diff options
Diffstat (limited to 'pkg/tcpip/network/ipv4')
| -rw-r--r-- | pkg/tcpip/network/ipv4/icmp.go | 99 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 351 |
2 files changed, 431 insertions, 19 deletions
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go index 1edb6de6b..cf287446e 100644 --- a/pkg/tcpip/network/ipv4/icmp.go +++ b/pkg/tcpip/network/ipv4/icmp.go @@ -15,6 +15,7 @@ package ipv4 import ( + "errors" "fmt" "gvisor.dev/gvisor/pkg/tcpip" @@ -23,10 +24,10 @@ import ( "gvisor.dev/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. +// handleControl handles the case when an ICMP error 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. We only expect the payload, not the enclosing ICMP packet. func (e *endpoint) handleControl(typ stack.ControlType, extra uint32, pkt *stack.PacketBuffer) { h, ok := pkt.Data.PullUp(header.IPv4MinimumSize) if !ok { @@ -73,20 +74,65 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) { } h := header.ICMPv4(v) + // Only do in-stack processing if the checksum is correct. + if header.ChecksumVV(pkt.Data, 0 /* initial */) != 0xffff { + received.Invalid.Increment() + // It's possible that a raw socket expects to receive this regardless + // of checksum errors. If it's an echo request we know it's safe because + // we are the only handler, however other types do not cope well with + // packets with checksum errors. + switch h.Type() { + case header.ICMPv4Echo: + e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt) + } + return + } + + iph := header.IPv4(pkt.NetworkHeader().View()) + var newOptions header.IPv4Options + if len(iph) > header.IPv4MinimumSize { + // RFC 1122 section 3.2.2.6 (page 43) (and similar for other round trip + // type ICMP packets): + // If a Record Route and/or Time Stamp option is received in an + // ICMP Echo Request, this option (these options) SHOULD be + // updated to include the current host and included in the IP + // header of the Echo Reply message, without "truncation". + // Thus, the recorded route will be for the entire round trip. + // + // So we need to let the option processor know how it should handle them. + var op optionsUsage + if h.Type() == header.ICMPv4Echo { + op = &optionUsageEcho{} + } else { + op = &optionUsageReceive{} + } + aux, tmp, err := processIPOptions(r, iph.Options(), op) + if err != nil { + switch { + case + errors.Is(err, header.ErrIPv4OptDuplicate), + errors.Is(err, errIPv4RecordRouteOptInvalidLength), + errors.Is(err, errIPv4RecordRouteOptInvalidPointer), + errors.Is(err, errIPv4TimestampOptInvalidLength), + errors.Is(err, errIPv4TimestampOptInvalidPointer), + errors.Is(err, errIPv4TimestampOptOverflow): + _ = e.protocol.returnError(r, &icmpReasonParamProblem{pointer: aux}, pkt) + e.protocol.stack.Stats().MalformedRcvdPackets.Increment() + r.Stats().IP.MalformedPacketsReceived.Increment() + } + return + } + newOptions = tmp + } + // TODO(b/112892170): Meaningfully handle all ICMP types. switch h.Type() { case header.ICMPv4Echo: received.Echo.Increment() - // Only send a reply if the checksum is valid. - headerChecksum := h.Checksum() - h.SetChecksum(0) - calculatedChecksum := ^header.ChecksumVV(pkt.Data, 0 /* initial */) - h.SetChecksum(headerChecksum) - if calculatedChecksum != headerChecksum { - // It's possible that a raw socket still expects to receive this. - e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt) - received.Invalid.Increment() + sent := stats.ICMP.V4PacketsSent + if !r.Stack().AllowICMPMessage() { + sent.RateLimited.Increment() return } @@ -98,9 +144,14 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) { // waiting endpoints. Consider moving responsibility for doing the copy to // DeliverTransportPacket so that is is only done when needed. replyData := pkt.Data.ToOwnedView() - replyIPHdr := header.IPv4(append(buffer.View(nil), pkt.NetworkHeader().View()...)) + // It's possible that a raw socket expects to receive this. e.dispatcher.DeliverTransportPacket(r, header.ICMPv4ProtocolNumber, pkt) + pkt = nil + // Take the base of the incoming request IP header but replace the options. + replyHeaderLength := uint8(header.IPv4MinimumSize + len(newOptions)) + replyIPHdr := header.IPv4(append(iph[:header.IPv4MinimumSize:header.IPv4MinimumSize], newOptions...)) + replyIPHdr.SetHeaderLength(replyHeaderLength) // As per RFC 1122 section 3.2.1.3, when a host sends any datagram, the IP // source address MUST be one of its own IP addresses (but not a broadcast @@ -139,7 +190,8 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) { // The fields we need to alter. // // We need to produce the entire packet in the data segment in order to - // use WriteHeaderIncludedPacket(). + // use WriteHeaderIncludedPacket(). WriteHeaderIncludedPacket sets the + // total length and the header checksum so we don't need to set those here. replyIPHdr.SetSourceAddress(r.LocalAddress) replyIPHdr.SetDestinationAddress(r.RemoteAddress) replyIPHdr.SetTTL(r.DefaultTTL()) @@ -157,8 +209,6 @@ func (e *endpoint) handleICMP(r *stack.Route, pkt *stack.PacketBuffer) { }) replyPkt.TransportProtocolNumber = header.ICMPv4ProtocolNumber - // The checksum will be calculated so we don't need to do it here. - sent := stats.ICMP.V4PacketsSent if err := r.WriteHeaderIncludedPacket(replyPkt); err != nil { sent.Dropped.Increment() return @@ -244,6 +294,14 @@ type icmpReasonReassemblyTimeout struct{} func (*icmpReasonReassemblyTimeout) isICMPReason() {} +// icmpReasonParamProblem is an error to use to request a Parameter Problem +// message to be sent. +type icmpReasonParamProblem struct { + pointer byte +} + +func (*icmpReasonParamProblem) isICMPReason() {} + // returnError takes an error descriptor and generates the appropriate ICMP // error packet for IPv4 and sends it back to the remote device that sent // the problematic packet. It incorporates as much of that packet as @@ -385,7 +443,7 @@ func (p *protocol) returnError(r *stack.Route, reason icmpReason, pkt *stack.Pac icmpHdr := header.ICMPv4(icmpPkt.TransportHeader().Push(header.ICMPv4MinimumSize)) var counter *tcpip.StatCounter - switch reason.(type) { + switch reason := reason.(type) { case *icmpReasonPortUnreachable: icmpHdr.SetType(header.ICMPv4DstUnreachable) icmpHdr.SetCode(header.ICMPv4PortUnreachable) @@ -398,6 +456,11 @@ func (p *protocol) returnError(r *stack.Route, reason icmpReason, pkt *stack.Pac icmpHdr.SetType(header.ICMPv4TimeExceeded) icmpHdr.SetCode(header.ICMPv4ReassemblyTimeout) counter = sent.TimeExceeded + case *icmpReasonParamProblem: + icmpHdr.SetType(header.ICMPv4ParamProblem) + icmpHdr.SetCode(header.ICMPv4UnusedCode) + icmpHdr.SetPointer(reason.pointer) + counter = sent.ParamProblem default: panic(fmt.Sprintf("unsupported ICMP type %T", reason)) } diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index e6b842d61..4592984a5 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -16,7 +16,9 @@ package ipv4 import ( + "errors" "fmt" + "math" "sync/atomic" "time" @@ -31,6 +33,8 @@ import ( ) const ( + // ReassembleTimeout is the time a packet stays in the reassembly + // system before being evicted. // As per RFC 791 section 3.2: // The current recommendation for the initial timer setting is 15 seconds. // This may be changed as experience with this protocol accumulates. @@ -569,9 +573,14 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { if !ready { return } - } + // The reassembler doesn't take care of fixing up the header, so we need + // to do it here. + h.SetTotalLength(uint16(pkt.Data.Size() + len((h)))) + h.SetFlagsFragmentOffset(0, 0) + } r.Stats().IP.PacketsDelivered.Increment() + p := h.TransportProtocol() if p == header.ICMPv4ProtocolNumber { // TODO(gvisor.dev/issues/3810): when we sort out ICMP and transport @@ -581,6 +590,27 @@ func (e *endpoint) HandlePacket(r *stack.Route, pkt *stack.PacketBuffer) { e.handleICMP(r, pkt) return } + if len(h.Options()) != 0 { + // TODO(gvisor.dev/issue/4586): + // When we add forwarding support we should use the verified options + // rather than just throwing them away. + aux, _, err := processIPOptions(r, h.Options(), &optionUsageReceive{}) + if err != nil { + switch { + case + errors.Is(err, header.ErrIPv4OptDuplicate), + errors.Is(err, errIPv4RecordRouteOptInvalidPointer), + errors.Is(err, errIPv4RecordRouteOptInvalidLength), + errors.Is(err, errIPv4TimestampOptInvalidLength), + errors.Is(err, errIPv4TimestampOptInvalidPointer), + errors.Is(err, errIPv4TimestampOptOverflow): + _ = e.protocol.returnError(r, &icmpReasonParamProblem{pointer: aux}, pkt) + e.protocol.stack.Stats().MalformedRcvdPackets.Increment() + r.Stats().IP.MalformedPacketsReceived.Increment() + } + return + } + } switch res := e.dispatcher.DeliverTransportPacket(r, p, pkt); res { case stack.TransportPacketHandled: @@ -905,3 +935,322 @@ func buildNextFragment(pf *fragmentation.PacketFragmenter, originalIPHeader head return fragPkt, more } + +// optionAction describes possible actions that may be taken on an option +// while processing it. +type optionAction uint8 + +const ( + // optionRemove says that the option should not be in the output option set. + optionRemove optionAction = iota + + // optionProcess says that the option should be fully processed. + optionProcess + + // optionVerify says the option should be checked and passed unchanged. + optionVerify + + // optionPass says to pass the output set without checking. + optionPass +) + +// optionActions list what to do for each option in a given scenario. +type optionActions struct { + // timestamp controls what to do with a Timestamp option. + timestamp optionAction + + // recordroute controls what to do with a Record Route option. + recordRoute optionAction + + // unknown controls what to do with an unknown option. + unknown optionAction +} + +// optionsUsage specifies the ways options may be operated upon for a given +// scenario during packet processing. +type optionsUsage interface { + actions() optionActions +} + +// optionUsageReceive implements optionsUsage for received packets. +type optionUsageReceive struct{} + +// actions implements optionsUsage. +func (*optionUsageReceive) actions() optionActions { + return optionActions{ + timestamp: optionVerify, + recordRoute: optionVerify, + unknown: optionPass, + } +} + +// TODO(gvisor.dev/issue/4586): Add an entry here for forwarding when it +// is enabled (Process, Process, Pass) and for fragmenting (Process, Process, +// Pass for frag1, but Remove,Remove,Remove for all other frags). + +// optionUsageEcho implements optionsUsage for echo packet processing. +type optionUsageEcho struct{} + +// actions implements optionsUsage. +func (*optionUsageEcho) actions() optionActions { + return optionActions{ + timestamp: optionProcess, + recordRoute: optionProcess, + unknown: optionRemove, + } +} + +var ( + errIPv4TimestampOptInvalidLength = errors.New("invalid Timestamp length") + errIPv4TimestampOptInvalidPointer = errors.New("invalid Timestamp pointer") + errIPv4TimestampOptOverflow = errors.New("overflow in Timestamp") + errIPv4TimestampOptInvalidFlags = errors.New("invalid Timestamp flags") +) + +// handleTimestamp does any required processing on a Timestamp option +// in place. +func handleTimestamp(tsOpt header.IPv4OptionTimestamp, localAddress tcpip.Address, clock tcpip.Clock, usage optionsUsage) (uint8, error) { + flags := tsOpt.Flags() + var entrySize uint8 + switch flags { + case header.IPv4OptionTimestampOnlyFlag: + entrySize = header.IPv4OptionTimestampSize + case + header.IPv4OptionTimestampWithIPFlag, + header.IPv4OptionTimestampWithPredefinedIPFlag: + entrySize = header.IPv4OptionTimestampWithAddrSize + default: + return header.IPv4OptTSOFLWAndFLGOffset, errIPv4TimestampOptInvalidFlags + } + + pointer := tsOpt.Pointer() + // To simplify processing below, base further work on the array of timestamps + // beyond the header, rather than on the whole option. Also to aid + // calculations set 'nextSlot' to be 0 based as in the packet it is 1 based. + nextSlot := pointer - (header.IPv4OptionTimestampHdrLength + 1) + optLen := tsOpt.Size() + dataLength := optLen - header.IPv4OptionTimestampHdrLength + + // In the section below, we verify the pointer, length and overflow counter + // fields of the option. The distinction is in which byte you return as being + // in error in the ICMP packet. Offsets 1 (length), 2 pointer) + // or 3 (overflowed counter). + // + // The following RFC sections cover this section: + // + // RFC 791 (page 22): + // If there is some room but not enough room for a full timestamp + // to be inserted, or the overflow count