Nsc conntrack fix (#305)

* added conntrack exit handling logic

* fixed regex

* regex fix again

Author: roffe

app/controllers/network_services_controller.go

@@ -10,6 +10,7 @@ import (
 	"os"
 	"os/exec"
 	"reflect"
+	"regexp"
 	"runtime"
 	"strconv"
 	"strings"
@@ -295,6 +296,10 @@ type externalIPService struct {
 func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInfoMap, endpointsInfoMap endpointsInfoMap) error {
 
 	var ipvsSvcs []*ipvs.Service
+
+	// Conntrack exits with non zero exit code when exiting if 0 flow entries have been deleted, use regex to check output and don't Error when matching
+	re := regexp.MustCompile("([[:space:]]0 flow entries have been deleted.)")
+
 	start := time.Now()
 
 	defer func() {
@@ -615,9 +620,11 @@ func (nsc *NetworkServicesController) syncIpvsServices(serviceInfoMap serviceInf
 
 					// flush conntrack when endpoint for a UDP service changes
 					if ipvsSvc.Protocol == syscall.IPPROTO_UDP {
-						_, err := exec.Command("conntrack", "-D", "--orig-dst", dst.Address.String(), "-p", "udp", "--dport", strconv.Itoa(int(dst.Port))).Output()
+						out, err := exec.Command("conntrack", "-D", "--orig-dst", dst.Address.String(), "-p", "udp", "--dport", strconv.Itoa(int(dst.Port))).CombinedOutput()
 						if err != nil {
-							glog.Error("Failed to delete conntrack entry for endpoint: " + dst.Address.String() + ":" + strconv.Itoa(int(dst.Port)) + " due to " + err.Error())
+							if matched := re.MatchString(string(out)); !matched {
+								glog.Error("Failed to delete conntrack entry for endpoint: " + dst.Address.String() + ":" + strconv.Itoa(int(dst.Port)) + " due to " + err.Error())
+							}
 						}
 						glog.V(1).Infof("Deleted conntrack entry for endpoint: " + dst.Address.String() + ":" + strconv.Itoa(int(dst.Port)))
 					}