diff --git a/cmd/derper/depaware.txt b/cmd/derper/depaware.txt
index 29f2efc89..167950d9c 100644
--- a/cmd/derper/depaware.txt
+++ b/cmd/derper/depaware.txt
@@ -12,7 +12,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         github.com/golang/groupcache/lru                             from tailscale.com/net/dnscache
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
-   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces
+   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
    L    github.com/jsimonetti/rtnetlink/internal/unix                from github.com/jsimonetti/rtnetlink
         github.com/klauspost/compress/flate                          from nhooyr.io/websocket
    L 💣 github.com/mdlayher/netlink                                  from github.com/jsimonetti/rtnetlink+
@@ -47,6 +47,7 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/net/netns                                      from tailscale.com/derp/derphttp
         tailscale.com/net/netutil                                    from tailscale.com/client/tailscale
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter
+        tailscale.com/net/sockstats                                  from tailscale.com/derp/derphttp
         tailscale.com/net/stun                                       from tailscale.com/cmd/derper
         tailscale.com/net/tlsdial                                    from tailscale.com/derp/derphttp
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn+
@@ -84,13 +85,14 @@ tailscale.com/cmd/derper dependencies: (generated by github.com/tailscale/depawa
         tailscale.com/util/lineread                                  from tailscale.com/hostinfo+
         tailscale.com/util/mak                                       from tailscale.com/syncs+
         tailscale.com/util/multierr                                  from tailscale.com/health
-        tailscale.com/util/set                                       from tailscale.com/health
+        tailscale.com/util/set                                       from tailscale.com/health+
         tailscale.com/util/singleflight                              from tailscale.com/net/dnscache
         tailscale.com/util/vizerror                                  from tailscale.com/tsweb
    W 💣 tailscale.com/util/winutil                                   from tailscale.com/hostinfo+
         tailscale.com/version                                        from tailscale.com/derp+
         tailscale.com/version/distro                                 from tailscale.com/hostinfo+
         tailscale.com/wgengine/filter                                from tailscale.com/types/netmap
+        tailscale.com/wgengine/monitor                               from tailscale.com/net/sockstats
         golang.org/x/crypto/acme                                     from golang.org/x/crypto/acme/autocert
         golang.org/x/crypto/acme/autocert                            from tailscale.com/cmd/derper
         golang.org/x/crypto/argon2                                   from tailscale.com/tka
diff --git a/cmd/tailscale/depaware.txt b/cmd/tailscale/depaware.txt
index a926d9eae..f8147d646 100644
--- a/cmd/tailscale/depaware.txt
+++ b/cmd/tailscale/depaware.txt
@@ -13,7 +13,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         github.com/google/uuid                                       from tailscale.com/util/quarantine+
         github.com/hdevalence/ed25519consensus                       from tailscale.com/tka
    L    github.com/josharian/native                                  from github.com/mdlayher/netlink+
-   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces
+   L 💣 github.com/jsimonetti/rtnetlink                              from tailscale.com/net/interfaces+
    L    github.com/jsimonetti/rtnetlink/internal/unix                from github.com/jsimonetti/rtnetlink
         github.com/kballard/go-shellquote                            from tailscale.com/cmd/tailscale/cli
         github.com/klauspost/compress/flate                          from nhooyr.io/websocket
@@ -79,6 +79,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/net/packet                                     from tailscale.com/wgengine/filter
         tailscale.com/net/ping                                       from tailscale.com/net/netcheck
         tailscale.com/net/portmapper                                 from tailscale.com/net/netcheck+
+        tailscale.com/net/sockstats                                  from tailscale.com/control/controlhttp+
         tailscale.com/net/stun                                       from tailscale.com/net/netcheck
         tailscale.com/net/tlsdial                                    from tailscale.com/derp/derphttp+
         tailscale.com/net/tsaddr                                     from tailscale.com/net/interfaces+
@@ -126,6 +127,7 @@ tailscale.com/cmd/tailscale dependencies: (generated by github.com/tailscale/dep
         tailscale.com/version/distro                                 from tailscale.com/cmd/tailscale/cli+
         tailscale.com/wgengine/capture                               from tailscale.com/cmd/tailscale/cli
         tailscale.com/wgengine/filter                                from tailscale.com/types/netmap
+        tailscale.com/wgengine/monitor                               from tailscale.com/net/sockstats
         golang.org/x/crypto/argon2                                   from tailscale.com/tka
         golang.org/x/crypto/blake2b                                  from golang.org/x/crypto/nacl/box+
         golang.org/x/crypto/blake2s                                  from tailscale.com/control/controlbase+
diff --git a/cmd/tailscaled/depaware.txt b/cmd/tailscaled/depaware.txt
index b4235f86a..9e6e0c45d 100644
--- a/cmd/tailscaled/depaware.txt
+++ b/cmd/tailscaled/depaware.txt
@@ -246,6 +246,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/net/proxymux                                   from tailscale.com/cmd/tailscaled
         tailscale.com/net/routetable                                 from tailscale.com/doctor/routetable
         tailscale.com/net/socks5                                     from tailscale.com/cmd/tailscaled
+        tailscale.com/net/sockstats                                  from tailscale.com/control/controlclient+
         tailscale.com/net/stun                                       from tailscale.com/net/netcheck+
         tailscale.com/net/tlsdial                                    from tailscale.com/control/controlclient+
         tailscale.com/net/tsaddr                                     from tailscale.com/ipn+
diff --git a/control/controlclient/auto.go b/control/controlclient/auto.go
index cfdb6b78b..bab7c7be3 100644
--- a/control/controlclient/auto.go
+++ b/control/controlclient/auto.go
@@ -13,6 +13,7 @@
 
