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Session Lifecycle

Detailed walkthrough of PPPoE and DHCP session establishment and termination.

PPPoE Session Lifecycle​

Phase 1: VLAN Interface Creation​

Phase 2: PPPoE Discovery​

Phase 3: PPP Negotiation​

Phase 4: RADIUS Authentication​

Phase 5: Session Registration​

Phase 6: QoS Application​

Phase 7: Session Termination​

DHCP/IPoE Session Lifecycle​

Phase 1: VLAN Interface Creation​

Phase 2: DHCP Relay​

Phase 3: RADIUS Authentication​

Phase 4: DHCP Offer​

Phase 5: DHCP Request/ACK​

Phase 6: QoS Application​

Phase 7: Session Termination​

Change of Authorization (CoA)​

Restart Recovery & Resilience​

The daemons self-heal across restarts without manual intervention. Recovery is built on idempotent, periodic re-assertions rather than a single brittle hand-off at startup, so a restart of any single service rebuilds its state from its peers within one reconcile interval.

abngd re-asserts demux bindings (~30s)​

abngd periodically re-asserts its known demux interfaces to abng-dhcpd and accel-ppp. The bind signals are idempotent, so when either of those services restarts it re-binds automatically — no need to re-create the demux interfaces.

abng-demux re-announces tracked interfaces (~30s)​

abng-demux periodically re-announces every tracked interface to abngd. After an abngd restart, this rebuilds abngd's in-memory demux registry (and therefore the downstream abng-dhcpd / accel-ppp bindings) from the demux side.

abng-demux re-adopts QinQ interfaces after its own restart​

If abng-demux restarts, the demux QinQ interfaces it created survive in the kernel. On startup abng-demux reconstructs each live VLAN stack via netlink, matches it against a profile, and re-announces it to abngd. Already-bound subscribers — even idle ones with no in-flight traffic — recover immediately instead of waiting for the next packet to re-trigger interface creation.

abngd re-applies QoS on reconcile​

On its periodic session reconcile, abngd re-applies QoS for surviving sessions (idempotent in abng-qos). This restores CAKE/IFB shaping after an abng-qos restart.

abng-qos triggers an immediate QoS resync on restart​

abng-qos loses all shaping state (CAKE qdiscs + IFB devices) when it restarts. On startup it sends a qos.resync message to abngd, which immediately re-applies QoS for every active session — so shaping is restored within seconds of an abng-qos restart instead of waiting for the next periodic reconcile (~60s). The applies are idempotent, so this complements (rather than conflicts with) the reconcile loop above.

abng-dhcpd restart only on relevant config change​

abng-dhcpd loads its DHCP/RADIUS config once at startup and has no live reload. On commit, abngd restarts abng-dhcpd only when the DHCP/RADIUS config it consumes actually changed. Unrelated commits leave abng-dhcpd — and its active leases — undisturbed.

Next Steps​