On iOS the tunnel reconfiguration (setTunnelNetworkSettings) was driven
from three independent Go paths without serialization: route prefix
updates via the route notifier's own delivery loop, interface IP/IPv6
set synchronously from the engine start goroutine, and DNS config
applied from the DNS apply chain through a separate Swift object. The
three sources mutated the shared Swift settings-manager state
concurrently and triggered overlapping updateTunnel() calls, losing or
half-applying route and DNS settings.
Introduce client/internal/tunnelnotifier: a single notifier that
implements both listener.NetworkChangeListener and dns.IosDnsManager,
queues all four callbacks (OnNetworkChanged, SetInterfaceIP,
SetInterfaceIPv6, ApplyDns) in one FIFO and delivers them one-by-one
from a single goroutine, so calls into Swift never overlap and arrive in
order. RunOniOS wraps the two Swift objects into the notifier and closes
it after the run loop exits.
The route notifier keeps its prefix dedup but delegates delivery to the
shared notifier instead of maintaining its own queue and loop; the dedup
check and the enqueue stay under one mutex so queue order matches
state-update order. Setting the interface IP becomes asynchronous, which
is safe: on iOS wgInterface.Create() only uses the TunFd, and the FIFO
preserves the IP -> routes/DNS relative order.
The package is build-tag free so the unit tests run on any platform
under -race. Android is unaffected: it receives all settings atomically
in one configureInterface call and serializes TUN rebuilds on a single
handler thread.
## Describe your changes
## Issue ticket number and link
## Stack
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### Checklist
- [x] Is it a bug fix
- [ ] Is a typo/documentation fix
- [ ] Is a feature enhancement
- [x] It is a refactor
- [ ] Created tests that fail without the change (if possible)
- [ ] This change does **not** modify the public API, gRPC protocols,
functionality behavior, CLI / service flags, or introduce a new feature
— **OR** I have discussed it with the NetBird team beforehand (link the
issue / Slack thread in the description). See
[CONTRIBUTING.md](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTING.md#discuss-changes-with-the-netbird-team-first).
> By submitting this pull request, you confirm that you have read and
agree to the terms of the [Contributor License
Agreement](https://github.com/netbirdio/netbird/blob/main/CONTRIBUTOR_LICENSE_AGREEMENT.md).
## Documentation
Select exactly one:
- [ ] I added/updated documentation for this change
- [x] Documentation is **not needed** for this change (explain why)
### Docs PR URL (required if "docs added" is checked)
Paste the PR link from https://github.com/netbirdio/docs here:
https://github.com/netbirdio/docs/pull/__
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<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit
* **New Features**
* Improved iOS tunnel networking by coordinating network, interface,
route, and DNS updates through a unified notifier.
* Updated iOS behavior so route/prefix changes are applied immediately
instead of via queued/background delivery.
* **Bug Fixes**
* Improved reliability by ensuring network and DNS-related callbacks are
invoked in order without overlap.
* Ensured pending updates are drained and handled correctly during
shutdown.
* **Tests**
* Added coverage for FIFO ordering, non-overlapping callback execution,
interleaved DNS/route updates, and graceful shutdown behavior.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
* [client] fix iOS route-update reordering that black-holed IPv6 on exit-node disable
On iOS the route notifier delivered each prefix update from its own
fire-and-forget goroutine (notify -> `go func`), so Go provided no ordering
guarantee between consecutive updates. It also read currentPrefixes inside
that goroutine without holding the lock, racing the next OnNewPrefixes write.
On exit-node disable the core removes the default routes as two separate
prefix updates (0.0.0.0/0, then the synthesized ::/0). When the two
goroutines were reordered, the stale snapshot still containing ::/0 was
delivered last and clobbered the correct default-free one. iOS then kept the
::/0 default route on the tunnel with no exit node to carry it, black-holing
all IPv6 traffic while IPv4 recovered correctly.
Fix: deliver updates through a single worker goroutine fed by a buffered
channel, preserving production order, and snapshot the joined prefix string
under the mutex so it can't race a concurrent update. Buffered so producers
(which run under the route manager lock) don't block on the listener callback.
* [client] close iOS notifier delivery goroutine on Stop, unbounded queue
The delivery goroutine was never stopped, leaking on every engine
restart. Add Notifier.Close, called from the route manager Stop after
routing cleanup.
Replace the buffered update channel with a cond-driven linked-list
queue so route-update producers (running under the route manager lock)
never block when the listener callback is slow.
extraInitialRoutes() was meant to preserve only the fake IP route
(240.0.0.0/8) across TUN rebuilds, but it re-injected any initial
route missing from the current set. When the management server
advertised exit node routes (0.0.0.0/0) that were later filtered
by the route selector, extraInitialRoutes() re-added them, causing
the Android VPN to capture all traffic with no peer to handle it.
Store the fake IP route explicitly and append only that in notify(),
removing the overly broad initial route diffing.
- Add GetSelectedClientRoutes() to the route manager that filters through FilterSelectedExitNodes, returning only active routes instead of all management routes
- Use GetSelectedClientRoutes() in the DNS route checker so deselected exit nodes' 0.0.0.0/0 no longer matches upstream DNS IPs — this prevented the resolver from switching
away from the utun-bound socket after exit node deselection
- Initialize iOS DNS server with host DNS fallback addresses (1.1.1.1:53, 1.0.0.1:53) and a permanent root zone handler, matching Android's behavior — without this, unmatched
DNS queries arriving via the 0.0.0.0/0 tunnel route had no handler and were silently dropped
If we get domain routes the Network prefix variable in route structure will be invalid (engine.go:1057). When we handower to Android the routes, we must to filter out the domain routes. If we do not do it the Android code will get "invalid prefix" string as a route.
