diff options
Diffstat (limited to 'pkg/tcpip/network/ipv6')
| -rw-r--r-- | pkg/tcpip/network/ipv6/icmp.go | 7 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv6/ipv6.go | 112 |
2 files changed, 76 insertions, 43 deletions
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index ead6bedcb..40908ddaa 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -170,8 +170,11 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer, hasFragme return } pkt.Data.TrimFront(header.ICMPv6PacketTooBigMinimumSize) - mtu := header.ICMPv6(hdr).MTU() - e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt) + networkMTU, err := calculateNetworkMTU(header.ICMPv6(hdr).MTU(), header.IPv6MinimumSize) + if err != nil { + networkMTU = 0 + } + e.handleControl(stack.ControlPacketTooBig, networkMTU, pkt) case header.ICMPv6DstUnreachable: received.DstUnreachable.Increment() diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go index 9670696c7..3c2578343 100644 --- a/pkg/tcpip/network/ipv6/ipv6.go +++ b/pkg/tcpip/network/ipv6/ipv6.go @@ -46,7 +46,7 @@ const ( // ProtocolNumber is the ipv6 protocol number. ProtocolNumber = header.IPv6ProtocolNumber - // maxTotalSize is maximum size that can be encoded in the 16-bit + // maxPayloadSize is the maximum size that can be encoded in the 16-bit // PayloadLength field of the ipv6 header. maxPayloadSize = 0xffff @@ -363,7 +363,11 @@ func (e *endpoint) DefaultTTL() uint8 { // MTU implements stack.NetworkEndpoint.MTU. It returns the link-layer MTU minus // the network layer max header length. func (e *endpoint) MTU() uint32 { - return calculateMTU(e.nic.MTU()) + networkMTU, err := calculateNetworkMTU(e.nic.MTU(), header.IPv6MinimumSize) + if err != nil { + return 0 + } + return networkMTU } // MaxHeaderLength returns the maximum length needed by ipv6 headers (and @@ -386,27 +390,40 @@ func (e *endpoint) addIPHeader(r *stack.Route, pkt *stack.PacketBuffer, params s pkt.NetworkProtocolNumber = ProtocolNumber } -func (e *endpoint) packetMustBeFragmented(pkt *stack.PacketBuffer, gso *stack.GSO) bool { - return (gso == nil || gso.Type == stack.GSONone) && pkt.Size() > int(e.nic.MTU()) +func packetMustBeFragmented(pkt *stack.PacketBuffer, networkMTU uint32, gso *stack.GSO) bool { + payload := pkt.TransportHeader().View().Size() + pkt.Data.Size() + return (gso == nil || gso.Type == stack.GSONone) && uint32(payload) > networkMTU } // handleFragments fragments pkt and calls the handler function on each // fragment. It returns the number of fragments handled and the number of // fragments left to be processed. The IP header must already be present in the -// original packet. The mtu is the maximum size of the packets. The transport -// header protocol number is required to avoid parsing the IPv6 extension -// headers. -func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, mtu uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) { - fragMTU := int(calculateFragmentInnerMTU(mtu, pkt)) - if fragMTU < pkt.TransportHeader().View().Size() { +// original packet. The transport header protocol number is required to avoid +// parsing the IPv6 extension headers. +func (e *endpoint) handleFragments(r *stack.Route, gso *stack.GSO, networkMTU uint32, pkt *stack.PacketBuffer, transProto tcpip.TransportProtocolNumber, handler func(*stack.PacketBuffer) *tcpip.Error) (int, int, *tcpip.Error) { + networkHeader := header.IPv6(pkt.NetworkHeader().View()) + + // TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are + // supported for outbound packets, their length should not affect the fragment + // maximum payload length because they should only be transmitted once. + fragmentPayloadLen := (networkMTU - header.IPv6FragmentHeaderSize) &^ 7 + if fragmentPayloadLen < header.IPv6FragmentExtHdrFragmentOffsetBytesPerUnit { + // We need at least 8 bytes of space left for the fragmentable part because + // the fragment payload must obviously be non-zero and must be a multiple + // of 8 as per RFC 8200 section 4.5: + // Each complete fragment, except possibly the last ("rightmost") one, is + // an integer multiple of 8 octets long. + return 0, 1, tcpip.ErrMessageTooLong + } + + if fragmentPayloadLen < uint32(pkt.TransportHeader().View().Size()) { // As per RFC 8200 Section 4.5, the Transport Header is expected to be small // enough to fit in the first fragment. return 0, 1, tcpip.ErrMessageTooLong } - pf := fragmentation.MakePacketFragmenter(pkt, fragMTU, calculateFragmentReserve(pkt)) + pf := fragmentation.MakePacketFragmenter(pkt, fragmentPayloadLen, calculateFragmentReserve(pkt)) id := atomic.AddUint32(&e.protocol.ids[hashRoute(r, e.protocol.hashIV)%buckets], 1) - networkHeader := header.IPv6(pkt.NetworkHeader().View()) var n int for { @@ -468,8 +485,14 @@ func (e *endpoint) writePacket(r *stack.Route, gso *stack.GSO, pkt *stack.Packet return nil } - if e.packetMustBeFragmented(pkt, gso) { - sent, remain, err := e.handleFragments(r, gso, e.nic.MTU(), pkt, protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error { + networkMTU, err := calculateNetworkMTU(e.nic.MTU(), uint32(pkt.NetworkHeader().View().Size())) + if err != nil { + r.Stats().IP.OutgoingPacketErrors.Increment() + return err + } + + if packetMustBeFragmented(pkt, networkMTU, gso) { + sent, remain, err := e.handleFragments(r, gso, networkMTU, pkt, protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error { // TODO(gvisor.dev/issue/3884): Evaluate whether we want to send each // fragment one by one using WritePacket() (current strategy) or if we // want to create a PacketBufferList from the fragments and feed it to @@ -499,13 +522,20 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe return pkts.Len(), nil } + linkMTU := e.nic.MTU() for pb := pkts.Front(); pb != nil; pb = pb.Next() { e.addIPHeader(r, pb, params) - if e.packetMustBeFragmented(pb, gso) { + + networkMTU, err := calculateNetworkMTU(linkMTU, uint32(pb.NetworkHeader().View().Size())) + if err != nil { + r.Stats().IP.OutgoingPacketErrors.IncrementBy(uint64(pkts.Len())) + return 0, err + } + if packetMustBeFragmented(pb, networkMTU, gso) { // Keep track of the packet that is about to be fragmented so it can be // removed once the fragmentation is done. originalPkt := pb - if _, _, err := e.handleFragments(r, gso, e.nic.MTU(), pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error { + if _, _, err := e.handleFragments(r, gso, networkMTU, pb, params.Protocol, func(fragPkt *stack.PacketBuffer) *tcpip.Error { // Modify the packet list in place with the new fragments. pkts.InsertAfter(pb, fragPkt) pb = fragPkt @@ -569,7 +599,7 @@ func (e *endpoint) WritePackets(r *stack.Route, gso *stack.GSO, pkts stack.Packe return n + len(dropped), nil } -// WriteHeaderIncludedPacker implements stack.NetworkEndpoint. +// WriteHeaderIncludedPacket implements stack.NetworkEndpoint. func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBuffer) *tcpip.Error { // The packet already has an IP header, but there are a few required checks. h, ok := pkt.Data.PullUp(header.IPv6MinimumSize) @@ -1427,14 +1457,31 @@ func (p *protocol) SetForwarding(v bool) { } } -// calculateMTU calculates the network-layer payload MTU based on the link-layer -// payload mtu. -func calculateMTU(mtu uint32) uint32 { - mtu -= header.IPv6MinimumSize - if mtu <= maxPayloadSize { - return mtu +// calculateNetworkMTU calculates the network-layer payload MTU based on the +// link-layer payload MTU and the length of every IPv6 header. +// Note that this is different than the Payload Length field of the IPv6 header, +// which includes the length of the extension headers. +func calculateNetworkMTU(linkMTU, networkHeadersLen uint32) (uint32, *tcpip.Error) { + if linkMTU < header.IPv6MinimumMTU { + return 0, tcpip.ErrInvalidEndpointState + } + + // As per RFC 7112 section 5, we should discard packets if their IPv6 header + // is bigger than 1280 bytes (ie, the minimum link MTU) since we do not + // support PMTU discovery: + // Hosts that do not discover the Path MTU MUST limit the IPv6 Header Chain + // length to 1280 bytes. Limiting the IPv6 Header Chain length to 1280 + // bytes ensures that the header chain length does not exceed the IPv6 + // minimum MTU. + if networkHeadersLen > header.IPv6MinimumMTU { + return 0, tcpip.ErrMalformedHeader } - return maxPayloadSize + + networkMTU := linkMTU - uint32(networkHeadersLen) + if networkMTU > maxPayloadSize { + networkMTU = maxPayloadSize + } + return networkMTU, nil } // Options holds options to configure a new protocol. @@ -1509,23 +1556,6 @@ func NewProtocol(s *stack.Stack) stack.NetworkProtocol { return NewProtocolWithOptions(Options{})(s) } -// calculateFragmentInnerMTU calculates the maximum number of bytes of -// fragmentable data a fragment can have, based on the link layer mtu and pkt's -// network header size. -func calculateFragmentInnerMTU(mtu uint32, pkt *stack.PacketBuffer) uint32 { - // TODO(gvisor.dev/issue/3912): Once the Authentication or ESP Headers are - // supported for outbound packets, their length should not affect the fragment - // MTU because they should only be transmitted once. - mtu -= uint32(pkt.NetworkHeader().View().Size()) - mtu -= header.IPv6FragmentHeaderSize - // Round the MTU down to align to 8 bytes. - mtu &^= 7 - if mtu <= maxPayloadSize { - return mtu - } - return maxPayloadSize -} - func calculateFragmentReserve(pkt *stack.PacketBuffer) int { return pkt.AvailableHeaderBytes() + pkt.NetworkHeader().View().Size() + header.IPv6FragmentHeaderSize } |