wgengine,wgcfg,feature/netlog: move network flow logging behind a feature hook

wgcfg.Config.NetworkLogging carried the network flow logging identity
inside the WireGuard config, where it was unrelated to WireGuard; it
lived there mainly so that identity changes would defeat Reconfig's
ErrNoChanges check and reach the netlog startup/shutdown logic.

Remove the field and move the whole netlog lifecycle into a new
feature/netlog package, installed on the engine via the new
wgengine.HookNewNetLogger hook, like other feature/* packages. The
logging identity now comes from LocalBackend's current netmap via the
widened NetLogSource interface (replacing Engine.SetNetLogNodeSource),
so nmcfg no longer parses audit log IDs into the config. The engine
still calls the hook before its ErrNoChanges return and before
router.Set (to capture initial packets), and again after router.Set
(to capture final packets), preserving the previous ordering.

Core wgengine no longer imports wgengine/netlog, so minimal builds
drop it entirely. tailscaled keeps netlog via feature/condregister,
and tsnet imports feature/condregister/netlog explicitly to keep
netlog enabled by default in tsnet-based binaries (tsidp,
k8s-operator).

This is pulled out of a future change that removes wgcfg.Config.Peers,
to make that PR smaller.

Updates #12542
Updates #12614

Change-Id: I41ca7dfe43c51e977c41b5f8e934bd1f0e6e6e24
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>

cmd/k8s-operator/depaware.txt

@@ -734,9 +734,11 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/c2n                                    from tailscale.com/tsnet
         tailscale.com/feature/condlite/expvar                        from tailscale.com/wgengine/magicsock
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/tsnet
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
+        tailscale.com/feature/netlog                                 from tailscale.com/feature/condregister/netlog
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
@@ -921,7 +923,7 @@ tailscale.com/cmd/k8s-operator dependencies: (generated by github.com/tailscale/
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
+        tailscale.com/wgengine/netlog                                from tailscale.com/feature/netlog
         tailscale.com/wgengine/netstack                              from tailscale.com/tsnet
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/ipn/ipnlocal+

cmd/tailscaled/depaware-min.txt

@@ -62,6 +62,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/buildfeatures                          from tailscale.com/cmd/tailscaled+
         tailscale.com/feature/condlite/expvar                        from tailscale.com/wgengine/magicsock
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/feature/condregister
         tailscale.com/health                                         from tailscale.com/control/controlclient+
@@ -195,7 +196,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/wgcfg                                 from tailscale.com/ipn/ipnlocal+

cmd/tailscaled/depaware-minbox.txt

@@ -75,6 +75,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
         tailscale.com/feature/condregister/awsparamstore             from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/identityfederation        from tailscale.com/cmd/tailscale/cli
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/cmd/tailscale/cli
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister+
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/cmd/tailscale/cli+
@@ -216,7 +217,6 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/wgcfg                                 from tailscale.com/ipn/ipnlocal+

cmd/tailscaled/depaware.txt

@@ -298,6 +298,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/clientupdate                           from tailscale.com/feature/condregister
         tailscale.com/feature/condlite/expvar                        from tailscale.com/wgengine/magicsock
         tailscale.com/feature/condregister                           from tailscale.com/cmd/tailscaled
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/portmapper                from tailscale.com/feature/condregister
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/feature/condregister
         tailscale.com/feature/conn25                                 from tailscale.com/feature/condregister
@@ -306,6 +307,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/feature/drive                                  from tailscale.com/feature/condregister
    L    tailscale.com/feature/linkspeed                              from tailscale.com/feature/condregister
    L    tailscale.com/feature/linuxdnsfight                          from tailscale.com/feature/condregister
+        tailscale.com/feature/netlog                                 from tailscale.com/feature/condregister/netlog
         tailscale.com/feature/portlist                               from tailscale.com/feature/condregister
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/posture                                from tailscale.com/feature/condregister
@@ -506,7 +508,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
+        tailscale.com/wgengine/netlog                                from tailscale.com/feature/netlog
         tailscale.com/wgengine/netstack                              from tailscale.com/cmd/tailscaled
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/cmd/tailscaled+

