From 32b823fcdb00a7d6eb5ddcd378f19a659edc3da3 Mon Sep 17 00:00:00 2001 From: Kevin Krakauer Date: Sun, 7 Jun 2020 13:37:25 -0700 Subject: netstack: parse incoming packet headers up-front Netstack has traditionally parsed headers on-demand as a packet moves up the stack. This is conceptually simple and convenient, but incompatible with iptables, where headers can be inspected and mangled before even a routing decision is made. This changes header parsing to happen early in the incoming packet path, as soon as the NIC gets the packet from a link endpoint. Even if an invalid packet is found (e.g. a TCP header of insufficient length), the packet is passed up the stack for proper stats bookkeeping. PiperOrigin-RevId: 315179302 --- pkg/tcpip/network/arp/arp.go | 17 +++- pkg/tcpip/network/fragmentation/fragmentation.go | 4 +- pkg/tcpip/network/ip_test.go | 48 +++++---- pkg/tcpip/network/ipv4/icmp.go | 3 + pkg/tcpip/network/ipv4/ipv4.go | 74 +++++++------- pkg/tcpip/network/ipv4/ipv4_test.go | 12 +++ pkg/tcpip/network/ipv6/icmp.go | 7 +- pkg/tcpip/network/ipv6/icmp_test.go | 43 ++++----- pkg/tcpip/network/ipv6/ipv6.go | 118 +++++++++++++++++++---- pkg/tcpip/network/ipv6/ndp_test.go | 33 ++++--- 10 files changed, 236 insertions(+), 123 deletions(-) (limited to 'pkg/tcpip/network') diff --git a/pkg/tcpip/network/arp/arp.go b/pkg/tcpip/network/arp/arp.go index ea1acba83..7f27a840d 100644 --- a/pkg/tcpip/network/arp/arp.go +++ b/pkg/tcpip/network/arp/arp.go @@ -99,11 +99,7 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu } func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { - v, ok := pkt.Data.PullUp(header.ARPSize) - if !ok { - return - } - h := header.ARP(v) + h := header.ARP(pkt.NetworkHeader) if !h.IsValid() { return } @@ -209,6 +205,17 @@ func (*protocol) Close() {} // Wait implements stack.TransportProtocol.Wait. func (*protocol) Wait() {} +// Parse implements stack.NetworkProtocol.Parse. +func (*protocol) Parse(pkt *stack.PacketBuffer) (proto tcpip.TransportProtocolNumber, hasTransportHdr bool, ok bool) { + hdr, ok := pkt.Data.PullUp(header.ARPSize) + if !ok { + return 0, false, false + } + pkt.NetworkHeader = hdr + pkt.Data.TrimFront(header.ARPSize) + return 0, false, true +} + var broadcastMAC = tcpip.LinkAddress([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff}) // NewProtocol returns an ARP network protocol. diff --git a/pkg/tcpip/network/fragmentation/fragmentation.go b/pkg/tcpip/network/fragmentation/fragmentation.go index f42abc4bb..2982450f8 100644 --- a/pkg/tcpip/network/fragmentation/fragmentation.go +++ b/pkg/tcpip/network/fragmentation/fragmentation.go @@ -81,8 +81,8 @@ func NewFragmentation(highMemoryLimit, lowMemoryLimit int, reassemblingTimeout t } } -// Process processes an incoming fragment belonging to an ID -// and returns a complete packet when all the packets belonging to that ID have been received. +// Process processes an incoming fragment belonging to an ID and returns a +// complete packet when all the packets belonging to that ID have been received. func (f *Fragmentation) Process(id uint32, first, last uint16, more bool, vv buffer.VectorisedView) (buffer.VectorisedView, bool, error) { f.mu.Lock() r, ok := f.reassemblers[id] diff --git a/pkg/tcpip/network/ip_test.go b/pkg/tcpip/network/ip_test.go index d9b62f2db..7c8fb3e0a 100644 --- a/pkg/tcpip/network/ip_test.go +++ b/pkg/tcpip/network/ip_test.go @@ -293,9 +293,9 @@ func