From 99decaadd6da0df2d8ec70ddea9d754c9d71a584 Mon Sep 17 00:00:00 2001 From: Julian Elischer Date: Wed, 23 Sep 2020 02:26:50 -0700 Subject: Extract ICMP error sender from UDP Store transport protocol number on packet buffers for use in ICMP error generation. Updates #2211. PiperOrigin-RevId: 333252762 --- pkg/tcpip/network/ipv6/icmp.go | 123 +++++++++++++++++++++++++++++++++++++++++ 1 file changed, 123 insertions(+) (limited to 'pkg/tcpip/network/ipv6/icmp.go') diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index 7430b8fcd..072c8ccd7 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -318,6 +318,7 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer, hasFragme ReserveHeaderBytes: int(r.MaxHeaderLength()) + header.ICMPv6NeighborAdvertMinimumSize + int(optsSerializer.Length()), }) packet := header.ICMPv6(pkt.TransportHeader().Push(header.ICMPv6NeighborAdvertSize)) + pkt.TransportProtocolNumber = header.ICMPv6ProtocolNumber packet.SetType(header.ICMPv6NeighborAdvert) na := header.NDPNeighborAdvert(packet.NDPPayload()) na.SetSolicitedFlag(solicited) @@ -438,6 +439,7 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer, hasFragme Data: pkt.Data, }) packet := header.ICMPv6(replyPkt.TransportHeader().Push(header.ICMPv6EchoMinimumSize)) + pkt.TransportProtocolNumber = header.ICMPv6ProtocolNumber copy(packet, icmpHdr) packet.SetType(header.ICMPv6EchoReply) packet.SetChecksum(header.ICMPv6Checksum(packet, r.LocalAddress, r.RemoteAddress, pkt.Data)) @@ -637,6 +639,7 @@ func (*protocol) LinkAddressRequest(addr, localAddr tcpip.Address, remoteLinkAdd ReserveHeaderBytes: int(linkEP.MaxHeaderLength()) + header.IPv6MinimumSize + header.ICMPv6NeighborAdvertSize, }) icmpHdr := header.ICMPv6(pkt.TransportHeader().Push(header.ICMPv6NeighborAdvertSize)) + pkt.TransportProtocolNumber = header.ICMPv6ProtocolNumber icmpHdr.SetType(header.ICMPv6NeighborSolicit) copy(icmpHdr[icmpV6OptOffset-len(addr):], addr) icmpHdr[icmpV6OptOffset] = ndpOptSrcLinkAddr @@ -665,3 +668,123 @@ func (*protocol) ResolveStaticAddress(addr tcpip.Address) (tcpip.LinkAddress, bo } return tcpip.LinkAddress([]byte(nil)), false } + +// ======= ICMP Error packet generation ========= + +// ReturnError implements stack.TransportProtocol.ReturnError. +func (p *protocol) ReturnError(r *stack.Route, reason tcpip.ICMPReason, pkt *stack.PacketBuffer) *tcpip.Error { + switch reason.(type) { + case *tcpip.ICMPReasonPortUnreachable: + return returnError(r, &icmpReasonPortUnreachable{}, pkt) + default: + return tcpip.ErrNotSupported + } +} + +// icmpReason is a marker interface for IPv6 specific ICMP errors. +type icmpReason interface { + isICMPReason() +} + +// icmpReasonPortUnreachable is an error where the transport protocol has no +// listener and no alternative means to inform the sender. +type icmpReasonPortUnreachable struct{} + +func (*icmpReasonPortUnreachable) isICMPReason() {} + +// returnError takes an error descriptor and generates the appropriate ICMP +// error packet for IPv6 and sends it. +func returnError(r *stack.Route, reason icmpReason, pkt *stack.PacketBuffer) *tcpip.Error { + stats := r.Stats().ICMP + sent := stats.V6PacketsSent + if !r.Stack().AllowICMPMessage() { + sent.RateLimited.Increment() + return nil + } + + // Only send ICMP error if the address is not a multicast v6 + // address and the source is not the unspecified address. + // + // TODO(b/164522993) There are exceptions to this rule. + // See: point e.3) RFC 4443 section-2.4 + // + // (e) An ICMPv6 error message MUST NOT be originated as a result of + // receiving the following: + // + // (e.1) An ICMPv6 error message. + // + // (e.2) An ICMPv6 redirect message [IPv6-DISC]. + // + // (e.3) A packet destined to an IPv6 multicast address. (There are + // two exceptions to this rule: (1) the Packet Too Big Message + // (Section 3.2) to allow Path MTU discovery to work for IPv6 + // multicast, and (2) the Parameter Problem Message, Code 2 + // (Section 3.4) reporting an unrecognized IPv6 option (see + // Section 4.2 of [IPv6]) that has the Option Type highest- + // order two bits set to 10). + // + if header.IsV6MulticastAddress(r.LocalAddress) || r.RemoteAddress == header.IPv6Any { + return nil + } + + network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View() + + if pkt.TransportProtocolNumber == header.ICMPv6ProtocolNumber { + // TODO(gvisor.dev/issues/3810): Sort this out when ICMP headers are stored. + // Unfortunately at this time ICMP Packets do not have a transport + // header separated out. It is in the Data part so we need to + // separate it out now. We will just pretend it is a minimal length + // ICMP packet as we don't really care if any later bits of a + // larger ICMP packet are in the header view or in the Data view. + transport, ok := pkt.TransportHeader().Consume(header.ICMPv6MinimumSize) + if !ok { + return nil + } + typ := header.ICMPv6(transport).Type() + if typ.IsErrorType() || typ == header.ICMPv6RedirectMsg { + return nil + } + } + + // As per RFC 4443 section 2.4 + // + // (c) Every ICMPv6 error message (type < 128) MUST include + // as much of the IPv6 offending (invoking) packet (the + // packet that caused the error) as possible without making + // the error message packet exceed the minimum IPv6 MTU + // [IPv6]. + mtu := int(r.MTU()) + if mtu > header.IPv6MinimumMTU { + mtu = header.IPv6MinimumMTU + } + headerLen := int(r.MaxHeaderLength()) + header.ICMPv6ErrorHeaderSize + available := int(mtu) - headerLen + if available < header.IPv6MinimumSize { + return nil + } + payloadLen := network.Size() + transport.Size() + pkt.Data.Size() + if payloadLen > available { + payloadLen = available + } + payload := buffer.NewVectorisedView(pkt.Size(), pkt.Views()) + payload.CapLength(payloadLen) + + newPkt := stack.NewPacketBuffer(stack.PacketBufferOptions{ + ReserveHeaderBytes: headerLen, + Data: payload, + }) + newPkt.TransportProtocolNumber = header.ICMPv6ProtocolNumber + + icmpHdr := header.ICMPv6(newPkt.TransportHeader().Push(header.ICMPv6DstUnreachableMinimumSize)) + icmpHdr.SetCode(header.ICMPv6PortUnreachable) + icmpHdr.SetType(header.ICMPv6DstUnreachable) + icmpHdr.SetChecksum(header.ICMPv6Checksum(icmpHdr, r.LocalAddress, r.RemoteAddress, newPkt.Data)) + counter := sent.DstUnreachable + err := r.WritePacket(nil /* gso */, stack.NetworkHeaderParams{Protocol: header.ICMPv6ProtocolNumber, TTL: r.DefaultTTL(), TOS: stack.DefaultTOS}, newPkt) + if err != nil { + sent.Dropped.Increment() + return err + } + counter.Increment() + return nil +} -- cgit v1.2.3