Populate IPPacketInfo with destination address

IPPacketInfo.DestinationAddr should hold the destination of the IP
packet, not the source. This change fixes that bug.

PiperOrigin-RevId: 325910766

5 files changed, 126 insertions, 11 deletions

diff --git a/pkg/tcpip/checker/BUILD b/pkg/tcpip/checker/BUILD
index ed434807f..c984470e6 100644
--- a/pkg/tcpip/checker/BUILD
+++ b/pkg/tcpip/checker/BUILD
@@ -12,5 +12,6 @@ go_library(
         "//pkg/tcpip/buffer",
         "//pkg/tcpip/header",
         "//pkg/tcpip/seqnum",
+        "@com_github_google_go_cmp//cmp:go_default_library",
     ],
 )
diff --git a/pkg/tcpip/checker/checker.go b/pkg/tcpip/checker/checker.go
index ee264b726..1e5f5abf2 100644
--- a/pkg/tcpip/checker/checker.go
+++ b/pkg/tcpip/checker/checker.go
@@ -21,6 +21,7 @@ import (
 	"reflect"
 	"testing"
 
+	"github.com/google/go-cmp/cmp"
 	"gvisor.dev/gvisor/pkg/tcpip"
 	"gvisor.dev/gvisor/pkg/tcpip/buffer"
 	"gvisor.dev/gvisor/pkg/tcpip/header"
@@ -169,10 +170,9 @@ func ReceiveTClass(want uint32) ControlMessagesChecker {
 	return func(t *testing.T, cm tcpip.ControlMessages) {
 		t.Helper()
 		if !cm.HasTClass {
-			t.Fatalf("got cm.HasTClass = %t, want cm.TClass = %d", cm.HasTClass, want)
-		}
-		if got := cm.TClass; got != want {
-			t.Fatalf("got cm.TClass = %d, want %d", got, want)
+			t.Errorf("got cm.HasTClass = %t, want = true", cm.HasTClass)
+		} else if got := cm.TClass; got != want {
+			t.Errorf("got cm.TClass = %d, want %d", got, want)
 		}
 	}
 }
@@ -182,10 +182,22 @@ func ReceiveTOS(want uint8) ControlMessagesChecker {
 	return func(t *testing.T, cm tcpip.ControlMessages) {
 		t.Helper()
 		if !cm.HasTOS {
-			t.Fatalf("got cm.HasTOS = %t, want cm.TOS = %d", cm.HasTOS, want)
+			t.Errorf("got cm.HasTOS = %t, want = true", cm.HasTOS)
+		} else if got := cm.TOS; got != want {
+			t.Errorf("got cm.TOS = %d, want %d", got, want)
 		}
-		if got := cm.TOS; got != want {
-			t.Fatalf("got cm.TOS = %d, want %d", got, want)
+	}
+}
+
+// ReceiveIPPacketInfo creates a checker that checks the PacketInfo field in
+// ControlMessages.
+func ReceiveIPPacketInfo(want tcpip.IPPacketInfo) ControlMessagesChecker {
+	return func(t *testing.T, cm tcpip.ControlMessages) {
+		t.Helper()
+		if !cm.HasIPPacketInfo {
+			t.Errorf("got cm.HasIPPacketInfo = %t, want = true", cm.HasIPPacketInfo)
+		} else if diff := cmp.Diff(want, cm.PacketInfo); diff != "" {
+			t.Errorf("IPPacketInfo mismatch (-want +got):\n%s", diff)
 		}
 	}
 }
diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go
index 45f59b60f..091bc5281 100644
--- a/pkg/tcpip/tcpip.go
+++ b/pkg/tcpip/tcpip.go
@@ -968,7 +968,7 @@ type IPPacketInfo struct {
 	// LocalAddr is the local address.
 	LocalAddr Address
 
-	// DestinationAddr is the destination address.
+	// DestinationAddr is the destination address found in the IP header.
 	DestinationAddr Address
 }
 
diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go
index 444b5b01c..4a2b6c03a 100644
--- a/pkg/tcpip/transport/udp/endpoint.go
+++ b/pkg/tcpip/transport/udp/endpoint.go
@@ -1444,13 +1444,16 @@ func (e *endpoint) HandlePacket(r *stack.Route, id stack.TransportEndpointID, pk
 	switch r.NetProto {
 	case header.IPv4ProtocolNumber:
 		packet.tos, _ = header.IPv4(pkt.NetworkHeader).TOS()
-		packet.packetInfo.LocalAddr = r.LocalAddress
-		packet.packetInfo.DestinationAddr = r.RemoteAddress
-		packet.packetInfo.NIC = r.NICID()
 	case header.IPv6ProtocolNumber:
 		packet.tos, _ = header.IPv6(pkt.NetworkHeader).TOS()
 	}
 
