Files
lab/labsim/vlan-leak-evidence/after-vlan1/client.txt
Michal 0481c38e09 labsim: prove the tagged-Management fix for kea's wrong-pool offers
Kea #1117: with dhcp-socket-type raw, a frame tagged for a sub-interface is
also delivered to the parent's AF_PACKET socket, and if the parent serves a
subnet kea answers from it too. Management being the native VLAN on bond0 is
what gives the parent that subnet. One DISCOVER on VLAN 3 produced two OFFERs,
and in the captures here the WRONG one arrives first as often as not -- which
is why this looked device-dependent rather than like a server bug.

labsim-vlan-leak-test.sh reproduces it and scores the SERVER's offers, not the
client's choice; a client picking correctly is how this hid. Fails on the old
shape, passes on the new one across all six LAN VLANs.

Three things the rehearsal caught that reasoning had not:

  - kea keeps its old raw socket. VyOS does not restart it for an interface
    address change, so the first post-fix test failed and looked exactly like
    the fix not working.
  - interface-group LAN names the bare bond0. Moving the address without
    moving the group drops every management session under default-deny.
  - there is no make-before-break. A port always egresses its native VLAN
    untagged, so while VLAN 1 is native the router can send tagged VLAN 1 but
    never receive it -- verified, the ARP landed on bond0 untagged.

What makes the cutover safe anyway is that tagged and untagged Management
coexist, so the firewalls convert one at a time: 0s of VIP downtime, versus
5m30s if both routers go before the switch does. In that state the healthy
BACKUP does NOT take over -- the sync group holds native BACKUP because the
other VLANs still hear the master.

Also fixes two ways the sim was lying. ovs_bond_router compared only the trunk
VLAN list on re-runs, so a VM restart left the bond holding taps that no longer
existed while the real ones sat in the bridge unbonded -- labsim-vyos2 had no
LACP at all. And the tap count included the primary's libvirt-NAT scaffold NIC,
so the primary's bond was skipped outright.

Runbook: migration/MANAGEMENT-VLAN-TAGGED.md

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DMVzWZgiKW2wquf5z8S1yH
2026-09-02 14:03:44 +01:00

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udhcpc: started, v1.37.0
udhcpc: broadcasting discover
udhcpc: broadcasting select for 172.31.1.6, server 172.31.1.252
udhcpc: lease of 172.31.1.6 obtained from 172.31.1.252, lease time 86400