cmd/tsidp/depaware.txt

@@ -151,9 +151,11 @@ tailscale.com/cmd/tsidp dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/c2n                                    from tailscale.com/tsnet
         tailscale.com/feature/condlite/expvar                        from tailscale.com/wgengine/magicsock
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/tsnet
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
+        tailscale.com/feature/netlog                                 from tailscale.com/feature/condregister/netlog
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
@@ -319,7 +321,7 @@ tailscale.com/cmd/tsidp dependencies: (generated by github.com/tailscale/depawar
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
+        tailscale.com/wgengine/netlog                                from tailscale.com/feature/netlog
         tailscale.com/wgengine/netstack                              from tailscale.com/tsnet
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/ipn/ipnlocal+

feature/condregister/maybe_netlog.go

@@ -0,0 +1,6 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+package condregister
+
+import _ "tailscale.com/feature/condregister/netlog"

feature/condregister/netlog/doc.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package netlog registers support for network flow logging if it's
+// not disabled via the ts_omit_netlog or ts_omit_logtail build tags.
+// It is pulled out separately from the main condregister package so
+// that tsnet can link it without linking every conditional feature.
+package netlog

feature/condregister/netlog/maybe_netlog.go

@@ -0,0 +1,8 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !ts_omit_netlog && !ts_omit_logtail
+
+package netlog
+
+import _ "tailscale.com/feature/netlog"

feature/netlog/netlog.go

@@ -0,0 +1,119 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package netlog registers the network flow logging feature and wires
+// it into the WireGuard engine. The logger implementation itself lives
+// in tailscale.com/wgengine/netlog.
+package netlog
+
+import (
+	"context"
+	"time"
+
+	"tailscale.com/envknob"
+	"tailscale.com/feature"
+	"tailscale.com/types/logid"
+	"tailscale.com/wgengine"
+	"tailscale.com/wgengine/netlog"
+	"tailscale.com/wgengine/router"
+)
+
+func init() {
+	feature.Register("netlog")
+	wgengine.HookNewNetLogger.Set(newNetLogger)
+}
+
+// uploadTimeout is the maximum time to wait when shutting down the
+// network logger as it uploads the final network log messages.
+const uploadTimeout = 5 * time.Second
+
+// netLogger implements [wgengine.NetLogger] on top of [netlog.Logger],
+// tracking the logging identity and running state across engine
+// reconfigurations. One netLogger exists per engine.
+type netLogger struct {
+	deps   wgengine.NetLoggerDeps
+	logger netlog.Logger
+
+	// The fields below are only accessed from Reconfig and
+	// ReconfigDone, which the engine serializes under its internal
+	// lock.
+
+	// nodeID and domainID are the logging IDs from the last Reconfig,
+	// or zero if logging was not enabled then.
+	nodeID, domainID logid.PrivateID
+	// logExitFlows is whether exit node flows were logged as of the
+	// last Reconfig.
+	logExitFlows bool
+	// shouldRun is whether the last Reconfig wanted the logger
+	// running. ReconfigDone consults it to shut down a stopping
+	// logger after the router has been reconfigured.
+	shouldRun bool
+}
+
+func newNetLogger(deps wgengine.NetLoggerDeps) wgengine.NetLogger {
+	return &netLogger{deps: deps}
+}
+
+func (nl *netLogger) Reconfig(routerCfg *router.Config, routerChanged bool) (changed bool) {
+	logf := nl.deps.Logf
+	src := nl.deps.Source()
+
+	var nodeID, domainID logid.PrivateID
+	var logExitFlows bool
+	if src != nil {
+		if nid, did, lef, ok := src.NetLogIDs(); ok {
+			nodeID, domainID, logExitFlows = nid, did, lef
+		}
+	}
+	idsValid := !nodeID.IsZero() && !domainID.IsZero()
+	idsWereValid := !nl.nodeID.IsZero() && !nl.domainID.IsZero()
+	changed = nodeID != nl.nodeID || domainID != nl.domainID || logExitFlows != nl.logExitFlows
+	idsChanged := idsValid && idsWereValid && changed
+	nl.nodeID, nl.domainID, nl.logExitFlows = nodeID, domainID, logExitFlows
+
+	nl.shouldRun = idsValid && !routerCfg.Equal(&router.Config{}) && !envknob.NoLogsNoSupport()
+
+	// Shut down the logger if the IDs changed while it was running,
+	// letting the startup logic below bring it back up with the new
+	// identity.
+	if idsChanged && nl.logger.Running() {
+		logf("wgengine: Reconfig: shutting down network logger")
+		nl.shutdown()
+	}
+
+	// Start the logger before the engine configures the router so
+	// that it captures initial packets.
+	if nl.shouldRun && !nl.logger.Running() {
+		logf("wgengine: Reconfig: starting up network logger (node:%s tailnet:%s)", nodeID.Public(), domainID.Public())
+		if err := nl.logger.Startup(logf, src, nodeID, domainID, nl.deps.Tun, nl.deps.Sock, nl.deps.NetMon, nl.deps.Health, nl.deps.Bus, logExitFlows); err != nil {
+			logf("wgengine: Reconfig: error starting up network logger: %v", err)
+		}
+		nl.logger.ReconfigRoutes(routerCfg)
+	} else if routerChanged && nl.logger.Running() {
+		nl.logger.ReconfigRoutes(routerCfg)
+	}
+	return changed
+}
+
+func (nl *netLogger) ReconfigDone() {
+	// Shut down a stopping logger only now, after the engine has
+	// configured the router, so that it captures final packets.
+	if !nl.shouldRun && nl.logger.Running() {
+		nl.deps.Logf("wgengine: Reconfig: shutting down network logger")
+		nl.shutdown()
+	}
+}
+
+func (nl *netLogger) Shutdown() {
+	nl.shutdown()
+}
+
+// shutdown stops the logger, waiting up to uploadTimeout for it to
+// flush its final messages.
+func (nl *netLogger) shutdown() {
+	ctx, cancel := context.WithTimeout(context.Background(), uploadTimeout)
+	defer cancel()
+	if err := nl.logger.Shutdown(ctx); err != nil {
+		nl.deps.Logf("wgengine: error shutting down network logger: %v", err)
+	}
+}

