopback
with urllib.request.urlopen(f"http://127.0.0.1:{port}/v3/version", timeout=2):
# S310: the address is ours (loopback or the scenario's veth fabric)
with urllib.request.urlopen(f"http://{host}:{port}/v3/version", timeout=2):
break
except Exception:
if process.poll() is not None:
@ -446,13 +479,13 @@ def _spawn_isolated(tmpdir, kernel):
return process, compute
def _start_isolated(kernel):
def _start_isolated(kernel, vxlan=False):
tmpdir = tempfile.mkdtemp(prefix="gns3-e2e-")
process, compute = _spawn_isolated(tmpdir, kernel)
process, compute = _spawn_isolated(tmpdir, kernel, vxlan=vxlan)
return Server(compute, process, tmpdir)
def live_server(kernel=True):
def live_server(kernel=True, vxlan=False):
"""The server under test.
With ``GNS3_E2E_URL`` set, that server is used for kernel mode (it must
@ -475,7 +508,7 @@ def live_server(kernel=True):
).login()
server = Server(compute)
else:
server = _start_isolated(kernel)
server = _start_isolated(kernel, vxlan=vxlan)
if not wait_until(lambda: (server.compute.capabilities() or {}).get("version"), timeout=45):
raise AssertionError(
f"{server.compute.url}: the controller's local compute did not report capabilities within 45s"
@ -1505,3 +1538,211 @@ def pcap_icmp_rtt(path, ethertype):
deltas.append((ts - pending) * 1000)
pending = None
return sum(deltas) / len(deltas) if deltas else None
# ---------------------------------------------------------------------------
# Cross-compute fabric: a second "machine" for VXLAN links
# ---------------------------------------------------------------------------
# The /24 both ends of the veth "fabric" are addressed in. RFC 2544's
# benchmarking range: never routed on a real network, so it cannot collide
# with anything the host legitimately talks to.
FABRIC_SUBNET_PREFIX = "198.18.7"
def fabric_privilege():
"""The command prefix for network-namespace operations: nothing when the
suite runs as root, ``sudo -n`` when passwordless sudo is configured,
None otherwise (the caller skips with the explanation).
A second network stack — the thing a cross-compute VXLAN link needs on
a single machine — is a network namespace, and Linux confines both
creating one and entering one to CAP_SYS_ADMIN of its owning user
namespace. uBridge's file capabilities do not help here (they are caps
for netlink *operations*, not for joining a namespace), so either the
whole run is root or sudo carries the two calls.
"""
if os.geteuid() == 0:
return []
sudo = shutil.which("sudo")
# S603: resolved binary, fixed argv, no shell
if sudo and subprocess.run([sudo, "-n", "true"], capture_output=True, check=False).returncode == 0: # noqa: S603
return [sudo, "-n"]
return None
class CrossComputeFabric:
"""A second "machine" on one host: a network namespace joined to the
host by a veth pair, both ends addressed inside ``198.18.7.0/24``.
Two computes on one machine cannot tunnel to each other from the host
namespace: the kernel keeps one VXLAN socket per (namespace, dstport)
and both ends must register the same VNI on it — the pair collides by
design. Distinct network namespaces give the pair its two sockets, and
the veth pair is the L2 fabric the tunnels ride. uBridge's file
capabilities make the *devices* work inside the namespace; only the
namespace itself needs privilege (see ``fabric_privilege``).
