The L2-anchor spec's behavioral guarantee — an idle link stays silent for
5 s once the enslavement burst settles — only ran in the Dynamips and
Docker suites. It now also runs in QEMU, IOU, the IOL container, the
switch fast path and the switch cascade, which covers every host-device
creation path:
* tap create (Dynamips/QEMU/IOU anchors), docker create_veth (Docker host
ends; the cascade's race-loser end is hardened after create by the
server), bridge add_nio_tap (the IOL container anchor, the fifth
creator), and the brctl switch bridges, whose multicast snooping is off
precisely so the bridge role can reach silence;
* each scenario silences its guests first (IOS interfaces shut through
the console; Docker guests' links down) and re-verifies the ping after;
* the cascade measures 8 devices at once (four absorbed router anchors,
both cascade ends, both switch bridges).
IOL 158 s, cascade 293 s, ESW fast path 378 s, QEMU 428 s, IOU 308 s —
all green.
The filter matrix (cls_bpf, the eBPF classifier) only ran on Docker veth
host ends; the IOU and IOL-container scenarios now spot-check it on their
TAP anchors and prove a filter survives a node restart:
* bpf "icmp" drops everything with clsact on the anchor, both ends, and
clears back to an empty qdisc;
* frequency_drop 3 (the eBPF every-nth mode) measured 56 % round-trip
loss (1 - (2/3)^2 = 55.6 % expected) in both scenarios;
* the IOU test applies delay 100 before a router stop/start: the fresh
anchor gets netem back (tc level) and the restarted router's pings
measure RTT >= 150 ms until the filter is cleared (a re-attach that
dropped the filter would show ~100 ms).
IOU file 492 s, IOL file 182 s, both green.
The spec's gns3-server alignment section promised three assertions the
suites never carried; they land in harness.py and run in every kernel
scenario (plus the relay controls' anchor checks):
- E.1 assert_pure_l2: anchors and bridges carry no L3 identity (addrgenmode
none, no address in /proc/net/if_inet6, no ip -o -4 addr) -- the kernel
scenarios' anchors and per-link/switch bridges, relay-mode anchors and
the switch's relay TAPs alike (hardening is a creation-time property,
not a datapath one);
- E.2 assert_idle_silence (Dynamips suite): guest interfaces shut to
silence IOS's own CDP/keepalives, settle 2.5 s, then a 5 s window of
zero traffic over both anchors and the per-link bridge;
- assert_forwarding: every attached port reports brport/state == 3 -- a
bridge left DOWN keeps its ports disabled and forwards nothing, with no
error anywhere; the assertion is the only signal.
harness.l2only_supported() probes a throwaway uBridge once (link l2only
against a nonexistent device: 208 = command present, 202-Unknown command
= old build); without the command the assertions skip -- the spec's
degradation contract, mirroring the tc-capability skip.
The first live run caught a fifth-creator gap: the switch's relay port
TAPs (minted implicitly by bridge add_nio_tap) carried a live fe80::.
Delivered uBridge-side per the spec (fb72758: the transient TAP is
hardened at creation, attaches untouched); the server needed no change,
and the relay-control E.1 check is that creator's end-to-end coverage.
Two real iol-xe containers (Cisco CML iol-runner images, real IOS-XE on
the telnet console) against an isolated instance, the real uBridge with
the swappable bridge TAP leg:
* kernel link reports kernel_datapath; anchors exist from node start
and the per-link bridge enslaves exactly the two of them;
* real ICMP crosses the [unix <-> tap] port-bridge relay; delay 100
lands as netem on both anchors with the measured RTT growing >= 150 ms
and returning < 50 ms when cleared;
* suspend admin-downs the anchor and kills the traffic; resume
restores; AF_PACKET capture writes a real pcap;
* link delete/re-create swaps the port leg out and back in with the
ping returning; node stop leaves no gx devices and a start recreates
the whole wiring from the NIO; project delete cleans everything;
* the relay control on a relay-configured instance keeps the link off
the kernel and still pings (anchors may exist idle — the same
semantics as QEMU's and Dynamips' anchors: the server flag decides
attachment, not anchor birth).
Harness: create_iol_router (the appliance's template properties),
docker_images, iol_anchor_name, stage_iol_base_config (the shipped
iol-xe-base.txt copied into the isolated instance's configs dir — the
GNS3_IOL_STARTUP_CONFIG lookup path), boot_wait(straight_prompt=True)
for images that boot from NVRAM straight into the CLI with no 'Press
RETURN' sentinel, and GNS3_E2E_DEBUG=1 to run the isolated instance
with debug logging (the uBridge command stream lands in server.log —
how the ensure-anchor EBUSY was pinned down).
