A VPCS node's single adapter anchors on a persistent TAP the server
creates (tap create + set_owner via uBridge) and the vpcs process
attaches to by name: -e -d <gp{id8}e0p0> -n, the same
server-creates/guest-attaches shape as QEMU's netdev. -n (a vpcs fork
feature) keeps the guest's ip command from ifconfig'ing the anchor on
the host; the vpcs build is probed once per binary identity
(vpcs_tap capability, usage scan) and gates kernel links together
with ubridge_tap — anything else keeps the node on the relay (the
legacy local UDP tunnel on a stock binary, an AF_PACKET endpoint on
the anchor with a capable one).
VPCSVM takes KernelDatapathMixin: _connect_nio dispatches kernel
(enslave into the per-link bridge) / relay-on-anchor / legacy,
captures pick capture start_kernel vs the bridge engine, stop runs
under an execute lock and terminates the process before deleting the
anchor TAPs (a held device refuses deletion), and the duplicate-port
guard backstops the controller's. The NIO routes accept nio_bridge
and write suspend back on update.
_delete_anchor_taps verifies each tap is gone from sysfs and retries
a bounded three times: a holder can release its fd a moment after its
process was reaped (vpcs's daemon parent kills its console child and
exits first), so the unconditional delete raced EBUSY and leaked the
anchor intermittently.
The vpcs side needs IFNAMSIZ (16) instead of its own IFNAMESIZ (12)
for the -d name buffer — anchor names are 14 chars and truncated to a
nonexistent device, which TUNSETIFF then tries to create without
CAP_NET_ADMIN (fixed in the vpcs fork).
e2e (tests/e2e/test_vpcs_kernel_datapath.py): kernel and relay
scenarios green against the real binary — real ICMP both ways, §E.1/§
E.2 on the anchors, delay/suspend/capture, link delete/re-create,
node stop/restart self-heal, zero leftovers; the relay control passes
with both the fork binary and a stock one.
Every node lifecycle call (start/stop) emitted a "starting"/"stopping"
node.updated notification on entry, and for the whole duration of the
call asdict() masked the real status with the transitional one — every
compute event forwarded in that window was re-emitted as a duplicate
transitional status.
Stop-all/start-all on a 13-node project pushed two transitional events
per node before the final state. Clients that do not render these
transitional statuses (the Web UI) showed nodes flickering through an
unexpected suspended-looking state before reaching started/stopped.
Remove the transitional notification and the status masking: clients
see the real statuses again (started/stopped), from the forwarded
compute events plus the controller-side confirmation. The wait option
on the lifecycle routes, the strict stop error handling and
wait_for_status() are unchanged.
The templated drawing_create_text/_rectangle/_ellipse tools cover the
LLM-relevant creation paths, and line/image/curve creation is not
needed from MCP or copilot for now. The management tools stay, so
existing drawings (including images and lines created in the Web UI)
remain fully manageable; drawing_update's raw svg parameter remains
the escape hatch for edits.
The text drawing tool was MCP-only; the copilot needs the same
capability and its area-annotation helper carried the same Web UI
compat bugs. Split into three layers with a single implementation:
- gns3server/utils/drawings.py: pure SVG builders (text, rectangle,
ellipse) with full input validation (ValueError) — the Web UI
format knowledge lives in core utils next to picture.py
- api_handlers.py: shared REST handlers (create_text_drawing_handler
moved here, create_rectangle/ellipse_drawing_handler added) — the
layer both consumers already share
- thin shells: MCP tools (drawing_create_text unchanged, plus new
drawing_create_rectangle/_ellipse) and three LangChain tools
(tools_v2/gns3_create_drawing.py) registered in both copilot mode
lists
Shape builder details:
- rectangle: solid fill or "none", stroke block emitted only when a
stroke is given, rx corner radius, dasharray validated against the
Web UI's Qt remap table (QtDasharrayFixer rewrites those patterns)
- ellipse: bounding-box API; cx/cy derived as offsets inside the
drawing box (the Web UI treats them as box-relative, not canvas
coordinates); odd sizes round down and the actual size is returned
gns3_drawing_utils now delegates to the shared builders, fixing the
px-blind sizing, the ignored text-anchor/x/y centering and the
missing XML escaping in the area-annotation path.
The Web UI re-parses drawing SVG into its own element model instead of
rendering it raw, which makes hand-assembled SVG error-prone for LLM
callers. The new tool assembles the SVG server-side, mirroring what the
Web UI itself serializes for text drawings:
- XML-escaped text content, validated color (#RGB/#RGBA/#RRGGBB/
#RRGGBBAA) and font family (attribute-safe charset)
- multi-line support: literal newlines render as stacked lines in the
Web UI (tspan split), width/height computed from the longest line
- pt-aware sizing: the Web UI renders font-size in pt (1pt = 4/3 px),
so width uses a 0.8/char factor for monospace (1.0 proportional) and
line height 1.9 x font_size, instead of the px-based 0.62 estimate
- ET.fromstring pre-check so bad input fails loudly instead of hitting
the controller's silent drop of unparseable 500+ char SVG
- computed width/height/line_height returned for label layout
Also correct the raw drawing_create docstring: root width/height are
required (the parser reads them for the selection box), x/y on rect are
ignored, <g> is unsupported, <path> is re-interpreted as a freehand
curve, and the old examples lacked the mandatory root dimensions.
Resolve conflicts against the upstream wave (PRs #2952-#2965, incl. the
typed-response/schema hardening and the drop of Python 3.10):
- controller/node.py: keep upstream's _transitioning/_confirm_status
lifecycle guard; the kernel-anchor link wiring (node_started) runs
after the transition completes.
- controller/link.py: keep upstream's add_node rollback (release_ports
on create failure) and delete via release_ports; release_ports now
resolves ports live (same staleness reason as _bind_members) and
discards the node link unconditionally.
- schemas/controller/links.py: extend LinkFilterType with the eight
kernel-datapath filter types and LinkFilterParameter.type with "str"
so the newly typed /available_filters response validates; Link.filters
stays a free-form dict — the vocabulary is capability-gated per link
and validated by the controller (409), not by a strict request schema.
- schemas/controller/topology.py: drop the type: ignore made redundant
by the dict filters field.
- tests: route-level filter validation now expects the controller's 409
(unknown types, out-of-range values); packet_loss correlation is a
valid kernel parameter (positive test added); OpenAPI assertions match
the free-form filters property.
The kernel's correlated-random generator (get_crandom, sch_netem.c) truncates
instead of wrapping, starving both edges of the stationary distribution: an
event threshold below the correlation value is almost never reached. Measured
with stock iproute2 on this kernel — uBridge's netlink encoding is identical:
loss 1% + correl 25% drops nothing over 2000 pings (expected ~2%), 10%/25%
measures ~1.8% one way, only the 50% symmetry point survives. duplicate and
reorder correl share the same comparison structure and collapse the same way;
gemodel is immune (Markov chain over plain uniform draws) and is the honest
tool for bursty loss at a chosen mean rate.
Documented in the packet-filters correlation-bias bullet, and surfaced in the
two machine-facing descriptions (MCP link_update packet_loss note, controller
filter schema) so agents and clients stop walking into the trap.
YueGuobin
grossmj
Guobin Yue
Mark Paronyan