diff options
author | Ghanan Gowripalan <ghanan@google.com> | 2020-07-30 12:48:18 -0700 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2020-07-30 12:50:02 -0700 |
commit | b00858d075fbc39c6fb2db9f903ac14f197566bd (patch) | |
tree | 30bcd5acc64d5f90e78d09429f5b8255c0e6141f | |
parent | bc8201d01bc98e9db4009d250454c5fe73c5d2b4 (diff) |
Use brodcast MAC for broadcast IPv4 packets
When sending packets to a known network's broadcast address, use the
broadcast MAC address.
Test:
- stack_test.TestOutgoingSubnetBroadcast
- udp_test.TestOutgoingSubnetBroadcast
PiperOrigin-RevId: 324062407
-rw-r--r-- | pkg/tcpip/stack/BUILD | 1 | ||||
-rw-r--r-- | pkg/tcpip/stack/route.go | 10 | ||||
-rw-r--r-- | pkg/tcpip/stack/stack.go | 15 | ||||
-rw-r--r-- | pkg/tcpip/stack/stack_test.go | 223 | ||||
-rw-r--r-- | pkg/tcpip/tcpip.go | 26 | ||||
-rw-r--r-- | pkg/tcpip/transport/udp/endpoint.go | 8 | ||||
-rw-r--r-- | pkg/tcpip/transport/udp/udp_test.go | 189 |
7 files changed, 464 insertions, 8 deletions
diff --git a/pkg/tcpip/stack/BUILD b/pkg/tcpip/stack/BUILD index 6b9a6b316..2b4455318 100644 --- a/pkg/tcpip/stack/BUILD +++ b/pkg/tcpip/stack/BUILD @@ -110,6 +110,7 @@ go_test( "//pkg/tcpip/transport/udp", "//pkg/waiter", "@com_github_google_go_cmp//cmp:go_default_library", + "@com_github_google_go_cmp//cmp/cmpopts:go_default_library", ], ) diff --git a/pkg/tcpip/stack/route.go b/pkg/tcpip/stack/route.go index d65f8049e..91e0110f1 100644 --- a/pkg/tcpip/stack/route.go +++ b/pkg/tcpip/stack/route.go @@ -48,6 +48,10 @@ type Route struct { // Loop controls where WritePacket should send packets. Loop PacketLooping + + // directedBroadcast indicates whether this route is sending a directed + // broadcast packet. + directedBroadcast bool } // makeRoute initializes a new route. It takes ownership of the provided @@ -275,6 +279,12 @@ func (r *Route) Stack() *Stack { return r.ref.stack() } +// IsBroadcast returns true if the route is to send a broadcast packet. +func (r *Route) IsBroadcast() bool { + // Only IPv4 has a notion of broadcast. + return r.directedBroadcast || r.RemoteAddress == header.IPv4Broadcast +} + // ReverseRoute returns new route with given source and destination address. func (r *Route) ReverseRoute(src tcpip.Address, dst tcpip.Address) Route { return Route{ diff --git a/pkg/tcpip/stack/stack.go b/pkg/tcpip/stack/stack.go index a6faa22c2..36626e051 100644 --- a/pkg/tcpip/stack/stack.go +++ b/pkg/tcpip/stack/stack.go @@ -1284,9 +1284,9 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n s.mu.RLock() defer s.mu.RUnlock() - isBroadcast := remoteAddr == header.IPv4Broadcast + isLocalBroadcast := remoteAddr == header.IPv4Broadcast isMulticast := header.IsV4MulticastAddress(remoteAddr) || header.IsV6MulticastAddress(remoteAddr) - needRoute := !(isBroadcast || isMulticast || header.IsV6LinkLocalAddress(remoteAddr)) + needRoute := !(isLocalBroadcast || isMulticast || header.IsV6LinkLocalAddress(remoteAddr)) if id != 0 && !needRoute { if nic, ok := s.nics[id]; ok && nic.enabled() { if ref := s.getRefEP(nic, localAddr, remoteAddr, netProto); ref != nil { @@ -1307,9 +1307,16 @@ func (s *Stack) FindRoute(id tcpip.NICID, localAddr, remoteAddr tcpip.Address, n } r := makeRoute(netProto, ref.ep.ID().LocalAddress, remoteAddr, nic.linkEP.LinkAddress(), ref, s.handleLocal && !nic.isLoopback(), multicastLoop && !nic.isLoopback()) - if needRoute { - r.NextHop = route.Gateway + r.directedBroadcast = route.Destination.IsBroadcast(remoteAddr) + + if len(route.Gateway) > 0 { + if needRoute { + r.NextHop = route.Gateway + } + } else if r.directedBroadcast { + r.RemoteLinkAddress = header.EthernetBroadcastAddress } + return r, nil } } diff --git a/pkg/tcpip/stack/stack_test.go b/pkg/tcpip/stack/stack_test.go index 101ca2206..f22062889 100644 --- a/pkg/tcpip/stack/stack_test.go +++ b/pkg/tcpip/stack/stack_test.go @@ -27,6 +27,7 @@ import ( "time" "github.com/google/go-cmp/cmp" + "github.com/google/go-cmp/cmp/cmpopts" "gvisor.dev/gvisor/pkg/rand" "gvisor.dev/gvisor/pkg/tcpip" "gvisor.dev/gvisor/pkg/tcpip/buffer" @@ -3418,3 +3419,225 @@ func TestStackSendBufferSizeOption(t *testing.T) { }) } } + +func TestOutgoingSubnetBroadcast(t *testing.T) { + const ( + unspecifiedNICID = 0 + nicID1 = 1 + ) + + defaultAddr := tcpip.AddressWithPrefix{ + Address: header.IPv4Any, + PrefixLen: 0, + } + defaultSubnet := defaultAddr.Subnet() + ipv4Addr := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 24, + } + ipv4Subnet := ipv4Addr.Subnet() + ipv4SubnetBcast := ipv4Subnet.Broadcast() + ipv4Gateway := tcpip.Address("\xc0\xa8\x01\x01") + ipv4AddrPrefix31 := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 31, + } + ipv4Subnet31 := ipv4AddrPrefix31.Subnet() + ipv4Subnet31Bcast := ipv4Subnet31.Broadcast() + ipv4AddrPrefix32 := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 32, + } + ipv4Subnet32 := ipv4AddrPrefix32.Subnet() + ipv4Subnet32Bcast := ipv4Subnet32.Broadcast() + ipv6Addr := tcpip.AddressWithPrefix{ + Address: "\x20\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01", + PrefixLen: 64, + } + ipv6Subnet := ipv6Addr.Subnet() + ipv6SubnetBcast := ipv6Subnet.Broadcast() + remNetAddr := tcpip.AddressWithPrefix{ + Address: "\x64\x0a\x7b\x18", + PrefixLen: 24, + } + remNetSubnet := remNetAddr.Subnet() + remNetSubnetBcast := remNetSubnet.Broadcast() + + tests := []struct { + name string + nicAddr tcpip.ProtocolAddress + routes []tcpip.Route + remoteAddr tcpip.Address + expectedRoute stack.Route + }{ + // Broadcast to a locally attached subnet populates the broadcast MAC. + { + name: "IPv4 Broadcast to local subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4Addr, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet, + NIC: nicID1, + }, + }, + remoteAddr: ipv4SubnetBcast, + expectedRoute: stack.Route{ + LocalAddress: ipv4Addr.Address, + RemoteAddress: ipv4SubnetBcast, + RemoteLinkAddress: header.EthernetBroadcastAddress, + NetProto: header.IPv4ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + // Broadcast to a locally attached /31 subnet does not populate the + // broadcast MAC. + { + name: "IPv4 Broadcast to local /31 subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4AddrPrefix31, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet31, + NIC: nicID1, + }, + }, + remoteAddr: ipv4Subnet31Bcast, + expectedRoute: stack.Route{ + LocalAddress: ipv4AddrPrefix31.Address, + RemoteAddress: ipv4Subnet31Bcast, + NetProto: header.IPv4ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + // Broadcast to a locally attached /32 subnet does not populate the + // broadcast MAC. + { + name: "IPv4 Broadcast to local /32 subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4AddrPrefix32, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet32, + NIC: nicID1, + }, + }, + remoteAddr: ipv4Subnet32Bcast, + expectedRoute: stack.Route{ + LocalAddress: ipv4AddrPrefix32.Address, + RemoteAddress: ipv4Subnet32Bcast, + NetProto: header.IPv4ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + // IPv6 has no notion of a broadcast. + { + name: "IPv6 'Broadcast' to local subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv6ProtocolNumber, + AddressWithPrefix: ipv6Addr, + }, + routes: []tcpip.Route{ + { + Destination: ipv6Subnet, + NIC: nicID1, + }, + }, + remoteAddr: ipv6SubnetBcast, + expectedRoute: stack.Route{ + LocalAddress: ipv6Addr.Address, + RemoteAddress: ipv6SubnetBcast, + NetProto: header.IPv6ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + // Broadcast to a remote subnet in the route table is send to the next-hop + // gateway. + { + name: "IPv4 Broadcast to remote subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4Addr, + }, + routes: []tcpip.Route{ + { + Destination: remNetSubnet, + Gateway: ipv4Gateway, + NIC: nicID1, + }, + }, + remoteAddr: remNetSubnetBcast, + expectedRoute: stack.Route{ + LocalAddress: ipv4Addr.Address, + RemoteAddress: remNetSubnetBcast, + NextHop: ipv4Gateway, + NetProto: header.IPv4ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + // Broadcast to an unknown subnet follows the default route. Note that this + // is essentially just routing an unknown destination IP, because w/o any + // subnet prefix information a subnet broadcast address is just a normal IP. + { + name: "IPv4 Broadcast to unknown subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4Addr, + }, + routes: []tcpip.Route{ + { + Destination: defaultSubnet, + Gateway: ipv4Gateway, + NIC: nicID1, + }, + }, + remoteAddr: remNetSubnetBcast, + expectedRoute: stack.Route{ + LocalAddress: ipv4Addr.Address, + RemoteAddress: remNetSubnetBcast, + NextHop: ipv4Gateway, + NetProto: header.IPv4ProtocolNumber, + Loop: stack.PacketOut, + }, + }, + } + + for _, test := range tests { + t.Run(test.name, func(t *testing.T) { + s := stack.New(stack.Options{ + NetworkProtocols: []stack.NetworkProtocol{ipv4.NewProtocol(), ipv6.NewProtocol()}, + }) + ep := channel.New(0, defaultMTU, "") + if err := s.CreateNIC(nicID1, ep); err != nil { + t.Fatalf("CreateNIC(%d, _): %s", nicID1, err) + } + if err := s.AddProtocolAddress(nicID1, test.nicAddr); err != nil { + t.Fatalf("AddProtocolAddress(%d, %+v): %s", nicID1, test.nicAddr, err) + } + + s.SetRouteTable(test.routes) + + var netProto tcpip.NetworkProtocolNumber + switch l := len(test.remoteAddr); l { + case header.IPv4AddressSize: + netProto = header.IPv4ProtocolNumber + case header.IPv6AddressSize: + netProto = header.IPv6ProtocolNumber + default: + t.Fatalf("got unexpected address length = %d bytes", l) + } + + if r, err := s.FindRoute(unspecifiedNICID, "" /* localAddr */, test.remoteAddr, netProto, false /* multicastLoop */); err != nil { + t.Fatalf("FindRoute(%d, '', %s, %d): %s", unspecifiedNICID, test.remoteAddr, netProto, err) + } else if diff := cmp.Diff(r, test.expectedRoute, cmpopts.IgnoreUnexported(r)); diff != "" { + t.Errorf("route mismatch (-want +got):\n%s", diff) + } + }) + } +} diff --git a/pkg/tcpip/tcpip.go b/pkg/tcpip/tcpip.go index 21aafb0a2..a634b9b60 100644 --- a/pkg/tcpip/tcpip.go +++ b/pkg/tcpip/tcpip.go @@ -43,6 +43,9 @@ import ( "gvisor.dev/gvisor/pkg/waiter" ) +// Using header.IPv4AddressSize would cause an import cycle. +const ipv4AddressSize = 4 + // Error represents an error in the netstack error space. Using a special type // ensures that errors outside of this space are not accidentally introduced. // @@ -320,6 +323,29 @@ func (s *Subnet) Broadcast() Address { return Address(addr) } +// IsBroadcast returns true if the address is considered a broadcast address. +func (s *Subnet) IsBroadcast(address Address) bool { + // Only IPv4 supports the