Handle removed NIC in NDP timer for packet tx

NDP packets are sent periodically from NDP timers. These timers do not
hold the NIC lock when sending packets as the packet write operation
may take some time. While the lock is not held, the NIC may be removed
by some other goroutine. This change handles that scenario gracefully.

Test: stack_test.TestRemoveNICWhileHandlingRSTimer
PiperOrigin-RevId: 315524143

1 files changed, 257 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/nic_test.go b/pkg/tcpip/stack/nic_test.go
index fea46158c..31f865260 100644
--- a/pkg/tcpip/stack/nic_test.go
+++ b/pkg/tcpip/stack/nic_test.go
@@ -15,11 +15,268 @@
 package stack
 
 import (
+	"math"
 	"testing"
+	"time"
 
+	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
 )
 
+var _ LinkEndpoint = (*testLinkEndpoint)(nil)
+
+// A LinkEndpoint that throws away outgoing packets.
+//
+// We use this instead of the channel endpoint as the channel package depends on
+// the stack package which this test lives in, causing a cyclic dependency.
+type testLinkEndpoint struct {
+	dispatcher NetworkDispatcher
+}
+
+// Attach implements LinkEndpoint.Attach.
+func (e *testLinkEndpoint) Attach(dispatcher NetworkDispatcher) {
+	e.dispatcher = dispatcher
+}
+
+// IsAttached implements LinkEndpoint.IsAttached.
+func (e *testLinkEndpoint) IsAttached() bool {
+	return e.dispatcher != nil
+}
+
+// MTU implements LinkEndpoint.MTU.
+func (*testLinkEndpoint) MTU() uint32 {
+	return math.MaxUint16
+}
+
+// Capabilities implements LinkEndpoint.Capabilities.
+func (*testLinkEndpoint) Capabilities() LinkEndpointCapabilities {
+	return CapabilityResolutionRequired
+}
+
+// MaxHeaderLength implements LinkEndpoint.MaxHeaderLength.
+func (*testLinkEndpoint) MaxHeaderLength() uint16 {
+	return 0
+}
+
+// LinkAddress returns the link address of this endpoint.
+func (*testLinkEndpoint) LinkAddress() tcpip.LinkAddress {
+	return ""
+}
+
+// Wait implements LinkEndpoint.Wait.
+func (*testLinkEndpoint) Wait() {}
+
+// WritePacket implements LinkEndpoint.WritePacket.
+func (e *testLinkEndpoint) WritePacket(*Route, *GSO, tcpip.NetworkProtocolNumber, *PacketBuffer) *tcpip.Error {
+	return nil
+}
+
+// WritePackets implements LinkEndpoint.WritePackets.
+func (e *testLinkEndpoint) WritePackets(*Route, *GSO, PacketBufferList, tcpip.NetworkProtocolNumber) (int, *tcpip.Error) {
+	// Our tests don't use this so we don't support it.
+	return 0, tcpip.ErrNotSupported
+}
+
+// WriteRawPacket implements LinkEndpoint.WriteRawPacket.
+func (e *testLinkEndpoint) WriteRawPacket(buffer.VectorisedView) *tcpip.Error {
+	// Our tests don't use this so we don't support it.
+	return tcpip.ErrNotSupported
+}
+
+var _ NetworkEndpoint = (*testIPv6Endpoint)(nil)
+
+// An IPv6 NetworkEndpoint that throws away outgoing packets.
+//
+// We use this instead of ipv6.endpoint because the ipv6 package depends on
+// the stack package which this test lives in, causing a cyclic dependency.
+type testIPv6Endpoint struct {
+	nicID     tcpip.NICID
+	id        NetworkEndpointID
+	prefixLen int
+	linkEP    LinkEndpoint
+	protocol  *testIPv6Protocol
+}
+
+// DefaultTTL implements NetworkEndpoint.DefaultTTL.
+func (*testIPv6Endpoint) DefaultTTL() uint8 {
+	return 0
+}
+
+// MTU implements NetworkEndpoint.MTU.
+func (e *testIPv6Endpoint) MTU() uint32 {
+	return e.linkEP.MTU() - header.IPv6MinimumSize
+}
+
+// Capabilities implements NetworkEndpoint.Capabilities.
+func (e *testIPv6Endpoint) Capabilities() LinkEndpointCapabilities {
+	return e.linkEP.Capabilities()
+}
+
+// MaxHeaderLength implements NetworkEndpoint.MaxHeaderLength.
+func (e *testIPv6Endpoint) MaxHeaderLength() uint16 {
+	return e.linkEP.MaxHeaderLength() + header.IPv6MinimumSize
+}
+
+// WritePacket implements NetworkEndpoint.WritePacket.
+func (*testIPv6Endpoint) WritePacket(*Route, *GSO, NetworkHeaderParams, *PacketBuffer) *tcpip.Error {
+	return nil
+}
+
+// WritePackets implements NetworkEndpoint.WritePackets.
+func (*testIPv6Endpoint) WritePackets(*Route, *GSO, PacketBufferList, NetworkHeaderParams) (int, *tcpip.Error) {
+	// Our tests don't use this so we don't support it.
+	return 0, tcpip.ErrNotSupported
+}
+
+// WriteHeaderIncludedPacket implements
+// NetworkEndpoint.WriteHeaderIncludedPacket.
+func (*testIPv6Endpoint) WriteHeaderIncludedPacket(*Route, *PacketBuffer) *tcpip.Error {
+	// Our tests don't use this so we don't support it.
+	return tcpip.ErrNotSupported
+}
+
+// ID implements NetworkEndpoint.ID.
+func (e *testIPv6Endpoint) ID() *NetworkEndpointID {
