[client] Keep interface discovery out of the bind open path (#8226)

* [client] Keep interface discovery out of the bind open path Since 0.81.0 a userspace-mode agent whose interface name is not covered by the interface blacklist deadlocks while bringing the device up, and the daemon, the GUI and the service stop all hang. wireguard-go holds the device net lock across bind.Open, our bind builds the UDP mux there, the mux enumerated interfaces in its constructor, and the interface filter probed every unlisted name through wgctrl. For the agent's own interface that probe connected to the daemon's own UAPI endpoint and waited, with no deadline, for a reply the handler could only give after taking the same lock. #7346 moved the first enumeration from the stdnet constructor, which ran before the device existed, to this call site. The mux no longer discovers interfaces when it is constructed. It records whether its socket is bound to an unspecified address and GetConn uses that instead of the length of the discovered list, while GetListenAddresses keeps refreshing on demand, which pion calls during candidate gathering outside the device locks. The WireGuard detector also answers for the agent's own interface without probing, so no filter asks the daemon about itself. * [client] Take the agent's own interface name in the detector constructor Every device implementation reports the configured name, so there is no later name to follow and the setter was state without a reader that needed it. The detector takes the name once and compares without a lock. * [client] Create the default mux Net in the constructor With discovery moved to GetListenAddresses, the nil Net fallback ran there as well, and the first concurrent callers raced on writing it. stdnet.NewNet does no discovery, so the constructor can create it before the mux is shared and the address refresh only reads it. * [client] Follow the created interface name in the detector Android ignores the configured interface name and keeps the TUN name returned by CreateUnmonitoredTUNFromFD, so the detector built from the configuration would still probe the agent's real interface. The engine updates the detector with wgInterface.Name() once the interface exists. * [client] Keep the detector's own interface name immutable On Android the kernel names the TUN and the name can change again on renew, while the UAPI socket cannot be opened there at all, so neither the probe nor a name set after creation can identify the agent's own interface reliably. Excluding that interface on Android belongs to the interface discovery the app provides. Everywhere else the configured name is the created name, so the constructor argument is enough and the detector needs no setter and no lock on the hot path.
2026-10-19 20:09:07 +02:00 · 2026-10-16 02:16:45 +02:00
parent afd5c6df6a
commit 28657607c1
6 changed files with 250 additions and 14 deletions
@@ -2,17 +2,22 @@ package bind

 import (
 	"fmt"
+	"io"
 	"net"
 	"net/netip"
 	"sync"
+	"sync/atomic"
 	"testing"
 	"time"

+	"github.com/pion/transport/v3"
 	"github.com/pion/transport/v3/stdnet"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 	"golang.org/x/net/ipv4"
 	"golang.org/x/net/ipv6"
+	"golang.zx2c4.com/wireguard/device"
+	"golang.zx2c4.com/wireguard/tun/netstack"

