From 3789c34b22e7a7466149bfbeedf05bf49188130c Mon Sep 17 00:00:00 2001 From: Bhasker Hariharan Date: Tue, 3 Sep 2019 15:59:58 -0700 Subject: Make UDP traceroute work. Adds support to generate Port Unreachable messages for UDP datagrams received on a port for which there is no valid endpoint. Fixes #703 PiperOrigin-RevId: 267034418 --- pkg/tcpip/transport/icmp/endpoint.go | 19 ++- pkg/tcpip/transport/icmp/protocol.go | 11 +- pkg/tcpip/transport/tcp/protocol.go | 2 +- pkg/tcpip/transport/tcp/testing/context/context.go | 8 +- pkg/tcpip/transport/udp/protocol.go | 101 ++++++++++++- pkg/tcpip/transport/udp/udp_test.go | 156 ++++++++++++++++++++- 6 files changed, 274 insertions(+), 23 deletions(-) (limited to 'pkg/tcpip/transport') diff --git a/pkg/tcpip/transport/icmp/endpoint.go b/pkg/tcpip/transport/icmp/endpoint.go index 451d3880e..e1f622af6 100644 --- a/pkg/tcpip/transport/icmp/endpoint.go +++ b/pkg/tcpip/transport/icmp/endpoint.go @@ -15,7 +15,6 @@ package icmp import ( - "encoding/binary" "sync" "gvisor.dev/gvisor/pkg/tcpip" @@ -368,14 +367,13 @@ func send4(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error { return tcpip.ErrInvalidEndpointState } - // Set the ident to the user-specified port. Sequence number should - // already be set by the user. - binary.BigEndian.PutUint16(data[header.ICMPv4PayloadOffset:], ident) - hdr := buffer.NewPrependable(header.ICMPv4MinimumSize + int(r.MaxHeaderLength())) icmpv4 := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize)) copy(icmpv4, data) + // Set the ident to the user-specified port. Sequence number should + // already be set by the user. + icmpv4.SetIdent(ident) data = data[header.ICMPv4MinimumSize:] // Linux performs these basic checks. @@ -394,14 +392,13 @@ func send6(r *stack.Route, ident uint16, data buffer.View) *tcpip.Error { return tcpip.ErrInvalidEndpointState } - // Set the ident. Sequence number is provided by the user. - binary.BigEndian.PutUint16(data[header.ICMPv6MinimumSize:], ident) - - hdr := buffer.NewPrependable(header.ICMPv6EchoMinimumSize + int(r.MaxHeaderLength())) + hdr := buffer.NewPrependable(header.ICMPv6MinimumSize + int(r.MaxHeaderLength())) - icmpv6 := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize)) + icmpv6 := header.ICMPv6(hdr.Prepend(header.ICMPv6MinimumSize)) copy(icmpv6, data) - data = data[header.ICMPv6EchoMinimumSize:] + // Set the ident. Sequence number is provided by the user. + icmpv6.SetIdent(ident) + data = data[header.ICMPv6MinimumSize:] if icmpv6.Type() != header.ICMPv6EchoRequest || icmpv6.Code() != 0 { return tcpip.ErrInvalidEndpointState diff --git a/pkg/tcpip/transport/icmp/protocol.go b/pkg/tcpip/transport/icmp/protocol.go index 7fdba5d56..1eb790932 100644 --- a/pkg/tcpip/transport/icmp/protocol.go +++ b/pkg/tcpip/transport/icmp/protocol.go @@ -23,7 +23,6 @@ package icmp import ( - "encoding/binary" "fmt" "gvisor.dev/gvisor/pkg/tcpip" @@ -92,7 +91,7 @@ func (p *protocol) MinimumPacketSize() int { case ProtocolNumber4: return header.ICMPv4MinimumSize case ProtocolNumber6: - return header.ICMPv6EchoMinimumSize + return header.ICMPv6MinimumSize } panic(fmt.Sprint("unknown protocol number: ", p.number)) } @@ -101,16 +100,18 @@ func (p *protocol) MinimumPacketSize() int { func (p *protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) { switch p.number { case ProtocolNumber4: - return 0, binary.BigEndian.Uint16(v[header.ICMPv4PayloadOffset:]), nil + hdr := header.ICMPv4(v) + return 0, hdr.Ident(), nil case ProtocolNumber6: - return 0, binary.BigEndian.Uint16(v[header.ICMPv6MinimumSize:]), nil + hdr := header.ICMPv6(v) + return 0, hdr.Ident(), nil } panic(fmt.Sprint("unknown protocol number: ", p.number)) } // HandleUnknownDestinationPacket handles packets targeted at this protocol but // that don't match any existing endpoint. -func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.VectorisedView) bool { +func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.View, buffer.VectorisedView) bool { return true } diff --git a/pkg/tcpip/transport/tcp/protocol.go