 	"tailscale.com/health"
 	"tailscale.com/logtail/backoff"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/tailcfg"
 	"tailscale.com/types/empty"
 	"tailscale.com/types/key"
@@ -118,7 +119,11 @@ func NewNoStart(opts Options) (_ *Auto, err error) {
 		statusFunc: opts.Status,
 	}
 	c.authCtx, c.authCancel = context.WithCancel(context.Background())
+	c.authCtx = sockstats.WithSockStats(c.authCtx, "controlclient.Auto:auth")
+
 	c.mapCtx, c.mapCancel = context.WithCancel(context.Background())
+	c.mapCtx = sockstats.WithSockStats(c.mapCtx, "controlclient.Auto:map")
+
 	c.unregisterHealthWatch = health.RegisterWatcher(direct.ReportHealthChange)
 	return c, nil
 
@@ -206,6 +211,7 @@ func (c *Auto) cancelAuth() {
 	}
 	if !c.closed {
 		c.authCtx, c.authCancel = context.WithCancel(context.Background())
+		c.authCtx = sockstats.WithSockStats(c.authCtx, "controlclient.Auto:auth")
 	}
 	c.mu.Unlock()
 }
@@ -216,6 +222,8 @@ func (c *Auto) cancelMapLocked() {
 	}
 	if !c.closed {
 		c.mapCtx, c.mapCancel = context.WithCancel(context.Background())
+		c.mapCtx = sockstats.WithSockStats(c.mapCtx, "controlclient.Auto:map")
+
 	}
 }
 
diff --git a/control/controlhttp/client.go b/control/controlhttp/client.go
index 4eebbee9a..bdb02013b 100644
--- a/control/controlhttp/client.go
+++ b/control/controlhttp/client.go
@@ -41,6 +41,7 @@
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/dnsfallback"
 	"tailscale.com/net/netutil"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/tailcfg"
@@ -272,6 +273,8 @@ func (a *Dialer) dialHost(ctx context.Context, addr netip.Addr) (*ClientConn, er
 	ctx, cancel := context.WithCancel(ctx)
 	defer cancel()
 