"""
def __init__(self, netns, host_ifc, peer_ifc, host_ip, peer_ip, prefix):
self.netns = netns
self.host_ifc = host_ifc
self.peer_ifc = peer_ifc
self.host_ip = host_ip
self.peer_ip = peer_ip
self.prefix = prefix
def netns_run(self, *argv, **kwargs):
"""Run a command inside the namespace (privileged, like every netns
access)."""
kwargs.setdefault("capture_output", True)
kwargs.setdefault("text", True)
# S603: fixed argv (the caller builds the netns-side command)
return subprocess.run( # noqa: S603
[*self.prefix, "ip", "netns", "exec", self.netns, *argv], check=False, **kwargs
)
def iface_mtu(self, name):
"""The MTU of an interface inside the namespace (None when absent)."""
out = self.netns_run("ip", "-o", "link", "show", name).stdout
match = re.search(r"\bmtu (\d+)", out)
return int(match.group(1)) if match else None
def iface_exists(self, name):
return self.netns_run("ip", "link", "show", name).returncode == 0
def vxlan_show(self, name):
"""``ip -d link show`` details of an interface inside the namespace,
as one string (None when absent) — carries the ``vxlan id <vni>
... dstport <port>`` attributes."""
result = self.netns_run("ip", "-d", "link", "show", name)
return result.stdout if result.returncode == 0 and name in result.stdout else None
def bridge_members(self, bridge):
"""Interfaces enslaved to a bridge inside the namespace, or None
when the bridge does not exist."""
result = self.netns_run("ls", f"/sys/class/net/{bridge}/brif")
if result.returncode != 0:
return None
return sorted(result.stdout.split())
def brport_state(self, name):
"""An interface's bridge-port STP state inside the namespace (None
when it is not enslaved; the kernel reports 3 for forwarding)."""
result = self.netns_run("cat", f"/sys/class/net/{name}/brport/state")
if result.returncode != 0:
return None
return result.stdout.strip() or None
def teardown(self):
"""Delete the namespace (all its devices go with it) and any host
end a half-created pair left behind."""
# S603: fixed argv, resolved ip binary, no shell
subprocess.run( # noqa: S603
[*self.prefix, "ip", "netns", "del", self.netns], capture_output=True, check=False
)
subprocess.run( # noqa: S603
[*self.prefix, "ip", "link", "del", self.host_ifc], capture_output=True, check=False
)
def cross_compute_fabric():
"""Create the fabric, or skip the calling test when this host cannot.
The names carry a random suffix so concurrent runs (and leftovers of a
crashed one) cannot collide; the caller must call ``teardown()`` in a
finally."""
prefix = fabric_privilege()
if prefix is None:
pytest.skip(
"cross-compute VXLAN needs a second network namespace: run the suite as root, e.g. "
"`sudo env GNS3_E2E_IMAGES=$HOME/GNS3/images pytest -m e2e "
"tests/e2e/test_vxlan_cross_compute.py -s`, or configure passwordless sudo"
)
suffix = uuid.uuid4().hex[:6]
fabric = CrossComputeFabric(
netns=f"gns3vx{suffix}",
host_ifc=f"vxh{suffix}",
peer_ifc=f"vxp{suffix}",
host_ip=f"{FABRIC_SUBNET_PREFIX}.1",
peer_ip=f"{FABRIC_SUBNET_PREFIX}.2",
prefix=prefix,
)
try:
# S603: fixed argv, resolved ip binary, no shell
subprocess.run( # noqa: S603
[*prefix, "ip", "netns", "add", fabric.netns], check=True, capture_output=True
)
subprocess.run( # noqa: S603
[*prefix, "ip", "link", "add", fabric.host_ifc, "type", "veth", "peer", "name", fabric.peer_ifc],
check=True,
capture_output=True,
)
subprocess.run( # noqa: S603
[*prefix, "ip", "link", "set", fabric.peer_ifc, "netns", fabric.netns], check=True, capture_output=True
)
subprocess.run( # noqa: S603
[*prefix, "ip", "addr", "add", f"{fabric.host_ip}/24", "dev", fabric.host_ifc],
check=True,
capture_output=True,
)
subprocess.run( # noqa: S603
[*prefix, "ip", "link", "set", fabric.host_ifc, "up"], check=True, capture_output=True
)
for argv in (
("ip", "addr", "add", f"{fabric.peer_ip}/24", "dev", fabric.peer_ifc),
("ip", "link", "set", fabric.peer_ifc, "up"),
("ip", "link", "set", "lo", "up"),
):
fabric.netns_run(*argv, check=True)
except subprocess.CalledProcessError:
fabric.teardown()
raise
return fabric
def start_isolated_peer(fabric, kernel=True):
"""An isolated instance on the other side of the fabric: spawned inside
the namespace and bound to its address, so the first server can register
it as a remote compute whose network stack is the second "machine"."""