 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 )
@@ -326,3 +331,86 @@ func listenUDP(t *testing.T, network, addr string) *net.UDPConn {
 	require.NoError(t, err)
 	return conn
 }
+
+type countingNet struct {
+	transport.Net
+	calls  atomic.Int64
+	ifaces []*transport.Interface
+	before func()
+}
+
+func (n *countingNet) Interfaces() ([]*transport.Interface, error) {
+	n.calls.Add(1)
+	if n.before != nil {
+		n.before()
+	}
+	return n.ifaces, nil
+}
+
+func TestICEBind_OpenDoesNotDiscoverInterfaces(t *testing.T) {
+	n := newCountingNet()
+	iceBind := NewICEBind(n, testAddress(), 1280)
+
+	for i := 0; i < 2; i++ {
+		_, port, err := iceBind.Open(0)
+		require.NoError(t, err)
+		require.NotZero(t, port, "the bind listens on a port")
+		assert.Equal(t, int64(0), n.calls.Load(), "opening the bind must not enumerate interfaces, attempt %d", i+1)
+		require.NoError(t, iceBind.Close())
+	}
+
+	_, _, err := iceBind.Open(0)
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = iceBind.Close() })
+
+	mux, err := iceBind.GetICEMux()
+	require.NoError(t, err)
+	assert.NotEmpty(t, mux.SingleSocketUDPMux.GetListenAddresses(), "listen addresses come from the discovered interfaces")
+	assert.Equal(t, int64(1), n.calls.Load(), "interfaces are discovered when the listen addresses are asked for")
+}
+
+func TestICEBind_DeviceUpDoesNotWaitOnInterfaceDiscovery(t *testing.T) {
+	tunDev, _, err := netstack.CreateNetTUN([]netip.Addr{netip.MustParseAddr("100.64.0.1")}, nil, 1280)
+	require.NoError(t, err)
+
+	var dev *device.Device
+	n := newCountingNet()
+	n.before = func() {
+		_ = dev.IpcGetOperation(io.Discard)
+	}
+	iceBind := NewICEBind(n, testAddress(), 1280)
+	dev = device.NewDevice(tunDev, iceBind, device.NewLogger(device.LogLevelSilent, ""))
+
+	upDone := make(chan error, 1)
+	go func() {
+		upDone <- dev.Up()
+	}()
+
+	select {
+	case err := <-upDone:
+		require.NoError(t, err)
+	case <-time.After(5 * time.Second):
+		t.Fatal("device Up did not return: interface discovery ran under the device lock and waited on the device itself")
+	}
+	t.Cleanup(dev.Close)
+
+	assert.Equal(t, int64(0), n.calls.Load(), "bringing the device up must not enumerate interfaces")
+
+	mux, err := iceBind.GetICEMux()
+	require.NoError(t, err)
+	assert.NotEmpty(t, mux.SingleSocketUDPMux.GetListenAddresses(), "discovery that talks to the device succeeds once the device is up")
+	assert.Equal(t, int64(1), n.calls.Load(), "interfaces are discovered outside the device lock")
+}
+
+func newCountingNet() *countingNet {
+	ifc := transport.NewInterface(net.Interface{Index: 1, MTU: 1500, Name: "eth0", Flags: net.FlagUp | net.FlagMulticast})
+	ifc.AddAddress(&net.IPNet{IP: net.IPv4(192, 168, 1, 10), Mask: net.CIDRMask(24, 32)})
+	return &countingNet{ifaces: []*transport.Interface{ifc}}
+}
+
+func testAddress() wgaddr.Address {
+	return wgaddr.Address{
+		IP:      netip.MustParseAddr("100.64.0.1"),
+		Network: netip.MustParsePrefix("100.64.0.0/10"),
+	}
+}
@@ -47,6 +47,7 @@ type SingleSocketUDPMux struct {

 	// for UDP connection listen at unspecified address
 	localAddrsForUnspecified []net.Addr
+	unspecified              bool
 }

 const maxAddrSize = 512
@@ -157,6 +158,9 @@ func NewSingleSocketUDPMux(params Params) *SingleSocketUDPMux {
 	if params.Logger == nil {
 		params.Logger = getLogger()
 	}
+	if params.Net == nil {
+		params.Net = stdnet.NewNet(context.Background(), nil, nil)
+	}

 	mux := &SingleSocketUDPMux{
 		addressMap:       map[string][]*udpMuxedConn{},
@@ -165,6 +169,7 @@ func NewSingleSocketUDPMux(params Params) *SingleSocketUDPMux {
 		connsIPv6:        make(map[string]*udpMuxedConn),
 		candidateConnMap: make(map[string]*udpMuxedConn),
 		closedChan:       make(chan struct{}, 1),
+		unspecified:      isUnspecified(params.UDPConn.LocalAddr()),
 		pool: &sync.Pool{
 			New: func() interface{} {
 				// big enough buffer to fit both packet and address
@@ -173,7 +178,6 @@ func NewSingleSocketUDPMux(params Params) *SingleSocketUDPMux {
 		},
 	}

-	mux.updateLocalAddresses()
 	return mux
 }

@@ -199,10 +203,6 @@ func (m *SingleSocketUDPMux) updateLocalAddresses() {
 			m.params.Logger.Errorf("LocalAddr expected IPV4 or IPV6, got %T", m.params.UDPConn.LocalAddr())
 		}
 		if len(networks) > 0 {
-			if m.params.Net == nil {
-				m.params.Net = stdnet.NewNet(context.Background(), nil, nil)
-			}
-
 			ips, err := localInterfaces(m.params.Net, m.params.InterfaceFilter, nil, networks, true)
 			if err == nil {
 				for _, ip := range ips {
@@ -241,10 +241,7 @@ func (m *SingleSocketUDPMux) GetListenAddresses() []net.Addr {
 // creates the connection if an existing one can't be found
 func (m *SingleSocketUDPMux) GetConn(ufrag string, addr net.Addr, candidateID string) (net.PacketConn, error) {
 	// don't check addr for mux using unspecified address
-	m.mu.Lock()
-	lenLocalAddrs := len(m.localAddrsForUnspecified)
-	m.mu.Unlock()
-	if lenLocalAddrs == 0 && m.params.UDPConn.LocalAddr().String() != addr.String() {
+	if !m.unspecified && m.params.UDPConn.LocalAddr().String() != addr.String() {
 		return nil, fmt.Errorf("invalid address %s", addr.String())
 	}

