The primary purpose is that return packets from the target app get
properly SNATed on connectors with --tun=userspace-networking, matching
the NAT behavior in the kernel tun path.
This is also necessary but not sufficient for clients of connectors in
userspace networking mode. The hook will DNAT MagicIPs, but won't
actually be sent MagicIPs until conn25 app connector DNS works with
userspace networking.
Fixestailscale/corp#43201
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Package features/conn25 wires up the hooks directly on the tun wrapper
without needing to go through the userspace engine, so this codepath is
unused and not needed.
Updates #cleanup
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
The hook fires when a flow is removed for any reason (LRU capacity eviction,
tuple-collision displacement, or idle-time expiry). The hook is invoked
exactly once per flow, after the flow table mutex is released, so callbacks
may safely acquire other locks.
We rename the IPMapper interface to Conn25Datapath, and add
ClientFlowCreated/ClientFlowRemoved methods so *Conn25 can keep client-side
address assignments alive while traffic is in flight. Those methods are
currently stubbed for future work.
Connector flows do not currently call these methods.
Updates tailscale/corp#38630
Updates tailscale/corp#43180
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
The returned error in the signature is left over from previous
implementations and was only returning nil.
If we know NewFlow will succeed we can fire a create hook (implemented
in a future commit) before NewFlow, which will prevent a remove hook for
a flow from firing before the create hook for the same flow.
Updates tailscale/corp#38630
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Track lastSeen on each cached flow and add a sweeper goroutine
that periodically removes flows idle past the idle timeout.
Introduce tunables for idle timeout, maximum flows removed per sweep (to
limit mutex hold time), and the sweeper interval.
Also cap the previously-unlimited tables: 10k client flows, 100k
connector flows.
Updates tailscale/corp#38630
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Previously we had two maps keyed on a direction-specific tuple, with
distinct values containing the data (action) for that direction.
Values pointed at each other across maps to ensure they were removed
at the same time in the case of tuple overwrite, but LRU eviction
was per-map. So if LRU was turned on, it was possible for one
direction's data (action) to be evicted and leave the other direction
dangling.
NewFlow replaces the two direction-specific flow constructors, and
lookups return the direction-specific PacketAction directly.
Now the values in each map point to the same element, with data for both
directions in the element. A linked list also points to the elements to
implement LRU. The previous flowtrack.Cache is removed.
The single LRU structure will allow us to implement idle time expiration
by walking the list backward starting with the least recently used flow, and
stopping after a fixed number of flows, or at the first non-expired flow.
We add commented-out unused placeholder fields for tracking the
"last seen" timestamp, and an on-removal hook, to document the intent for
the follow-up expiry work.
Updates tailscale/corp#38630
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
We have two sources of truth for configuration state: the node view
(from the netmap/policy) and prefs (the --advertise-connector option).
These come with two independent update paths: onSelfChange for node view
changes and profileStateChange for pref changes.
Centralize config on Conn25 so that onSelfChange and profileStateChange
can update their independent parts without bundling changes together.
The old bundled approach required read-modify-write, which opened the
door to potential TOCTOU bugs. The node view config is
stored as an atomic.Pointer[config] and the prefs-derived field
(advertise-connector) becomes an independent atomic.Bool. onSelfChange
creates a fresh config and stores it atomically. profileStateChange sets
the bool.
This also establishes clearer lines of responsibility:
- Configuration state lives on Conn25. Methods that need to read
config (isConnectorDomain, mapDNSResponse, the IPMapper methods)
are on Conn25, and use the atomics for synchronization.
- "Active" state (address allocations, transit IP mappings) lives on
client and connector, and use a mutex for synchronization on that
state, without conflicting with configuration synchronization.
It's fine for active state to be out of sync with config — e.g. a
transit IP allocated for an app should still be tracked, and gracefully
expired, even if the app is removed from the node view.
Removing config responsibility from client/connector makes these
cases clearer to handle.
- In cases where the client or connector does need access to
config-derived state, e.g. a client reconfiguring its IP pools from
the IPSets in the config, we can use closures for the
client or connector to get just the latest state it needs from the
config. See getIPSets() in this commit.
- As of this commit, the connector doesn't need config-derived state at
all.
Fixestailscale/corp#40872
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
modifying DNS responses for domains they are also connectors for
For Connectors 2025, determine if a client is configured as a
connector and what domains it is a connector for. When acting as a
client, don't install Split DNS routes to other connectors for those
domains, and don't alter DNS responses for those domains. The responses
are forwarded back to the original client, which in turn does the alteration,
swapping the real IP for a Magic IP.