tmpdir = tempfile.mkdtemp(prefix="gns3-e2e-peer-")
process, compute = _spawn_isolated(tmpdir, kernel, host=fabric.peer_ip, netns=fabric.netns, privilege=fabric.prefix)
return Server(compute, process, tmpdir, privilege=fabric.prefix)
def register_remote_compute(server, peer, name="vxlan-peer"):
"""Register the peer's server on the first server's controller, so links
between nodes on the two computes are cross-compute links. Waits until
the controller connected it (capabilities reported — the vxlan probe in
particular: the controller gates tunnel eligibility on it)."""
compute = server.compute.call(
"POST",
"/computes",
{
"name": name,
"protocol": "http",
"host": peer.compute.url.split("://", 1)[1].split(":", 1)[0],
"port": int(peer.compute.url.rsplit(":", 1)[1].split("/", 1)[0]),
"user": peer.compute.username,
"password": peer.compute.password,
},
)
compute_id = compute["compute_id"]
if not wait_until(lambda: (server.compute.call("GET", f"/computes/{compute_id}") or {}).get("version"), timeout=60):
raise AssertionError(f"controller did not connect the remote compute {compute_id} within 60s")
if not wait_until(
lambda: (
((server.compute.call("GET", f"/computes/{compute_id}") or {}).get("capabilities") or {}).get(
"ubridge_vxlan"
)
is True
),
timeout=60,
):
raise AssertionError(f"remote compute {compute_id} never reported ubridge_vxlan (its netns probe failed)")
return compute_id

View File

@ -0,0 +1,305 @@
#
# Copyright (C) 2026 GNS3 Technologies Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
"""
Live end-to-end test for cross-compute VXLAN links (pytest marker ``e2e``):
two computes on one machine — the harness's isolated instance on the host and
a second isolated instance inside a network namespace joined to the host by a
veth pair (``harness.cross_compute_fabric``) — with one real Alpine container
per compute, linked across the tunnel.
Two computes on one machine cannot tunnel from the host namespace: the kernel
keeps one VXLAN socket per (namespace, dstport), and both ends of a link must
register the same VNI on it, so the pair collides by design (the controller
falls back to the relay for same-host pairs). Separate network namespaces
give the pair its two sockets, and the veth pair is the L2 fabric the tunnels
ride — the closest a single machine gets to two hosts. The same-host
fallback itself is asserted by the controller unit tests; this scenario is
the real-kernel proof of the tunnel.
Needs root: a network namespace is privileged to create and to enter, and the
second compute's node files (its project directories) are written by the
test. Run it as::
sudo env GNS3_E2E_IMAGES=$HOME/GNS3/images pytest -m e2e \\
tests/e2e/test_vxlan_cross_compute.py -s
What it asserts:
* both ends report the same VNI on the shared dstport, each pointing at the
other machine's address, and each per-link bridge enslaves exactly
``[anchor, tunnel]``;
* the tunnel device's MTU is the underlay MTU minus 50 (the kernel derives
it from the lower device the peer route resolves to), the bridges inherit
it, and a frame past it is dropped at the bridge egress while one at it
crosses — the reason the datapath is opt-in on non-jumbo fabrics;
* real dual-stack ICMP crosses, a ``delay 100`` filter shapes it (one end
per direction), link delete leaves no device or bridge on either machine;
* a stale tunnel device squatting on the link's deterministic name is
replaced by the attach path, and the tunnel recovers;
* a device squatting the link's VNI at node start self-heals: the start
re-wires the link on a fresh VNI — the peer re-wired too — and succeeds.