ipn/ipnlocal/local.go

@@ -103,7 +103,6 @@ import (
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/magicsock"
-	"tailscale.com/wgengine/netlog"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 	"tailscale.com/wgengine/wgcfg/nmcfg"
@@ -636,7 +635,7 @@ func NewLocalBackend(logf logger.Logf, logID logid.PublicID, sys *tsd.System, lo
 	e.SetPeerByIPPacketFunc(b.lookupPeerByIP)
 	e.SetPeerForIPFunc(b.peerForIP)
 	e.SetPeerSessionStateFunc(b.onPeerWireGuardState)
-	e.SetNetLogNodeSource(netLogNodeSource{b})
+	e.SetNetLogSource(netLogNodeSource{b})
 	e.SetWGPeerLookup(b.lookupPeerWireGuardString)
 	b.dialer.SetResolveMagicDNS(b.resolveMagicDNS)
 
@@ -8017,9 +8016,10 @@ func (n noiseRoundTripper) RoundTrip(req *http.Request) (*http.Response, error)
 	return n.lb.DoNoiseRequest(req)
 }
 
-// netLogNodeSource adapts LocalBackend's nodeBackend to [netlog.NodeSource].
+// netLogNodeSource adapts LocalBackend to [wgengine.NetLogSource].
-// Each method consults [LocalBackend.currentNode] so that profile rotations
+// Each method consults [LocalBackend.currentNode] or the current netmap
-// are picked up automatically without re-installing the source.
+// so that profile rotations are picked up automatically without
+// re-installing the source.
 type netLogNodeSource struct {
 	b *LocalBackend
 }
@@ -8048,8 +8048,37 @@ func (s netLogNodeSource) NodeByAddr(addr netip.Addr) (_ tailcfg.NodeView, _ tai
 	return nv, up, true
 }
 
-// Compile-time assertion that netLogNodeSource implements [netlog.NodeSource].
+// NetLogIDs implements [wgengine.NetLogSource], returning the network
-var _ netlog.NodeSource = netLogNodeSource{}
+// flow logging identity from the current netmap. ok is false if the
+// netmap does not enable network flow logging for this node.
+func (s netLogNodeSource) NetLogIDs() (nodeID, domainID logid.PrivateID, logExitFlows bool, ok bool) {
+	nm := s.b.NetMap()
+	if nm == nil || !nm.SelfNode.Valid() {
+		return
+	}
+	if !nm.SelfNode.HasCap(tailcfg.CapabilityDataPlaneAuditLogs) {
+		return
+	}
+	if nm.SelfNode.DataPlaneAuditLogID() == "" || nm.DomainAuditLogID == "" {
+		return
+	}
+	nodeID, errNode := logid.ParsePrivateID(nm.SelfNode.DataPlaneAuditLogID())
+	if errNode != nil {
+		s.b.logf("[v1] netlog: unable to parse node audit log ID: %v", errNode)
+	}
+	domainID, errDomain := logid.ParsePrivateID(nm.DomainAuditLogID)
+	if errDomain != nil {
+		s.b.logf("[v1] netlog: unable to parse domain audit log ID: %v", errDomain)
+	}
+	if errNode != nil || errDomain != nil {
+		return logid.PrivateID{}, logid.PrivateID{}, false, false
+	}
+	return nodeID, domainID, nm.SelfNode.HasCap(tailcfg.NodeAttrLogExitFlows), true
+}
+
+// Compile-time assertion that netLogNodeSource implements
+// [wgengine.NetLogSource].
+var _ wgengine.NetLogSource = netLogNodeSource{}
 
