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// Copyright 2018 Google LLC
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package ipv6
import (
"encoding/binary"
"gvisor.googlesource.com/gvisor/pkg/tcpip"
"gvisor.googlesource.com/gvisor/pkg/tcpip/buffer"
"gvisor.googlesource.com/gvisor/pkg/tcpip/header"
"gvisor.googlesource.com/gvisor/pkg/tcpip/stack"
)
// handleControl handles the case when an ICMP packet contains the headers of
// the original packet that caused the ICMP one to be sent. This information is
// used to find out which transport endpoint must be notified about the ICMP
// packet.
func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv buffer.VectorisedView) {
h := header.IPv6(vv.First())
// We don't use IsValid() here because ICMP only requires that up to
// 1280 bytes of the original packet be included. So it's likely that it
// is truncated, which would cause IsValid to return false.
//
// Drop packet if it doesn't have the basic IPv6 header or if the
// original source address doesn't match the endpoint's address.
if len(h) < header.IPv6MinimumSize || h.SourceAddress() != e.id.LocalAddress {
return
}
// Skip the IP header, then handle the fragmentation header if there
// is one.
vv.TrimFront(header.IPv6MinimumSize)
p := h.TransportProtocol()
if p == header.IPv6FragmentHeader {
f := header.IPv6Fragment(vv.First())
if !f.IsValid() || f.FragmentOffset() != 0 {
// We can't handle fragments that aren't at offset 0
// because they don't have the transport headers.
return
}
// Skip fragmentation header and find out the actual protocol
// number.
vv.TrimFront(header.IPv6FragmentHeaderSize)
p = f.TransportProtocol()
}
// Deliver the control packet to the transport endpoint.
e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, vv)
}
func (e *endpoint) handleICMP(r *stack.Route, vv buffer.VectorisedView) {
v := vv.First()
if len(v) < header.ICMPv6MinimumSize {
return
}
h := header.ICMPv6(v)
switch h.Type() {
case header.ICMPv6PacketTooBig:
if len(v) < header.ICMPv6PacketTooBigMinimumSize {
return
}
vv.TrimFront(header.ICMPv6PacketTooBigMinimumSize)
mtu := binary.BigEndian.Uint32(v[header.ICMPv6MinimumSize:])
e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), vv)
case header.ICMPv6DstUnreachable:
if len(v) < header.ICMPv6DstUnreachableMinimumSize {
return
}
vv.TrimFront(header.ICMPv6DstUnreachableMinimumSize)
switch h.Code() {
case header.ICMPv6PortUnreachable:
e.handleControl(stack.ControlPortUnreachable, 0, vv)
}
case header.ICMPv6NeighborSolicit:
if len(v) < header.ICMPv6NeighborSolicitMinimumSize {
return
}
targetAddr := tcpip.Address(v[8 : 8+16])
if e.linkAddrCache.CheckLocalAddress(e.nicid, ProtocolNumber, targetAddr) == 0 {
// We don't have a useful answer; the best we can do is ignore the request.
return
}
hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize)
pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
pkt.SetType(header.ICMPv6NeighborAdvert)
pkt[icmpV6FlagOffset] = ndpSolicitedFlag | ndpOverrideFlag
copy(pkt[icmpV6OptOffset-len(targetAddr):], targetAddr)
pkt[icmpV6OptOffset] = ndpOptDstLinkAddr
pkt[icmpV6LengthOffset] = 1
copy(pkt[icmpV6LengthOffset+1:], r.LocalLinkAddress[:])
// ICMPv6 Neighbor Solicit messages are always sent to
// specially crafted IPv6 multicast addresses. As a result, the
// route we end up with here has as its LocalAddress such a
// multicast address. It would be nonsense to claim that our
// source address is a multicast address, so we manually set
// the source address to the target address requested in the
// solicit message. Since that requires mutating the route, we
// must first clone it.
