Support SO_BINDTODEVICE in ICMP sockets

Adds support for the SO_BINDTODEVICE socket option in ICMP sockets with an
accompanying packetimpact test to exercise use of this socket option.

Adds a unit test to exercise the NIC selection logic introduced by this change.
The remaining unit tests for ICMP sockets need to be added in a subsequent CL.
See https://gvisor.dev/issues/5623 for the list of remaining unit tests.

Adds a "timeout" field to PacketimpactTestInfo, necessary due to the long
runtime of the newly added packetimpact test.

Fixes #5678
Fixes #4896
Updates #5623
Updates #5681
Updates #5763
Updates #5956
Updates #5966
Updates #5967

PiperOrigin-RevId: 376271581

3 files changed, 270 insertions, 6 deletions

diff --git a/pkg/tcpip/transport/icmp/BUILD b/pkg/tcpip/transport/icmp/BUILD
index 7e5c79776..bbc0e3ecc 100644
--- a/pkg/tcpip/transport/icmp/BUILD
+++ b/pkg/tcpip/transport/icmp/BUILD
@@ -1,4 +1,4 @@
-load("//tools:defs.bzl", "go_library")
+load("//tools:defs.bzl", "go_library", "go_test")
 load("//tools/go_generics:defs.bzl", "go_template_instance")
 
 package(licenses = ["notice"])
@@ -38,3 +38,22 @@ go_library(
         "//pkg/waiter",
     ],
 )
+
+go_test(
+    name = "icmp_x_test",
+    size = "small",
+    srcs = ["icmp_test.go"],
+    deps = [
+        ":icmp",
+        "//pkg/tcpip",
+        "//pkg/tcpip/buffer",
+        "//pkg/tcpip/checker",
+        "//pkg/tcpip/header",
+        "//pkg/tcpip/link/channel",
+        "//pkg/tcpip/link/sniffer",
+        "//pkg/tcpip/network/ipv4",
+        "//pkg/tcpip/stack",
+        "//pkg/tcpip/testutil",
+        "//pkg/waiter",
+    ],
+)
diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go
index 39f526023..fb77febcf 100644
--- a/pkg/tcpip/transport/icmp/endpoint.go
+++ b/pkg/tcpip/transport/icmp/endpoint.go
@@ -27,8 +27,6 @@ import (
 	"gvisor.dev/gvisor/pkg/waiter"
 )
 
-// TODO(https://gvisor.dev/issues/5623): Unit test this package.
-
 // +stateify savable
 type icmpPacket struct {
 	icmpPacketEntry
@@ -134,7 +132,8 @@ func (e *endpoint) Close() {
 	e.shutdownFlags = tcpip.ShutdownRead | tcpip.ShutdownWrite
 	switch e.state {
 	case stateBound, stateConnected:
-		e.stack.UnregisterTransportEndpoint([]tcpip.NetworkProtocolNumber{e.NetProto}, e.TransProto, e.ID, e, ports.Flags{}, 0 /* bindToDevice */)
+		bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
+		e.stack.UnregisterTransportEndpoint([]tcpip.NetworkProtocolNumber{e.NetProto}, e.TransProto, e.ID, e, ports.Flags{}, bindToDevice)
 	}
 
 	// Close the receive list and drain it.
@@ -305,6 +304,9 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 		// Reject destination address if it goes through a different
 		// NIC than the endpoint was bound to.
 		nicID := to.NIC
+		if nicID == 0 {
+			nicID = tcpip.NICID(e.ops.GetBindToDevice())
+		}
 		if e.BindNICID != 0 {
 			if nicID != 0 && nicID != e.BindNICID {
 				return 0, &tcpip.ErrNoRoute{}
@@ -349,6 +351,13 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, tcp
 	return int64(len(v)), nil
 }
 