 // lookupPeerWireGuardString returns the Tailscale-conventional short string
 // (e.g. "[IMTBr]") for the peer whose wireguard-go-formatted public key

ipn/ipnlocal/state_test.go

@@ -47,7 +47,6 @@ import (
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/magicsock"
-	"tailscale.com/wgengine/netlog"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 	"tailscale.com/wgengine/wgint"
@@ -1989,7 +1988,7 @@ func (e *mockEngine) PeerKeyForIP(netip.Addr) (_ key.NodePublic, _ netip.Prefix,
 }
 func (e *mockEngine) SetPeerSessionStateFunc(func(key.NodePublic, wgengine.PeerWireGuardState)) {
 }
-func (e *mockEngine) SetNetLogNodeSource(netlog.NodeSource)                            {}
+func (e *mockEngine) SetNetLogSource(wgengine.NetLogSource)                            {}
 func (e *mockEngine) SetWGPeerLookup(func(wgString string) (tsString string, ok bool)) {}
 func (e *mockEngine) ProbeLocks()                                                      {}
 

tsnet/depaware.txt

@@ -147,9 +147,11 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         tailscale.com/feature/buildfeatures                          from tailscale.com/wgengine/magicsock+
         tailscale.com/feature/c2n                                    from tailscale.com/tsnet
         tailscale.com/feature/condlite/expvar                        from tailscale.com/wgengine/magicsock
+        tailscale.com/feature/condregister/netlog                    from tailscale.com/tsnet
         tailscale.com/feature/condregister/oauthkey                  from tailscale.com/tsnet
         tailscale.com/feature/condregister/portmapper                from tailscale.com/tsnet
         tailscale.com/feature/condregister/useproxy                  from tailscale.com/tsnet
+        tailscale.com/feature/netlog                                 from tailscale.com/feature/condregister/netlog
         tailscale.com/feature/oauthkey                               from tailscale.com/feature/condregister/oauthkey
         tailscale.com/feature/portmapper                             from tailscale.com/feature/condregister/portmapper
         tailscale.com/feature/useproxy                               from tailscale.com/feature/condregister/useproxy
@@ -314,7 +316,7 @@ tailscale.com/tsnet dependencies: (generated by github.com/tailscale/depaware)
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+
         tailscale.com/wgengine/filter/filtertype                     from tailscale.com/types/netmap+
      💣 tailscale.com/wgengine/magicsock                             from tailscale.com/ipn/ipnlocal+
-        tailscale.com/wgengine/netlog                                from tailscale.com/wgengine+
+        tailscale.com/wgengine/netlog                                from tailscale.com/feature/netlog
         tailscale.com/wgengine/netstack                              from tailscale.com/tsnet
         tailscale.com/wgengine/netstack/gro                          from tailscale.com/net/tstun+
         tailscale.com/wgengine/router                                from tailscale.com/ipn/ipnlocal+

tsnet/tsnet.go

@@ -163,6 +163,7 @@ import (
 	"tailscale.com/control/controlclient"
 	"tailscale.com/envknob"
 	_ "tailscale.com/feature/c2n"
+	_ "tailscale.com/feature/condregister/netlog"
 	_ "tailscale.com/feature/condregister/oauthkey"
 	_ "tailscale.com/feature/condregister/portmapper"
 	_ "tailscale.com/feature/condregister/useproxy"

