Merge pull request #622 from intel-go/agadiyar/decrementTTL

new example decrementTTL

examples/.gitignore

@@ -14,3 +14,4 @@ devbind
 OSforwarding
 generate
 jumbo
+decrementTTL

examples/Dockerfile

@@ -22,3 +22,4 @@ COPY netlink .
 COPY generate .
 COPY OSforwarding .
 COPY jumbo .
+COPY decrementTTL .

examples/Makefile

@@ -7,7 +7,8 @@ IMAGENAME = nff-go-examples
 EXECUTABLES = dump clonablePcapDumper kni copy errorHandling timer \
 		createPacket sendFixedPktsNumber gtpu pingReplay \
 		netlink gopacketParserExample devbind generate \
-		OSforwarding jumbo
+		OSforwarding jumbo decrementTTL
+
 SUBDIRS = tutorial antiddos demo fileReadWrite firewall forwarding ipsec lb
 
 .PHONY: dpi nffPktgen

examples/decrementTTL.go

@@ -0,0 +1,40 @@
+// Copyright 2017 Intel Corporation.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+import (
+	"flag"
+
+	"github.com/intel-go/nff-go/flow"
+	"github.com/intel-go/nff-go/packet"
+)
+
+// Main function for constructing packet processing graph.
+func main() {
+	inPort := flag.Uint("inPort", 0, "port for receiver")
+	outPort := flag.Uint("outPort", 1, "port for sender")
+	flag.Parse()
+
+	flow.SystemInit(nil)
+	inputFlow, _ := flow.SetReceiver(uint16(*inPort))
+	flow.SetHandlerDrop(inputFlow, decrementTTL, nil)
+	flow.SetSender(inputFlow, uint16(*outPort))
+	flow.SystemStart()
+}
+
+func decrementTTL(current *packet.Packet, c flow.UserContext) bool {
+	current.ParseL3() // must parse before header can be read
+	header := current.GetIPv4()
+	if header == nil { // not IPv4
+		return false
+	}
+
+	header.TimeToLive--
+	if header.TimeToLive == 0 { // TTL exceeded, drop
+		return false
+	} else {
+		return true
+	}
+}