"""
import os
import re
import subprocess
import time
import pytest
from gns3server.utils.vxlan import VXLAN_VNI_MAX, VXLAN_VNI_MIN, vxlan_device_name
from tests.e2e import harness
pytestmark = pytest.mark.e2e
# every standard Docker adapter has a single port
ETH = (0, 0)
G1_IP = "10.66.1.1"
G2_IP = "10.66.1.2"
# the dual-stack half: a ULA mirroring the v4 addressing
G1_IP6 = "fd00:66:1::1"
G2_IP6 = "fd00:66:1::2"
# ICMP payloads against the derived tunnel MTU (underlay 1500 -> tunnel
# 1450): 1400 + 42 bytes of headers is a 1442-byte frame, under the bridge
# egress gate; 1500 + 42 is a 1542-byte frame, over it — and over the
# guest's own 1500 MTU too, so the IP stack may fragment it; either way the
# pieces cannot cross the 1450-wide egress and the ping must fail silently.
FIT_PAYLOAD = 1400
TOO_BIG_PAYLOAD = 1500
def _ip(*argv):
"""Run an iproute2 command on the host (the scenario runs as root)."""
ip = harness.IP
assert ip, "ip binary not found"
# S603: resolved binary, fixed argv from the test itself
return subprocess.run([ip, *argv], capture_output=True, text=True, check=True) # noqa: S603
def _host_vxlan_attrs(name):
"""(vni, dstport, remote) of a host-side tunnel device, from
``ip -d link show``."""
details = _ip("-d", "link", "show", name).stdout
vni = re.search(r"\bvxlan id (\d+)", details)
dstport = re.search(r"\bdstport (\d+)", details)
remote = re.search(r"\bremote (\S+)", details)
assert vni and dstport and remote, details
return int(vni.group(1)), int(dstport.group(1)), remote.group(1)
def _peer_vxlan_attrs(fabric, name):
details = fabric.vxlan_show(name)
assert details, f"tunnel device {name} missing inside {fabric.netns}"
vni = re.search(r"\bvxlan id (\d+)", details)
dstport = re.search(r"\bdstport (\d+)", details)
remote = re.search(r"\bremote (\S+)", details)
assert vni and dstport and remote, details
return int(vni.group(1)), int(dstport.group(1)), remote.group(1)
def _container_id(daemon, node):
container_id = daemon.container_id(f"GNS3.{node['name']}.{node['project_id']}")
assert container_id, f"container for {node['name']} not found on the Docker daemon"
node["container_id"] = container_id
return container_id
def _start_pair(compute, pid, daemon, n1, n2):
"""Start both containers and wait for their userspace to be reachable:
the v4 address from the interfaces file (init.sh), the v6 twin from the
harness (the daemon's disable_ipv6 on bridge networks makes the
interfaces-file route fail). The container ids are re-resolved after the
starts: a project reopen can replace a stale container with a fresh one
under the same deterministic name (a new id)."""