wgengine/netlog_hooks.go

@@ -0,0 +1,86 @@
+// Copyright (c) Tailscale Inc & contributors
+// SPDX-License-Identifier: BSD-3-Clause
+
+package wgengine
+
+import (
+	"net/netip"
+
+	"tailscale.com/feature"
+	"tailscale.com/health"
+	"tailscale.com/net/netmon"
+	"tailscale.com/net/tstun"
+	"tailscale.com/tailcfg"
+	"tailscale.com/types/logger"
+	"tailscale.com/types/logid"
+	"tailscale.com/util/eventbus"
+	"tailscale.com/wgengine/magicsock"
+	"tailscale.com/wgengine/router"
+)
+
+// NetLogSource provides the network flow logging feature what it needs
+// from the rest of the system (in practice, ipnlocal.LocalBackend):
+// on-demand node lookups and the current audit logging identity.
+type NetLogSource interface {
+	// SelfNode returns the current self node and its owning user profile.
+	// The views are invalid if there is no current node.
+	SelfNode() (tailcfg.NodeView, tailcfg.UserProfileView)
+
+	// NodeByAddr returns the node assigned the given address along with
+	// its owning user profile.
+	// ok is false if no node is known to own addr.
+	NodeByAddr(addr netip.Addr) (node tailcfg.NodeView, user tailcfg.UserProfileView, ok bool)
+
+	// NetLogIDs returns the audit logging IDs from the current netmap,
+	// along with whether exit node flows should be logged.
+	// ok is false if network flow logging should not run.
+	NetLogIDs() (nodeID, domainID logid.PrivateID, logExitFlows bool, ok bool)
+}
+
+// NetLogger is the engine's handle on the network flow logger
+// lifecycle, implemented by the feature/netlog package.
+//
+// Reconfig and ReconfigDone are only called from [Engine.Reconfig],
+// serialized by the engine's internal lock. Shutdown may be called
+// concurrently with them from [Engine.Close].
+type NetLogger interface {
+	// Reconfig is called near the top of every [Engine.Reconfig],
+	// before its ErrNoChanges early return (so identity-only changes
+	// still take effect) and before the router is configured (so a
+	// starting logger captures initial packets). It reports whether
+	// network logging state changed, which suppresses the engine's
+	// ErrNoChanges early return.
+	Reconfig(routerCfg *router.Config, routerChanged bool) (changed bool)
+
+	// ReconfigDone is called at the end of [Engine.Reconfig], after
+	// the router is configured, so that a logger stopping as a result
+	// of the preceding Reconfig call captures final packets. It may
+	// block to flush pending messages.
+	ReconfigDone()
+
+	// Shutdown stops the logger. It may block to flush pending
+	// messages, bounded by an internal upload timeout.
+	Shutdown()
+}
+
+// NetLoggerDeps are the engine-owned dependencies passed to
+// [HookNewNetLogger] to construct a [NetLogger].
+type NetLoggerDeps struct {
+	Logf   logger.Logf
+	Tun    *tstun.Wrapper
+	Sock   *magicsock.Conn
+	NetMon *netmon.Monitor
+	Health *health.Tracker
+	Bus    *eventbus.Bus
+
+	// Source returns the [NetLogSource] installed via
+	// [Engine.SetNetLogSource], or nil if none has been installed yet.
+	// It is a func because the source is installed after the engine
+	// (and thus the NetLogger) is constructed.
+	Source func() NetLogSource
+}
+
+// HookNewNetLogger is set by the feature/netlog package to construct
+// each engine's [NetLogger]. If unset, network flow logging is not
+// linked into the binary and the engine skips all NetLogger calls.
+var HookNewNetLogger feature.Hook[func(NetLoggerDeps) NetLogger]

wgengine/userspace.go

@@ -58,7 +58,6 @@ import (
 	"tailscale.com/version"
 	"tailscale.com/wgengine/filter"
 	"tailscale.com/wgengine/magicsock"
-	"tailscale.com/wgengine/netlog"
 	"tailscale.com/wgengine/netstack/gro"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
@@ -66,10 +65,6 @@ import (
 	"tailscale.com/wgengine/wglog"
 )
 
-// networkLoggerUploadTimeout is the maximum timeout to wait when
-// shutting down the network logger as it uploads the last network log messages.
-const networkLoggerUploadTimeout = 5 * time.Second
-
 type userspaceEngine struct {
 	// eventBus will eventually become required, but for now may be nil.
 	eventBus    *eventbus.Bus
@@ -156,13 +151,16 @@ type userspaceEngine struct {
 	// value of the ICMP identifier and sequence number concatenated.
 	icmpEchoResponseCallback map[uint32]func()
 
-	// networkLogger logs statistics about network connections.
+	// netlogger is the network flow logger handle constructed via
-	networkLogger netlog.Logger
+	// [HookNewNetLogger], or nil if the feature/netlog package is not
+	// linked into the binary.
+	netlogger NetLogger
 