+	ctx = sockstats.WithSockStats(ctx, "controlclient.Dialer")
+
 	// u80 and u443 are the URLs we'll try to hit over HTTP or HTTPS,
 	// respectively, in order to do the HTTP upgrade to a net.Conn over which
 	// we'll speak Noise.
diff --git a/derp/derphttp/derphttp_client.go b/derp/derphttp/derphttp_client.go
index 4a1427c4c..160ae8bd3 100644
--- a/derp/derphttp/derphttp_client.go
+++ b/derp/derphttp/derphttp_client.go
@@ -32,6 +32,7 @@
 	"tailscale.com/envknob"
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/netns"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tlsdial"
 	"tailscale.com/net/tshttpproxy"
 	"tailscale.com/syncs"
@@ -615,6 +616,8 @@ type res struct {
 	ctx, cancel := context.WithTimeout(ctx, dialNodeTimeout)
 	defer cancel()
 
+	ctx = sockstats.WithSockStats(ctx, "derphttp.Client")
+
 	nwait := 0
 	startDial := func(dstPrimary, proto string) {
 		nwait++
diff --git a/go.toolchain.rev b/go.toolchain.rev
index 235d5ae0a..4ff879a8e 100644
--- a/go.toolchain.rev
+++ b/go.toolchain.rev
@@ -1 +1 @@
-ec180cbca39fcb5dc420399b37583e53fcf382c9
+fb11c0df588717a3ee13b09dacae1e7093279d67
diff --git a/ipn/ipnlocal/peerapi.go b/ipn/ipnlocal/peerapi.go
index 1a85775ff..16c2f496e 100644
--- a/ipn/ipnlocal/peerapi.go
+++ b/ipn/ipnlocal/peerapi.go
@@ -45,6 +45,7 @@
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/netutil"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/tailcfg"
 	"tailscale.com/util/clientmetric"
 	"tailscale.com/util/multierr"
@@ -709,6 +710,8 @@ func (h *peerAPIHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 		return
 	case "/v0/doctor":
 		h.handleServeDoctor(w, r)
+	case "/v0/sockstats":
+		h.handleServeSockStats(w, r)
 		return
 	case "/v0/ingress":
 		metricIngressCalls.Add(1)
@@ -850,6 +853,76 @@ func (h *peerAPIHandler) handleServeDoctor(w http.ResponseWriter, r *http.Reques
 	fmt.Fprintln(w, "</pre>")
 }
 