+	// TODO(gvisor.dev/issue/3556): r.LocalAddress may be a multicast or broadcast
+	// address. packetInfo.LocalAddr should hold a unicast address that can be
+	// used to respond to the incoming packet.
+	packet.packetInfo.LocalAddr = r.LocalAddress
+	packet.packetInfo.DestinationAddr = r.LocalAddress
+	packet.packetInfo.NIC = r.NICID()
 	packet.timestamp = e.stack.Clock().NowNanoseconds()
 
 	e.rcvMu.Unlock()
diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go
index 66e8911c8..1a32622ca 100644
--- a/pkg/tcpip/transport/udp/udp_test.go
+++ b/pkg/tcpip/transport/udp/udp_test.go
@@ -1309,6 +1309,105 @@ func TestReadIncrementsPacketsReceived(t *testing.T) {
 	}
 }
 
+func TestReadIPPacketInfo(t *testing.T) {
+	tests := []struct {
+		name              string
+		proto             tcpip.NetworkProtocolNumber
+		flow              testFlow
+		expectedLocalAddr tcpip.Address
+		expectedDestAddr  tcpip.Address
+	}{
+		{
+			name:              "IPv4 unicast",
+			proto:             header.IPv4ProtocolNumber,
+			flow:              unicastV4,
+			expectedLocalAddr: stackAddr,
+			expectedDestAddr:  stackAddr,
+		},
+		{
+			name:  "IPv4 multicast",
+			proto: header.IPv4ProtocolNumber,
+			flow:  multicastV4,
+			// This should actually be a unicast address assigned to the interface.
+			//
+			// TODO(gvisor.dev/issue/3556): This check is validating incorrect
+			// behaviour. We still include the test so that once the bug is
+			// resolved, this test will start to fail and the individual tasked
+			// with fixing this bug knows to also fix this test :).
+			expectedLocalAddr: multicastAddr,
+			expectedDestAddr:  multicastAddr,
+		},
+		{
+			name:  "IPv4 broadcast",
+			proto: header.IPv4ProtocolNumber,
+			flow:  broadcast,
+			// This should actually be a unicast address assigned to the interface.
+			//
+			// TODO(gvisor.dev/issue/3556): This check is validating incorrect
+			// behaviour. We still include the test so that once the bug is
+			// resolved, this test will start to fail and the individual tasked
+			// with fixing this bug knows to also fix this test :).
+			expectedLocalAddr: broadcastAddr,
+			expectedDestAddr:  broadcastAddr,
+		},
+		{
+			name:              "IPv6 unicast",
+			proto:             header.IPv6ProtocolNumber,
+			flow:              unicastV6,
+			expectedLocalAddr: stackV6Addr,
+			expectedDestAddr:  stackV6Addr,
+		},
+		{
+			name:  "IPv6 multicast",
+			proto: header.IPv6ProtocolNumber,
+			flow:  multicastV6,
+			// This should actually be a unicast address assigned to the interface.
+			//
+			// TODO(gvisor.dev/issue/3556): This check is validating incorrect
+			// behaviour. We still include the test so that once the bug is
+			// resolved, this test will start to fail and the individual tasked
+			// with fixing this bug knows to also fix this test :).
+			expectedLocalAddr: multicastV6Addr,
+			expectedDestAddr:  multicastV6Addr,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			c := newDualTestContext(t, defaultMTU)
+			defer c.cleanup()
+
+			c.createEndpoint(test.proto)
+
+			bindAddr := tcpip.FullAddress{Port: stackPort}
+			if err := c.ep.Bind(bindAddr); err != nil {
+				t.Fatalf("Bind(%+v): %s", bindAddr, err)
+			}
+
+			if test.flow.isMulticast() {
+				ifoptSet := tcpip.AddMembershipOption{NIC: 1, MulticastAddr: test.flow.getMcastAddr()}
+				if err := c.ep.SetSockOpt(ifoptSet); err != nil {
+					c.t.Fatalf("SetSockOpt(%+v): %s:", ifoptSet, err)
+				}
+			}
+
+			if err := c.ep.SetSockOptBool(tcpip.ReceiveIPPacketInfoOption, true); err != nil {
+				t.Fatalf("c.ep.SetSockOptBool(tcpip.ReceiveIPPacketInfoOption, true): %s", err)
+			}
+
+			testRead(c, test.flow, checker.ReceiveIPPacketInfo(tcpip.IPPacketInfo{
+				NIC:             1,
+				LocalAddr:       test.expectedLocalAddr,
+				DestinationAddr: test.expectedDestAddr,
+			}))
+
+			if got := c.s.Stats().UDP.PacketsReceived.Value(); got != 1 {
+				t.Fatalf("Read did not increment PacketsReceived: got = %d, want = 1", got)
+			}
+		})
+	}
+}
+
 func TestWriteIncrementsPacketsSent(t *testing.T) {
 	c := newDualTestContext(t, defaultMTU)
 	defer c.cleanup()