for node in (n1, n2):
compute.call("POST", f"/projects/{pid}/nodes/{node['node_id']}/start")
_container_id(daemon, node)
for node, address in ((n1, G1_IP), (n2, G2_IP)):
harness.docker_wait_address(daemon, node["container_id"], address)
for node, address6 in ((n1, G1_IP6), (n2, G2_IP6)):
harness.docker_bring_up_ipv6(daemon, node["container_id"], address6)
def test_vxlan_cross_compute_link():
if os.geteuid() != 0:
pytest.skip(
"cross-compute VXLAN needs a second network stack (a netns) and writes the second "
"compute's node files: run as root, e.g. `sudo env GNS3_E2E_IMAGES=$HOME/GNS3/images "
"pytest -m e2e tests/e2e/test_vxlan_cross_compute.py -s`"
)
fabric = harness.cross_compute_fabric()
server = harness.live_server(kernel=True, vxlan=True)
peer = harness.start_isolated_peer(fabric)
compute = server.compute
daemon = harness.DockerDaemon()
failed = True
pid = None
try:
peer_id = harness.register_remote_compute(server, peer)
image = harness.ensure_docker_image(server)
project = compute.create_project("vxlan-e2e")
pid = project["project_id"]
print(".. creating one container per compute")
n1 = compute.create_docker_node(pid, "VXE1", image)
harness.configure_docker_interfaces(n1, G1_IP)
_container_id(daemon, n1)
n2 = compute.create_docker_node(pid, "VXE2", image, compute_id=peer_id)
harness.configure_docker_interfaces(n2, G2_IP)
_container_id(daemon, n2)
assert n1["compute_id"] == "local", n1["compute_id"]
assert n2["compute_id"] == peer_id, n2["compute_id"]
print(".. linking them across the computes")
link = compute.create_link(pid, (n1["node_id"], *ETH), (n2["node_id"], *ETH))
lid = link["link_id"]
assert link["kernel_datapath"] is True, link
bridge = harness.link_bridge_name(lid)
a1 = harness.docker_anchor_name(n1["node_id"], *ETH)
a2 = harness.docker_anchor_name(n2["node_id"], *ETH)
vx1 = vxlan_device_name(lid, n1["node_id"])
vx2 = vxlan_device_name(lid, n2["node_id"])
assert not harness.tap_exists(vx1), "the tunnel lands with node start"
print(".. starting the containers (the wiring lands with node start)")
_start_pair(compute, pid, daemon, n1, n2)
print(".. asserting the tunnel on both machines")
assert harness.tap_exists(vx1), f"tunnel device {vx1} missing on the host"
assert harness.bridge_members(bridge) == sorted([a1, vx1]), harness.bridge_members(bridge)
assert fabric.bridge_members(bridge) == sorted([a2, vx2]), fabric.bridge_members(bridge)
vni1, port1, remote1 = _host_vxlan_attrs(vx1)
vni2, port2, remote2 = _peer_vxlan_attrs(fabric, vx2)
assert vni1 == vni2, (vni1, vni2)
assert VXLAN_VNI_MIN <= vni1 <= VXLAN_VNI_MAX, vni1
assert port1 == port2, (port1, port2)
assert remote1 == fabric.peer_ip, (remote1, fabric.peer_ip)
assert remote2 == fabric.host_ip, (remote2, fabric.host_ip)
# MTU: the kernel derives the tunnel device's MTU from the lower
# device the peer route resolves to (underlay - 50 for the outer
# headers), and the per-link bridge — no MTU of its own — reports
# the minimum of its ports, i.e. the honest "what this fabric can
# carry".
underlay_mtu = int(harness.sysfs(f"/sys/class/net/{fabric.host_ifc}/mtu"))
assert underlay_mtu == 1500, underlay_mtu # the veth default; the derived MTU follows from it
