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

6 files changed, 226 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()
diff --git a/test/syscalls/linux/socket_ipv4_udp_unbound.cc b/test/syscalls/linux/socket_ipv4_udp_unbound.cc
index de0f5f01b..bc005e2bb 100644
--- a/test/syscalls/linux/socket_ipv4_udp_unbound.cc
+++ b/test/syscalls/linux/socket_ipv4_udp_unbound.cc
@@ -2452,5 +2452,105 @@ TEST_P(IPv4UDPUnboundSocketTest, SetSocketSendBuf) {
 
   ASSERT_EQ(quarter_sz, val);
 }
+
+TEST_P(IPv4UDPUnboundSocketTest, IpMulticastIPPacketInfo) {
+  auto sender_socket = ASSERT_NO_ERRNO_AND_VALUE(NewSocket());
+  auto receiver_socket = ASSERT_NO_ERRNO_AND_VALUE(NewSocket());
+
+  // Bind the first FD to the loopback. This is an alternative to
+  // IP_MULTICAST_IF for setting the default send interface.
+  auto sender_addr = V4Loopback();
+  ASSERT_THAT(
+      bind(sender_socket->get(), reinterpret_cast<sockaddr*>(&sender_addr.addr),
+           sender_addr.addr_len),
+      SyscallSucceeds());
+
+  // Bind the second FD to the v4 any address to ensure that we can receive the
+  // multicast packet.
+  auto receiver_addr = V4Any();
+  ASSERT_THAT(bind(receiver_socket->get(),
+                   reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                   receiver_addr.addr_len),
+              SyscallSucceeds());
+  socklen_t receiver_addr_len = receiver_addr.addr_len;
+  ASSERT_THAT(getsockname(receiver_socket->get(),
+                          reinterpret_cast<sockaddr*>(&receiver_addr.addr),
+                          &receiver_addr_len),
+              SyscallSucceeds());
+  EXPECT_EQ(receiver_addr_len, receiver_addr.addr_len);
+
+  // Register to receive multicast packets.
+  ip_mreqn group = {};
+  group.imr_multiaddr.s_addr = inet_addr(kMulticastAddress);
+  group.imr_ifindex = ASSERT_NO_ERRNO_AND_VALUE(InterfaceIndex("lo"));
+  ASSERT_THAT(setsockopt(receiver_socket->get(), IPPROTO_IP, IP_ADD_MEMBERSHIP,
+                         &group, sizeof(group)),
+              SyscallSucceeds());
+
+  // Register to receive IP packet info.
+  const int one = 1;
+  ASSERT_THAT(setsockopt(receiver_socket->get(), IPPROTO_IP, IP_PKTINFO, &one,
+                         sizeof(one)),
+              SyscallSucceeds());
+
+  // Send a multicast packet.
+  auto send_addr = V4Multicast();
+  reinterpret_cast<sockaddr_in*>(&send_addr.addr)->sin_port =
+      reinterpret_cast<sockaddr_in*>(&receiver_addr.addr)->sin_port;
+  char send_buf[200];
+  RandomizeBuffer(send_buf, sizeof(send_buf));
+  ASSERT_THAT(
+      RetryEINTR(sendto)(sender_socket->get(), send_buf, sizeof(send_buf), 0,
+                         reinterpret_cast<sockaddr*>(&send_addr.addr),
+                         send_addr.addr_len),
+      SyscallSucceedsWithValue(sizeof(send_buf)));
+
+  // Check that we received the multicast packet.
+  msghdr recv_msg = {};
+  iovec recv_iov = {};
+  char recv_buf[sizeof(send_buf)];
+  char recv_cmsg_buf[CMSG_SPACE(sizeof(in_pktinfo))] = {};
+  size_t cmsg_data_len = sizeof(in_pktinfo);
+  recv_iov.iov_base = recv_buf;
+  recv_iov.iov_len = sizeof(recv_buf);
+  recv_msg.msg_iov = &recv_iov;
+  recv_msg.msg_iovlen = 1;
+  recv_msg.msg_controllen = CMSG_LEN(cmsg_data_len);
+  recv_msg.msg_control = recv_cmsg_buf;
+  ASSERT_THAT(RetryEINTR(recvmsg)(receiver_socket->get(), &recv_msg, 0),
+              SyscallSucceedsWithValue(sizeof(send_buf)));
+  EXPECT_EQ(0, memcmp(send_buf, recv_buf, sizeof(send_buf)));
+
+  // Check the IP_PKTINFO control message.
+  cmsghdr* cmsg = CMSG_FIRSTHDR(&recv_msg);
+  ASSERT_NE(cmsg, nullptr);
+  EXPECT_EQ(cmsg->cmsg_len, CMSG_LEN(cmsg_data_len));
+  EXPECT_EQ(cmsg->cmsg_level, IPPROTO_IP);
+  EXPECT_EQ(cmsg->cmsg_type, IP_PKTINFO);
+
+  // Get loopback index.
+  ifreq ifr = {};
+  absl::SNPrintF(ifr.ifr_name, IFNAMSIZ, "lo");
+  ASSERT_THAT(ioctl(receiver_socket->get(), SIOCGIFINDEX, &ifr),
+              SyscallSucceeds());
+  ASSERT_NE(ifr.ifr_ifindex, 0);
+
+  in_pktinfo received_pktinfo = {};
+  memcpy(&received_pktinfo, CMSG_DATA(cmsg), sizeof(in_pktinfo));
+  EXPECT_EQ(received_pktinfo.ipi_ifindex, ifr.ifr_ifindex);
+  if (IsRunningOnGvisor()) {
+    // 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 :).
+    EXPECT_EQ(received_pktinfo.ipi_spec_dst.s_addr, group.imr_multiaddr.s_addr);
+  } else {
+    EXPECT_EQ(received_pktinfo.ipi_spec_dst.s_addr, htonl(INADDR_LOOPBACK));
+  }
+  EXPECT_EQ(received_pktinfo.ipi_addr.s_addr, group.imr_multiaddr.s_addr);
+}
+
 }  // namespace testing
 }  // namespace gvisor