-	// netLogSource is the [netlog.NodeSource] installed via
+	// netLogSource is the [NetLogSource] installed via
-	// [Engine.SetNetLogNodeSource]; it is read when starting up the network
+	// [Engine.SetNetLogSource]; the netlogger reads it on each
-	// logger from inside Reconfig. It may be nil if no source was installed.
+	// Reconfig via [NetLoggerDeps.Source]. It may be nil if no source
-	netLogSource syncs.AtomicValue[netlog.NodeSource]
+	// was installed.
+	netLogSource syncs.AtomicValue[NetLogSource]
 
 	// wgPeerLookup is the lookup function installed via
 	// [Engine.SetWGPeerLookup]; it is consulted by [wgLogger] to translate
@@ -454,6 +452,18 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 	closePool.add(e.magicConn)
 	e.magicConn.SetNetworkUp(e.netMon.InterfaceState().AnyInterfaceUp())
 
+	if newNetLogger, ok := HookNewNetLogger.GetOk(); ok {
+		e.netlogger = newNetLogger(NetLoggerDeps{
+			Logf:   logf,
+			Tun:    e.tundev,
+			Sock:   e.magicConn,
+			NetMon: e.netMon,
+			Health: e.health,
+			Bus:    e.eventBus,
+			Source: e.netLogSource.Load,
+		})
+	}
+
 	tsTUNDev.SetDiscoKey(e.magicConn.DiscoPublicKey())
 
 	if conf.RespondToPing {
@@ -758,9 +768,9 @@ func (e *userspaceEngine) SetPeerSessionStateFunc(fn func(key.NodePublic, PeerWi
 	})
 }
 
-// SetNetLogNodeSource installs the [netlog.NodeSource] used by the engine's
+// SetNetLogSource installs the [NetLogSource] consulted by the engine's
-// network logger.
+// network flow logger.
-func (e *userspaceEngine) SetNetLogNodeSource(src netlog.NodeSource) {
+func (e *userspaceEngine) SetNetLogSource(src NetLogSource) {
 	e.netLogSource.Store(src)
 }
 
@@ -864,17 +874,18 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
 
 	listenPortChanged := listenPort != e.magicConn.LocalPort()
 	peerMTUChanged := peerMTUEnable != e.magicConn.PeerMTUEnabled()
-	if !engineChanged && !routerChanged && !dnsChanged && !listenPortChanged && !isSubnetRouterChanged && !peerMTUChanged {
+
-		return ErrNoChanges
+	// Let the network flow logger react before the early return below,
+	// so that logging identity changes take effect even when nothing
+	// else changed, and before the router is configured, so that a
+	// starting logger captures initial packets.
+	netlogChanged := false
+	if e.netlogger != nil {
+		netlogChanged = e.netlogger.Reconfig(routerCfg, routerChanged)
 	}
-	newLogIDs := cfg.NetworkLogging
+
-	oldLogIDs := e.lastCfgFull.NetworkLogging
+	if !engineChanged && !routerChanged && !dnsChanged && !listenPortChanged && !isSubnetRouterChanged && !peerMTUChanged && !netlogChanged {
-	netLogIDsNowValid := !newLogIDs.NodeID.IsZero() && !newLogIDs.DomainID.IsZero()
+		return ErrNoChanges
-	netLogIDsWasValid := !oldLogIDs.NodeID.IsZero() && !oldLogIDs.DomainID.IsZero()
-	netLogIDsChanged := netLogIDsNowValid && netLogIDsWasValid && newLogIDs != oldLogIDs
-	netLogRunning := netLogIDsNowValid && !routerCfg.Equal(&router.Config{})
-	if !buildfeatures.HasNetLog || envknob.NoLogsNoSupport() {
-		netLogRunning = false
 	}
 
 	// TODO(bradfitz,danderson): maybe delete this isDNSIPOverTailscale
@@ -982,36 +993,8 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
 		}
 	}
 