TestIPv4Receive(t *testing.T) { if err != nil { t.Fatalf("could not find route: %v", err) } - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: view.ToVectorisedView(), - }) + pkt := stack.PacketBuffer{Data: view.ToVectorisedView()} + proto.Parse(&pkt) + ep.HandlePacket(&r, &pkt) if o.dataCalls != 1 { t.Fatalf("Bad number of data calls: got %x, want 1", o.dataCalls) } @@ -382,10 +382,7 @@ func TestIPv4ReceiveControl(t *testing.T) { o.typ = c.expectedTyp o.extra = c.expectedExtra - vv := view[:len(view)-c.trunc].ToVectorisedView() - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: vv, - }) + ep.HandlePacket(&r, truncatedPacket(view, c.trunc, header.IPv4MinimumSize)) if want := c.expectedCount; o.controlCalls != want { t.Fatalf("Bad number of control calls for %q case: got %v, want %v", c.name, o.controlCalls, want) } @@ -448,17 +445,17 @@ func TestIPv4FragmentationReceive(t *testing.T) { } // Send first segment. - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: frag1.ToVectorisedView(), - }) + pkt := stack.PacketBuffer{Data: frag1.ToVectorisedView()} + proto.Parse(&pkt) + ep.HandlePacket(&r, &pkt) if o.dataCalls != 0 { t.Fatalf("Bad number of data calls: got %x, want 0", o.dataCalls) } // Send second segment. - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: frag2.ToVectorisedView(), - }) + pkt = stack.PacketBuffer{Data: frag2.ToVectorisedView()} + proto.Parse(&pkt) + ep.HandlePacket(&r, &pkt) if o.dataCalls != 1 { t.Fatalf("Bad number of data calls: got %x, want 1", o.dataCalls) } @@ -538,9 +535,9 @@ func TestIPv6Receive(t *testing.T) { t.Fatalf("could not find route: %v", err) } - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: view.ToVectorisedView(), - }) + pkt := stack.PacketBuffer{Data: view.ToVectorisedView()} + proto.Parse(&pkt) + ep.HandlePacket(&r, &pkt) if o.dataCalls != 1 { t.Fatalf("Bad number of data calls: got %x, want 1", o.dataCalls) } @@ -652,12 +649,25 @@ func TestIPv6ReceiveControl(t *testing.T) { // Set ICMPv6 checksum. icmp.SetChecksum(header.ICMPv6Checksum(icmp, outerSrcAddr, localIpv6Addr, buffer.VectorisedView{})) - ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: view[:len(view)-c.trunc].ToVectorisedView(), - }) + ep.HandlePacket(&r, truncatedPacket(view, c.trunc, header.IPv6MinimumSize)) if want := c.expectedCount; o.controlCalls != want { t.Fatalf("Bad number of control calls for %q case: got %v, want %v", c.name, o.controlCalls, want) } }) } } + +// truncatedPacket returns a PacketBuffer based on a truncated view. If view, +// after truncation, is large enough to hold a network header, it makes part of +// view the packet's NetworkHeader and the rest its Data. Otherwise all of view +// becomes Data. +func truncatedPacket(view buffer.View, trunc, netHdrLen int) *stack.PacketBuffer { + v := view[:len(view)-trunc] + if len(v) < netHdrLen { + return &stack.PacketBuffer{Data: v.ToVectorisedView()} + } + return &stack.PacketBuffer{ + NetworkHeader: v[:netHdrLen], + Data: v[netHdrLen:].ToVectorisedView(), + } +} diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go index d1c3ae835..1b67aa066 100644 --- a/pkg/tcpip/network/ipv4/icmp.go +++ b/pkg/tcpip/network/ipv4/icmp.go @@ -59,6 +59,9 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt *stack func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) { stats := r.Stats() received := stats.ICMP.V4PacketsReceived + // TODO(gvisor.dev/issue/170): ICMP packets don't