+var _ tcpip.SocketOptionsHandler = (*endpoint)(nil)
+
+// HasNIC implements tcpip.SocketOptionsHandler.
+func (e *endpoint) HasNIC(id int32) bool {
+	return e.stack.HasNIC(tcpip.NICID(id))
+}
+
 // SetSockOpt sets a socket option.
 func (*endpoint) SetSockOpt(tcpip.SettableSocketOption) tcpip.Error {
 	return nil
@@ -608,17 +617,18 @@ func (*endpoint) Accept(*tcpip.FullAddress) (tcpip.Endpoint, *waiter.Queue, tcpi
 }
 
 func (e *endpoint) registerWithStack(_ tcpip.NICID, netProtos []tcpip.NetworkProtocolNumber, id stack.TransportEndpointID) (stack.TransportEndpointID, tcpip.Error) {
+	bindToDevice := tcpip.NICID(e.ops.GetBindToDevice())
 	if id.LocalPort != 0 {
 		// The endpoint already has a local port, just attempt to
 		// register it.
-		err := e.stack.RegisterTransportEndpoint(netProtos, e.TransProto, id, e, ports.Flags{}, 0 /* bindToDevice */)
+		err := e.stack.RegisterTransportEndpoint(netProtos, e.TransProto, id, e, ports.Flags{}, bindToDevice)
 		return id, err
 	}
 