r := r.Clone()
defer r.Release()
r.LocalAddress = targetAddr
pkt.SetChecksum(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
r.WritePacket(hdr, buffer.VectorisedView{}, header.ICMPv6ProtocolNumber, r.DefaultTTL())
e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
case header.ICMPv6NeighborAdvert:
if len(v) < header.ICMPv6NeighborAdvertSize {
return
}
targetAddr := tcpip.Address(v[8 : 8+16])
e.linkAddrCache.AddLinkAddress(e.nicid, targetAddr, r.RemoteLinkAddress)
if targetAddr != r.RemoteAddress {
e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress)
}
case header.ICMPv6EchoRequest:
if len(v) < header.ICMPv6EchoMinimumSize {
return
}
vv.TrimFront(header.ICMPv6EchoMinimumSize)
hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6EchoMinimumSize)
pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize))
copy(pkt, h)
pkt.SetType(header.ICMPv6EchoReply)
pkt.SetChecksum(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, vv))
r.WritePacket(hdr, vv, header.ICMPv6ProtocolNumber, r.DefaultTTL())
case header.ICMPv6EchoReply:
if len(v) < header.ICMPv6EchoMinimumSize {
return
}
e.dispatcher.DeliverTransportPacket(r, header.ICMPv6ProtocolNumber, vv)
}
}
const (
ndpSolicitedFlag = 1 << 6
ndpOverrideFlag = 1 << 5
ndpOptSrcLinkAddr = 1
ndpOptDstLinkAddr = 2
icmpV6FlagOffset = 4
icmpV6OptOffset = 24
icmpV6LengthOffset = 25
)
var broadcastMAC = tcpip.LinkAddress([]byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff})
var _ stack.LinkAddressResolver = (*protocol)(nil)
// LinkAddressProtocol implements stack.LinkAddressResolver.
func (*protocol) LinkAddressProtocol() tcpip.NetworkProtocolNumber {
return header.IPv6ProtocolNumber
}
// LinkAddressRequest implements stack.LinkAddressResolver.
func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack.LinkEndpoint) *tcpip.Error {
snaddr := header.SolicitedNodeAddr(addr)
r := &stack.Route{
LocalAddress: localAddr,
RemoteAddress: snaddr,
RemoteLinkAddress: broadcastMAC,
}
hdr := buffer.NewPrependable(int(linkEP.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize)
pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize))
pkt.SetType(header.ICMPv6NeighborSolicit)
copy(pkt[icmpV6OptOffset-len(addr):], addr)
pkt[icmpV6OptOffset] = ndpOptSrcLinkAddr
pkt[icmpV6LengthOffset] = 1
copy(pkt[icmpV6LengthOffset+1:], linkEP.LinkAddress())
pkt.SetChecksum(icmpChecksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{}))
length := uint16(hdr.UsedLength())
ip := header.IPv6(hdr.Prepend(header.IPv6MinimumSize))
ip.Encode(&header.IPv6Fields{
PayloadLength: length,
NextHeader: uint8(header.ICMPv6ProtocolNumber),
HopLimit: defaultIPv6HopLimit,
SrcAddr: r.LocalAddress,
DstAddr: r.RemoteAddress,
})
return linkEP.WritePacket(r, hdr, buffer.VectorisedView{}, ProtocolNumber)
}
// ResolveStaticAddress implements stack.LinkAddressResolver.
func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bool) {
return "", false
}
func icmpChecksum(h header.ICMPv6, src, dst tcpip.Address, vv buffer.VectorisedView) uint16 {
// Calculate the IPv6 pseudo-header upper-layer checksum.
xsum := header.Checksum([]byte(src), 0)
xsum = header.Checksum([]byte(dst), xsum)
var upperLayerLength [4]byte
binary.BigEndian.PutUint32(upperLayerLength[:], uint32(len(h)+vv.Size()))
xsum = header.Checksum(upperLayerLength[:], xsum)
xsum = header.Checksum([]byte{0, 0, 0, uint8(header.ICMPv6ProtocolNumber)}, xsum)
for _, v := range vv.Views() {
xsum = header.Checksum(v, xsum)
}
// h[2:4] is the checksum itself, set it aside to avoid checksumming the checksum.
h2, h3 := h[2], h[3]
h[2], h[3] = 0, 0
xsum = ^header.Checksum(h, xsum)
h[2], h[3] = h2, h3
return xsum
}
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