have their + // TransportHeader fields set. See icmp/protocol.go:protocol.Parse for a + // full explanation. v, ok := pkt.Data.PullUp(header.ICMPv4MinimumSize) if !ok { received.Invalid.Increment() diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index 959f7e007..7e9f16c90 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -21,6 +21,7 @@ package ipv4 import ( + "fmt" "sync/atomic" "gvisor.dev/gvisor/pkg/tcpip" @@ -268,14 +269,14 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw ep, err := e.stack.FindNetworkEndpoint(header.IPv4ProtocolNumber, netHeader.DestinationAddress()) if err == nil { route := r.ReverseRoute(netHeader.SourceAddress(), netHeader.DestinationAddress()) - handleLoopback(&route, pkt, ep) + ep.HandlePacket(&route, pkt) return nil } } if r.Loop&stack.PacketLoop != 0 { loopedR := r.MakeLoopedRoute() - handleLoopback(&loopedR, pkt, e) + e.HandlePacket(&loopedR, pkt) loopedR.Release() } if r.Loop&stack.PacketOut == 0 { @@ -291,17 +292,6 @@ func (e *endpoint) WritePacket(r *stack.Route, gso *stack.GSO, params stack.Netw return nil } -func handleLoopback(route *stack.Route, pkt *stack.PacketBuffer, ep stack.NetworkEndpoint) { - // The inbound path expects the network header to still be in - // the PacketBuffer's Data field. - views := make([]buffer.View, 1, 1+len(pkt.Data.Views())) - views[0] = pkt.Header.View() - views = append(views, pkt.Data.Views()...) - ep.HandlePacket(route, &stack.PacketBuffer{ - Data: buffer.NewVectorisedView(len(views[0])+pkt.Data.Size(), views), - }) -} - // WritePackets implements stack.NetworkEndpoint.WritePackets. func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.PacketBufferList, params stack.NetworkHeaderParams) (int, *tcpip.Error) { if r.Loop&stack.PacketLoop != 0 { @@ -339,12 +329,11 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe } if _, ok := natPkts[pkt]; ok { netHeader := header.IPv4(pkt.NetworkHeader) - ep, err := e.stack.FindNetworkEndpoint(header.IPv4ProtocolNumber, netHeader.DestinationAddress()) - if err == nil { + if ep, err := e.stack.FindNetworkEndpoint(header.IPv4ProtocolNumber, netHeader.DestinationAddress()); err == nil { src := netHeader.SourceAddress() dst := netHeader.DestinationAddress() route := r.ReverseRoute(src, dst) - handleLoopback(&route, pkt, ep) + ep.HandlePacket(&route, pkt) n++ continue } @@ -418,22 +407,11 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu // HandlePacket is called by the link layer when new ipv4 packets arrive for // this endpoint. func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { - headerView, ok := pkt.Data.PullUp(header.IPv4MinimumSize) - if !ok { + h := header.IPv4(pkt.NetworkHeader) + if !h.IsValid(pkt.Data.Size() + len(pkt.NetworkHeader) + len(pkt.TransportHeader)) { r.Stats().IP.MalformedPacketsReceived.Increment() return } - h := header.IPv4(headerView) - if !h.IsValid(pkt.Data.Size()) { - r.Stats().IP.MalformedPacketsReceived.Increment() - return - } - pkt.NetworkHeader = headerView[:h.HeaderLength()] - - hlen := int(h.HeaderLength()) - tlen := int(h.TotalLength()) - pkt.Data.TrimFront(hlen) - pkt.Data.CapLength(tlen - hlen) // iptables filtering. All packets that reach here are intended for // this machine and will not be forwarded. @@ -443,9 +421,8 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { return } - more := (h.Flags() & header.IPv4FlagMoreFragments) != 0 - if more || h.FragmentOffset() != 0 { - if pkt.Data.Size() == 