Arping capabilities for CNM

New config option will allow to configure libnetwork
to automatically arping and advertise ARP bindings
on container IFup.

Signed-off-by: eduards <eduards@plumgrid.com>

Author: eduards

plugin/driver/config.go

@@ -15,16 +15,18 @@
 package driver
 
 import (
-	"github.com/alyu/configparser"
 	"log"
+
+	"github.com/alyu/configparser"
 )
 
 var (
-	vip            string
-	username       string
-	password       string
-	default_vd     string
-	scope          string
+	vip        string
+	username   string
+	password   string
+	default_vd string
+	scope      string
+	auto_arp   bool = false
 )
 
 // Read configuration file
@@ -43,6 +45,7 @@ func ReadConfig() {
 		username = pg_section.ValueOf("pg_username")
 		password = pg_section.ValueOf("pg_password")
 		default_vd = pg_section.ValueOf("default_domain")
+
 	}
 
 	// get Libnetwork config
@@ -51,5 +54,6 @@ func ReadConfig() {
 		log.Fatal(lib_err)
 	} else {
 		scope = lib_section.ValueOf("scope")
+		auto_arp = lib_section.Exists("auto_arp")
 	}
 }

plugin/driver/driver.go

@@ -23,6 +23,7 @@ import (
 	"net"
 	"net/http"
 	"os/exec"
+	"runtime"
 
 	Log "github.com/Sirupsen/logrus"
 	"github.com/docker/libnetwork/drivers/remote/api"
@@ -331,6 +332,23 @@ func (driver *driver) joinEndpoint(w http.ResponseWriter, r *http.Request) {
 
 	objectResponse(w, res)
 	Log.Infof("Join endpoint %s:%s to %s", j.NetworkID, j.EndpointID, j.SandboxKey)
+
+	if auto_arp {
+		go func(net_ns_path string, pg_ifc_prefix string) {
+
+			// Disallow this goroutine to work on any other thread than this one
+			// since namespace ops (unshare, setns) are done for a single thread, we
+			// must ensure that the goroutine does not jump from OS thread to thread
+			runtime.LockOSThread()
+			defer runtime.UnlockOSThread()
+
+			err := RunContainerArping(net_ns_path, pg_ifc_prefix)
+			if err != nil {
+				Log.Printf("Error while running arping : %v", err)
+			}
+
+		}(j.SandboxKey, ifname.DstPrefix)
+	}
 }
 
 // leave call

plugin/driver/network_utils.go

@@ -0,0 +1,159 @@
+// Copyright 2016 PLUMgrid
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.package main
+
+package driver
+
+import (
+	"fmt"
+	"net"
+	"strings"
+	"time"
+
+	"github.com/google/gopacket"
+	"github.com/google/gopacket/layers"
+	"github.com/google/gopacket/pcap"
+
+	Log "github.com/Sirupsen/logrus"
+	"github.com/eduser25/cni/pkg/ns"
+)
+
+// Plumgrid just specifies the prefix, so we will arping on all ifcs
+// that match with the prefix given to libnetwork
+func RunContainerArping(net_ns_path string, pg_ifc_prefix string) error {
+
+	Log.Printf("Attempting to acces the container %s NetNS", net_ns_path)
+	var netns ns.NetNS
+	var err error
+	success := false
+
+	for attempts := 0; attempts <= 5; attempts++ {
+
+		netns, err = ns.GetNS(net_ns_path)
+
+		if err != nil {
+			Log.Printf("Attempt %d: failed to open netns %s: %v", attempts, net_ns_path, err)
+			time.Sleep(1 * time.Second)
+		} else {
+			success = true
+			break
+		}
+		attempts += 1
+	}
+
+	if !success {
+		return fmt.Errorf("Attempts exhaused, could not access %s, exiting", net_ns_path)
+	}
+	defer netns.Close()
+
+	// Let's go in
+	err = netns.Do(func(_ ns.NetNS) error {
+
+		// Get Ifcs on container
+		ifc_list, err := net.Interfaces()
+		if err != nil {
+			return fmt.Errorf("Failed to get interfaces in Netns: %v", err)
+		}
+
+		// Iterate Ifcs
+		for _, ifc := range ifc_list {
+			if strings.HasPrefix(ifc.Name, pg_ifc_prefix) {
+				// Valid PG-created ifc
+
+				// TODO we might want to add a retry here to make sure,
+				// in case the IFC is up but still has no IP, we retry
+				address_slice, err := ifc.Addrs()
+				if err != nil {
+					Log.Errorf("Failed to get Address slice for ifc %s: %v", ifc.Name, err)
+					continue
+				}
+
+				if len(address_slice) == 0 {
+					Log.Errorf("Interface %s had no IP address at the moment we checked", ifc.Name)
+					continue
+				}
+
+				Log.Printf("Attempting raw socket open on %s", ifc.Name)
+				handle, err := pcap.OpenLive(ifc.Name, 65536, true, pcap.BlockForever)
+				if err != nil {
+					return fmt.Errorf("Failed to open raw socket %s : %v", ifc.Name, err)
+				}
+
+				// We will just arping for all IPv4 addresses on this ifc, just in case
+				for _, ifc_addr := range address_slice {
+					ip, _, err := net.ParseCIDR(ifc_addr.String())
+					if err != nil {
+						Log.Printf("Failed to parse network %s : %v", ifc_addr.String(), err)
+						continue
+					}
+
+					if ip.To4() == nil {
+						// ignoring IPV6 addr
+						continue
+					}
+
+					// Get ARP packet
+					arp_pkt := getGratuitousArp(ifc.HardwareAddr, ip)
+
+					for i := 0; i <= 3; i++ {
+						Log.Printf("Sending %d GARP on %s : %s - %s",
+							i, ifc.Name, ifc.HardwareAddr.String(), ip.String())
+
+						if err := handle.WritePacketData(arp_pkt); err != nil {
+							handle.Close()
+							return fmt.Errorf("Failed to write ARP packet data on %s : %v", ifc.Name, err)
+						}
+						time.Sleep(750 * time.Millisecond)
+					}
+				}
+
+				// Close the socket
+				handle.Close()
+			}
+		}
+		return nil
+	})
+
+	return err
+}
+
+func getGratuitousArp(mac net.HardwareAddr, ip net.IP) []byte {
+	// Set up all the layers' fields we can.
+	eth := layers.Ethernet{
+		SrcMAC:       mac,
+		DstMAC:       net.HardwareAddr{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+		EthernetType: layers.EthernetTypeARP,
+	}
+	arp := layers.ARP{
+		AddrType:          layers.LinkTypeEthernet,
+		Protocol:          layers.EthernetTypeIPv4,
+		HwAddressSize:     6,
+		ProtAddressSize:   4,
+		Operation:         layers.ARPReply,
+		SourceHwAddress:   mac,
+		SourceProtAddress: ip.To4(),
+		DstHwAddress:      []byte{0xff, 0xff, 0xff, 0xff, 0xff, 0xff},
+		DstProtAddress:    ip.To4(),
+	}
+	// Set up buffer and options for serialization.
+	buf := gopacket.NewSerializeBuffer()
+
+	opts := gopacket.SerializeOptions{
+		FixLengths:       true,
+		ComputeChecksums: true,
+	}
+	// Send one packet for every address.
+	gopacket.SerializeLayers(buf, opts, &eth, &arp)
+
+	return buf.Bytes()
+}