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21b866aeed
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.
72 lines
2.5 KiB
Python
72 lines
2.5 KiB
Python
#
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# Copyright (C) 2026 GNS3 Technologies Inc.
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#
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# This program is free software: you can redistribute it and/or modify
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# it under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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# GNU General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see <http://www.gnu.org/licenses/>.
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#
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"""
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Cross-compute VXLAN link identity: the derived VNI and device name.
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"""
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import uuid
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from gns3server.utils.vxlan import VXLAN_NAME_PREFIX, VXLAN_VNI_MAX, VXLAN_VNI_MIN, derive_vni, vxlan_device_name
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def test_derive_vni_is_deterministic_and_bounded():
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link_id = str(uuid.uuid4())
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vni = derive_vni(link_id)
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assert derive_vni(link_id) == vni
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assert VXLAN_VNI_MIN <= vni <= VXLAN_VNI_MAX
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def test_derive_vni_salt_moves_the_value():
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link_id = str(uuid.uuid4())
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values = {derive_vni(link_id, salt) for salt in range(16)}
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# Every salt lands in range; a bumped salt is a fresh point of the space
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# (a collision here would defeat the retry, and 16 draws out of ~16.8M
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# values collapsing is a hash failure, not bad luck).
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assert all(VXLAN_VNI_MIN <= v <= VXLAN_VNI_MAX for v in values)
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assert len(values) == 16
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def test_derive_vni_avoids_low_well_known_vnis():
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# Flannel starts at 1, Docker overlay networks at 256: derived links
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# must never land in the low range whatever the link id.
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for _ in range(200):
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assert derive_vni(str(uuid.uuid4()), uuid.uuid4().int) >= VXLAN_VNI_MIN
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def test_vxlan_device_name_deterministic_and_within_ifnamsiz():
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link_id = str(uuid.uuid4())
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node_id = str(uuid.uuid4())
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name = vxlan_device_name(link_id, node_id)
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assert name == vxlan_device_name(link_id, node_id)
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assert name.startswith(VXLAN_NAME_PREFIX)
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# IFNAMSIZ (16) includes the NUL terminator: the kernel accepts 15 chars.
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assert len(name) <= 15
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def test_vxlan_device_name_unique_per_endpoint_and_link():
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link1 = str(uuid.uuid4())
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link2 = str(uuid.uuid4())
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node1 = str(uuid.uuid4())
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node2 = str(uuid.uuid4())
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names = {
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vxlan_device_name(link1, node1),
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vxlan_device_name(link1, node2),
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vxlan_device_name(link2, node1),
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}
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assert len(names) == 3
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