0 { + if h.More() || h.FragmentOffset() != 0 { + if pkt.Data.Size()+len(pkt.TransportHeader) == 0 { // Drop the packet as it's marked as a fragment but has // no payload. r.Stats().IP.MalformedPacketsReceived.Increment() @@ -464,7 +441,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { } var ready bool var err error - pkt.Data, ready, err = e.fragmentation.Process(hash.IPv4FragmentHash(h), h.FragmentOffset(), last, more, pkt.Data) + pkt.Data, ready, err = e.fragmentation.Process(hash.IPv4FragmentHash(h), h.FragmentOffset(), last, h.More(), pkt.Data) if err != nil { r.Stats().IP.MalformedPacketsReceived.Increment() r.Stats().IP.MalformedFragmentsReceived.Increment() @@ -476,7 +453,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { } p := h.TransportProtocol() if p == header.ICMPv4ProtocolNumber { - headerView.CapLength(hlen) + pkt.NetworkHeader.CapLength(int(h.HeaderLength())) e.handleICMP(r, pkt) return } @@ -556,6 +533,35 @@ func (*protocol) Close() {} // Wait implements stack.TransportProtocol.Wait. func (*protocol) Wait() {} +// Parse implements stack.TransportProtocol.Parse. +func (*protocol) Parse(pkt *stack.PacketBuffer) (proto tcpip.TransportProtocolNumber, hasTransportHdr bool, ok bool) { + hdr, ok := pkt.Data.PullUp(header.IPv4MinimumSize) + if !ok { + return 0, false, false + } + ipHdr := header.IPv4(hdr) + + // If there are options, pull those into hdr as well. + if headerLen := int(ipHdr.HeaderLength()); headerLen > header.IPv4MinimumSize && headerLen <= pkt.Data.Size() { + hdr, ok = pkt.Data.PullUp(headerLen) + if !ok { + panic(fmt.Sprintf("There are only %d bytes in pkt.Data, but there should be at least %d", pkt.Data.Size(), headerLen)) + } + ipHdr = header.IPv4(hdr) + } + + // If this is a fragment, don't bother parsing the transport header. + parseTransportHeader := true + if ipHdr.More() || ipHdr.FragmentOffset() != 0 { + parseTransportHeader = false + } + + pkt.NetworkHeader = hdr + pkt.Data.TrimFront(len(hdr)) + pkt.Data.CapLength(int(ipHdr.TotalLength()) - len(hdr)) + return ipHdr.TransportProtocol(), parseTransportHeader, true +} + // calculateMTU calculates the network-layer payload MTU based on the link-layer // payload mtu. func calculateMTU(mtu uint32) uint32 { diff --git a/pkg/tcpip/network/ipv4/ipv4_test.go b/pkg/tcpip/network/ipv4/ipv4_test.go index c208ebd99..11e579c4b 100644 --- a/pkg/tcpip/network/ipv4/ipv4_test.go +++ b/pkg/tcpip/network/ipv4/ipv4_test.go @@ -652,6 +652,18 @@ func TestReceiveFragments(t *testing.T) { }, expectedPayloads: [][]byte{udpPayload1, udpPayload2}, }, + { + name: "Fragment without followup", + fragments: []fragmentData{ + { + id: 1, + flags: header.IPv4FlagMoreFragments, + fragmentOffset: 0, + payload: ipv4Payload1[:64], + }, + }, + expectedPayloads: nil, + }, } for _, test := range tests { diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index b62fb1de6..2ff7eedf4 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -70,17 +70,20 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt *stack e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, hdr.