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netstack: add ICMP echo forwarder reply API #13413

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netstack: add ICMP echo forwarder reply API #13413

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31 changes: 25 additions & 6 deletions pkg/tcpip/network/ipv4/icmp.go
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Original file line number Diff line number Diff line change
Expand Up @@ -356,8 +356,19 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
// DeliverTransportPacket so that is is only done when needed.
replyData := stack.PayloadSince(pkt.TransportHeader())
defer replyData.Release()
localAddressTemporary := pkt.NetworkPacketInfo.LocalAddressTemporary
ipHdr := iph
localAddressBroadcast := pkt.NetworkPacketInfo.LocalAddressBroadcast
localAddressTemporary := pkt.NetworkPacketInfo.LocalAddressTemporary
replied := false
reply := func() bool {
if replied {
return true
}
replied = true
e.sendICMPEchoReply(replyData, ipHdr, newOptions, localAddressBroadcast, localAddressTemporary)
return true
}
pkt.SetICMPEchoReply(reply)

// It's possible that a raw socket or per-stack default handler expects
// to receive this packet.
Expand All @@ -367,17 +378,17 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
} else {
e.dispatcher.DeliverTransportPacket(header.ICMPv4ProtocolNumber, pkt)
}
pkt.ClearICMPEchoReply()
pkt = nil

// Skip the built-in ICMP echo reply if the request was consumed by a
// per-stack default handler. Also preserve the IPv4 behavior for
// temporary local addresses: the packet is delivered above, but the
// stack does not synthesize an echo reply for it.
// temporary local addresses unless the handler explicitly replied above.
if defaultHandlerHandled || localAddressTemporary {
return
}

e.sendICMPEchoReply(replyData, iph, newOptions, localAddressBroadcast)
reply()

case header.ICMPv4EchoReply:
received.echoReply.Increment()
Expand Down Expand Up @@ -421,6 +432,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
case header.ICMPv4DestinationHostUnknown:
e.handleControl(&icmpv4DestinationHostUnknownSockError{}, pkt)
}

case header.ICMPv4SrcQuench:
received.srcQuench.Increment()

Expand Down Expand Up @@ -450,7 +462,7 @@ func (e *endpoint) handleICMP(pkt *stack.PacketBuffer) {
}
}

func (e *endpoint) sendICMPEchoReply(replyData *buffer.View, ipHdr header.IPv4, newOptions header.IPv4Options, localAddressBroadcast bool) {
func (e *endpoint) sendICMPEchoReply(replyData *buffer.View, ipHdr header.IPv4, newOptions header.IPv4Options, localAddressBroadcast, localAddressTemporary bool) {
sent := e.stats.icmp.packetsSent
if !e.protocol.allowICMPReply(header.ICMPv4EchoReply, header.ICMPv4UnusedCode) {
sent.rateLimited.Increment()
Expand All @@ -461,8 +473,12 @@ func (e *endpoint) sendICMPEchoReply(replyData *buffer.View, ipHdr header.IPv4,
// source address MUST be one of its own IP addresses (but not a broadcast
// or multicast address).
localAddr := ipHdr.DestinationAddress()
replySourceAddr := localAddr
if localAddressBroadcast || header.IsV4MulticastAddress(localAddr) {
localAddr = tcpip.Address{}
replySourceAddr = tcpip.Address{}
} else if localAddressTemporary {
localAddr = tcpip.Address{}
}

r, err := e.protocol.stack.FindRoute(e.nic.ID(), localAddr, ipHdr.SourceAddress(), ProtocolNumber, false /* multicastLoop */)
Expand Down Expand Up @@ -507,7 +523,10 @@ func (e *endpoint) sendICMPEchoReply(replyData *buffer.View, ipHdr header.IPv4,
replyIPHdrView.Write(newOptions)
replyIPHdr := header.IPv4(replyIPHdrView.AsSlice())
replyIPHdr.SetHeaderLength(replyHeaderLength)
replyIPHdr.SetSourceAddress(r.LocalAddress())
if replySourceAddr.BitLen() == 0 {
replySourceAddr = r.LocalAddress()
}
replyIPHdr.SetSourceAddress(replySourceAddr)
replyIPHdr.SetDestinationAddress(r.RemoteAddress())
replyIPHdr.SetTTL(r.DefaultTTL())
replyIPHdr.SetTotalLength(uint16(len(replyIPHdr) + len(replyData.AsSlice())))
Expand Down
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