298 lines
10 KiB
Go
298 lines
10 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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"encoding/binary"
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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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// 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 := binary.BigEndian.Uint32(v[header.ICMPv6MinimumSize:])
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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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e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
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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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targetAddr := tcpip.Address(v[8:][:16])
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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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hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6NeighborAdvertSize)
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pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
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pkt.SetType(header.ICMPv6NeighborAdvert)
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pkt[icmpV6FlagOffset] = ndpSolicitedFlag | ndpOverrideFlag
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copy(pkt[icmpV6OptOffset-len(targetAddr):], targetAddr)
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pkt[icmpV6OptOffset] = ndpOptDstLinkAddr
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pkt[icmpV6LengthOffset] = 1
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copy(pkt[icmpV6LengthOffset+1:], r.LocalLinkAddress[:])
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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(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
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if err := r.WritePacket(nil /* gso */, hdr, buffer.VectorisedView{}, header.ICMPv6ProtocolNumber, r.DefaultTTL()); 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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targetAddr := tcpip.Address(v[8:][:16])
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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(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, vv))
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if err := r.WritePacket(nil /* gso */, hdr, vv, header.ICMPv6ProtocolNumber, r.DefaultTTL()); 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(icmpChecksum(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: defaultIPv6HopLimit,
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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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func icmpChecksum(h header.ICMPv6, src, dst tcpip.Address, vv buffer.VectorisedView) uint16 {
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// Calculate the IPv6 pseudo-header upper-layer checksum.
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xsum := header.Checksum([]byte(src), 0)
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xsum = header.Checksum([]byte(dst), xsum)
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var upperLayerLength [4]byte
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binary.BigEndian.PutUint32(upperLayerLength[:], uint32(len(h)+vv.Size()))
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xsum = header.Checksum(upperLayerLength[:], xsum)
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xsum = header.Checksum([]byte{0, 0, 0, uint8(header.ICMPv6ProtocolNumber)}, xsum)
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for _, v := range vv.Views() {
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xsum = header.Checksum(v, xsum)
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}
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// h[2:4] is the checksum itself, set it aside to avoid checksumming the checksum.
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h2, h3 := h[2], h[3]
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h[2], h[3] = 0, 0
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xsum = ^header.Checksum(h, xsum)
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h[2], h[3] = h2, h3
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return xsum
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}
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