diff options
Diffstat (limited to 'pkg/tcpip/network/ipv6/icmp.go')
| -rw-r--r-- | pkg/tcpip/network/ipv6/icmp.go | 254 |
1 files changed, 205 insertions, 49 deletions
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index b4d0295bf..1c3410618 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -21,21 +21,12 @@ import ( "gvisor.dev/gvisor/pkg/tcpip/stack" ) -const ( - // ndpHopLimit is the expected IP hop limit value of 255 for received - // NDP packets, as per RFC 4861 sections 4.1 - 4.5, 6.1.1, 6.1.2, 7.1.1, - // 7.1.2 and 8.1. If the hop limit value is not 255, nodes MUST silently - // drop the NDP packet. All outgoing NDP packets must use this value for - // its IP hop limit field. - ndpHopLimit = 255 -) - // 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()) +func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt tcpip.PacketBuffer) { + h := header.IPv6(pkt.Data.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 @@ -49,10 +40,10 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv buffer. // Skip the IP header, then handle the fragmentation header if there // is one. - vv.TrimFront(header.IPv6MinimumSize) + pkt.Data.TrimFront(header.IPv6MinimumSize) p := h.TransportProtocol() if p == header.IPv6FragmentHeader { - f := header.IPv6Fragment(vv.First()) + f := header.IPv6Fragment(pkt.Data.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. @@ -61,35 +52,54 @@ func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, vv buffer. // Skip fragmentation header and find out the actual protocol // number. - vv.TrimFront(header.IPv6FragmentHeaderSize) + pkt.Data.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) + e.dispatcher.DeliverTransportControlPacket(e.id.LocalAddress, h.DestinationAddress(), ProtocolNumber, p, typ, extra, pkt) } -func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.VectorisedView) { +func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, pkt tcpip.PacketBuffer) { stats := r.Stats().ICMP sent := stats.V6PacketsSent received := stats.V6PacketsReceived - v := vv.First() + v := pkt.Data.First() if len(v) < header.ICMPv6MinimumSize { received.Invalid.Increment() return } h := header.ICMPv6(v) + iph := header.IPv6(netHeader) + + // Validate ICMPv6 checksum before processing the packet. + // + // Only the first view in vv is accounted for by h. To account for the + // rest of vv, a shallow copy is made and the first view is removed. + // This copy is used as extra payload during the checksum calculation. + payload := pkt.Data + payload.RemoveFirst() + if got, want := h.Checksum(), header.ICMPv6Checksum(h, iph.SourceAddress(), iph.DestinationAddress(), payload); got != want { + received.Invalid.Increment() + return + } // As per RFC 4861 sections 4.1 - 4.5, 6.1.1, 6.1.2, 7.1.1, 7.1.2 and // 8.1, nodes MUST silently drop NDP packets where the Hop Limit field - // in the IPv6 header is not set to 255. + // in the IPv6 header is not set to 255, or the ICMPv6 Code field is not + // set to 0. switch h.Type() { case header.ICMPv6NeighborSolicit, header.ICMPv6NeighborAdvert, header.ICMPv6RouterSolicit, header.ICMPv6RouterAdvert, header.ICMPv6RedirectMsg: - if header.IPv6(netHeader).HopLimit() != ndpHopLimit { + if iph.HopLimit() != header.NDPHopLimit { + received.Invalid.Increment() + return + } + + if h.Code() != 0 { received.Invalid.Increment() return } @@ -103,9 +113,9 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.Invalid.Increment() return } - vv.TrimFront(header.ICMPv6PacketTooBigMinimumSize) + pkt.Data.TrimFront(header.ICMPv6PacketTooBigMinimumSize) mtu := h.MTU() - e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), vv) + e.handleControl(stack.ControlPacketTooBig, calculateMTU(mtu), pkt) case header.ICMPv6DstUnreachable: received.DstUnreachable.Increment() @@ -113,33 +123,80 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.Invalid.Increment() return } - vv.TrimFront(header.ICMPv6DstUnreachableMinimumSize) + pkt.Data.TrimFront(header.ICMPv6DstUnreachableMinimumSize) switch h.Code() { case header.ICMPv6PortUnreachable: - e.handleControl(stack.ControlPortUnreachable, 0, vv) + e.handleControl(stack.ControlPortUnreachable, 0, pkt) } case header.ICMPv6NeighborSolicit: received.NeighborSolicit.Increment() - if len(v) < header.ICMPv6NeighborSolicitMinimumSize { received.Invalid.Increment() return } - targetAddr := tcpip.Address(v[8:][:header.IPv6AddressSize]) - if e.linkAddrCache.CheckLocalAddress(e.nicid, ProtocolNumber, targetAddr) == 0 { + + ns := header.NDPNeighborSolicit(h.NDPPayload()) + targetAddr := ns.TargetAddress() + s := r.Stack() + rxNICID := r.NICID() + + isTentative, err := s.IsAddrTentative(rxNICID, targetAddr) + if err != nil { + // We will only get an error if rxNICID is unrecognized, + // which should not happen. For now short-circuit this + // packet. + // + // TODO(b/141002840): Handle this better? + return + } + + if isTentative { + // If the target address is tentative and the source + // of the packet is a unicast (specified) address, then + // the source of the packet is attempting to perform + // address resolution on the target. In this case, the + // solicitation is silently ignored, as per RFC 4862 + // section 5.4.3. + // + // If the target address is tentative and the source of + // the packet is the unspecified address (::), then we + // know another node is also performing DAD for the + // same address (since targetAddr is tentative for us, + // we know we are also performing DAD on it). In this + // case we let the stack know so it can handle such a + // scenario and do nothing further with the NDP NS. + if iph.SourceAddress() == header.IPv6Any { + s.DupTentativeAddrDetected(rxNICID, targetAddr) + } + + // Do not handle neighbor solicitations targeted + // to an address that is tentative on the received + // NIC any further. + return + } + + // At this point we know that targetAddr is not tentative on + // rxNICID so the packet is processed as defined in RFC 4861, + // as per RFC 4862 section 5.4.3. + + 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.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[:]) + optsSerializer := header.NDPOptionsSerializer{ + header.NDPTargetLinkLayerAddressOption(r.LocalLinkAddress[:]), + } + hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6NeighborAdvertMinimumSize + int(optsSerializer.Length())) + packet := header.ICMPv6(hdr.Prepend(header.ICMPv6NeighborAdvertSize)) + packet.SetType(header.ICMPv6NeighborAdvert) + na := header.NDPNeighborAdvert(packet.NDPPayload()) + na.SetSolicitedFlag(true) + na.SetOverrideFlag(true) + na.SetTargetAddress(targetAddr) + opts := na.Options() + opts.Serialize(optsSerializer) // ICMPv6 Neighbor Solicit messages are always sent to // specially crafted IPv6 multicast addresses. As a result, the @@ -152,9 +209,26 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V r := r.Clone() defer r.Release() r.LocalAddress = targetAddr - pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{})) + packet.SetChecksum(header.ICMPv6Checksum(packet, r.LocalAddress, r.RemoteAddress, buffer.VectorisedView{})) - if err := r.WritePacket(nil /* gso */, hdr, buffer.VectorisedView{}, header.ICMPv6ProtocolNumber, r.DefaultTTL()); err != nil { + // TODO(tamird/ghanan): there exists an explicit NDP option that is + // used to update the neighbor table with link addresses for a + // neighbor from an NS (see the Source Link Layer option RFC + // 4861 section 4.6.1 and section 7.2.3). + // + // Furthermore, the entirety of NDP handling here seems to be + // contradicted by RFC 4861. + e.linkAddrCache.AddLinkAddress(e.nicID, r.RemoteAddress, r.RemoteLinkAddress) + + // RFC 4861 Neighbor Discovery for IP version 6 (IPv6) + // + // 7.1.2. Validation of Neighbor Advertisements + // + // The IP Hop Limit field has a value of 255, i.e., the packet + // could not possibly have been forwarded by a router. + if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: header.NDPHopLimit, TOS: stack.DefaultTOS}, tcpip.PacketBuffer{ + Header: hdr, + }); err != nil { sent.Dropped.Increment() return } @@ -166,10 +240,45 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.Invalid.Increment() return } - targetAddr := tcpip.Address(v[8:][:header.IPv6AddressSize]) - e.linkAddrCache.AddLinkAddress(e.nicid, targetAddr, r.RemoteLinkAddress) + + na := header.NDPNeighborAdvert(h.NDPPayload()) + targetAddr := na.TargetAddress() + stack := r.Stack() + rxNICID := r.NICID() + + isTentative, err := stack.IsAddrTentative(rxNICID, targetAddr) + if err != nil { + // We will only get an error if rxNICID is unrecognized, + // which should not happen. For now short-circuit this + // packet. + // + // TODO(b/141002840): Handle this