+func (h *peerAPIHandler) handleServeSockStats(w http.ResponseWriter, r *http.Request) {
+	if !h.canDebug() {
+		http.Error(w, "denied; no debug access", http.StatusForbidden)
+		return
+	}
+	w.Header().Set("Content-Type", "text/html; charset=utf-8")
+	fmt.Fprintln(w, "<!DOCTYPE html><h1>Socket Stats</h1>")
+
+	stats := sockstats.Get()
+	if stats == nil {
+		fmt.Fprintln(w, "No socket stats available")
+		return
+	}
+
+	fmt.Fprintln(w, "<table border='1' cellspacing='0' style='border-collapse: collapse;'>")
+	fmt.Fprintln(w, "<thead>")
+	fmt.Fprintln(w, "<th>Label</th>")
+	fmt.Fprintln(w, "<th>Tx</th>")
+	fmt.Fprintln(w, "<th>Rx</th>")
+	for _, iface := range stats.Interfaces {
+		fmt.Fprintf(w, "<th>Tx (%s)</th>", html.EscapeString(iface))
+		fmt.Fprintf(w, "<th>Rx (%s)</th>", html.EscapeString(iface))
+	}
+	fmt.Fprintln(w, "</thead>")
+
+	fmt.Fprintln(w, "<tbody>")
+	labels := make([]string, 0, len(stats.Stats))
+	for label := range stats.Stats {
+		labels = append(labels, label)
+	}
+	sort.Strings(labels)
+
+	txTotal := int64(0)
+	rxTotal := int64(0)
+	txTotalByInterface := map[string]int64{}
+	rxTotalByInterface := map[string]int64{}
+
+	for _, label := range labels {
+		stat := stats.Stats[label]
+		fmt.Fprintln(w, "<tr>")
+		fmt.Fprintf(w, "<td>%s</td>", html.EscapeString(label))
+		fmt.Fprintf(w, "<td align=right>%d</td>", stat.TxBytes)
+		fmt.Fprintf(w, "<td align=right>%d</td>", stat.RxBytes)
+
+		txTotal += stat.TxBytes
+		rxTotal += stat.RxBytes
+
+		for _, iface := range stats.Interfaces {
+			fmt.Fprintf(w, "<td align=right>%d</td>", stat.TxBytesByInterface[iface])
+			fmt.Fprintf(w, "<td align=right>%d</td>", stat.RxBytesByInterface[iface])
+			txTotalByInterface[iface] += stat.TxBytesByInterface[iface]
+			rxTotalByInterface[iface] += stat.RxBytesByInterface[iface]
+		}
+		fmt.Fprintln(w, "</tr>")
+	}
+	fmt.Fprintln(w, "</tbody>")
+
+	fmt.Fprintln(w, "<tfoot>")
+	fmt.Fprintln(w, "<th>Total</th>")
+	fmt.Fprintf(w, "<th>%d</th>", txTotal)
+	fmt.Fprintf(w, "<th>%d</th>", rxTotal)
+	for _, iface := range stats.Interfaces {
+		fmt.Fprintf(w, "<th>%d</th>", txTotalByInterface[iface])
+		fmt.Fprintf(w, "<th>%d</th>", rxTotalByInterface[iface])
+	}
+	fmt.Fprintln(w, "</tfoot>")
+
+	fmt.Fprintln(w, "</table>")
+}
+
 type incomingFile struct {
 	name        string // "foo.jpg"
 	started     time.Time
diff --git a/logtail/logtail.go b/logtail/logtail.go
index 8979c914f..7f19e3a84 100644
--- a/logtail/logtail.go
+++ b/logtail/logtail.go
@@ -24,6 +24,7 @@
 	"tailscale.com/envknob"
 	"tailscale.com/logtail/backoff"
 	"tailscale.com/net/interfaces"
+	"tailscale.com/net/sockstats"
 	tslogger "tailscale.com/types/logger"
 	"tailscale.com/util/set"
 	"tailscale.com/wgengine/monitor"
@@ -426,6 +427,7 @@ func (l *Logger) awaitInternetUp(ctx context.Context) {
 // origlen of -1 indicates that the body is not compressed.
 func (l *Logger) upload(ctx context.Context, body []byte, origlen int) (uploaded bool, err error) {
 	const maxUploadTime = 45 * time.Second
+	ctx = sockstats.WithSockStats(ctx, "logtail.Logger")
 	ctx, cancel := context.WithTimeout(ctx, maxUploadTime)
 	defer cancel()
 
diff --git a/net/dns/resolver/forwarder.go b/net/dns/resolver/forwarder.go
index 47be991c8..7c0ff42ec 100644
--- a/net/dns/resolver/forwarder.go
+++ b/net/dns/resolver/forwarder.go
@@ -26,6 +26,7 @@
 	"tailscale.com/net/dnscache"
 	"tailscale.com/net/neterror"
 	"tailscale.com/net/netns"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/types/dnstype"
 	"tailscale.com/types/logger"
@@ -406,6 +407,7 @@ func (f *forwarder) getKnownDoHClientForProvider(urlBase string) (c *http.Client
 const dohType = "application/dns-message"
 
 func (f *forwarder) sendDoH(ctx context.Context, urlBase string, c *http.Client, packet []byte) ([]byte, error) {
+	ctx = sockstats.WithSockStats(ctx, "dns.forwarder:doh")
 	metricDNSFwdDoH.Add(1)
 	req, err := http.NewRequestWithContext(ctx, "POST", urlBase, bytes.NewReader(packet))
 	if err != nil {
@@ -485,6 +487,7 @@ func (f *forwarder) sendUDP(ctx context.Context, fq *forwardQuery, rr resolverAn
 		return nil, fmt.Errorf("unrecognized resolver type %q", rr.name.Addr)
 	}
 	metricDNSFwdUDP.Add(1)
+	ctx = sockstats.WithSockStats(ctx, "dns.forwarder:udp")
 