 	// We need to find a port for the endpoint.
 	_, err := e.stack.PickEphemeralPort(e.stack.Rand(), func(p uint16) (bool, tcpip.Error) {
 		id.LocalPort = p
-		err := e.stack.RegisterTransportEndpoint(netProtos, e.TransProto, id, e, ports.Flags{}, 0 /* bindtodevice */)
+		err := e.stack.RegisterTransportEndpoint(netProtos, e.TransProto, id, e, ports.Flags{}, bindToDevice)
 		switch err.(type) {
 		case nil:
 			return true, nil
diff --git a/pkg/tcpip/transport/icmp/icmp_test.go b/pkg/tcpip/transport/icmp/icmp_test.go
new file mode 100644
index 000000000..cc950cbde
--- /dev/null
+++ b/pkg/tcpip/transport/icmp/icmp_test.go
@@ -0,0 +1,235 @@
+// Copyright 2021 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package icmp_test
+
+import (
+	"testing"
+
+	"gvisor.dev/gvisor/pkg/tcpip"
+	"gvisor.dev/gvisor/pkg/tcpip/buffer"
+	"gvisor.dev/gvisor/pkg/tcpip/checker"
+	"gvisor.dev/gvisor/pkg/tcpip/header"
+	"gvisor.dev/gvisor/pkg/tcpip/link/channel"
+	"gvisor.dev/gvisor/pkg/tcpip/link/sniffer"
+	"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
+	"gvisor.dev/gvisor/pkg/tcpip/stack"
+	"gvisor.dev/gvisor/pkg/tcpip/testutil"
+	"gvisor.dev/gvisor/pkg/tcpip/transport/icmp"
+	"gvisor.dev/gvisor/pkg/waiter"
+)
+
+// TODO(https://gvisor.dev/issues/5623): Finish unit testing the icmp package.
+// See the issue for remaining areas of work.
+
+var (
+	localV4Addr1 = testutil.MustParse4("10.0.0.1")
+	localV4Addr2 = testutil.MustParse4("10.0.0.2")
+	remoteV4Addr = testutil.MustParse4("10.0.0.3")
+)
+
+func addNICWithDefaultRoute(t *testing.T, s *stack.Stack, id tcpip.NICID, name string, addrV4 tcpip.Address) *channel.Endpoint {
+	t.Helper()
+
+	ep := channel.New(1 /* size */, header.IPv4MinimumMTU, "" /* linkAddr */)
+	t.Cleanup(ep.Close)
+
+	wep := stack.LinkEndpoint(ep)
+	if testing.Verbose() {
+		wep = sniffer.New(ep)
+	}
+
+	opts := stack.NICOptions{Name: name}
+	if err := s.CreateNICWithOptions(id, wep, opts); err != nil {
+		t.Fatalf("s.CreateNIC(%d, _) = %s", id, err)
+	}
+
+	if err := s.AddAddress(id, ipv4.ProtocolNumber, addrV4); err != nil {
+		t.Fatalf("s.AddAddress(%d, %d, %s) = %s", id, ipv4.ProtocolNumber, addrV4, err)
+	}
+
+	s.AddRoute(tcpip.Route{
+		Destination: header.IPv4EmptySubnet,
+		NIC:         id,
+	})
+
+	return ep
+}
+
+func writePayload(buf []byte) {
+	for i := range buf {
+		buf[i] = byte(i)
+	}
+}
+
+func newICMPv4EchoRequest(payloadSize uint32) buffer.View {
+	buf := buffer.NewView(header.ICMPv4MinimumSize + int(payloadSize))
+	writePayload(buf[header.ICMPv4MinimumSize:])
+
+	icmp := header.ICMPv4(buf)
+	icmp.SetType(header.ICMPv4Echo)
+	// No need to set the checksum; it is reset by the socket before the packet
+	// is sent.
+
+	return buf
+}
+
+// TestWriteUnboundWithBindToDevice exercises writing to an unbound ICMP socket
+// when SO_BINDTODEVICE is set to the non-default NIC for that subnet.
+//
+// Only IPv4 is tested. The logic to determine which NIC to use is agnostic to
+// the version of IP.
+func TestWriteUnboundWithBindToDevice(t *testing.T) {
+	s := stack.New(stack.Options{
+		NetworkProtocols:   []stack.NetworkProtocolFactory{ipv4.NewProtocol},
+		TransportProtocols: []stack.TransportProtocolFactory{icmp.NewProtocol4},
+		HandleLocal:        true,
+	})
+
+	// Add two NICs, both with default routes on the same subnet. The first NIC
+	// added will be the default NIC for that subnet.
+	defaultEP := addNICWithDefaultRoute(t, s, 1, "default", localV4Addr1)
+	alternateEP := addNICWithDefaultRoute(t, s, 2, "alternate", localV4Addr2)
+
+	socket, err := s.NewEndpoint(icmp.ProtocolNumber4, ipv4.ProtocolNumber, &waiter.Queue{})
+	if err != nil {
+		t.Fatalf("s.NewEndpoint(%d, %d, _) = %s", icmp.ProtocolNumber4, ipv4.ProtocolNumber, err)
+	}
+	defer socket.Close()
+
+	echoPayloadSize := defaultEP.MTU() - header.IPv4MinimumSize - header.ICMPv4MinimumSize
+