itself overflows, the + // original datagram is considered to be in error and is discarded. + // In either case an ICMP parameter problem message may be sent to + // the source host [3]. + // + // You can get this situation in two ways. Firstly if the data area is not + // a multiple of the entry size or secondly, if the pointer is not at a + // multiple of the entry size. The wording of the RFC suggests that + // this is not an error until you actually run out of space. + if pointer > optLen { + // RFC 791 (page 22) says we should switch to using the overflow count. + // If the timestamp data area is already full (the pointer exceeds + // the length) the datagram is forwarded without inserting the + // timestamp, but the overflow count is incremented by one. + if flags == header.IPv4OptionTimestampWithPredefinedIPFlag { + // By definition we have nothing to do. + return 0, nil + } + + if tsOpt.IncOverflow() != 0 { + return 0, nil + } + // The overflow count is also full. + return header.IPv4OptTSOFLWAndFLGOffset, errIPv4TimestampOptOverflow + } + if nextSlot+entrySize > dataLength { + // The data area isn't full but there isn't room for a new entry. + // Either Length or Pointer could be bad. + if false { + // We must select Pointer for Linux compatibility, even if + // only the length is bad. + // The Linux code is at (in October 2020) + // https://github.com/torvalds/linux/blob/bbf5c979011a099af5dc76498918ed7df445635b/net/ipv4/ip_options.c#L367-L370 + // if (optptr[2]+3 > optlen) { + // pp_ptr = optptr + 2; + // goto error; + // } + // which doesn't distinguish between which of optptr[2] or optlen + // is wrong, but just arbitrarily decides on optptr+2. + if dataLength%entrySize != 0 { + // The Data section size should be a multiple of the expected + // timestamp entry size. + return header.IPv4OptionLengthOffset, errIPv4TimestampOptInvalidLength + } + // If the size is OK, the pointer must be corrupted. + } + return header.IPv4OptTSPointerOffset, errIPv4TimestampOptInvalidPointer + } + + if usage.actions().timestamp == optionProcess { + tsOpt.UpdateTimestamp(localAddress, clock) + } + return 0, nil +} + +var ( + errIPv4RecordRouteOptInvalidLength = errors.New("invalid length in Record Route") + errIPv4RecordRouteOptInvalidPointer = errors.New("invalid pointer in Record Route") +) + +// handleRecordRoute checks and processes a Record route option. It is much +// like the timestamp type 1 option, but without timestamps. The passed in +// address is stored in the option in the correct spot if possible. +func handleRecordRoute(rrOpt header.IPv4OptionRecordRoute, localAddress tcpip.Address, usage optionsUsage) (uint8, error) { + optlen := rrOpt.Size() + + if optlen < header.IPv4AddressSize+header.IPv4OptionRecordRouteHdrLength { + return header.IPv4OptionLengthOffset, errIPv4RecordRouteOptInvalidLength + } + + nextSlot := rrOpt.Pointer() - 1 // Pointer is 1 based. + + // RFC 791 page 21 says + // If the route data area is already full (the pointer exceeds the + // length) the datagram is forwarded without inserting the address + // into the recorded route. If there is some room but not enough + // room for a full address to be inserted, the original datagram is + // considered to be in error and is discarded. In either case an + // ICMP parameter problem message may be sent to the source + // host. + // The use of the words "In either case" suggests that a 'full' RR option + // could generate an ICMP at every hop after it fills up. We chose to not + // do this (as do most implementations). It is probable that the inclusion + // of these words is a copy/paste error from the timestamp option where + // there are two failure reasons given. + if nextSlot >= optlen { + return 0, nil + } + + // The data area isn't full but there isn't room for a new entry. + // Either Length or Pointer could be bad. We must select Pointer for Linux + // compatibility, even if only the length is bad. + if nextSlot+header.IPv4AddressSize > optlen { + if false { + // This is what we would do if we were not being Linux compatible. + // Check for bad pointer or length value. Must be a multiple of 4 after + // accounting for the 3 byte header and