b/pkg/tcpip/transport/tcp/protocol.go index ee04dcfcc..2a13b2022 100644 --- a/pkg/tcpip/transport/tcp/protocol.go +++ b/pkg/tcpip/transport/tcp/protocol.go @@ -129,7 +129,7 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) { // a reset is sent in response to any incoming segment except another reset. In // particular, SYNs addressed to a non-existent connection are rejected by this // means." -func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, vv buffer.VectorisedView) bool { +func (*protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, netHeader buffer.View, vv buffer.VectorisedView) bool { s := newSegment(r, id, vv) defer s.decRef() diff --git a/pkg/tcpip/transport/tcp/testing/context/context.go b/pkg/tcpip/transport/tcp/testing/context/context.go index 272481aa0..18c707a57 100644 --- a/pkg/tcpip/transport/tcp/testing/context/context.go +++ b/pkg/tcpip/transport/tcp/testing/context/context.go @@ -267,7 +267,7 @@ func (c *Context) GetPacketNonBlocking() []byte { // SendICMPPacket builds and sends an ICMPv4 packet via the link layer endpoint. func (c *Context) SendICMPPacket(typ header.ICMPv4Type, code uint8, p1, p2 []byte, maxTotalSize int) { // Allocate a buffer data and headers. - buf := buffer.NewView(header.IPv4MinimumSize + header.ICMPv4PayloadOffset + len(p1) + len(p2)) + buf := buffer.NewView(header.IPv4MinimumSize + header.ICMPv4PayloadOffset + len(p2)) if len(buf) > maxTotalSize { buf = buf[:maxTotalSize] } @@ -286,9 +286,9 @@ func (c *Context) SendICMPPacket(typ header.ICMPv4Type, code uint8, p1, p2 []byt icmp := header.ICMPv4(buf[header.IPv4MinimumSize:]) icmp.SetType(typ) icmp.SetCode(code) - - copy(icmp[header.ICMPv4PayloadOffset:], p1) - copy(icmp[header.ICMPv4PayloadOffset+len(p1):], p2) + const icmpv4VariableHeaderOffset = 4 + copy(icmp[icmpv4VariableHeaderOffset:], p1) + copy(icmp[header.ICMPv4PayloadOffset:], p2) // Inject packet. c.linkEP.Inject(ipv4.ProtocolNumber, buf.ToVectorisedView()) diff --git a/pkg/tcpip/transport/udp/protocol.go b/pkg/tcpip/transport/udp/protocol.go index f76e7fbe1..068d9a272 100644 --- a/pkg/tcpip/transport/udp/protocol.go +++ b/pkg/tcpip/transport/udp/protocol.go @@ -69,7 +69,106 @@ func (*protocol) ParsePorts(v buffer.View) (src, dst uint16, err *tcpip.Error) { // HandleUnknownDestinationPacket handles packets targeted at this protocol but // that don't match any existing endpoint. -func (p *protocol) HandleUnknownDestinationPacket(*stack.Route, stack.TransportEndpointID, buffer.VectorisedView) bool { +func (p *protocol) HandleUnknownDestinationPacket(r *stack.Route, id stack.TransportEndpointID, netHeader buffer.View, vv buffer.VectorisedView) bool { + // Get the header then trim it from the view. + hdr := header.UDP(vv.First()) + if int(hdr.Length()) > vv.Size() { + // Malformed packet. + r.Stack().Stats().UDP.MalformedPacketsReceived.Increment() + return true + } + // TODO(b/129426613): only send an ICMP message if UDP checksum is valid. + + // Only send ICMP error if the address is not a multicast/broadcast + // v4/v6 address or the source is not the unspecified address. + // + // See: point e) in https://tools.ietf.org/html/rfc4443#section-2.4 + if id.LocalAddress == header.IPv4Broadcast || header.IsV4MulticastAddress(id.LocalAddress) || header.IsV6MulticastAddress(id.LocalAddress) || id.RemoteAddress == header.IPv6Any || id.RemoteAddress == header.IPv4Any { + return true + } + + // As per RFC: 1122 Section 3.2.2.1 A host SHOULD generate Destination + // Unreachable messages with code: + // + // 2 (Protocol Unreachable), when the designated transport protocol + // is not supported; or + // + // 3 (Port Unreachable), when the designated transport protocol + // (e.g., UDP) is unable to demultiplex the datagram but has no + // protocol mechanism to inform the sender. + switch len(id.LocalAddress) { + case header.IPv4AddressSize: + if !r.Stack().AllowICMPMessage() { + r.Stack().Stats().ICMP.V4PacketsSent.RateLimited.Increment() + return true + } + // As per RFC 1812 Section 4.3.2.3 + // + // ICMP datagram SHOULD contain as much of the