assert int(harness.sysfs(f"/sys/class/net/{vx1}/mtu")) == underlay_mtu - 50
assert int(harness.sysfs(f"/sys/class/net/{bridge}/mtu")) == underlay_mtu - 50
assert fabric.iface_mtu(vx2) == underlay_mtu - 50
assert fabric.iface_mtu(bridge) == underlay_mtu - 50
assert fabric.iface_mtu(fabric.peer_ifc) == underlay_mtu
# The tunnel device is an L2 anchor like any other: hardened
# (lenient — the shared with plain `ip` in the doc's example) and
# FORWARDING on both bridges.
if harness.l2only_supported():
harness.assert_pure_l2(vx1)
harness.assert_forwarding(vx1)
assert fabric.brport_state(vx2) == "3", fabric.brport_state(vx2)
print(".. pinging across the tunnel")
ping = harness.docker_wait_ping(daemon, n1["container_id"], G2_IP)
assert ping["loss"] == 0, ping["raw"]
assert ping["avg"] is not None and ping["avg"] < 50, ping
ping6 = harness.docker_wait_ping(daemon, n1["container_id"], G2_IP6)
assert ping6["loss"] == 0, ping6["raw"]
# The derived MTU is the hard limit: a frame at it crosses, one past
# it is dropped at the bridge egress — silently, which is why the
# deployment has to size the underlay for the frames its guests send.
fit = harness.docker_ping(daemon, n1["container_id"], G2_IP, size=FIT_PAYLOAD)
assert fit["loss"] == 0, fit["raw"]
too_big = harness.docker_ping(daemon, n1["container_id"], G2_IP, count=2, size=TOO_BIG_PAYLOAD)
assert too_big["loss"] > 0 or too_big["exit"] != 0, too_big["raw"]
print(".. delay 100 shapes the tunnel on both ends (one direction each)")
compute.call("PUT", f"/projects/{pid}/links/{lid}", {"filters": {"delay": [100]}})
time.sleep(1)
delayed = harness.docker_ping(daemon, n1["container_id"], G2_IP, count=5, interval=None, timeout=2)
assert delayed["loss"] == 0, delayed["raw"]
assert 150 <= (delayed["avg"] or 0) <= 450, delayed
compute.call("PUT", f"/projects/{pid}/links/{lid}", {"filters": {}})
print(".. a stale device on the link's name is replaced on node restart")
compute.call("POST", f"/projects/{pid}/nodes/{n1['node_id']}/stop")
_ip("link", "del", vx1)
# A stale tunnel: same deterministic name, some other VNI/port —
# what a crashed run or a hand-made device would leave behind.
_ip("link", "add", vx1, "type", "vxlan", "id", "4242", "dstport", "47999", "remote", "127.0.0.1")
compute.call("POST", f"/projects/{pid}/nodes/{n1['node_id']}/start")
harness.docker_wait_address(daemon, n1["container_id"], G1_IP)
harness.docker_bring_up_ipv6(daemon, n1["container_id"], G1_IP6)
stale_vni, stale_port, stale_remote = _host_vxlan_attrs(vx1)
assert (stale_vni, stale_port, stale_remote) == (vni1, port1, remote1), (stale_vni, stale_port, stale_remote)
assert harness.bridge_members(bridge) == sorted([a1, vx1]), harness.bridge_members(bridge)
assert int(harness.sysfs(f"/sys/class/net/{bridge}/mtu")) == underlay_mtu - 50
assert harness.docker_wait_ping(daemon, n1["container_id"], G2_IP, attempts=5)["loss"] == 0
print(".. a VNI squatted at node start self-heals on a fresh VNI")
compute.call("POST", f"/projects/{pid}/nodes/{n1['node_id']}/stop")