@@ -508,3 +505,8 @@ func getLogger() logging.LeveledLogger {
 	//fac.Writer = log.StandardLogger().Writer()
 	return fac.NewLogger("ice")
 }
+
+func isUnspecified(addr net.Addr) bool {
+	udpAddr, ok := addr.(*net.UDPAddr)
+	return ok && udpAddr.IP.IsUnspecified()
+}
@@ -0,0 +1,99 @@
+package udpmux
+
+import (
+	"fmt"
+	"net"
+	"sync"
+	"sync/atomic"
+	"testing"
+
+	"github.com/pion/transport/v3"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type countingNet struct {
+	transport.Net
+	calls  atomic.Int64
+	ifaces []*transport.Interface
+}
+
+func (n *countingNet) Interfaces() ([]*transport.Interface, error) {
+	n.calls.Add(1)
+	return n.ifaces, nil
+}
+
+func TestNewSingleSocketUDPMux_DoesNotDiscoverInterfaces(t *testing.T) {
+	conn := listenUDP(t, net.IPv4zero)
+	n := &countingNet{ifaces: []*transport.Interface{testInterface("eth0", net.IPv4(192, 168, 1, 10))}}
+
+	mux := NewSingleSocketUDPMux(Params{UDPConn: conn, Net: n})
+	t.Cleanup(func() { _ = mux.Close() })
+
+	assert.Equal(t, int64(0), n.calls.Load(), "constructing the mux must not enumerate interfaces")
+
+	addrs := mux.GetListenAddresses()
+	assert.Equal(t, int64(1), n.calls.Load(), "listen addresses are discovered when they are asked for")
+
+	port := conn.LocalAddr().(*net.UDPAddr).Port
+	require.Len(t, addrs, 1, "one address per discovered interface IP")
+	assert.Equal(t, fmt.Sprintf("192.168.1.10:%d", port), addrs[0].String(), "the discovered IP is paired with the socket port")
+}
+
+func TestSingleSocketUDPMux_GetConnWithoutListenAddresses(t *testing.T) {
+	t.Run("unspecified socket accepts any address", func(t *testing.T) {
+		conn := listenUDP(t, net.IPv4zero)
+		n := &countingNet{}
+		mux := NewSingleSocketUDPMux(Params{UDPConn: conn, Net: n})
+		t.Cleanup(func() { _ = mux.Close() })
+
+		port := conn.LocalAddr().(*net.UDPAddr).Port
+		pc, err := mux.GetConn("ufrag", &net.UDPAddr{IP: net.IPv4(192, 168, 1, 10), Port: port}, "candidate")
+		require.NoError(t, err)
+		assert.NotNil(t, pc, "a connection is created for a local address of an unspecified socket")
+		assert.Equal(t, int64(0), n.calls.Load(), "GetConn must not depend on a prior discovery")
+	})
+
+	t.Run("specific socket rejects a foreign address", func(t *testing.T) {
+		conn := listenUDP(t, net.IPv4(127, 0, 0, 1))
+		mux := NewSingleSocketUDPMux(Params{UDPConn: conn})
+		t.Cleanup(func() { _ = mux.Close() })
+
+		_, err := mux.GetConn("ufrag", &net.UDPAddr{IP: net.IPv4(192, 168, 1, 10), Port: 1234}, "candidate")
+		assert.Error(t, err, "an address the socket is not bound to must be rejected")
+
+		pc, err := mux.GetConn("ufrag", conn.LocalAddr(), "candidate")
+		require.NoError(t, err)
+		assert.NotNil(t, pc, "the bound address is accepted")
+	})
+}
+
+func listenUDP(t *testing.T, ip net.IP) *net.UDPConn {
+	t.Helper()
+	conn, err := net.ListenUDP("udp4", &net.UDPAddr{IP: ip, Port: 0})
+	require.NoError(t, err)
+	t.Cleanup(func() { _ = conn.Close() })
+	return conn
+}
+
+func testInterface(name string, ip net.IP) *transport.Interface {
+	ifc := transport.NewInterface(net.Interface{Index: 1, MTU: 1500, Name: name, Flags: net.FlagUp | net.FlagMulticast})
+	ifc.AddAddress(&net.IPNet{IP: ip, Mask: net.CIDRMask(24, 32)})
+	return ifc
+}
+
+func TestSingleSocketUDPMux_ConcurrentListenAddressesWithDefaultNet(t *testing.T) {
+	conn := listenUDP(t, net.IPv4zero)
+	mux := NewSingleSocketUDPMux(Params{UDPConn: conn})
+	t.Cleanup(func() { _ = mux.Close() })
+
+	var wg sync.WaitGroup
+	for i := 0; i < 8; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			assert.NotEmpty(t, mux.GetListenAddresses(), "every caller gets at least the socket address")
+		}()
+	}
+	wg.Wait()
+}