kubenet: fix up CNI bridge TX queue length if needed

pkg/kubelet/network/kubenet/kubenet_linux.go

@@ -26,6 +26,7 @@ import (
 	"syscall"
 
 	"github.com/vishvananda/netlink"
+	"github.com/vishvananda/netlink/nl"
 
 	"github.com/appc/cni/libcni"
 	"github.com/golang/glog"
@@ -197,6 +198,37 @@ func (plugin *kubenetNetworkPlugin) clearBridgeAddressesExcept(keep string) {
 	}
 }
 
+// ensureBridgeTxQueueLen() ensures that the bridge interface's TX queue
+// length is greater than zero.  Due to a CNI <= 0.3.0 'bridge' plugin bug,
+// the bridge is initially created with a TX queue length of 0, which gets
+// used as the packet limit for FIFO traffic shapers, which drops packets.
+// TODO: remove when we can depend on a fixed CNI
+func (plugin *kubenetNetworkPlugin) ensureBridgeTxQueueLen() {
+	bridge, err := netlink.LinkByName(BridgeName)
+	if err != nil {
+		return
+	}
+
+	if bridge.Attrs().TxQLen > 0 {
+		return
+	}
+
+	req := nl.NewNetlinkRequest(syscall.RTM_NEWLINK, syscall.NLM_F_ACK)
+	msg := nl.NewIfInfomsg(syscall.AF_UNSPEC)
+	req.AddData(msg)
+
+	nameData := nl.NewRtAttr(syscall.IFLA_IFNAME, nl.ZeroTerminated(BridgeName))
+	req.AddData(nameData)
+
+	qlen := nl.NewRtAttr(syscall.IFLA_TXQLEN, nl.Uint32Attr(1000))
+	req.AddData(qlen)
+
+	_, err = req.Execute(syscall.NETLINK_ROUTE, 0)
+	if err != nil {
+		glog.V(5).Infof("Failed to set bridge tx queue length: %v", err)
+	}
+}
+
 func (plugin *kubenetNetworkPlugin) Name() string {
 	return KubenetPluginName
 }
@@ -244,6 +276,7 @@ func (plugin *kubenetNetworkPlugin) SetUpPod(namespace string, name string, id k
 		if plugin.shaper == nil {
 			return fmt.Errorf("Failed to create bandwidth shaper!")
 		}
+		plugin.ensureBridgeTxQueueLen()
 		plugin.shaper.ReconcileInterface()
 	}