Auto-generate an IPv6 link-local address based on the NIC's MAC Address.

This change adds support for optionally auto-generating an IPv6 link-local
address based on the NIC's MAC Address on NIC enable.

Note, this change will not break existing uses of netstack as the default
configuration for the stack options is set in such a way that a link-local
address will not be auto-generated unless the stack is explicitly configured.
See `stack.Options` for more details. Specifically, see
`stack.Options.AutoGenIPv6LinkLocal`.

Tests: Tests to make sure that the IPb6 link-local address is only
auto-generated if the stack is specifically configured to do so. Also tests to
make sure that an auto-generated address goes through the DAD process.
PiperOrigin-RevId: 276059813

1 files changed, 144 insertions, 0 deletions

diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go
index 10fd1065f..0a184fabe 100644
--- a/pkg/tcpip/stack/stack_test.go
+++ b/pkg/tcpip/stack/stack_test.go
@@ -24,11 +24,13 @@ import (
 	"sort"
 	"strings"
 	"testing"
+	"time"
 
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
 	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
 	"gvisor.dev/gvisor/pkg/tcpip/stack"
 )
 
@@ -1864,3 +1866,145 @@ func TestNICForwarding(t *testing.T) {
 		t.Errorf("got Tx.Bytes.Value() = %d, want = %d", got, want)
 	}
 }
+
+// TestNICAutoGenAddr tests the auto-generation of IPv6 link-local addresses
+// (or lack there-of if disabled (default)). Note, DAD will be disabled in
+// these tests.
+func TestNICAutoGenAddr(t *testing.T) {
+	tests := []struct {
+		name      string
+		autoGen   bool
+		linkAddr  tcpip.LinkAddress
+		shouldGen bool
+	}{
+		{
+			"Disabled",
+			false,
+			linkAddr1,
+			false,
+		},
+		{
+			"Enabled",
+			true,
+			linkAddr1,
+			true,
+		},
+		{
+			"Nil MAC",
+			true,
+			tcpip.LinkAddress([]byte(nil)),
+			false,
+		},
+		{
+			"Empty MAC",
+			true,
+			tcpip.LinkAddress(""),
+			false,
+		},
+		{
+			"Invalid MAC",
+			true,
+			tcpip.LinkAddress("\x01\x02\x03"),
+			false,
+		},
+		{
+			"Multicast MAC",
+			true,
+			tcpip.LinkAddress("\x01\x02\x03\x04\x05\x06"),
+			false,
+		},
+		{
+			"Unspecified MAC",
+			true,
+			tcpip.LinkAddress("\x00\x00\x00\x00\x00\x00"),
+			false,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			opts := stack.Options{
+				NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
+			}
+
+			if test.autoGen {
+				// Only set opts.AutoGenIPv6LinkLocal when
+				// test.autoGen is true because
+				// opts.AutoGenIPv6LinkLocal should be false by
+				// default.
+				opts.AutoGenIPv6LinkLocal = true
+			}
+
+			e := channel.New(10, 1280, test.linkAddr)
+			s := stack.New(opts)
+			if err := s.CreateNIC(1, e); err != nil {
+				t.Fatalf("CreateNIC(_) = %s", err)
+			}
+
+			addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
+			if err != nil {
+				t.Fatalf("stack.GetMainNICAddress(_, _) err = %s", err)
+			}
+
+			if test.shouldGen {
+				// Should have auto-generated an address and
+				// resolved immediately (DAD is disabled).
+				if want := (tcpip.AddressWithPrefix{Address: header.LinkLocalAddr(test.linkAddr), PrefixLen: header.IPv6LinkLocalPrefix.PrefixLen}); addr != want {
+					t.Fatalf("got stack.GetMainNICAddress(_, _) = %s, want = %s", addr, want)
+				}
+			} else {
+				// Should not have auto-generated an address.
+				if want := (tcpip.AddressWithPrefix{}); addr != want {
+					t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
+				}
+			}
+		})
+	}
+}
+
+// TestNICAutoGenAddrDoesDAD tests that the successful auto-generation of IPv6
+// link-local addresses will only be assigned after the DAD process resolves.
+func TestNICAutoGenAddrDoesDAD(t *testing.T) {
+	opts := stack.Options{
+		NetworkProtocols: []stack.NetworkProtocol{ipv6.NewProtocol()},
+		NDPConfigs: stack.NDPConfigurations{
+			RetransmitTimer:        time.Second,
+			DupAddrDetectTransmits: 1,
+		},
+		AutoGenIPv6LinkLocal: true,
+	}
+
+	e := channel.New(10, 1280, linkAddr1)
+	s := stack.New(opts)
+	if err := s.CreateNIC(1, e); err != nil {
+		t.Fatalf("CreateNIC(_) = %s", err)
+	}
+
+	// Address should not be considered bound to the
+	// NIC yet (DAD ongoing).
+	addr, err := s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
+	if err != nil {
+		t.Fatalf("got stack.GetMainNICAddress(_, _) = (_, %v), want = (_, nil)", err)
+	}
+	if want := (tcpip.AddressWithPrefix{}); addr != want {
+		t.Fatalf("got stack.GetMainNICAddress(_, _) = (%s, nil), want = (%s, nil)", addr, want)
+	}
+
+	// Wait for the address to resolve (an extra
+	// 250ms to make sure the address resolves).
+	//
+	// TODO(b/140896005): Use events from the
+	// netstack to know immediately when DAD
+	// completes.
+	time.Sleep(time.Second + 250*time.Millisecond)
+
+	// Should have auto-generated an address and
+	// resolved (if DAD).
+	addr, err = s.GetMainNICAddress(1, header.IPv6ProtocolNumber)
+	if err != nil {
+		t.Fatalf("stack.GetMainNICAddress(_, _) err = %s", err)
+	}
+	if want := (tcpip.AddressWithPrefix{Address: header.LinkLocalAddr(linkAddr1), PrefixLen: header.IPv6LinkLocalPrefix.PrefixLen}); addr != want {
+		t.Fatalf("got stack.GetMainNICAddress(_, _) = %s, want = %s", addr, want)
+	}
+}