diff options
author | gVisor bot <gvisor-bot@google.com> | 2020-11-13 21:17:13 +0000 |
---|---|---|
committer | gVisor bot <gvisor-bot@google.com> | 2020-11-13 21:17:13 +0000 |
commit | 4e9636928b2b9e596c9430c13d586afad9058fd2 (patch) | |
tree | 49cec3c3d4063203df1ba269ab0ecf5582f18dff /pkg/tcpip/network/ipv4 | |
parent | 5db8a54b3fe642484c49c597787407533c3a3de2 (diff) | |
parent | 6c0f53002a7f3a518befbe667d308c3d64cc9a59 (diff) |
Merge release-20201030.0-91-g6c0f53002 (automated)
Diffstat (limited to 'pkg/tcpip/network/ipv4')
-rw-r--r-- | pkg/tcpip/network/ipv4/icmp.go | 33 | ||||
-rw-r--r-- | pkg/tcpip/network/ipv4/ipv4.go | 29 |
2 files changed, 56 insertions, 6 deletions
diff --git a/pkg/tcpip/network/ipv4/icmp.go b/pkg/tcpip/network/ipv4/icmp.go index 9b5e37fee..58a19e74a 100644 --- a/pkg/tcpip/network/ipv4/icmp.go +++ b/pkg/tcpip/network/ipv4/icmp.go @@ -290,6 +290,13 @@ type icmpReasonProtoUnreachable struct{} func (*icmpReasonProtoUnreachable) isICMPReason() {} +// icmpReasonTTLExceeded is an error where a packet's time to live exceeded in +// transit to its final destination, as per RFC 792 page 6, Time Exceeded +// Message. +type icmpReasonTTLExceeded struct{} + +func (*icmpReasonTTLExceeded) 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. @@ -342,11 +349,31 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi return nil } + // If we hit a TTL Exceeded error, then we know we are operating as a router. + // 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. + // + // ... + // + // Code 0 may be received from a gateway. ... + // + // Note, Code 0 is the TTL exceeded error. + // + // If we are operating as a router/gateway, don't use the packet's destination + // address as the response's source address as we should not not own the + // destination address of a packet we are forwarding. + localAddr := origIPHdrDst + if _, ok := reason.(*icmpReasonTTLExceeded); 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 } @@ -454,6 +481,10 @@ func (p *protocol) returnError(reason icmpReason, pkt *stack.PacketBuffer) *tcpi icmpHdr.SetType(header.ICMPv4DstUnreachable) icmpHdr.SetCode(header.ICMPv4ProtoUnreachable) counter = sent.DstUnreachable + case *icmpReasonTTLExceeded: + icmpHdr.SetType(header.ICMPv4TimeExceeded) + icmpHdr.SetCode(header.ICMPv4TTLExceeded) + counter = sent.TimeExceeded case *icmpReasonReassemblyTimeout: icmpHdr.SetType(header.ICMPv4TimeExceeded) icmpHdr.SetCode(header.ICMPv4ReassemblyTimeout) 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(), })) } |