A node behind a NAT falls back to bootstrap A's relay and announces its circuit address. A reachable node C finds it as a provider and downloads its data through the relay.

Topology

node B ──── lan ──── router (NAT) ──── wan ──── bootstrap A (relay)
                                        └────── node C (reachable)

bootstrap A — public node on the wan, autonat + relay server, started with --nat=extip.
router — lan -> wan masquerade and no inbound forward, so B can dial out but nothing can dial back in.
node B — nat=auto, on the lan. AutoNAT finds it unreachable, so it takes a relay reservation on A and announces its circuit address.
node C — nat=auto, directly on the wan, so AutoNAT finds it Reachable. It is the peer that downloads from B through the relay.

Run

make testNatIntegration \
  STORAGE_INTEGRATION_TEST_INCLUDES=tests/integration/nat/relay-download/testrelaydownload.nim

Builds the shared image and brings the compose topology up and down. Rootless, but needs the host netfilter modules — if the router fails on iptables: sudo modprobe iptable_nat nf_conntrack.

Expected result

B is NotReachable and announces its circuit address, while C is Reachable. B uploads a file, then C fetches it over the network through the relay and gets the same content back.

Per-run container logs (router, bootstrap, client, node) are written before teardown to tests/integration/logs/<timestamp>__NAT_relay_download/<test>/<service>.log.