original + // datagram as possible without the length of the ICMP + // datagram exceeding 576 bytes + // + // NOTE: The above RFC referenced is different from the original + // recommendation in RFC 1122 where it mentioned that at least 8 + // bytes of the payload must be included. Today linux and other + // systems implement the] RFC1812 definition and not the original + // RFC 1122 requirement. + mtu := int(r.MTU()) + if mtu > header.IPv4MinimumProcessableDatagramSize { + mtu = header.IPv4MinimumProcessableDatagramSize + } + headerLen := int(r.MaxHeaderLength()) + header.ICMPv4MinimumSize + available := int(mtu) - headerLen + payloadLen := len(netHeader) + vv.Size() + if payloadLen > available { + payloadLen = available + } + + payload := buffer.NewVectorisedView(len(netHeader), []buffer.View{netHeader}) + payload.Append(vv) + payload.CapLength(payloadLen) + + hdr := buffer.NewPrependable(headerLen) + pkt := header.ICMPv4(hdr.Prepend(header.ICMPv4MinimumSize)) + pkt.SetType(header.ICMPv4DstUnreachable) + pkt.SetCode(header.ICMPv4PortUnreachable) + pkt.SetChecksum(header.ICMPv4Checksum(pkt, payload)) + r.WritePacket(nil /* gso */, hdr, payload, header.ICMPv4ProtocolNumber, r.DefaultTTL()) + + case header.IPv6AddressSize: + if !r.Stack().AllowICMPMessage() { + r.Stack().Stats().ICMP.V6PacketsSent.RateLimited.Increment() + return true + } + + // As per RFC 4443 section 2.4 + // + // (c) Every ICMPv6 error message (type < 128) MUST include + // as much of the IPv6 offending (invoking) packet (the + // packet that caused the error) as possible without making + // the error message packet exceed the minimum IPv6 MTU + // [IPv6]. + mtu := int(r.MTU()) + if mtu > header.IPv6MinimumMTU { + mtu = header.IPv6MinimumMTU + } + headerLen := int(r.MaxHeaderLength()) + header.ICMPv6DstUnreachableMinimumSize + available := int(mtu) - headerLen + payloadLen := len(netHeader) + vv.Size() + if payloadLen > available { + payloadLen = available + } + payload := buffer.NewVectorisedView(len(netHeader), []buffer.View{netHeader}) + payload.Append(vv) + payload.CapLength(payloadLen) + + hdr := buffer.NewPrependable(headerLen) + pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6DstUnreachableMinimumSize)) + pkt.SetType(header.ICMPv6DstUnreachable) + pkt.SetCode(header.ICMPv6PortUnreachable) + pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, payload)) + r.WritePacket(nil /* gso */, hdr, payload, header.ICMPv6ProtocolNumber, r.DefaultTTL()) + } return true } diff --git a/pkg/tcpip/transport/udp/udp_test.go b/pkg/tcpip/transport/udp/udp_test.go index 9da6edce2..995d6e8a1 100644 --- a/pkg/tcpip/transport/udp/udp_test.go +++ b/pkg/tcpip/transport/udp/udp_test.go @@ -461,7 +461,11 @@ func (c *testContext) injectV4Packet(payload []byte, h *header4Tuple) { } func newPayload() []byte { - b := make([]byte, 30+rand.Intn(100)) + return newMinPayload(30) +} + +func newMinPayload(minSize int) []byte { + b := make([]byte, minSize+rand.Intn(100)) for i := range b { b[i] = byte(rand.Intn(256)) } @@ -1238,3 +1242,153 @@ func TestMulticastInterfaceOption(t *testing.T) { }) } } + +// TestV4UnknownDestination verifies that we generate an ICMPv4 Destination +// Unreachable message when a udp datagram is received on ports for which there +// is no bound udp socket. +func TestV4UnknownDestination(t *testing.T) { + c := newDualTestContext(t, defaultMTU) + defer c.cleanup() + + testCases := []struct { + flow testFlow + icmpRequired bool + // largePayload if true, will result in a payload large enough + // so that the final generated IPv4 packet is larger than + // header.IPv4MinimumProcessableDatagramSize. + largePayload bool + }{ + {unicastV4, true, false}, + {unicastV4, true, true}, + {multicastV4, false, false}, + {multicastV4, false, true}, + {broadcast, false, false}, + {broadcast, false, true}, + } + for _, tc := range testCases { + t.Run(fmt.Sprintf("flow:%s icmpRequired:%t largePayload:%t", tc.flow, tc.icmpRequired, tc.largePayload), func(t *testing.T) { + payload := newPayload() + if tc.largePayload { + payload = newMinPayload(576) + } + c.injectPacket(tc.flow, payload) + if !tc.icmpRequired { + select { + case p := <-c.linkEP.C: + t.Fatalf("unexpected packet received: %+v", p) + case <-time.After(1 * time.Second): + return + } + } + + select { + case p := <-c.linkEP.C: + var pkt []byte + pkt = append(pkt, p.Header...) + pkt = append(pkt, p.Payload...) + if got, want := len(pkt), header.IPv4MinimumProcessableDatagramSize; got > want { + t.Fatalf("got an ICMP packet of size: %d, want: sz <= %d", got, want) + } + + hdr := header.IPv4(pkt) + checker.IPv4(t, hdr, checker.ICMPv4( + checker.ICMPv4Type(header.ICMPv4DstUnreachable), + checker.ICMPv4Code(header.ICMPv4PortUnreachable))) + + icmpPkt := header.ICMPv4(hdr.Payload()) + payloadIPHeader := header.IPv4(icmpPkt.Payload()) + wantLen := len(payload) + if tc.largePayload { + wantLen = header.IPv4MinimumProcessableDatagramSize - header.IPv4MinimumSize*2 - header.ICMPv4MinimumSize - header.UDPMinimumSize + } + + // In case of large payloads the IP packet may be truncated. Update + // the length field before retrieving the udp datagram payload. + payloadIPHeader.SetTotalLength(uint16(wantLen + header.UDPMinimumSize + header.IPv4MinimumSize)) + + origDgram := header.UDP(payloadIPHeader.Payload()) + if got, want := len(origDgram.Payload()), wantLen; got != want { + t.Fatalf("unexpected payload length got: %d, want: %d", got, want) + } + if got, want := origDgram.Payload(), payload[:wantLen]; !bytes.Equal(got, want) { + t.Fatalf("unexpected payload got: %d, want: %d", got, want) + } + case <-time.After(1 * time.Second): + t.Fatalf("packet wasn't written out") + } + }) + } +} + +// TestV6UnknownDestination verifies that we generate an ICMPv6 Destination +// Unreachable message when a udp datagram is received on ports for which there +// is no bound udp socket. +func TestV6UnknownDestination(t *testing.T) { + c := newDualTestContext(t, defaultMTU) + defer c.cleanup() + + testCases := []struct { + flow testFlow + icmpRequired bool + // largePayload if true will result in a payload large enough to + // create an IPv6 packet > header.IPv6MinimumMTU bytes. + largePayload bool + }{ + {unicastV6, true, false}, + {unicastV6, true, true}, + {multicastV6, false, false}, + {multicastV6, false, true}, + } + for _, tc := range testCases { + t.Run(fmt.Sprintf("flow:%s icmpRequired:%t largePayload:%t", tc.flow, tc.icmpRequired, tc.largePayload), func(t *testing.T) { + payload := newPayload() + if tc.largePayload { + payload = newMinPayload(1280) + } + c.injectPacket(tc.flow, payload) + if !tc.icmpRequired { + select { + case p := <-c.linkEP.C: + t.Fatalf("unexpected packet received: %+v", p) + case <-time.After(1 * time.Second): + return + } + } + + select { + case p := <-c.linkEP.C: + var pkt []byte + pkt = append(pkt, p.Header...) + pkt = append(pkt, p.Payload...) + if got, want := len(pkt), header.IPv6MinimumMTU; got > want { + t.Fatalf("got an ICMP packet of size: %d, want: sz <= %d", got, want) + } + + hdr := header.IPv6(pkt) + checker.IPv6(t, hdr, checker.ICMPv6( + checker.ICMPv6Type(header.ICMPv6DstUnreachable), + checker.ICMPv6Code(header.ICMPv6PortUnreachable))) + + icmpPkt := header.ICMPv6(hdr.Payload()) + payloadIPHeader := header.IPv6(icmpPkt.Payload()) + wantLen := len(payload) + if tc.largePayload { + wantLen = header.IPv6MinimumMTU - header.IPv6MinimumSize*2 - header.ICMPv6MinimumSize - header.UDPMinimumSize + } + // In case of large payloads the IP packet may be truncated. Update + // the length field before retrieving the udp datagram payload. + payloadIPHeader.SetPayloadLength(uint16(wantLen + header.UDPMinimumSize)) + + origDgram := header.UDP(payloadIPHeader.Payload()) + if got, want := len(origDgram.Payload()), wantLen; got != want { + t.Fatalf("unexpected payload length got: %d, want: %d", got, want) + } + if got, want := origDgram.Payload(), payload[:wantLen]; !bytes.Equal(got, want) { + t.Fatalf("unexpected payload got: %v, want: %v", got, want) + } + case <-time.After(1 * time.Second): + t.Fatalf("packet wasn't written out") + } + }) + } +} -- cgit v1.2.3