diff options
Diffstat (limited to 'pkg/tcpip/network/ipv6')
| -rw-r--r-- | pkg/tcpip/network/ipv6/icmp.go | 32 | ||||
| -rw-r--r-- | pkg/tcpip/network/ipv6/ipv6.go | 29 |
2 files changed, 53 insertions, 8 deletions
diff --git a/pkg/tcpip/network/ipv6/icmp.go b/pkg/tcpip/network/ipv6/icmp.go index 8502b848c..8d788af80 100644 --- a/pkg/tcpip/network/ipv6/icmp.go +++ b/pkg/tcpip/network/ipv6/icmp.go @@ -750,6 +750,12 @@ type icmpReasonPortUnreachable struct{} func (*icmpReasonPortUnreachable) isICMPReason() {} +// icmpReasonHopLimitExceeded is an error where a packet's hop limit exceeded in +// transit to its final destination, as per RFC 4443 section 3.3. +type icmpReasonHopLimitExceeded struct{} + +func (*icmpReasonHopLimitExceeded) isICMPReason() {} + // icmpReasonReassemblyTimeout is an error where insufficient fragments are // received to complete reassembly of a packet within a configured time after // the reception of the first-arriving fragment of that packet. @@ -794,11 +800,27 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi return nil } + // If we hit a Hop Limit Exceeded error, then we know we are operating as a + // router. As per RFC 4443 section 3.3: + // + // If a router receives a packet with a Hop Limit of zero, or if a + // router decrements a packet's Hop Limit to zero, it MUST discard the + // packet and originate an ICMPv6 Time Exceeded message with Code 0 to + // the source of the packet. This indicates either a routing loop or + // too small an initial Hop Limit value. + // + // If we are operating as a router, do not use the packet's destination + // address as the response's source address as we should not own the + // destination address of a packet we are forwarding. + localAddr := origIPHdrDst + if _, ok := reason.(*icmpReasonHopLimitExceeded); ok { + localAddr = "" + } // Even if we were able to receive a packet from some remote, we may not have // a route to it - the remote may be blocked via routing rules. We must always // consult our routing table and find a route to the remote before sending any // packet. - route, err := p.stack.FindRoute(pkt.NICID, origIPHdrDst, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) + route, err := p.stack.FindRoute(pkt.NICID, localAddr, origIPHdrSrc, ProtocolNumber, false /* multicastLoop */) if err != nil { return err } @@ -811,8 +833,6 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi 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 @@ -830,6 +850,8 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi } } + network, transport := pkt.NetworkHeader().View(), pkt.TransportHeader().View() + // As per RFC 4443 section 2.4 // // (c) Every ICMPv6 error message (type < 128) MUST include @@ -873,6 +895,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi icmpHdr.SetType(header.ICMPv6DstUnreachable) icmpHdr.SetCode(header.ICMPv6PortUnreachable) counter = sent.DstUnreachable + case *icmpReasonHopLimitExceeded: + icmpHdr.SetType(header.ICMPv6TimeExceeded) + icmpHdr.SetCode(header.ICMPv6HopLimitExceeded) + counter = sent.TimeExceeded case *icmpReasonReassemblyTimeout: icmpHdr.SetType(header.ICMPv6TimeExceeded) icmpHdr.SetCode(header.ICMPv6ReassemblyTimeout) diff --git a/pkg/tcpip/network/ipv6/ipv6.go b/pkg/tcpip/network/ipv6/ipv6.go index 38a0633bd..7697ff987 100644 --- a/pkg/tcpip/network/ipv6/ipv6.go +++ b/pkg/tcpip/network/ipv6/ipv6.go @@ -645,6 +645,18 @@ func (e *endpoint) WriteHeaderIncludedPacket(r *stack.Route, pkt *stack.PacketBu // forwardPacket attempts to forward a packet to its final destination. func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { h := header.IPv6(pkt.NetworkHeader().View()) + hopLimit := h.HopLimit() + if hopLimit <= 1 { + // As per RFC 4443 section 3.3, + // + // If a router receives a packet with a Hop Limit of zero, or if a + // router decrements a packet's Hop Limit to zero, it MUST discard the + // packet and originate an ICMPv6 Time Exceeded message with Code 0 to + // the source of the packet. This indicates either a routing loop or + // too small an initial Hop Limit value. + return e.protocol.returnError(&icmpReasonHopLimitExceeded{}, pkt) + } + dstAddr := h.DestinationAddress() // Check if the destination is owned by the stack. @@ -663,13 +675,20 @@ func (e *endpoint) forwardPacket(pkt *stack.PacketBuffer) *tcpip.Error { } defer r.Release() - // TODO(b/143425874) Decrease the TTL field in forwarded packets. + // We need to do a deep copy of the IP packet because + // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do + // not own it. + newHdr := header.IPv6(stack.PayloadSince(pkt.NetworkHeader())) + + // As per RFC 8200 section 3, + // + // Hop Limit 8-bit unsigned integer. Decremented by 1 by + // each node that forwards the packet. + newHdr.SetHopLimit(hopLimit - 1) + return r.WriteHeaderIncludedPacket(stack.NewPacketBuffer(stack.PacketBufferOptions{ ReserveHeaderBytes: int(r.MaxHeaderLength()), - // We need to do a deep copy of the IP packet because - // WriteHeaderIncludedPacket takes ownership of the packet buffer, but we do - // not own it. - Data: stack.PayloadSince(pkt.NetworkHeader()).ToVectorisedView(), + Data: buffer.View(newHdr).ToVectorisedView(), })) } |