 	ln, err := f.packetListener(ipp.Addr())
 	if err != nil {
diff --git a/net/netcheck/netcheck.go b/net/netcheck/netcheck.go
index 2705bcb92..2b8f76133 100644
--- a/net/netcheck/netcheck.go
+++ b/net/netcheck/netcheck.go
@@ -31,6 +31,7 @@
 	"tailscale.com/net/netns"
 	"tailscale.com/net/ping"
 	"tailscale.com/net/portmapper"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/stun"
 	"tailscale.com/syncs"
 	"tailscale.com/tailcfg"
@@ -783,6 +784,8 @@ func (c *Client) GetReport(ctx context.Context, dm *tailcfg.DERPMap) (_ *Report,
 	ctx, cancel := context.WithTimeout(ctx, overallProbeTimeout)
 	defer cancel()
 
+	ctx = sockstats.WithSockStats(ctx, "netcheck.Client")
+
 	if dm == nil {
 		return nil, errors.New("netcheck: GetReport: DERP map is nil")
 	}
diff --git a/net/portmapper/portmapper.go b/net/portmapper/portmapper.go
index 8cb565b68..29bddc9d2 100644
--- a/net/portmapper/portmapper.go
+++ b/net/portmapper/portmapper.go
@@ -22,6 +22,7 @@
 	"tailscale.com/net/netaddr"
 	"tailscale.com/net/neterror"
 	"tailscale.com/net/netns"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/types/logger"
 	"tailscale.com/types/nettype"
 	"tailscale.com/util/clientmetric"
@@ -238,6 +239,8 @@ func (c *Client) upnpPort() uint16 {
 }
 
