93fed7826b
Some checks failed
Full run green: baseline (one AC session, held by the VIP holder), clean
failover (pppoe0 moves in 26s, old master releases), 10 gig down (route falls to
pppoe0 and the LAN is back online in 5s), lease expiry (the guard hangs up), and
a missing peers file (NRestarts=0, no loop). Evidence in
labsim/wan-failover-evidence/.
The 10 gig test found a genuine bug in vrrp-wan-health, not in the sim. GRACE
was measured from PROMOTION, so an established master had no grace at all --
after hours of uptime `now - since` far exceeds any window. The first moment
bond0.53 went down while pppoe0 was mid-redial, the master failed its own check,
shed every VIP, and the peer inherited the same WAN outage and did the same. A
brief WAN blip would have flapped the production pair. The stamp is now
refreshed on every healthy tick, so grace measures time since the box last
demonstrably HAD a WAN -- survivable wherever the gap happens, not only just
after a promotion.
Three harness bugs, all the same shape, all of which produced a confident wrong
answer before being caught:
- waiting for "exactly one pppoe0 holder" returns INSTANTLY during a handover,
because it was already true. The useful question is who holds it.
- judging connectivity on a single ping 20s after a link drop reported an
outage that had already healed. Poll, do not sample.
- `-o PreferredAuthentications=password` suits the routers but not the Alpine
LAN VMs, whose sshd offers keyboard-interactive: ssh exited 255 before
running anything and the test read that as "the LAN lost the internet". A
tcpdump on the router showed the pings leaving pppoe0 NATed to
198.51.100.117 and the replies coming back the whole time. An exit code that
can mean "the network is broken" or "I could not log in" is not a
connectivity test, so the check now asserts on what the guest reported.
That last one is why the harness asks the routers and the access concentrator
rather than a client, and why it refuses to run at all while either router still
has a default route via eth2 -- the libvirt-NAT scaffold answers connectivity
checks the WAN under test would have failed.
Still to run: hard failover (destroy the master), and the session-control
replace/deny/disable axis that brackets Vodafone's unknown behaviour and sets
the final GRACE. Nothing applied to production.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH
142 lines
7.3 KiB
Bash
Executable File
142 lines
7.3 KiB
Bash
Executable File
#!/bin/sh
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# VRRP health check: may THIS router hold the floating IPs?
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#
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# It may only if it can actually carry the WAN. Without this, VRRP decides
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# mastership purely on whether the peer is still advertising -- so a router with
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# no WAN at all happily takes the VIPs and blackholes the entire LAN's internet
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# while looking perfectly healthy. That is not hypothetical: it is the outage of
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# 2026-09-02, reproduced in labsim.
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#
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# ---------------------------------------------------------------------------
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# The first version of this script asked one question: "do I have an address on
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# a WAN interface". That is correct for a pair where both routers hold WAN all
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# the time. Ours cannot: the 10 gig lease is bound to a cloned MAC and the
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# PPPoE line to a single credential, so the WAN follows mastership (see
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# vrrp-wan-take). Against that design the old check DEADLOCKS --
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#
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# may I be master? -> only if I already have WAN
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# do I have WAN? -> only if I am master
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#
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# -- and the backup sits in FAULT for ever. vyos002 sat exactly there, which
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# meant the pair could not fail over at all: the safety check had quietly
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# removed the redundancy it was protecting.
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#
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# So the question is now asked in the right order: enforce "must have WAN" only
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# on the router that is actually HOLDING the VIPs, and give a new master time to
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# bring the WAN up before judging it.
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# ---------------------------------------------------------------------------
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#
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# exit 0 = eligible for MASTER, non-zero = release and let the peer have it.
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CONF=/config/vrrp-wan.conf
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[ -r "$CONF" ] && . "$CONF"
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STATE=/run/vrrp-wan
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VIP="${VRRP_WAN_VIP:-192.168.1.1}"
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# Seconds a new master may go without any WAN. Sourced from vrrp-wan.conf; the
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# fallback is deliberately NOT the old 90. accel-ppp's dead-peer budget is
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# lcp-echo-interval(30) x lcp-echo-failure(3) = 90s, so a hard failover into an
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# access concentrator that does not replace the stale session lands exactly on
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# the boundary: the new master fails its own check, sheds the VIPs, and the peer
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# -- in the same position -- does likewise. Both end in FAULT, which is worse
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# than the outage this check exists to prevent.
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GRACE="${GRACE:-180}"
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# A deliberate hand-over lever.
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#
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# There is no reliable way to MAKE this pair fail over on demand. VyOS offers
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# only `restart vrrp`, and neither that nor `systemctl restart keepalived` is
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# dependable: with advert_int 1 the peer declares the master dead after ~3.6s,
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# and a restart usually finishes inside that window. Measured in labsim -- the
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# same command moved mastership on one run and not on the next three. A
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# fail-back procedure you cannot trigger on purpose is not a procedure.
