385 lines
13 KiB
Go
385 lines
13 KiB
Go
// Copyright 2018 The gVisor Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package ipv6
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import (
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"gvisor.dev/gvisor/pkg/tcpip"
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"gvisor.dev/gvisor/pkg/tcpip/buffer"
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"gvisor.dev/gvisor/pkg/tcpip/header"
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"gvisor.dev/gvisor/pkg/tcpip/stack"
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)
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// handleControl handles the case when an ICMP packet contains the headers of
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// the original packet that caused the ICMP one to be sent. This information is
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// used to find out which transport endpoint must be notified about the ICMP
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// packet.
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func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
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h := header.IPv6(vv.First())
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// We don't use IsValid() here because ICMP only requires that up to
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// 1280 bytes of the original packet be included. So it's likely that it
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// is truncated, which would cause IsValid to return false.
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//
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// Drop packet if it doesn't have the basic IPv6 header or if the
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// original source address doesn't match the endpoint's address.
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if len(h) < header.IPv6MinimumSize || h.SourceAddress() != e.id.LocalAddress {
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return
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}
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// Skip the IP header, then handle the fragmentation header if there
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// is one.
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vv.TrimFront(header.IPv6MinimumSize)
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p := h.TransportProtocol()
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if p == header.IPv6FragmentHeader {
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f := header.IPv6Fragment(vv.First())
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if !f.IsValid() || f.FragmentOffset() != 0 {
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// We can't handle fragments that aren't at offset 0
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// because they don't have the transport headers.
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return
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}
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// Skip fragmentation header and find out the actual protocol
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// number.
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vv.TrimFront(header.IPv6FragmentHeaderSize)
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p = f.TransportProtocol()
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}
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// Deliver the control packet to the transport endpoint.
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e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, vv)
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}
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func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.VectorisedView) {
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stats := r.Stats().ICMP
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sent := stats.V6PacketsSent
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received := stats.V6PacketsReceived
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v := vv.First()
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if len(v) < header.ICMPv6MinimumSize {
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received.Invalid.Increment()
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return
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}
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h := header.ICMPv6(v)
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iph := header.IPv6(netHeader)
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// As per RFC 4861 sections 4.1 - 4.5, 6.1.1, 6.1.2, 7.1.1, 7.1.2 and
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// 8.1, nodes MUST silently drop NDP packets where the Hop Limit field
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// in the IPv6 header is not set to 255.
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switch h.Type() {
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case header.ICMPv6NeighborSolicit,
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header.ICMPv6NeighborAdvert,
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header.ICMPv6RouterSolicit,
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header.ICMPv6RouterAdvert,
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header.ICMPv6RedirectMsg:
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if iph.HopLimit() != header.NDPHopLimit {
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received.Invalid.Increment()
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return
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}
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}
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// TODO(b/112892170): Meaningfully handle all ICMP types.
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switch h.Type() {
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case header.ICMPv6PacketTooBig:
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received.PacketTooBig.Increment()
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if len(v) < header.ICMPv6PacketTooBigMinimumSize {
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received.Invalid.Increment()
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return
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}
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vv.TrimFront(header.ICMPv6PacketTooBigMinimumSize)
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mtu := h.MTU()
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e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), vv)
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case header.ICMPv6DstUnreachable:
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received.DstUnreachable.Increment()
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if len(v) < header.ICMPv6DstUnreachableMinimumSize {
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received.Invalid.Increment()
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return
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}
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vv.TrimFront(header.ICMPv6DstUnreachableMinimumSize)
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switch h.Code() {
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case header.ICMPv6PortUnreachable:
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e.handleControl(stack.ControlPortUnreachable, 0, vv)
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}
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case header.ICMPv6NeighborSolicit:
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received.NeighborSolicit.Increment()
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if len(v) < header.ICMPv6NeighborSolicitMinimumSize {
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received.Invalid.Increment()
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return
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}
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ns := header.NDPNeighborSolicit(h.NDPPayload())
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targetAddr := ns.TargetAddress()
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s := r.Stack()
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rxNICID := r.NICID()
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isTentative, err := s.IsAddrTentative(rxNICID, targetAddr)
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if err != nil {
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// We will only get an error if rxNICID is unrecognized,
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// which should not happen. For now short-circuit this
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// packet.
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//
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// TODO(b/141002840): Handle this better?