# A device holding the link's exact VNI on the shared dstport socket
# — what a colliding link (or an operator) would have registered.
# The node's start replays the stored NIO, the kernel refuses the
# VNI, and the controller must re-wire the link on a fresh one and
# retry the start instead of failing it.
_ip("link", "add", "gvxsquat", "type", "vxlan", "id", str(vni1), "dstport", str(port1), "remote", "127.0.0.1")
try:
compute.call("POST", f"/projects/{pid}/nodes/{n1['node_id']}/start")
harness.docker_wait_address(daemon, n1["container_id"], G1_IP)
harness.docker_bring_up_ipv6(daemon, n1["container_id"], G1_IP6)
healed_vni, healed_port, healed_remote = _host_vxlan_attrs(vx1)
assert healed_vni != vni1, (healed_vni, vni1)
assert VXLAN_VNI_MIN <= healed_vni <= VXLAN_VNI_MAX, healed_vni
assert healed_port == port1, (healed_port, port1)
assert healed_remote == remote1, (healed_remote, remote1)
# the peer was re-wired to the fresh VNI too — the pair must agree
peer_vni, _, _ = _peer_vxlan_attrs(fabric, vx2)
assert peer_vni == healed_vni, (peer_vni, healed_vni)
assert harness.docker_wait_ping(daemon, n1["container_id"], G2_IP, attempts=5)["loss"] == 0
finally:
_ip("link", "del", "gvxsquat")
print(".. deleting the link leaves no tunnel or bridge behind on either machine")
compute.call("DELETE", f"/projects/{pid}/links/{lid}")
assert not harness.tap_exists(vx1)
assert not harness.tap_exists(bridge)
assert not fabric.iface_exists(vx2), f"tunnel device {vx2} survived on the peer"
assert fabric.bridge_members(bridge) is None
print(".. closing and reopening the project rebuilds the tunnel through the batch path")
compute.call("POST", f"/projects/{pid}/close")
compute.call("POST", f"/projects/{pid}/open")
_start_pair(compute, pid, daemon, n1, n2)
assert harness.tap_exists(vx1), f"tunnel device {vx1} not rebuilt on reopen"
assert fabric.iface_exists(vx2), f"tunnel device {vx2} not rebuilt on reopen"
assert harness.docker_wait_ping(daemon, n1["container_id"], G2_IP, attempts=5)["loss"] == 0
failed = False
finally:
keep = failed and harness.keep_on_failure()
if not keep:
peer.stop()
if pid is not None:
harness.release(server, pid, failed=failed)
else:
server.stop()
if keep:
print(f"\n!! kept the fabric {fabric.netns} (and its peer compute) for inspection")
else:
fabric.teardown()

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#
# Copyright (C) 2026 GNS3 Technologies Inc.
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#
"""
Cross-compute VXLAN link identity: the derived VNI and device name.
"""
import uuid
from gns3server.utils.vxlan import VXLAN_NAME_PREFIX, VXLAN_VNI_MAX, VXLAN_VNI_MIN, derive_vni, vxlan_device_name
def test_derive_vni_is_deterministic_and_bounded():
link_id = str(uuid.uuid4())
vni = derive_vni(link_id)
assert derive_vni(link_id) == vni
assert VXLAN_VNI_MIN <= vni <= VXLAN_VNI_MAX
def test_derive_vni_salt_moves_the_value():
link_id = str(uuid.uuid4())
values = {derive_vni(link_id, salt) for salt in range(16)}
# Every salt lands in range; a bumped salt is a fresh point of the space
# (a collision here would defeat the retry, and 16 draws out of ~16.8M
# values collapsing is a hash failure, not bad luck).
assert all(VXLAN_VNI_MIN <= v <= VXLAN_VNI_MAX for v in values)
assert len(values) == 16
def test_derive_vni_avoids_low_well_known_vnis():
# Flannel starts at 1, Docker overlay networks at 256: derived links
# must never land in the low range whatever the link id.
for _ in range(200):
assert derive_vni(str(uuid.uuid4()), uuid.uuid4().int) >= VXLAN_VNI_MIN
def test_vxlan_device_name_deterministic_and_within_ifnamsiz():
link_id = str(uuid.uuid4())
node_id = str(uuid.uuid4())
name = vxlan_device_name(link_id, node_id)
assert name == vxlan_device_name(link_id, node_id)
assert name.startswith(VXLAN_NAME_PREFIX)
# IFNAMSIZ (16) includes the NUL terminator: the kernel accepts 15 chars.
assert len(name) <= 15
def test_vxlan_device_name_unique_per_endpoint_and_link():
link1 = str(uuid.uuid4())
link2 = str(uuid.uuid4())
node1 = str(uuid.uuid4())
node2 = str(uuid.uuid4())
names = {
vxlan_device_name(link1, node1),
vxlan_device_name(link1, node2),
vxlan_device_name(link2, node1),
}
assert len(names) == 3