notion of a broadcast address. + if len(address) != ipv4AddressSize { + return false + } + + // Normally, we would just compare address with the subnet's broadcast + // address but there is an exception where a simple comparison is not + // correct. This exception is for /31 and /32 IPv4 subnets where all + // addresses are considered valid host addresses. + // + // For /31 subnets, the case is easy. RFC 3021 Section 2.1 states that + // both addresses in a /31 subnet "MUST be interpreted as host addresses." + // + // For /32, the case is a bit more vague. RFC 3021 makes no mention of /32 + // subnets. However, the same reasoning applies - if an exception is not + // made, then there do not exist any host addresses in a /32 subnet. RFC + // 4632 Section 3.1 also vaguely implies this interpretation by referring + // to addresses in /32 subnets as "host routes." + return s.Prefix() <= 30 && s.Broadcast() == address +} + // Equal returns true if s equals o. // // Needed to use cmp.Equal on Subnet as its fields are unexported. diff --git a/pkg/tcpip/transport/udp/endpoint.go b/pkg/tcpip/transport/udp/endpoint.go index 6e692da07..b7d735889 100644 --- a/pkg/tcpip/transport/udp/endpoint.go +++ b/pkg/tcpip/transport/udp/endpoint.go @@ -483,10 +483,6 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c nicID = e.BindNICID } - if to.Addr == header.IPv4Broadcast && !e.broadcast { - return 0, nil, tcpip.ErrBroadcastDisabled - } - dst, netProto, err := e.checkV4MappedLocked(*to) if err != nil { return 0, nil, err @@ -503,6 +499,10 @@ func (e *endpoint) write(p tcpip.Payloader, opts tcpip.WriteOptions) (int64, <-c resolve = route.Resolve } + if !e.broadcast && route.IsBroadcast() { + return 0, nil, tcpip.ErrBroadcastDisabled + } + if route.IsResolutionRequired() { if ch, err := resolve(nil); err != nil { if err == tcpip.ErrWouldBlock { diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go index 90781cf49..66e8911c8 100644 --- a/pkg/tcpip/transport/udp/udp_test.go +++ b/pkg/tcpip/transport/udp/udp_test.go @@ -2142,3 +2142,192 @@ func (c *testContext) checkEndpointReadStats(incr uint64, want tcpip.TransportEn c.t.Errorf("Endpoint stats not matching for error %s got %+v want %+v", err, got, want) } } + +func TestOutgoingSubnetBroadcast(t *testing.T) { + const nicID1 = 1 + + ipv4Addr := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 24, + } + ipv4Subnet := ipv4Addr.Subnet() + ipv4SubnetBcast := ipv4Subnet.Broadcast() + ipv4Gateway := tcpip.Address("\xc0\xa8\x01\x01") + ipv4AddrPrefix31 := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 31, + } + ipv4Subnet31 := ipv4AddrPrefix31.Subnet() + ipv4Subnet31Bcast := ipv4Subnet31.Broadcast() + ipv4AddrPrefix32 := tcpip.AddressWithPrefix{ + Address: "\xc0\xa8\x01\x3a", + PrefixLen: 32, + } + ipv4Subnet32 := ipv4AddrPrefix32.Subnet() + ipv4Subnet32Bcast := ipv4Subnet32.Broadcast() + ipv6Addr := tcpip.AddressWithPrefix{ + Address: "\x20\x0a\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x01", + PrefixLen: 64, + } + ipv6Subnet := ipv6Addr.Subnet() + ipv6SubnetBcast := ipv6Subnet.Broadcast() + remNetAddr := tcpip.AddressWithPrefix{ + Address: "\x64\x0a\x7b\x18", + PrefixLen: 24, + } + remNetSubnet := remNetAddr.Subnet() + remNetSubnetBcast := remNetSubnet.Broadcast() + + tests := []struct { + name string + nicAddr tcpip.ProtocolAddress + routes []tcpip.Route + remoteAddr tcpip.Address + requiresBroadcastOpt bool + }{ + { + name: "IPv4 Broadcast to local subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4Addr, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet, + NIC: nicID1, + }, + }, + remoteAddr: ipv4SubnetBcast, + requiresBroadcastOpt: true, + }, + { + name: "IPv4 Broadcast to local /31 subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4AddrPrefix31, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet31, + NIC: nicID1, + }, + }, + remoteAddr: ipv4Subnet31Bcast, + requiresBroadcastOpt: false, + }, + { + name: "IPv4 Broadcast to local /32 subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4AddrPrefix32, + }, + routes: []tcpip.Route{ + { + Destination: ipv4Subnet32, + NIC: nicID1, + }, + }, + remoteAddr: ipv4Subnet32Bcast, + requiresBroadcastOpt: false, + }, + // IPv6 has no notion of a broadcast. + { + name: "IPv6 'Broadcast' to local subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv6ProtocolNumber, + AddressWithPrefix: ipv6Addr, + }, + routes: []tcpip.Route{ + { + Destination: ipv6Subnet, + NIC: nicID1, + }, + }, + remoteAddr: ipv6SubnetBcast, + requiresBroadcastOpt: false, + }, + { + name: "IPv4 Broadcast to remote subnet", + nicAddr: tcpip.ProtocolAddress{ + Protocol: header.IPv4ProtocolNumber, + AddressWithPrefix: ipv4Addr, + }, + routes: []tcpip.Route{ + { + Destination: remNetSubnet, + Gateway: ipv4Gateway, + NIC: nicID1, + }, + }, + remoteAddr: remNetSubnetBcast, + requiresBroadcastOpt: true, + }, + } + + for _, test := range tests { + t.Run(test.name, func(t *testing.T) { + s := stack.New(stack.Options{ + NetworkProtocols: []stack.NetworkProtocol{ipv4.NewProtocol(), ipv6.NewProtocol()}, + + TransportProtocols: []stack.TransportProtocol{udp.NewProtocol()}, + }) + e := channel.New(0, defaultMTU, "") + if err := s.CreateNIC(nicID1, e); err != nil { + t.Fatalf("CreateNIC(%d, _): %s", nicID1, err) + } + if err := s.AddProtocolAddress(nicID1, test.nicAddr); err != nil { + t.Fatalf("AddProtocolAddress(%d, %+v): %s", nicID1, test.nicAddr, err) + } + + s.SetRouteTable(test.routes) + + var netProto tcpip.NetworkProtocolNumber + switch l := len(test.remoteAddr); l { + case header.IPv4AddressSize: + netProto = header.IPv4ProtocolNumber + case header.IPv6AddressSize: + netProto = header.IPv6ProtocolNumber + default: + t.Fatalf("got unexpected address length = %d bytes", l) + } + + wq := waiter.Queue{} + ep, err := s.NewEndpoint(udp.ProtocolNumber, netProto, &wq) + if err != nil { + t.Fatalf("NewEndpoint(%d, %d, _): %s", udp.ProtocolNumber, netProto, err) + } + defer ep.Close() + + data := tcpip.SlicePayload([]byte{1, 2, 3, 4}) + to := tcpip.FullAddress{ + Addr: test.remoteAddr, + Port: 80, + } + opts := tcpip.WriteOptions{To: &to} + expectedErrWithoutBcastOpt := tcpip.ErrBroadcastDisabled + if !test.requiresBroadcastOpt { + expectedErrWithoutBcastOpt = nil + } + + if n, _, err := ep.Write(data, opts); err != expectedErrWithoutBcastOpt { + t.Fatalf("got ep.Write(_, _) = (%d, _, %v), want = (_, _, %v)", n, err, expectedErrWithoutBcastOpt) + } + + if err := ep.SetSockOptBool(tcpip.BroadcastOption, true); err != nil { + t.Fatalf("got SetSockOptBool(BroadcastOption, true): %s", err) + } + + if n, _, err := ep.Write(data, opts); err != nil { + t.Fatalf("got ep.Write(_, _) = (%d, _, %s), want = (_, _, nil)", n, err) + } + + if err := ep.SetSockOptBool(tcpip.BroadcastOption, false); err != nil { + t.Fatalf("got SetSockOptBool(BroadcastOption, false): %s", err) + } + + if n, _, err := ep.Write(data, opts); err != expectedErrWithoutBcastOpt { + t.Fatalf("got ep.Write(_, _) = (%d, _, %v), want = (_, _, %v)", n, err, expectedErrWithoutBcastOpt) + } + }) + } +} |