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt) } -func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt *stack.PacketBuffer, hasFragmentHeader bool) { +func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer, hasFragmentHeader bool) { stats := r.Stats().ICMP sent := stats.V6PacketsSent received := stats.V6PacketsReceived + // TODO(gvisor.dev/issue/170): ICMP packets don't have their + // TransportHeader fields set. See icmp/protocol.go:protocol.Parse for a + // full explanation. v, ok := pkt.Data.PullUp(header.ICMPv6HeaderSize) if !ok { received.Invalid.Increment() return } h := header.ICMPv6(v) - iph := header.IPv6(netHeader) + iph := header.IPv6(pkt.NetworkHeader) // Validate ICMPv6 checksum before processing the packet. // diff --git a/pkg/tcpip/network/ipv6/icmp_test.go b/pkg/tcpip/network/ipv6/icmp_test.go index a720f626f..52a01b44e 100644 --- a/pkg/tcpip/network/ipv6/icmp_test.go +++ b/pkg/tcpip/network/ipv6/icmp_test.go @@ -179,36 +179,32 @@ func TestICMPCounts(t *testing.T) { }, } - handleIPv6Payload := func(hdr buffer.Prependable) { - payloadLength := hdr.UsedLength() - ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize)) + handleIPv6Payload := func(icmp header.ICMPv6) { + ip := header.IPv6(buffer.NewView(header.IPv6MinimumSize)) ip.Encode(&header.IPv6Fields{ - PayloadLength: uint16(payloadLength), + PayloadLength: uint16(len(icmp)), NextHeader: uint8(header.ICMPv6ProtocolNumber), HopLimit: header.NDPHopLimit, SrcAddr: r.LocalAddress, DstAddr: r.RemoteAddress, }) ep.HandlePacket(&r, &stack.PacketBuffer{ - Data: hdr.View().ToVectorisedView(), + NetworkHeader: buffer.View(ip), + Data: buffer.View(icmp).ToVectorisedView(), }) } for _, typ := range types { - extraDataLen := len(typ.extraData) - hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen) - extraData := buffer.View(hdr.Prepend(extraDataLen)) - copy(extraData, typ.extraData) - pkt := header.ICMPv6(hdr.Prepend(typ.size)) - pkt.SetType(typ.typ) - pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, extraData.ToVectorisedView())) - - handleIPv6Payload(hdr) + icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData))) + copy(icmp[typ.size:], typ.extraData) + icmp.SetType(typ.typ) + icmp.SetChecksum(header.ICMPv6Checksum(icmp[:typ.size], r.LocalAddress, r.RemoteAddress, buffer.View(typ.extraData).ToVectorisedView())) + handleIPv6Payload(icmp) } // Construct an empty ICMP packet so that // Stats().ICMP.ICMPv6ReceivedPacketStats.Invalid is incremented. - handleIPv6Payload(buffer.NewPrependable(header.IPv6MinimumSize)) + handleIPv6Payload(header.ICMPv6(buffer.NewView(header.IPv6MinimumSize))) icmpv6Stats := s.Stats().ICMP.V6PacketsReceived visitStats(reflect.ValueOf(&icmpv6Stats).Elem(), func(name string, s *tcpip.StatCounter) { @@ -546,25 +542,22 @@ func TestICMPChecksumValidationSimple(t *testing.T) { } handleIPv6Payload := func(checksum bool) { - extraDataLen := len(typ.extraData) - hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen) - extraData := buffer.View(hdr.Prepend(extraDataLen)) - copy(extraData, typ.extraData) - pkt := header.ICMPv6(hdr.Prepend(typ.size)) - pkt.SetType(typ.typ) + icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData))) + copy(icmp[typ.size:], typ.extraData) + icmp.SetType(typ.typ) if checksum { - pkt.SetChecksum(header.ICMPv6Checksum(pkt, lladdr1, lladdr0, extraData.ToVectorisedView())) + icmp.SetChecksum(header.ICMPv6Checksum(icmp, lladdr1, lladdr0, buffer.View{}.ToVectorisedView())) } - ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize)) + ip := header.IPv6(buffer.NewView(header.IPv6MinimumSize)) ip.Encode(&header.IPv6Fields{ - PayloadLength: uint16(typ.size + extraDataLen), + PayloadLength: uint16(len(icmp)), NextHeader: uint8(header.ICMPv6ProtocolNumber), HopLimit: header.NDPHopLimit, SrcAddr: lladdr1, DstAddr: lladdr0, }) e.InjectInbound(ProtocolNumber, &stack.PacketBuffer{ - Data: hdr.View().ToVectorisedView(), + Data: buffer.NewVectorisedView(len(ip)+len(icmp), []buffer.View{buffer.View(ip), buffer.View(icmp)}), }) } diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go index 0d94ad122..95fbcf2d1 100644 --- a/pkg/tcpip/network/ipv6/ipv6.go +++ b/pkg/tcpip/network/ipv6/ipv6.go @@ -171,22 +171,20 @@ func (*endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuff // HandlePacket is called by the link layer when new ipv6 packets arrive for // this endpoint. func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { - headerView, ok := pkt.Data.PullUp(header.IPv6MinimumSize) - if !ok { + h := header.IPv6(pkt.NetworkHeader) + if !h.IsValid(pkt.Data.Size() + len(pkt.NetworkHeader) + len(pkt.TransportHeader)) { r.Stats().IP.MalformedPacketsReceived.Increment() return } - h := header.IPv6(headerView) - if !h.IsValid(pkt.Data.Size()) { - r.Stats().IP.MalformedPacketsReceived.Increment() - return - } - - pkt.NetworkHeader = headerView[:header.IPv6MinimumSize] - pkt.Data.TrimFront(header.IPv6MinimumSize) - pkt.Data.CapLength(int(h.PayloadLength())) - it := header.MakeIPv6PayloadIterator(header.IPv6ExtensionHeaderIdentifier(h.NextHeader()), pkt.Data) + // vv consists of: + // - Any IPv6 header bytes after the first 40 (i.e. extensions). + // - The transport header, if present. + // - Any other payload data. + vv := pkt.NetworkHeader[header.IPv6MinimumSize:].ToVectorisedView() + vv.AppendView(pkt.TransportHeader) + vv.Append(pkt.Data) + it := header.MakeIPv6PayloadIterator(header.IPv6ExtensionHeaderIdentifier(h.NextHeader()), vv) hasFragmentHeader := false for firstHeader := true; ; firstHeader = false { @@ -262,9 +260,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { case header.IPv6FragmentExtHdr: hasFragmentHeader = true - fragmentOffset := extHdr.FragmentOffset() - more := extHdr.More() - if !more && fragmentOffset == 0 { + if extHdr.IsAtomic() { // This fragment extension header indicates that this packet is an // atomic fragment. An atomic fragment is a fragment that contains // all the data required to reassemble a full packet. As per RFC 6946, @@ -277,9 +273,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { // Don't consume the iterator if we have the first fragment because we // will use it to validate that the first fragment holds the upper layer // header. - rawPayload := it.AsRawHeader(fragmentOffset != 0 /* consume */) + rawPayload := it.AsRawHeader(extHdr.FragmentOffset() != 0 /* consume */) - if fragmentOffset == 0 { + if extHdr.FragmentOffset() == 0 { // Check that the iterator ends with a raw payload as the first fragment // should include all headers up to and including any upper layer // headers, as per RFC 8200 section 4.5; only upper layer data @@ -332,7 +328,7 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { } // The packet is a fragment, let's try to reassemble it. - start := fragmentOffset * header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit + start := extHdr.FragmentOffset() * header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit last := start + uint16(fragmentPayloadLen) - 1 // Drop the packet if the fragmentOffset is incorrect. i.e the @@ -345,7 +341,9 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { } var ready bool - pkt.Data, ready, err = e.fragmentation.Process(hash.IPv6FragmentHash(h, extHdr.ID()), start, last, more, rawPayload.Buf) + // Note that pkt doesn't have its transport header set after reassembly, + // and won't until DeliverNetworkPacket sets it. + pkt.Data, ready, err = e.fragmentation.Process(hash.IPv6FragmentHash(h, extHdr.ID()), start, last, extHdr.More(), rawPayload.Buf) if err != nil { r.Stats().IP.MalformedPacketsReceived.Increment() r.Stats().IP.MalformedFragmentsReceived.Increment() @@ -394,10 +392,17 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { case header.IPv6RawPayloadHeader: // If the last header in the payload isn't a known IPv6 extension header, // handle it as if it is transport layer data. + + // For unfragmented packets, extHdr still contains the transport header. + // Get rid of it. + // + // For reassembled fragments, pkt.TransportHeader is unset, so this is a + // no-op and pkt.Data begins with the transport header. + extHdr.Buf.TrimFront(len(pkt.TransportHeader)) pkt.Data = extHdr.Buf if p := tcpip.TransportProtocolNumber(extHdr.Identifier); p == header.ICMPv6ProtocolNumber { - e.handleICMP(r, headerView, pkt, hasFragmentHeader) + e.handleICMP(r, pkt, hasFragmentHeader) } else { r.Stats().IP.PacketsDelivered.Increment() // TODO(b/152019344): Send an ICMPv6 Parameter Problem, Code 1 error @@ -505,6 +510,79 @@ func (*protocol) Close() {} // Wait implements stack.TransportProtocol.Wait. func (*protocol) Wait() {} +// Parse implements stack.TransportProtocol.Parse. +func (*protocol) Parse(pkt *stack.PacketBuffer) (proto tcpip.TransportProtocolNumber, hasTransportHdr bool, ok bool) { + hdr, ok := pkt.Data.PullUp(header.IPv6MinimumSize) + if !ok { + return 0, false, false + } + ipHdr := header.IPv6(hdr) + + // dataClone consists of: + // - Any IPv6 header bytes after the first 40 (i.e. extensions). + // - The transport header, if present. + // - Any other payload data. + views := [8]buffer.View{} + dataClone := pkt.Data.Clone(views[:]) + dataClone.TrimFront(header.IPv6MinimumSize) + it := header.MakeIPv6PayloadIterator(header.IPv6ExtensionHeaderIdentifier(ipHdr.NextHeader()), dataClone) + + // Iterate over the IPv6 extensions to find their length. + // + // Parsing occurs again in HandlePacket because we don't track the + // extensions in PacketBuffer. Unfortunately, that means HandlePacket + // has to do the parsing work again. + var nextHdr tcpip.TransportProtocolNumber + foundNext := true + extensionsSize := 0 +traverseExtensions: + for extHdr, done, err := it.Next(); ; extHdr, done, err = it.Next() { + if err != nil { + break + } + // If we exhaust the extension list, the entire packet is the IPv6 header + // and (possibly) extensions. + if done { + extensionsSize = dataClone.Size() + foundNext = false + break + } + + switch extHdr := extHdr.(type) { + case header.IPv6FragmentExtHdr: + // If this is an atomic fragment, we don't have to treat it specially. + if !extHdr.More() && extHdr.FragmentOffset() == 0 { + continue + } + // This is a non-atomic fragment and has to be re-assembled before we can + // examine the payload for a transport header. + foundNext = false + + case header.IPv6RawPayloadHeader: + // We've found the payload after any extensions. + extensionsSize = dataClone.Size() - extHdr.Buf.Size() + nextHdr = tcpip.TransportProtocolNumber(extHdr.Identifier) + break traverseExtensions + + default: + // Any other extension is a no-op, keep looping until we find the payload. + } + } + + // Put