-	// Shutdown the network logger because the IDs changed.
-	// Let it be started back up by subsequent logic.
-	if buildfeatures.HasNetLog && netLogIDsChanged && e.networkLogger.Running() {
-		e.logf("wgengine: Reconfig: shutting down network logger")
-		ctx, cancel := context.WithTimeout(context.Background(), networkLoggerUploadTimeout)
-		defer cancel()
-		if err := e.networkLogger.Shutdown(ctx); err != nil {
-			e.logf("wgengine: Reconfig: error shutting down network logger: %v", err)
-		}
-	}
-
-	// Startup the network logger.
-	// Do this before configuring the router so that we capture initial packets.
-	if buildfeatures.HasNetLog && netLogRunning && !e.networkLogger.Running() {
-		nid := cfg.NetworkLogging.NodeID
-		tid := cfg.NetworkLogging.DomainID
-		logExitFlowEnabled := cfg.NetworkLogging.LogExitFlowEnabled
-		e.logf("wgengine: Reconfig: starting up network logger (node:%s tailnet:%s)", nid.Public(), tid.Public())
-		src := e.netLogSource.Load()
-		if src == nil {
-			e.logf("wgengine: Reconfig: no NodeSource installed; network logger not started")
-		} else if err := e.networkLogger.Startup(e.logf, src, nid, tid, e.tundev, e.magicConn, e.netMon, e.health, e.eventBus, logExitFlowEnabled); err != nil {
-			e.logf("wgengine: Reconfig: error starting up network logger: %v", err)
-		}
-		e.networkLogger.ReconfigRoutes(routerCfg)
-	}
-
 	if routerChanged {
 		e.logf("wgengine: Reconfig: configuring router")
-		e.networkLogger.ReconfigRoutes(routerCfg)
 		err := e.router.Set(routerCfg)
 		e.health.SetRouterHealth(err)
 		if err != nil {
@@ -1050,16 +1033,11 @@ func (e *userspaceEngine) Reconfig(cfg *wgcfg.Config, routerCfg *router.Config,
 		}
 	}
 
-	// Shutdown the network logger.
+	// Let the network flow logger finish reacting after the router is
-	// Do this after configuring the router so that we capture final packets.
+	// configured, so that a stopping logger captures final packets.
-	// This attempts to flush out any log messages and may block.
+	// This may block to flush pending log messages.
-	if !netLogRunning && e.networkLogger.Running() {
+	if e.netlogger != nil {
-		e.logf("wgengine: Reconfig: shutting down network logger")
+		e.netlogger.ReconfigDone()
-		ctx, cancel := context.WithTimeout(context.Background(), networkLoggerUploadTimeout)
-		defer cancel()
-		if err := e.networkLogger.Shutdown(ctx); err != nil {
-			e.logf("wgengine: Reconfig: error shutting down network logger: %v", err)
-		}
 	}
 
 	if buildfeatures.HasBird && isSubnetRouterChanged && e.birdClient != nil {
@@ -1252,10 +1230,8 @@ func (e *userspaceEngine) Close() {
 	}
 	close(e.waitCh)
 
-	ctx, cancel := context.WithTimeout(context.Background(), networkLoggerUploadTimeout)
+	if e.netlogger != nil {
-	defer cancel()
+		e.netlogger.Shutdown()
-	if err := e.networkLogger.Shutdown(ctx); err != nil {
-		e.logf("wgengine: Close: error shutting down network logger: %v", err)
 	}
 }
 

wgengine/wgcfg/config.go

@@ -9,7 +9,6 @@ import (
 	"slices"
 
 	"tailscale.com/types/key"
-	"tailscale.com/types/logid"
 )
 
 //go:generate go run tailscale.com/cmd/cloner -type=Config,Peer
@@ -20,15 +19,6 @@ type Config struct {
 	PrivateKey key.NodePrivate
 	Addresses  []netip.Prefix
 	Peers      []Peer
-
-	// NetworkLogging enables network logging.
-	// It is disabled if either ID is the zero value.
-	// LogExitFlowEnabled indicates whether or not exit flows should be logged.
-	NetworkLogging struct {
-		NodeID             logid.PrivateID
-		DomainID           logid.PrivateID
-		LogExitFlowEnabled bool
-	}
 }
 
 func (c *Config) Equal(o *Config) bool {
@@ -36,7 +26,6 @@ func (c *Config) Equal(o *Config) bool {
 		return c == o
 	}
 	return c.PrivateKey.Equal(o.PrivateKey) &&
-		c.NetworkLogging == o.NetworkLogging &&
 		slices.Equal(c.Addresses, o.Addresses) &&
 		slices.EqualFunc(c.Peers, o.Peers, Peer.Equal)
 }

wgengine/wgcfg/config_test.go

@@ -14,8 +14,7 @@ func TestConfigEqual(t *testing.T) {
 	rt := reflect.TypeFor[Config]()
 	for sf := range rt.Fields() {
 		switch sf.Name {
-		case "Name", "NodeID", "PrivateKey", "Addresses", "Peers",
+		case "Name", "NodeID", "PrivateKey", "Addresses", "Peers":
-			"NetworkLogging":
 			// These are compared in [Config.Equal].
 		default:
 			t.Errorf("Have you added field %q to Config.Equal? Do so if not, and then update TestConfigEqual", sf.Name)