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return
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}
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if isTentative {
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// If the target address is tentative and the source
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// of the packet is a unicast (specified) address, then
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// the source of the packet is attempting to perform
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// address resolution on the target. In this case, the
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// solicitation is silently ignored, as per RFC 4862
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// section 5.4.3.
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//
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// If the target address is tentative and the source of
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// the packet is the unspecified address (::), then we
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// know another node is also performing DAD for the
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// same address (since targetAddr is tentative for us,
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// we know we are also performing DAD on it). In this
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// case we let the stack know so it can handle such a
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// scenario and do nothing further with the NDP NS.
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if iph.SourceAddress() == header.IPv6Any {
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s.DupTentativeAddrDetected(rxNICID, targetAddr)
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}
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// Do not handle neighbor solicitations targeted
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// to an address that is tentative on the received
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// NIC any further.
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return
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}
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// At this point we know that targetAddr is not tentative on
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// rxNICID so the packet is processed as defined in RFC 4861,
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// as per RFC 4862 section 5.4.3.
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if e.linkAddrCache.CheckLocalAddress(e.nicid, ProtocolNumber, targetAddr) == 0 {
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// We don't have a useful answer; the best we can do is ignore the request.
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return
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}
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optsSerializer := header.NDPOptionsSerializer{
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header.NDPTargetLinkLayerAddressOption(r.LocalLinkAddress[:]),
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}
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hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6NeighborAdvertMinimumSize + int(optsSerializer.Length()))
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pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
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pkt.SetType(header.ICMPv6NeighborAdvert)
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na := header.NDPNeighborAdvert(pkt.NDPPayload())
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na.SetSolicitedFlag(true)
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na.SetOverrideFlag(true)
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na.SetTargetAddress(targetAddr)
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opts := na.Options()
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opts.Serialize(optsSerializer)
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// ICMPv6 Neighbor Solicit messages are always sent to
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// specially crafted IPv6 multicast addresses. As a result, the
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// route we end up with here has as its LocalAddress such a
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// multicast address. It would be nonsense to claim that our
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// source address is a multicast address, so we manually set
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// the source address to the target address requested in the
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// solicit message. Since that requires mutating the route, we
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// must first clone it.
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r := r.Clone()
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defer r.Release()
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r.LocalAddress = targetAddr
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pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
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// TODO(tamird/ghanan): there exists an explicit NDP option that is
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// used to update the neighbor table with link addresses for a
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// neighbor from an NS (see the Source Link Layer option RFC
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// 4861 section 4.6.1 and section 7.2.3).
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//
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// Furthermore, the entirety of NDP handling here seems to be
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// contradicted by RFC 4861.
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e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
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// RFC 4861 Neighbor Discovery for IP version 6 (IPv6)
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//
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// 7.1.2. Validation of Neighbor Advertisements
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//
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// The IP Hop Limit field has a value of 255, i.e., the packet
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// could not possibly have been forwarded by a router.
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if err := r.WritePacket(nil /* gso */, hdr, buffer.VectorisedView{}, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}); err != nil {
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sent.Dropped.Increment()
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return
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}
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sent.NeighborAdvert.Increment()
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case header.ICMPv6NeighborAdvert:
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received.NeighborAdvert.Increment()
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if len(v) < header.ICMPv6NeighborAdvertSize {
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received.Invalid.Increment()
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return
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}
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na := header.NDPNeighborAdvert(h.NDPPayload())
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targetAddr := na.TargetAddress()
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stack := r.Stack()
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rxNICID := r.NICID()
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isTentative, err := stack.IsAddrTentative(rxNICID, targetAddr)
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if err != nil {
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// We will only get an error if rxNICID is unrecognized,
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// which should not happen. For now short-circuit this
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// packet.
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//
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// TODO(b/141002840): Handle this better?
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return
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}
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if isTentative {
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// We just got an NA from a node that owns an address we
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// are performing DAD on, implying the address is not
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// unique. In this case we let the stack know so it can
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// handle such a scenario and do nothing furthur with
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// the NDP NA.
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stack.DupTentativeAddrDetected(rxNICID, targetAddr)
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return
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}
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// At this point we know that the targetAddress is not tentaive
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// on rxNICID. However, targetAddr may still be assigned to
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// rxNICID but not tentative (it could be permanent). Such a
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// scenario is beyond the scope of RFC 4862. As such, we simply
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// ignore such a scenario for now and proceed as normal.