the IPv6 header with extensions in pkt.NetworkHeader. + hdr, ok = pkt.Data.PullUp(header.IPv6MinimumSize + extensionsSize) + if !ok { + panic(fmt.Sprintf("pkt.Data should have at least %d bytes, but only has %d.", header.IPv6MinimumSize+extensionsSize, pkt.Data.Size())) + } + ipHdr = header.IPv6(hdr) + + pkt.NetworkHeader = hdr + pkt.Data.TrimFront(len(hdr)) + pkt.Data.CapLength(int(ipHdr.PayloadLength())) + + return nextHdr, foundNext, true +} + // calculateMTU calculates the network-layer payload MTU based on the link-layer // payload mtu. func calculateMTU(mtu uint32) uint32 { diff --git a/pkg/tcpip/network/ipv6/ndp_test.go b/pkg/tcpip/network/ipv6/ndp_test.go index 3c141b91b..64239ce9a 100644 --- a/pkg/tcpip/network/ipv6/ndp_test.go +++ b/pkg/tcpip/network/ipv6/ndp_test.go @@ -551,25 +551,29 @@ func TestNDPValidation(t *testing.T) { return s, ep, r } - handleIPv6Payload := func(hdr buffer.Prependable, hopLimit uint8, atomicFragment bool, ep stack.NetworkEndpoint, r *stack.Route) { + handleIPv6Payload := func(payload buffer.View, hopLimit uint8, atomicFragment bool, ep stack.NetworkEndpoint, r *stack.Route) { nextHdr := uint8(header.ICMPv6ProtocolNumber) + var extensions buffer.View if atomicFragment { - bytes := hdr.Prepend(header.IPv6FragmentExtHdrLength) - bytes[0] = nextHdr + extensions = buffer.NewView(header.IPv6FragmentExtHdrLength) + extensions[0] = nextHdr nextHdr = uint8(header.IPv6FragmentExtHdrIdentifier) } - payloadLength := hdr.UsedLength() - ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize)) + ip := header.IPv6(buffer.NewView(header.IPv6MinimumSize + len(extensions))) ip.Encode(&header.IPv6Fields{ - PayloadLength: uint16(payloadLength), + PayloadLength: uint16(len(payload) + len(extensions)), NextHeader: nextHdr, HopLimit: hopLimit, SrcAddr: r.LocalAddress, DstAddr: r.RemoteAddress, }) + if n := copy(ip[header.IPv6MinimumSize:], extensions); n != len(extensions) { + t.Fatalf("expected to write %d bytes of extensions, but wrote %d", len(extensions), n) + } ep.HandlePacket(r, &stack.PacketBuffer{ - Data: hdr.View().ToVectorisedView(), + NetworkHeader: buffer.View(ip), + Data: payload.ToVectorisedView(), }) } @@ -676,14 +680,11 @@ func TestNDPValidation(t *testing.T) { invalid := stats.Invalid typStat := typ.statCounter(stats) - extraDataLen := len(typ.extraData) - hdr := buffer.NewPrependable(header.IPv6MinimumSize + typ.size + extraDataLen + header.IPv6FragmentExtHdrLength) - extraData := buffer.View(hdr.Prepend(extraDataLen)) - copy(extraData, typ.extraData) - pkt := header.ICMPv6(hdr.Prepend(typ.size)) - pkt.SetType(typ.typ) - pkt.SetCode(test.code) - pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, extraData.ToVectorisedView())) + icmp := header.ICMPv6(buffer.NewView(typ.size + len(typ.extraData))) + copy(icmp[typ.size:], typ.extraData) + icmp.SetType(typ.typ) + icmp.SetCode(test.code) + icmp.SetChecksum(header.ICMPv6Checksum(icmp[:typ.size], r.LocalAddress, r.RemoteAddress, buffer.View(typ.extraData).ToVectorisedView())) // Rx count of the NDP message should initially be 0. if got := typStat.Value(); got != 0 { @@ -699,7 +700,7 @@ func TestNDPValidation(t *testing.T) { t.FailNow() } - handleIPv6Payload(hdr, test.hopLimit, test.atomicFragment, ep, &r) + handleIPv6Payload(buffer.View(icmp), test.hopLimit, test.atomicFragment, ep, &r) // Rx count of the NDP packet should have increased. if got := typStat.Value(); got != 1 { -- cgit v1.2.3