+	return &e.id
+}
+
+// PrefixLen implements NetworkEndpoint.PrefixLen.
+func (e *testIPv6Endpoint) PrefixLen() int {
+	return e.prefixLen
+}
+
+// NICID implements NetworkEndpoint.NICID.
+func (e *testIPv6Endpoint) NICID() tcpip.NICID {
+	return e.nicID
+}
+
+// HandlePacket implements NetworkEndpoint.HandlePacket.
+func (*testIPv6Endpoint) HandlePacket(*Route, *PacketBuffer) {
+}
+
+// Close implements NetworkEndpoint.Close.
+func (*testIPv6Endpoint) Close() {}
+
+// NetworkProtocolNumber implements NetworkEndpoint.NetworkProtocolNumber.
+func (*testIPv6Endpoint) NetworkProtocolNumber() tcpip.NetworkProtocolNumber {
+	return header.IPv6ProtocolNumber
+}
+
+var _ NetworkProtocol = (*testIPv6Protocol)(nil)
+
+// An IPv6 NetworkProtocol that supports the bare minimum to make a stack
+// believe it supports IPv6.
+//
+// We use this instead of ipv6.protocol because the ipv6 package depends on
+// the stack package which this test lives in, causing a cyclic dependency.
+type testIPv6Protocol struct{}
+
+// Number implements NetworkProtocol.Number.
+func (*testIPv6Protocol) Number() tcpip.NetworkProtocolNumber {
+	return header.IPv6ProtocolNumber
+}
+
+// MinimumPacketSize implements NetworkProtocol.MinimumPacketSize.
+func (*testIPv6Protocol) MinimumPacketSize() int {
+	return header.IPv6MinimumSize
+}
+
+// DefaultPrefixLen implements NetworkProtocol.DefaultPrefixLen.
+func (*testIPv6Protocol) DefaultPrefixLen() int {
+	return header.IPv6AddressSize * 8
+}
+
+// ParseAddresses implements NetworkProtocol.ParseAddresses.
+func (*testIPv6Protocol) ParseAddresses(v buffer.View) (src, dst tcpip.Address) {
+	h := header.IPv6(v)
+	return h.SourceAddress(), h.DestinationAddress()
+}
+
+// NewEndpoint implements NetworkProtocol.NewEndpoint.
+func (p *testIPv6Protocol) NewEndpoint(nicID tcpip.NICID, addrWithPrefix tcpip.AddressWithPrefix, _ LinkAddressCache, _ TransportDispatcher, linkEP LinkEndpoint, _ *Stack) (NetworkEndpoint, *tcpip.Error) {
+	return &testIPv6Endpoint{
+		nicID:     nicID,
+		id:        NetworkEndpointID{LocalAddress: addrWithPrefix.Address},
+		prefixLen: addrWithPrefix.PrefixLen,
+		linkEP:    linkEP,
+		protocol:  p,
+	}, nil
+}
+
+// SetOption implements NetworkProtocol.SetOption.
+func (*testIPv6Protocol) SetOption(interface{}) *tcpip.Error {
+	return nil
+}
+
+// Option implements NetworkProtocol.Option.
+func (*testIPv6Protocol) Option(interface{}) *tcpip.Error {
+	return nil
+}
+
+// Close implements NetworkProtocol.Close.
+func (*testIPv6Protocol) Close() {}
+
+// Wait implements NetworkProtocol.Wait.
+func (*testIPv6Protocol) Wait() {}
+
+// Parse implements NetworkProtocol.Parse.
+func (*testIPv6Protocol) Parse(*PacketBuffer) (tcpip.TransportProtocolNumber, bool, bool) {
+	return 0, false, false
+}
+
+var _ LinkAddressResolver = (*testIPv6Protocol)(nil)
+
+// LinkAddressProtocol implements LinkAddressResolver.
+func (*testIPv6Protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
+	return header.IPv6ProtocolNumber
+}
+
+// LinkAddressRequest implements LinkAddressResolver.
+func (*testIPv6Protocol) LinkAddressRequest(_, _ tcpip.Address, _ LinkEndpoint) *tcpip.Error {
+	return nil
+}
+
+// ResolveStaticAddress implements LinkAddressResolver.
+func (*testIPv6Protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bool) {
+	if header.IsV6MulticastAddress(addr) {
+		return header.EthernetAddressFromMulticastIPv6Address(addr), true
+	}
+	return "", false
+}
+
+// Test the race condition where a NIC is removed and an RS timer fires at the
+// same time.
+func TestRemoveNICWhileHandlingRSTimer(t *testing.T) {
+	const (
+		nicID = 1
+
+		maxRtrSolicitations = 5
+	)
+
+	e := testLinkEndpoint{}
+	s := New(Options{
+		NetworkProtocols: []NetworkProtocol{&testIPv6Protocol{}},
+		NDPConfigs: NDPConfigurations{
+			MaxRtrSolicitations:     maxRtrSolicitations,
+			RtrSolicitationInterval: minimumRtrSolicitationInterval,
+		},
+	})
+
+	if err := s.CreateNIC(nicID, &e); err != nil {
+		t.Fatalf("s.CreateNIC(%d, _) = %s", nicID, err)
+	}
+
+	s.mu.Lock()
+	// Wait for the router solicitation timer to fire and block trying to obtain
+	// the stack lock when doing link address resolution.
+	time.Sleep(minimumRtrSolicitationInterval * 2)
+	if err := s.removeNICLocked(nicID); err != nil {
+		t.Fatalf("s.removeNICLocked(%d) = %s", nicID, err)
+	}
+	s.mu.Unlock()
+}
+
 func TestDisabledRxStatsWhenNICDisabled(t *testing.T) {
 	// When the NIC is disabled, the only field that matters is the stats field.
 	// This test is limited to stats counter checks.