Make the FIPS core build and run as an embedded Android library. The host
app owns the TUN (e.g. an Android VpnService) and FIPS performs no
system-TUN or CAP_NET_ADMIN operations.
Squashed from the following changes:
- gate desktop transports/TUN by target_os, not features: a plain
`cargo build` now compiles for every target with no flags. Ethernet (raw
AF_PACKET / BPF) is gated to linux/macos, so Android (target_os =
"android", not "linux") self-excludes it as Windows already did; real
system-TUN ops are gated per linux/macos and Android gets a no-op stub;
the ipi6_ifindex cast handles it being i32 on Android vs u32 on macOS. No
Cargo features are introduced; desktop builds are unchanged.
- app-owned TUN seam: Node::enable_app_owned_tun() lets an embedder that
owns the TUN fd exchange IPv6 packet bytes with FIPS over channels
instead of FIPS creating a system TUN device. It returns (app_outbound_tx,
app_inbound_rx): the embedder pushes packets read from its fd into the
outbound sender (app -> mesh) and pulls packets destined for its fd from
the inbound receiver (mesh -> app). start() gates system-TUN creation on
tun_tx being unset, so with the channels pre-installed it skips device
creation and does no system-TUN ops; both directions reuse the existing
inbound-shim and run_rx_loop wiring. Packets entering via app_outbound_tx
bypass handle_tun_packet, so the embedder must push only fd00::/8-destined
packets and clamp TCP MSS on outbound SYNs; the rustdoc and the
IPv6-adapter design doc spell this out.
- keep the android target warning-clean so the cross-compile check passes
clippy -D warnings.
- add an Android cross-compile CI check: cross-compile the library for
aarch64-linux-android via cargo-ndk and run clippy -D warnings. Android
ships as an embedded library (the host app owns the TUN), so there is no
daemon binary to package; this is a check job, not a packaging one.
- docs: list Android as a supported platform.
Tests: app_owned_tun_seam_wires_channels covers the channel round-trip and
the Active state; start_skips_system_tun_when_app_owned runs start() and
asserts no named system device is created.
On Ubuntu 22 (systemd 249), systemd-resolved applies interface-scoped
routing to per-link DNS servers. Configuring `resolvectl dns fips0
127.0.0.1:5354` caused resolved to attempt reaching 127.0.0.1 through
fips0 (a TUN with only fd00::/8 routes), silently failing. The DNS
responder never received queries. Newer systemd versions (250+) have
explicit handling for loopback servers on non-loopback interfaces.
Changes:
- DNS responder default bind_addr changed from "127.0.0.1" to "::"
so it listens on all interfaces, including fips0. Bind logic in
lifecycle.rs now parses bind_addr as IpAddr and constructs a
SocketAddr, handling IPv6 literal formatting. Factored into
Node::bind_dns_socket with explicit IPV6_V6ONLY=0 via socket2, so
IPv4 clients on 127.0.0.1:5354 still reach the responder
regardless of the kernel's net.ipv6.bindv6only sysctl.
- fips-dns-setup resolvectl backend now waits for fips0 to have a
global IPv6 address, then configures resolved with
[<fips0-addr>]:5354. That address is locally delivered by the
kernel regardless of which interface resolved tries to route
through. The dnsmasq and NetworkManager backends still use
127.0.0.1 (they don't have the interface-scoping issue).
- Dropped hardcoded `bind_addr: "127.0.0.1"` from the packaged
fips.yaml (Debian + OpenWrt). The shipped config was overriding
the new default.
- DNS queries are only accepted from the localhost.
Verified end-to-end in a privileged Ubuntu 22.04 systemd container:
dig @127.0.0.53 AAAA <npub>.fips resolves cleanly through
systemd-resolved.
The dns-delegate backend (systemd 258+) still uses 127.0.0.1; it
has not been verified whether that backend has the same routing
issue.
The DNS responder returned NXDOMAIN for non-AAAA queries (e.g. A record)
on valid .fips names. This caused resolvers like nslookup and tinyproxy
to give up without attempting AAAA, since NXDOMAIN means "name does not
exist." Return NOERROR with an empty answer section instead, which tells
the client the name exists but has no records of that type.
Fixesjmcorgan/fips#9.
Add a HostMap that resolves human-readable hostnames to npubs,
enabling `gateway.fips` instead of the full `npub1...xyz.fips`.
Two sources populate the map: peer `alias` fields from the YAML
config and an operator-maintained hosts file at /etc/fips/hosts.
The DNS responder auto-reloads the hosts file on each request by
checking the file modification time, so operators can update
mappings without restarting the daemon.
- New src/upper/hosts.rs: HostMap, HostMapReloader, hostname
validation, hosts file parser with auto-reload on mtime change
- DNS resolver checks host map before falling back to direct npub
- Node uses host map for peer display names
- Default hosts file added to both .deb and tarball packaging
- 26 new tests (789 total)
ArjenandJohnathan Corgan