+	// Send a packet without SO_BINDTODEVICE. This verifies that the first NIC
+	// to be added is the default NIC to send packets when not explicitly bound.
+	{
+		buf := newICMPv4EchoRequest(echoPayloadSize)
+		r := buf.Reader()
+		n, err := socket.Write(&r, tcpip.WriteOptions{
+			To: &tcpip.FullAddress{Addr: remoteV4Addr},
+		})
+		if err != nil {
+			t.Fatalf("socket.Write(_, {To:%s}) = %s", remoteV4Addr, err)
+		}
+		if n != int64(len(buf)) {
+			t.Fatalf("got n = %d, want n = %d", n, len(buf))
+		}
+
+		// Verify the packet was sent out the default NIC.
+		p, ok := defaultEP.Read()
+		if !ok {
+			t.Fatalf("got defaultEP.Read(_) = _, false; want = _, true (packet wasn't written out)")
+		}
+
+		vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+		b := vv.ToView()
+
+		checker.IPv4(t, b, []checker.NetworkChecker{
+			checker.SrcAddr(localV4Addr1),
+			checker.DstAddr(remoteV4Addr),
+			checker.ICMPv4(
+				checker.ICMPv4Type(header.ICMPv4Echo),
+				checker.ICMPv4Payload(buf[header.ICMPv4MinimumSize:]),
+			),
+		}...)
+
+		// Verify the packet was not sent out the alternate NIC.
+		if p, ok := alternateEP.Read(); ok {
+			t.Fatalf("got alternateEP.Read(_) = %+v, true; want = _, false", p)
+		}
+	}
+
+	// Send a packet with SO_BINDTODEVICE. This exercises reliance on
+	// SO_BINDTODEVICE to route the packet to the alternate NIC.
+	{
+		// Use SO_BINDTODEVICE to send over the alternate NIC by default.
+		socket.SocketOptions().SetBindToDevice(2)
+
+		buf := newICMPv4EchoRequest(echoPayloadSize)
+		r := buf.Reader()
+		n, err := socket.Write(&r, tcpip.WriteOptions{
+			To: &tcpip.FullAddress{Addr: remoteV4Addr},
+		})
+		if err != nil {
+			t.Fatalf("socket.Write(_, {To:%s}) = %s", tcpip.Address(remoteV4Addr), err)
+		}
+		if n != int64(len(buf)) {
+			t.Fatalf("got n = %d, want n = %d", n, len(buf))
+		}
+
+		// Verify the packet was not sent out the default NIC.
+		if p, ok := defaultEP.Read(); ok {
+			t.Fatalf("got defaultEP.Read(_) = %+v, true; want = _, false", p)
+		}
+
+		// Verify the packet was sent out the alternate NIC.
+		p, ok := alternateEP.Read()
+		if !ok {
+			t.Fatalf("got alternateEP.Read(_) = _, false; want = _, true (packet wasn't written out)")
+		}
+
+		vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+		b := vv.ToView()
+
+		checker.IPv4(t, b, []checker.NetworkChecker{
+			checker.SrcAddr(localV4Addr2),
+			checker.DstAddr(remoteV4Addr),
+			checker.ICMPv4(
+				checker.ICMPv4Type(header.ICMPv4Echo),
+				checker.ICMPv4Payload(buf[header.ICMPv4MinimumSize:]),
+			),
+		}...)
+	}
+
+	// Send a packet with SO_BINDTODEVICE cleared. This verifies that clearing
+	// the device binding will fallback to using the default NIC to send
+	// packets.
+	{
+		socket.SocketOptions().SetBindToDevice(0)
+
+		buf := newICMPv4EchoRequest(echoPayloadSize)
+		r := buf.Reader()
+		n, err := socket.Write(&r, tcpip.WriteOptions{
+			To: &tcpip.FullAddress{Addr: remoteV4Addr},
+		})
+		if err != nil {
+			t.Fatalf("socket.Write(_, {To:%s}) = %s", tcpip.Address(remoteV4Addr), err)
+		}
+		if n != int64(len(buf)) {
+			t.Fatalf("got n = %d, want n = %d", n, len(buf))
+		}
+
+		// Verify the packet was sent out the default NIC.
+		p, ok := defaultEP.Read()
+		if !ok {
+			t.Fatalf("got defaultEP.Read(_) = _, false; want = _, true (packet wasn't written out)")
+		}
+
+		vv := buffer.NewVectorisedView(p.Pkt.Size(), p.Pkt.Views())
+		b := vv.ToView()
+
+		checker.IPv4(t, b, []checker.NetworkChecker{
+			checker.SrcAddr(localV4Addr1),
+			checker.DstAddr(remoteV4Addr),
+			checker.ICMPv4(
+				checker.ICMPv4Type(header.ICMPv4Echo),
+				checker.ICMPv4Payload(buf[header.ICMPv4MinimumSize:]),
+			),
+		}...)
+
+		// Verify the packet was not sent out the alternate NIC.
+		if p, ok := alternateEP.Read(); ok {
+			t.Fatalf("got alternateEP.Read(_) = %+v, true; want = _, false", p)
+		}
+	}
+}