Protect initializedIfnames with mutex

With booster 0.8 release network udev events are handled concurrently.
initializedIfnames slice might be modified by different threads.
To prevent corruption we need to proted the access with mutex.

Issue #155

init/network.go

@@ -6,6 +6,7 @@ import (
 	"net"
 	"os"
 	"strings"
+	"sync"
 	"time"
 
 	"github.com/insomniacslk/dhcp/dhcpv4"
@@ -69,7 +70,10 @@ func runDhcp(ifname string) error {
 }
 
 func shutdownNetwork() {
-	for _, ifname := range initializedIfnames {
+	initializedIfnames.Lock()
+	defer initializedIfnames.Unlock()
+
+	for _, ifname := range initializedIfnames.v {
 		debug("shutting down network interface %s", ifname)
 		link, err := netlink.LinkByName(ifname)
 		if err != nil {
@@ -90,7 +94,10 @@ func shutdownNetwork() {
 	}
 }
 
-var initializedIfnames []string
+var initializedIfnames = struct {
+	v []string
+	sync.Mutex
+}{}
 
 func initializeNetworkInterface(ifname string) error {
 	debug("%s: start initializing network interface", ifname)
@@ -109,7 +116,9 @@ func initializeNetworkInterface(ifname string) error {
 	if err := netlink.LinkSetUp(link); err != nil {
 		return err
 	}
-	initializedIfnames = append(initializedIfnames, ifname)
+	initializedIfnames.Lock()
+	initializedIfnames.v = append(initializedIfnames.v, ifname)
+	initializedIfnames.Unlock()
 
 	timeout := time.After(20 * time.Second)
 	debug("%s waiting interface to be UP", ifname)