When isolateContainers=true, claude (and all egress) broke in every
container: agents came up with an IP but no way off the bridge subnet.
Two container-side gaps, both confirmed against nixpkgs
nixos-containers.nix:
1. No default route. hive-priv wrote HOST_ADDRESS= empty in the nspawn
conf. nixos-container's container-side setup only installs
`ip route add default via $HOST_ADDRESS` when HOST_ADDRESS is
non-empty, so the container had an address but no gateway -> nothing
off-subnet (incl. api.anthropic.com) was reachable. Fix: write
HOST_ADDRESS=<bridge-ip>. In bridge mode the host-side address/route
setup is skipped, so this only affects the container's default route.
2. No usable resolver. nixos-container copies the host's /etc/resolv.conf
into the container at every start; the host resolver (e.g. 127.0.0.53)
is unreachable from a private netns and isn't authoritative for the
hive's own zones. Fix: hive-priv drops a marker carrying the gateway
IP only when isolated, and a new harness-base oneshot
(hyperhive-isolated-dns) rewrites resolv.conf to point at the bridge
dnsmasq. Inert in shared-netns mode (no marker), so the shared
container toplevel does the right thing in both modes.
The gateway IP is the address part of HIVE_NETWORK_SUBNET (the bridge IP
verbatim, honouring a non-.1 operator override), via a new validated
bridge_gateway_ip() helper with unit tests.
Unblocks defaulting isolation on.
d993ad2c47