 func (c *Client) listenPacket(ctx context.Context, network, addr string) (nettype.PacketConn, error) {
+	ctx = sockstats.WithSockStats(ctx, "portmapper.Client")
+
 	// When running under testing conditions, we bind the IGD server
 	// to localhost, and may be running in an environment where our
 	// netns code would decide that binding the portmapper client
diff --git a/net/sockstats/sockstats.go b/net/sockstats/sockstats.go
new file mode 100644
index 000000000..28055d201
--- /dev/null
+++ b/net/sockstats/sockstats.go
@@ -0,0 +1,39 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+// Package sockstats collects statistics about network sockets used by
+// the Tailscale client. The context where sockets are used must be
+// instrumented with the WithSockStats() function.
+//
+// Only available on POSIX platforms when built with Tailscale's fork of Go.
+package sockstats
+
+import (
+	"context"
+
+	"tailscale.com/wgengine/monitor"
+)
+
+type SockStats struct {
+	Stats      map[string]SockStat
+	Interfaces []string
+}
+
+type SockStat struct {
+	TxBytes            int64
+	RxBytes            int64
+	TxBytesByInterface map[string]int64
+	RxBytesByInterface map[string]int64
+}
+
+func WithSockStats(ctx context.Context, label string) context.Context {
+	return withSockStats(ctx, label)
+}
+
+func Get() *SockStats {
+	return get()
+}
+
+func SetLinkMonitor(lm *monitor.Mon) {
+	setLinkMonitor(lm)
+}
diff --git a/net/sockstats/sockstats_noop.go b/net/sockstats/sockstats_noop.go
new file mode 100644
index 000000000..913f62d4d
--- /dev/null
+++ b/net/sockstats/sockstats_noop.go
@@ -0,0 +1,23 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build !tailscale_go || !(darwin || ios || android)
+
+package sockstats
+
+import (
+	"context"
+
+	"tailscale.com/wgengine/monitor"
+)
+
+func withSockStats(ctx context.Context, label string) context.Context {
+	return ctx
+}
+
+func get() *SockStats {
+	return nil
+}
+
+func setLinkMonitor(lm *monitor.Mon) {
+}
diff --git a/net/sockstats/sockstats_tsgo.go b/net/sockstats/sockstats_tsgo.go
new file mode 100644
index 000000000..58a737d1c
--- /dev/null
+++ b/net/sockstats/sockstats_tsgo.go
@@ -0,0 +1,151 @@
+// Copyright (c) Tailscale Inc & AUTHORS
+// SPDX-License-Identifier: BSD-3-Clause
+
+//go:build tailscale_go && (darwin || ios || android)
+
+package sockstats
+
+import (
+	"context"
+	"log"
+	"net"
+	"sync"
+	"sync/atomic"
+
+	"tailscale.com/net/interfaces"
+	"tailscale.com/wgengine/monitor"
+)
+
+type sockStatCounters struct {
+	txBytes, rxBytes                       atomic.Uint64
+	rxBytesByInterface, txBytesByInterface map[int]*atomic.Uint64
+}
+
+var sockStats = struct {
+	// mu protects fields in this group. It should not be held in the per-read/
+	// write callbacks.
+	mu              sync.Mutex
+	countersByLabel map[string]*sockStatCounters
+	knownInterfaces map[int]string // interface index -> name
+	usedInterfaces  map[int]int    // set of interface indexes
+
+	// Separate atomic since the current interface is accessed in the per-read/
+	// write callbacks.
+	currentInterface atomic.Uint32
+}{
+	countersByLabel: make(map[string]*sockStatCounters),
+	knownInterfaces: make(map[int]string),
+	usedInterfaces:  make(map[int]int),
+}
+
+func withSockStats(ctx context.Context, label string) context.Context {
+	sockStats.mu.Lock()
+	defer sockStats.mu.Unlock()
+	counters, ok := sockStats.countersByLabel[label]
+	if !ok {
+		counters = &sockStatCounters{
+			rxBytesByInterface: make(map[int]*atomic.Uint64),
+			txBytesByInterface: make(map[int]*atomic.Uint64),
+		}
+		for iface := range sockStats.knownInterfaces {
+			counters.rxBytesByInterface[iface] = &atomic.Uint64{}
+			counters.txBytesByInterface[iface] = &atomic.Uint64{}
+		}
+		sockStats.countersByLabel[label] = counters
+	}
+
+	didRead := func(n int) {
+		counters.rxBytes.Add(uint64(n))
+		if currentInterface := int(sockStats.currentInterface.Load()); currentInterface != 0 {
+			if a := counters.rxBytesByInterface[currentInterface]; a != nil {
+				a.Add(uint64(n))
+			}
+		}
+	}
+	didWrite := func(n int) {
+		counters.txBytes.Add(uint64(n))
+		if currentInterface := int(sockStats.currentInterface.Load()); currentInterface != 0 {
+			if a := counters.txBytesByInterface[currentInterface]; a != nil {
+				a.Add(uint64(n))
+			}
+		}
+	}
+	willOverwrite := func(trace *net.SockTrace) {