A client is also a connector for a domain if it has tags that overlap
with tags in the configured policy, and --advertise-connector=true
in the prefs (not in the self-node Hostinfo from the netmap). We use the prefs
as the source of truth because control only gets a copy from the prefs, and
may drift. And the AppConnector field is currently zeroed out in the
self-node Hostinfo from control.
The extension adds a ProfileStateChange hook to process prefs changes,
and the config type is split into prefs and nodeview sub-configs.
Fixestailscale/corp#39317
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Install the previously uninstalled hooks for the filter and tstun
intercepts. Move the DNS manager hook installation into Init() with all
the others. Protect all implementations with a short-circuit if the node
is not configured to use Connectors 2025. The short-circuit pattern
replaces the previous pattern used in managing the DNS manager hook, of
setting it to nil in response to CapMap changes.
Fixestailscale/corp#38716
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Also implement a limit of one on the number of goroutines that can be
waiting to do a reconfig via AuthReconfig, to prevent extensions from
calling too fast and taxing resources.
Even with the protection, the new method should only be used in
experimental or proof-of-concept contexts. The current intended use is
for an extension to be able force a reconfiguration of WireGuard, and
have the reconfiguration call back into the extension for extra Allowed
IPs.
If in the future if WireGuard is able to reconfigure individual peers more
dynamically, an extension might be able to hook into that process, and
this method on ipnext.Host may be deprecated.
Fixestailscale/corp#38120
Updates tailscale/corp#38124
Updates tailscale/corp#38125
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Introduce a datapathHandler that implements hooks that will
receive packets from the tstun.Wrapper. This commit does not wire
those up just yet.
Perform DNAT from Magic IP to Transit IP on outbound flows on clients,
and reverse SNAT in the reverse direction.
Perform DNAT from Transit IP to final destination IP on outbound flows
on connectors, and reverse SNAT in the reverse direction.
Introduce FlowTable to cache validated flows by 5-tuple for fast lookups
after the first packet.
Flow expiration is not covered, and is intended as future work before
the feature is officially released.
Fixestailscale/corp#34249Fixestailscale/corp#35995
Co-authored-by: Fran Bull <fran@tailscale.com>
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
This hook addition is motivated by the Connectors 2025 work, in which
NATed "Transit IPs" are used to route interesting traffic to the
appropriate peer, without advertising the actual real IPs.
It overlaps with #17858, and specifically with the WIP PR #17861.
If that work completes, this hook may be replaced by other ones
that fit the new WireGuard configuration paradigm.
Fixestailscale/corp#37146
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Add PacketMatch hooks to the packet filter, allowing extensions to
customize filtering decisions:
- IngressAllowHooks: checked in RunIn after pre() but before the
standard runIn4/runIn6 match rules. Hooks can accept packets to
destinations outside the local IP set. First match wins; the
returned why string is used for logging.
- LinkLocalAllowHooks: checked inside pre() for both ingress and
egress, providing exceptions to the default policy of dropping
link-local unicast packets. First match wins. The GCP DNS address
(169.254.169.254) is always allowed regardless of hooks.
PacketMatch returns (match bool, why string) to provide a log reason
consistent with the existing filter functions.
Hooks are registered via the new FilterHooks struct in ipnext.Hooks
and wired through to filter.Filter in LocalBackend.updateFilterLocked.
Fixestailscale/corp#35989Fixestailscale/corp#37207
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
app connector packets
We introduce the Conn25PacketHooks interface to be used as a nil-able
field in userspaceEngine. The engine then plumbs through the functions
to the corresponding tstun.Wrapper intercepts.
The new intercepts run pre-filter when egressing toward WireGuard,
and post-filter when ingressing from WireGuard. This is preserve the
design invariant that the filter recognizes the traffic as interesting
app connector traffic.
This commit does not plumb through implementation of the interface, so
should be a functional no-op.
Fixestailscale/corp#35985
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
dnstype.Resolver adds a boolean UseWithExitNode that controls
whether the resolver should be used in tailscale exit node contexts
(not wireguard exit nodes). If UseWithExitNode resolvers are found,
they are installed as the global resolvers. If no UseWithExitNode resolvers
are found, the exit node resolver continues to be installed as the global
resolver. Split DNS Routes referencing UseWithExitNode resolvers are also
installed.
Updates #8237Fixestailscale/corp#30906Fixestailscale/corp#30907
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Michael Ben-Ami