not within that header. + // RFC 791, page 20 says: + // The pointer is relative to this option, and the + // smallest legal value for the pointer is 4. + // + // A recorded route is composed of a series of internet addresses. + // Each internet address is 32 bits or 4 octets. + // Linux skips this test so we must too. See Linux code at: + // https://github.com/torvalds/linux/blob/bbf5c979011a099af5dc76498918ed7df445635b/net/ipv4/ip_options.c#L338-L341 + // if (optptr[2]+3 > optlen) { + // pp_ptr = optptr + 2; + // goto error; + // } + if (optlen-header.IPv4OptionRecordRouteHdrLength)%header.IPv4AddressSize != 0 { + // Length is bad, not on integral number of slots. + return header.IPv4OptionLengthOffset, errIPv4RecordRouteOptInvalidLength + } + // If not length, the fault must be with the pointer. + } + return header.IPv4OptRRPointerOffset, errIPv4RecordRouteOptInvalidPointer + } + if usage.actions().recordRoute == optionVerify { + return 0, nil + } + rrOpt.StoreAddress(localAddress) + return 0, nil +} + +// processIPOptions parses the IPv4 options and produces a new set of options +// suitable for use in the next step of packet processing as informed by usage. +// The original will not be touched. +// +// Returns +// - The location of an error if there was one (or 0 if no error) +// - If there is an error, information as to what it was was. +// - The replacement option set. +func processIPOptions(r *stack.Route, orig header.IPv4Options, usage optionsUsage) (uint8, header.IPv4Options, error) { + + opts := header.IPv4Options(orig) + optIter := opts.MakeIterator() + + // Each option other than NOP must only appear (RFC 791 section 3.1, at the + // definition of every type). Keep track of each of the possible types in + // the 8 bit 'type' field. + var seenOptions [math.MaxUint8 + 1]bool + + // TODO(gvisor.dev/issue/4586): + // This will need tweaking when we start really forwarding packets + // as we may need to get two addresses, for rx and tx interfaces. + // We will also have to take usage into account. + prefixedAddress, err := r.Stack().GetMainNICAddress(r.NICID(), ProtocolNumber) + localAddress := prefixedAddress.Address + if err != nil { + if r.IsInboundBroadcast() || header.IsV4MulticastAddress(r.LocalAddress) { + return 0 /* errCursor */, nil, header.ErrIPv4OptionAddress + } + localAddress = r.LocalAddress + } + + for { + option, done, err := optIter.Next() + if done || err != nil { + return optIter.ErrCursor, optIter.Finalize(), err + } + optType := option.Type() + if optType == header.IPv4OptionNOPType { + optIter.PushNOPOrEnd(optType) + continue + } + if optType == header.IPv4OptionListEndType { + optIter.PushNOPOrEnd(optType) + return 0 /* errCursor */, optIter.Finalize(), nil /* err */ + } + + // check for repeating options (multiple NOPs are OK) + if seenOptions[optType] { + return optIter.ErrCursor, nil, header.ErrIPv4OptDuplicate + } + seenOptions[optType] = true + + optLen := int(option.Size()) + switch option := option.(type) { + case *header.IPv4OptionTimestamp: + r.Stats().IP.OptionTSReceived.Increment() + if usage.actions().timestamp != optionRemove { + clock := r.Stack().Clock() + newBuffer := optIter.RemainingBuffer()[:len(*option)] + _ = copy(newBuffer, option.Contents()) + offset, err := handleTimestamp(header.IPv4OptionTimestamp(newBuffer), localAddress, clock, usage) + if err != nil { + return optIter.ErrCursor + offset, nil, err + } + optIter.ConsumeBuffer(optLen) + } + + case *header.IPv4OptionRecordRoute: + r.Stats().IP.OptionRRReceived.Increment() + if usage.actions().recordRoute != optionRemove { + newBuffer := optIter.RemainingBuffer()[:len(*option)] + _ = copy(newBuffer, option.Contents()) + offset, err := handleRecordRoute(header.IPv4OptionRecordRoute(newBuffer), localAddress, usage) + if err != nil { + return optIter.ErrCursor + offset, nil, err + } + optIter.ConsumeBuffer(optLen) + } + + default: + r.Stats().IP.OptionUnknownReceived.Increment() + if usage.actions().unknown == optionPass { + newBuffer := optIter.RemainingBuffer()[:optLen] + // Arguments already heavily checked.. ignore result. + _ = copy(newBuffer, option.Contents()) + optIter.ConsumeBuffer(optLen) + } + } + } +} |