diff options
Diffstat (limited to 'pkg/tcpip/network/ipv4/ipv4.go')
| -rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 29 |
1 files changed, 24 insertions, 5 deletions
diff --git a/pkg/tcpip/network/ipv4/ipv4.go b/pkg/tcpip/network/ipv4/ipv4.go index 0c828004a..b4f21d61e 100644 --- a/pkg/tcpip/network/ipv4/ipv4.go +++ b/pkg/tcpip/network/ipv4/ipv4.go @@ -485,6 +485,16 @@ 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.IPv4(pkt.NetworkHeader().View()) + ttl := h.TTL() + if ttl == 0 { + // As per RFC 792 page 6, Time Exceeded Message, + // + // If the gateway processing a datagram finds the time to live field + // is zero it must discard the datagram. The gateway may also notify + // the source host via the time exceeded message. + return e.protocol.returnError(&icmpReasonTTLExceeded{}, pkt) + } + dstAddr := h.DestinationAddress() // Check if the destination is owned by the stack. @@ -503,13 +513,22 @@ 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.IPv4(stack.PayloadSince(pkt.NetworkHeader())) + + // As per RFC 791 page 30, Time to Live, + // + // This field must be decreased at each point that the internet header + // is processed to reflect the time spent processing the datagram. + // Even if no local information is available on the time actually + // spent, the field must be decremented by 1. + newHdr.SetTTL(ttl - 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(), })) } |