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#
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# Failing the health check IS the supported way to shed mastership: the sync
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# group goes FAULT, releases every VIP, and the peer takes over -- the same path
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# a genuine WAN loss takes, so the planned drill exercises the real mechanism
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# rather than a special case.
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#
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# touch /run/vrrp-wan/force-fault hand over within failure-count*interval
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# rm /run/vrrp-wan/force-fault become eligible again (no-preempt keeps
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# it BACKUP until the peer hands back)
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#
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# It lives in /run deliberately: a reboot clears it, so a forgotten drill cannot
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# leave a router permanently ineligible.
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[ -f /run/vrrp-wan/force-fault ] && exit 1
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# Am I holding the VIPs? Asked of REALITY -- is the management VIP actually on
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# this box -- and not of a /run marker.
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#
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# The marker was the first design and it is unsafe: it is written by the VRRP
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# transition script, and in labsim that script silently failed to run on a
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# promotion (VyOS's keepalived-fifo.py helper stopped delivering while
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# keepalived's own notifies kept working). The router then believed it was
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# backup, passed this check, and sat holding every VIP with no WAN -- the exact
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# outage this script exists to prevent, re-created by trusting the reporter
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# instead of the fact.
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if [ -z "$(ip -4 -o addr show 2>/dev/null | grep " ${VIP}/")" ]; then
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# Clear the grace stamp on the way down, HERE, not only in the reconciler.
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# The reconciler runs every 30s; this runs every 5s. A promotion that
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# inherited a stamp from an earlier mastership scored grace = hours, failed
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# immediately, and took the sync group to FAULT ~5s after passing -- with the
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# peer already faulted, that left BOTH routers in FAULT and the LAN with no
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# gateway. The stamp must belong to the CURRENT mastership or it is worse
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# than useless.
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rm -f "$STATE/since" 2>/dev/null
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exit 0
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fi
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# Start the grace clock HERE, the moment mastership is first observed.
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#
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# It used to be stamped only by vrrp-wan-reconcile, which runs on a 30s timer --
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# so a freshly promoted master reached this check with no stamp, scored grace=0,
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# failed, and went FAULT before it had any chance to bring the WAN up. The peer
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# then found itself alone with no WAN either and did the same. Observed in
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# labsim: BOTH routers in FAULT, nobody holding the VIPs, the LAN with no
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# gateway at all. That is worse than the outage this script exists to prevent,
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# and it would have hit a REAL failover, not just a drill -- the health check
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# runs every 5s and the reconciler had not yet ticked.
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mkdir -p "$STATE" 2>/dev/null
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[ -f "$STATE/since" ] || date +%s > "$STATE/since"
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# Master with an address on a WAN interface: healthy.
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#
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# Deliberately NOT "can I reach the internet" and NOT "do I have a default
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# route". During a real ISP outage the route disappears on BOTH routers; a check
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# keyed on that would put both into FAULT, nobody would hold the VIPs, and the
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# LAN would lose inter-VLAN routing too -- turning an internet outage into a
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# total one. A DHCP lease survives an ISP outage, so an address still
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# distinguishes "this box structurally cannot route" from "the internet is down
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# right now", which is the distinction that matters.
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# Any WAN counts. Requiring the 10 gig specifically would fault a healthy master
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# during a genuine 10 gig outage and turn a degraded state into a total one --
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# the same reasoning as the default-route note above. Which one satisfied it is
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# recorded for the operator and the test harness, but does not affect the verdict.
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for ifc in bond0.53 pppoe0; do
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if ip -4 addr show dev "$ifc" 2>/dev/null | grep -q 'inet '; then
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echo "$ifc" > "$STATE/wan" 2>/dev/null
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# Re-stamp on every healthy tick, so the grace window below measures
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# time since this box last DEMONSTRABLY had a WAN.
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date +%s > "$STATE/since" 2>/dev/null
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exit 0
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fi
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done
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rm -f "$STATE/wan" 2>/dev/null
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# No WAN right now, but there was one within GRACE: ride it out.
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#
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# `since` is re-stamped on every healthy tick, so this measures time since the
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# box last HAD a WAN -- not time since it was promoted. Measuring from promotion
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# was wrong in a way that only shows up on an established master: after hours of
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# uptime `now - since` far exceeds any grace, so the first moment bond0.53 went
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# down and pppoe0 was mid-redial, the master failed its own check, shed every
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# VIP, and the peer -- inheriting the same WAN outage -- did the same. Observed
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# in labsim: taking the 10 gig down flapped the pair instead of falling back to
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# PPPoE. A WAN gap must be survivable wherever it happens, not only just after a
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# promotion.
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since=$(cat "$STATE/since" 2>/dev/null || echo 0)
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[ $(( $(date +%s) - since )) -lt "$GRACE" ] && exit 0
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# Master, past grace, still no WAN: release. This is the 2026-09-02 case.
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exit 1
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