better? + return + } + + if isTentative { + // We just got an NA from a node that owns an address we + // are performing DAD on, implying the address is not + // unique. In this case we let the stack know so it can + // handle such a scenario and do nothing furthur with + // the NDP NA. + stack.DupTentativeAddrDetected(rxNICID, targetAddr) + return + } + + // At this point we know that the targetAddress is not tentative + // on rxNICID. However, targetAddr may still be assigned to + // rxNICID but not tentative (it could be permanent). Such a + // scenario is beyond the scope of RFC 4862. As such, we simply + // ignore such a scenario for now and proceed as normal. + // + // TODO(b/143147598): Handle the scenario described above. Also + // inform the netstack integration that a duplicate address was + // detected outside of DAD. + + e.linkAddrCache.AddLinkAddress(e.nicID, targetAddr, r.RemoteLinkAddress) if targetAddr != r.RemoteAddress { - e.linkAddrCache.AddLinkAddress(e.nicid, r.RemoteAddress, r.RemoteLinkAddress) + e.linkAddrCache.AddLinkAddress(e.nicID, r.RemoteAddress, r.RemoteLinkAddress) } case header.ICMPv6EchoRequest: @@ -178,14 +287,16 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.Invalid.Increment() return } - - vv.TrimFront(header.ICMPv6EchoMinimumSize) + pkt.Data.TrimFront(header.ICMPv6EchoMinimumSize) hdr := buffer.NewPrependable(int(r.MaxHeaderLength()) + header.ICMPv6EchoMinimumSize) - pkt := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize)) - copy(pkt, h) - pkt.SetType(header.ICMPv6EchoReply) - pkt.SetChecksum(header.ICMPv6Checksum(pkt, r.LocalAddress, r.RemoteAddress, vv)) - if err := r.WritePacket(nil /* gso */, hdr, vv, header.ICMPv6ProtocolNumber, r.DefaultTTL()); err != nil { + packet := header.ICMPv6(hdr.Prepend(header.ICMPv6EchoMinimumSize)) + copy(packet, h) + packet.SetType(header.ICMPv6EchoReply) + packet.SetChecksum(header.ICMPv6Checksum(packet, r.LocalAddress, r.RemoteAddress, pkt.Data)) + if err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, tcpip.PacketBuffer{ + Header: hdr, + Data: pkt.Data, + }); err != nil { sent.Dropped.Increment() return } @@ -197,7 +308,7 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.Invalid.Increment() return } - e.dispatcher.DeliverTransportPacket(r, header.ICMPv6ProtocolNumber, netHeader, vv) + e.dispatcher.DeliverTransportPacket(r, header.ICMPv6ProtocolNumber, pkt) case header.ICMPv6TimeExceeded: received.TimeExceeded.Increment() @@ -209,8 +320,51 @@ func (e *endpoint) handleICMP(r *stack.Route, netHeader buffer.View, vv buffer.V received.RouterSolicit.Increment() case header.ICMPv6RouterAdvert: + routerAddr := iph.SourceAddress() + + // + // Validate the RA as per RFC 4861 section 6.1.2. + // + + // Is the IP Source Address a link-local address? + if !header.IsV6LinkLocalAddress(routerAddr) { + // ...No, silently drop the packet. + received.Invalid.Increment() + return + } + + p := h.NDPPayload() + + // Is the NDP payload of sufficient size to hold a Router + // Advertisement? + if len(p) < header.NDPRAMinimumSize { + // ...No, silently drop the packet. + received.Invalid.Increment() + return + } + + ra := header.NDPRouterAdvert(p) + opts := ra.Options() + + // Are options valid as per the wire format? + if _, err := opts.Iter(true); err != nil { + // ...No, silently drop the packet. + received.Invalid.Increment() + return + } + + // + // At this point, we have a valid Router Advertisement, as far + // as RFC 4861 section 6.1.2 is concerned. + // + received.RouterAdvert.Increment() + // Tell the NIC to handle the RA. + stack := r.Stack() + rxNICID := r.NICID() + stack.HandleNDPRA(rxNICID, routerAddr, ra) + case header.ICMPv6RedirectMsg: received.RedirectMsg.Increment() @@ -262,13 +416,15 @@ func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, linkEP stack. ip.Encode(&header.IPv6Fields{ PayloadLength: length, NextHeader: uint8(header.ICMPv6ProtocolNumber), - HopLimit: defaultIPv6HopLimit, + HopLimit: header.NDPHopLimit, SrcAddr: r.LocalAddress, DstAddr: r.RemoteAddress, }) // TODO(stijlist): count this in ICMP stats. - return linkEP.WritePacket(r, nil /* gso */, hdr, buffer.VectorisedView{}, ProtocolNumber) + return linkEP.WritePacket(r, nil /* gso */, ProtocolNumber, tcpip.PacketBuffer{ + Header: hdr, + }) } // ResolveStaticAddress implements stack.LinkAddressResolver. |