wgengine/wgcfg/nmcfg/nmcfg.go

@@ -15,7 +15,6 @@ import (
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/key"
 	"tailscale.com/types/logger"
-	"tailscale.com/types/logid"
 	"tailscale.com/types/netmap"
 	"tailscale.com/wgengine/wgcfg"
 )
@@ -53,27 +52,6 @@ func WGCfg(pk key.NodePrivate, nm *netmap.NetworkMap, logf logger.Logf, flags ne
 		Peers:      make([]wgcfg.Peer, 0, len(nm.Peers)),
 	}
 
-	// Setup log IDs for data plane audit logging.
-	if nm.SelfNode.Valid() {
-		canNetworkLog := nm.SelfNode.HasCap(tailcfg.CapabilityDataPlaneAuditLogs)
-		logExitFlowEnabled := nm.SelfNode.HasCap(tailcfg.NodeAttrLogExitFlows)
-		if canNetworkLog && nm.SelfNode.DataPlaneAuditLogID() != "" && nm.DomainAuditLogID != "" {
-			nodeID, errNode := logid.ParsePrivateID(nm.SelfNode.DataPlaneAuditLogID())
-			if errNode != nil {
-				logf("[v1] wgcfg: unable to parse node audit log ID: %v", errNode)
-			}
-			domainID, errDomain := logid.ParsePrivateID(nm.DomainAuditLogID)
-			if errDomain != nil {
-				logf("[v1] wgcfg: unable to parse domain audit log ID: %v", errDomain)
-			}
-			if errNode == nil && errDomain == nil {
-				cfg.NetworkLogging.NodeID = nodeID
-				cfg.NetworkLogging.DomainID = domainID
-				cfg.NetworkLogging.LogExitFlowEnabled = logExitFlowEnabled
-			}
-		}
-	}
-
 	var skippedExitNode, skippedSubnetRouter, skippedExpired []tailcfg.NodeView
 
 	for _, peer := range nm.Peers {

wgengine/wgcfg/wgcfg_clone.go

@@ -9,7 +9,6 @@ import (
 	"net/netip"
 
 	"tailscale.com/types/key"
-	"tailscale.com/types/logid"
 )
 
 // Clone makes a deep copy of Config.
@@ -32,14 +31,9 @@ func (src *Config) Clone() *Config {
 
 // A compilation failure here means this code must be regenerated, with the command at the top of this file.
 var _ConfigCloneNeedsRegeneration = Config(struct {
-	PrivateKey     key.NodePrivate
+	PrivateKey key.NodePrivate
-	Addresses      []netip.Prefix
+	Addresses  []netip.Prefix
-	Peers          []Peer
+	Peers      []Peer
-	NetworkLogging struct {
-		NodeID             logid.PrivateID
-		DomainID           logid.PrivateID
-		LogExitFlowEnabled bool
-	}
 }{})
 
 // Clone makes a deep copy of Peer.

wgengine/wgengine.go

@@ -16,7 +16,6 @@ import (
 	"tailscale.com/types/key"
 	"tailscale.com/types/netmap"
 	"tailscale.com/wgengine/filter"
-	"tailscale.com/wgengine/netlog"
 	"tailscale.com/wgengine/router"
 	"tailscale.com/wgengine/wgcfg"
 	"tailscale.com/wgengine/wgint"
@@ -198,12 +197,13 @@ type Engine interface {
 	// look up which peer should handle an outbound packet by destination IP.
 	SetPeerByIPPacketFunc(func(netip.Addr) (_ key.NodePublic, ok bool))
 
-	// SetNetLogNodeSource installs the [netlog.NodeSource] used by the engine's
+	// SetNetLogSource installs the [NetLogSource] consulted by the
-	// network logger to look up Tailscale node info on demand.
+	// engine's network flow logger for node lookups and the current
+	// audit logging identity.
 	//
 	// It is expected to be called once during LocalBackend construction,
 	// before any [Engine.Reconfig] call that starts up the network logger.
-	SetNetLogNodeSource(netlog.NodeSource)
+	SetNetLogSource(NetLogSource)
 
 	// SetWGPeerLookup installs the function used by the engine's
 	// wireguard-go log wrapper to rewrite peer references in log lines