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//
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// TODO(b/140896005): Handle the scenario described above
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// (inform the netstack integration that a duplicate address was
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// was detected)
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e.linkAddrCache.AddLinkAddress(e.nicid, targetAddr, r.RemoteLinkAddress)
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if targetAddr != r.RemoteAddress {
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e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
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}
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case header.ICMPv6EchoRequest:
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received.EchoRequest.Increment()
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if len(v) < header.ICMPv6EchoMinimumSize {
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received.Invalid.Increment()
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return
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}
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vv.TrimFront(header.ICMPv6EchoMinimumSize)
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hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6EchoMinimumSize)
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pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
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copy(pkt, h)
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pkt.SetType(header.ICMPv6EchoReply)
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pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, vv))
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if err := r.WritePacket(nil /* gso */, hdr, vv, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}); err != nil {
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sent.Dropped.Increment()
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return
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}
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sent.EchoReply.Increment()
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case header.ICMPv6EchoReply:
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received.EchoReply.Increment()
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if len(v) < header.ICMPv6EchoMinimumSize {
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received.Invalid.Increment()
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return
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}
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e.dispatcher.DeliverTransportPacket(r, header.ICMPv6ProtocolNumber, netHeader, vv)
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case header.ICMPv6TimeExceeded:
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received.TimeExceeded.Increment()
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case header.ICMPv6ParamProblem:
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received.ParamProblem.Increment()
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case header.ICMPv6RouterSolicit:
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received.RouterSolicit.Increment()
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case header.ICMPv6RouterAdvert:
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received.RouterAdvert.Increment()
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case header.ICMPv6RedirectMsg:
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received.RedirectMsg.Increment()
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default:
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received.Invalid.Increment()
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}
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}
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const (
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ndpSolicitedFlag = 1 << 6
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ndpOverrideFlag = 1 << 5
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ndpOptSrcLinkAddr = 1
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ndpOptDstLinkAddr = 2
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icmpV6FlagOffset = 4
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icmpV6OptOffset = 24
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icmpV6LengthOffset = 25
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)
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var broadcastMAC = tcpip.LinkAddress([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff})
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var _ stack.LinkAddressResolver = (*protocol)(nil)
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// LinkAddressProtocol implements stack.LinkAddressResolver.
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func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
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return header.IPv6ProtocolNumber
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}
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// LinkAddressRequest implements stack.LinkAddressResolver.
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func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.LinkEndpoint) *tcpip.Error {
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snaddr := header.SolicitedNodeAddr(addr)
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r := &stack.Route{
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LocalAddress: localAddr,
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RemoteAddress: snaddr,
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RemoteLinkAddress: broadcastMAC,
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}
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hdr := buffer.NewPrependable(int(linkEP.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize)
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pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
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pkt.SetType(header.ICMPv6NeighborSolicit)
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copy(pkt[icmpV6OptOffset-len(addr):], addr)
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pkt[icmpV6OptOffset] = ndpOptSrcLinkAddr
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pkt[icmpV6LengthOffset] = 1
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copy(pkt[icmpV6LengthOffset+1:], linkEP.LinkAddress())
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pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
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length := uint16(hdr.UsedLength())
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ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
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ip.Encode(&header.IPv6Fields{
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PayloadLength: length,
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NextHeader: uint8(header.ICMPv6ProtocolNumber),
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HopLimit: header.NDPHopLimit,
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SrcAddr: r.LocalAddress,
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DstAddr: r.RemoteAddress,
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})
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// TODO(stijlist): count this in ICMP stats.
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return linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber)
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}
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// ResolveStaticAddress implements stack.LinkAddressResolver.
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func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bool) {
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if header.IsV6MulticastAddress(addr) {
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// RFC 2464 Transmission of IPv6 Packets over Ethernet Networks
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//
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// 7. Address Mapping -- Multicast
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//
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// An IPv6 packet with a multicast destination address DST,
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// consisting of the sixteen octets DST[1] through DST[16], is
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// transmitted to the Ethernet multicast address whose first
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// two octets are the value 3333 hexadecimal and whose last
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// four octets are the last four octets of DST.
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return tcpip.LinkAddress([]byte{
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0x33,
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0x33,
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addr[header.IPv6AddressSize-4],
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addr[header.IPv6AddressSize-3],
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addr[header.IPv6AddressSize-2],
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addr[header.IPv6AddressSize-1],
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}), true
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}
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return "", false
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}
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