+		log.Printf("sockstats: trace %q was overwritten by another", label)
+	}
+
+	return net.WithSockTrace(ctx, &net.SockTrace{
+		DidRead:       didRead,
+		DidWrite:      didWrite,
+		WillOverwrite: willOverwrite,
+	})
+}
+
+func get() *SockStats {
+	sockStats.mu.Lock()
+	defer sockStats.mu.Unlock()
+
+	r := &SockStats{
+		Stats:      make(map[string]SockStat),
+		Interfaces: make([]string, 0, len(sockStats.usedInterfaces)),
+	}
+	for iface := range sockStats.usedInterfaces {
+		r.Interfaces = append(r.Interfaces, sockStats.knownInterfaces[iface])
+	}
+
+	for label, counters := range sockStats.countersByLabel {
+		r.Stats[label] = SockStat{
+			TxBytes:            int64(counters.txBytes.Load()),
+			RxBytes:            int64(counters.rxBytes.Load()),
+			TxBytesByInterface: make(map[string]int64),
+			RxBytesByInterface: make(map[string]int64),
+		}
+		for iface, a := range counters.rxBytesByInterface {
+			ifName := sockStats.knownInterfaces[iface]
+			r.Stats[label].RxBytesByInterface[ifName] = int64(a.Load())
+		}
+		for iface, a := range counters.txBytesByInterface {
+			ifName := sockStats.knownInterfaces[iface]
+			r.Stats[label].TxBytesByInterface[ifName] = int64(a.Load())
+		}
+	}
+
+	return r
+}
+
+func setLinkMonitor(lm *monitor.Mon) {
+	sockStats.mu.Lock()
+	defer sockStats.mu.Unlock()
+
+	// We intentionally populate all known interfaces now, so that we can
+	// increment stats for them without holding mu.
+	state := lm.InterfaceState()
+	for ifName, iface := range state.Interface {
+		sockStats.knownInterfaces[iface.Index] = ifName
+	}
+	if ifName := state.DefaultRouteInterface; ifName != "" {
+		ifIndex := state.Interface[ifName].Index
+		sockStats.currentInterface.Store(uint32(ifIndex))
+		sockStats.usedInterfaces[ifIndex] = 1
+	}
+
+	lm.RegisterChangeCallback(func(changed bool, state *interfaces.State) {
+		if changed {
+			if ifName := state.DefaultRouteInterface; ifName != "" {
+				ifIndex := state.Interface[ifName].Index
+				sockStats.mu.Lock()
+				defer sockStats.mu.Unlock()
+				// Ignore changes to unknown interfaces -- it would require
+				// updating the tx/rxBytesByInterface maps and thus
+				// additional locking for every read/write. Most of the time
+				// the set of interfaces is static.
+				if _, ok := sockStats.knownInterfaces[ifIndex]; ok {
+					sockStats.currentInterface.Store(uint32(ifIndex))
+					sockStats.usedInterfaces[ifIndex] = 1
+				} else {
+					sockStats.currentInterface.Store(0)
+				}
+			}
+		}
+	})
+}
diff --git a/wgengine/magicsock/magicsock.go b/wgengine/magicsock/magicsock.go
index 7daafc024..05f6b1abc 100644
--- a/wgengine/magicsock/magicsock.go
+++ b/wgengine/magicsock/magicsock.go
@@ -49,6 +49,7 @@
 	"tailscale.com/net/neterror"
 	"tailscale.com/net/netns"
 	"tailscale.com/net/portmapper"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/stun"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/syncs"
@@ -3049,7 +3050,7 @@ func (c *Conn) ReSTUN(why string) {
 // listenPacket opens a packet listener.
 // The network must be "udp4" or "udp6".
 func (c *Conn) listenPacket(network string, port uint16) (nettype.PacketConn, error) {
-	ctx := context.Background() // unused without DNS name to resolve
+	ctx := sockstats.WithSockStats(context.Background(), fmt.Sprintf("magicsock.Conn:%s", network)) // unused without DNS name to resolve
 	addr := net.JoinHostPort("", fmt.Sprint(port))
 	if c.testOnlyPacketListener != nil {
 		return nettype.MakePacketListenerWithNetIP(c.testOnlyPacketListener).ListenPacket(ctx, network, addr)
diff --git a/wgengine/userspace.go b/wgengine/userspace.go
index c31288229..7def6c971 100644
--- a/wgengine/userspace.go
+++ b/wgengine/userspace.go
@@ -29,6 +29,7 @@
 	"tailscale.com/net/flowtrack"
 	"tailscale.com/net/interfaces"
 	"tailscale.com/net/packet"
+	"tailscale.com/net/sockstats"
 	"tailscale.com/net/tsaddr"
 	"tailscale.com/net/tsdial"
 	"tailscale.com/net/tshttpproxy"
@@ -332,6 +333,9 @@ func NewUserspaceEngine(logf logger.Logf, conf Config) (_ Engine, reterr error)
 	conf.Dialer.SetLinkMonitor(e.linkMon)
 	e.dns = dns.NewManager(logf, conf.DNS, e.linkMon, conf.Dialer, fwdDNSLinkSelector{e, tunName})
 
+	// TODO: there's probably a better place for this
+	sockstats.SetLinkMonitor(e.linkMon)
+
 	logf("link state: %+v", e.linkMon.InterfaceState())
 
 	unregisterMonWatch := e.linkMon.RegisterChangeCallback(func(changed bool, st *interfaces.State) {