1. Added a basic version of network stats inside network package.

2. Introducing a new checkpoint file 'network.stats' which will contain the network runtime information (veth interface names for now).
3. Adding network stats to 'nsinit stats'.
4. Added a libcontainer Stats API to get both network and cgroup stats

Docker-DCO-1.1-Signed-off-by: Vishnu Kannan <vishnuk@google.com> (github: vishh)

api/api.go

@@ -0,0 +1,25 @@
+package api
+
+import (
+	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/cgroups/fs"
+
+	"github.com/docker/libcontainer/network"
+)
+
+// Returns all available stats for the given container.
+func GetContainerStats(container *libcontainer.Container, networkInfo *network.NetworkRuntimeInfo) (*ContainerStats, error) {
+	containerStats := NewContainerStats()
+	stats, err := fs.GetStats(container.Cgroups)
+	if err != nil {
+		return containerStats, err
+	}
+	containerStats.CgroupStats = stats
+	networkStats, err := network.GetStats(networkInfo)
+	if err != nil {
+		return containerStats, err
+	}
+	containerStats.NetworkStats = networkStats
+
+	return containerStats, nil
+}

api/types.go

@@ -0,0 +1,16 @@
+package api
+
+import (
+	"github.com/docker/libcontainer/cgroups"
+	"github.com/docker/libcontainer/network"
+)
+
+type ContainerStats struct {
+	NetworkStats network.NetworkStats `json:"network_stats, omitempty"`
+	CgroupStats  *cgroups.Stats       `json:"cgroup_stats, omitempty"`
+}
+
+func NewContainerStats() *ContainerStats {
+	cgroupStats := cgroups.NewStats()
+	return &ContainerStats{CgroupStats: cgroupStats}
+}

namespaces/exec.go

@@ -81,7 +81,7 @@ func Exec(container *libcontainer.Config, term Terminal, rootfs, dataPath string
 		defer cleaner.Cleanup()
 	}
 
-	if err := InitializeNetworking(container, command.Process.Pid, syncPipe); err != nil {
+	if err := InitializeNetworking(container, command.Process.Pid, syncPipe, dataPath); err != nil {
 		command.Process.Kill()
 		command.Wait()
 		return -1, err
@@ -156,14 +156,14 @@ func SetupCgroups(container *libcontainer.Config, nspid int) (cgroups.ActiveCgro
 
 // InitializeNetworking creates the container's network stack outside of the namespace and moves
 // interfaces into the container's net namespaces if necessary
-func InitializeNetworking(container *libcontainer.Config, nspid int, pipe *SyncPipe) error {
+func InitializeNetworking(container *libcontainer.Config, nspid int, pipe *SyncPipe, dataPath string) error {
 	context := map[string]string{}
 	for _, config := range container.Networks {
 		strategy, err := network.GetStrategy(config.Type)
 		if err != nil {
 			return err
 		}
-		if err := strategy.Create((*network.Network)(config), nspid, context); err != nil {
+		if err := strategy.Create((*network.Network)(config), nspid, context, dataPath); err != nil {
 			return err
 		}
 	}

network/checkpoint.go

@@ -0,0 +1,63 @@
+package network
+
+import (
+	"encoding/json"
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"path/filepath"
+)
+
+// Struct describing the network specific checkpoint that will be maintained by libcontainer for all running containers
+// This is an internal checkpoint, so do not depend on it outside of libcontainer.
+type NetworkRuntimeInfo struct {
+	// The name of the veth interface on the Host.
+	VethHost string `json:"veth_host,omitempty"`
+	// The name of the veth interface created inside the container for the child.
+	VethChild string `json:"veth_child,omitempty"`
+}
+
+// The name of the network checkpoint file
+const networkInfoFile = "network.json"
+
+var ErrNetworkRuntimeInfoNotFound = errors.New("Network Checkpoint not found")
+
+// Returns the path to the network checkpoint given the path to the base directory of network checkpoint.
+func getNetworkRuntimeInfoPath(basePath string) string {
+	return filepath.Join(basePath, networkInfoFile)
+}
+
+// Marshalls the input network runtime info struct into a json object and stores it inside basepath.
+func writeNetworkRuntimeInfo(networkInfo *NetworkRuntimeInfo, basePath string) error {
+	data, err := json.Marshal(networkInfo)
+	if err != nil {
+		return fmt.Errorf("Failed to checkpoint network runtime information - %s", err)
+	}
+	return ioutil.WriteFile(getNetworkRuntimeInfoPath(basePath), data, 0655)
+}
+
+// Loads the network runtime info from the checkpoint and returns the unmarshaled content.
+func LoadNetworkRuntimeInfo(basePath string) (NetworkRuntimeInfo, error) {
+	var networkRuntimeInfo NetworkRuntimeInfo
+	checkpointPath := getNetworkRuntimeInfoPath(basePath)
+	f, err := os.Open(checkpointPath)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return networkRuntimeInfo, ErrNetworkRuntimeInfoNotFound
+		}
+		return networkRuntimeInfo, err
+	}
+	defer f.Close()
+
+	if err := json.NewDecoder(f).Decode(&networkRuntimeInfo); err != nil {
+		return networkRuntimeInfo, err
+	}
+
+	return networkRuntimeInfo, nil
+}
+
+// Deletes the network checkpoint under basePath
+func deleteNetworkRuntimeInfo(basePath string) error {
+	return os.Remove(getNetworkRuntimeInfoPath(basePath))
+}

network/loopback.go

@@ -10,7 +10,7 @@ import (
 type Loopback struct {
 }
 
-func (l *Loopback) Create(n *Network, nspid int, context map[string]string) error {
+func (l *Loopback) Create(n *Network, nspid int, context map[string]string, _ string) error {
 	return nil
 }
 

network/netns.go

@@ -14,7 +14,7 @@ import (
 type NetNS struct {
 }
 
-func (v *NetNS) Create(n *Network, nspid int, context map[string]string) error {
+func (v *NetNS) Create(n *Network, nspid int, context map[string]string, _ string) error {
 	context["nspath"] = n.NsPath
 	return nil
 }

network/stats.go

@@ -0,0 +1,69 @@
+package network
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+)
+
+type NetworkStats struct {
+	RxBytes   uint64 `json:"rx_bytes,omitempty"`
+	RxPackets uint64 `json:"rx_packets,omitempty"`
+	RxErrors  uint64 `json:"rx_errors,omitempty"`
+	RxDropped uint64 `json:"rx_dropped,omitempty"`
+	TxBytes   uint64 `json:"tx_bytes,omitempty"`
+	TxPackets uint64 `json:"tx_packets,omitempty"`
+	TxErrors  uint64 `json:"tx_errors,omitempty"`
+	TxDropped uint64 `json:"tx_dropped,omitempty"`
+}
+
+// Returns the network statistics for the network interfaces represented by the NetworkRuntimeInfo.
+func GetStats(networkRuntimeInfo *NetworkRuntimeInfo) (NetworkStats, error) {
+	// This can happen if the network runtime information is missing - possible if the container was created by an old version of libcontainer.
+	if networkRuntimeInfo.VethHost == "" {
+		return NetworkStats{}, nil
+	}
+	data, err := readSysfsNetworkStats(networkRuntimeInfo.VethHost)
+	if err != nil {
+		return NetworkStats{}, err
+	}
+
+	return NetworkStats{RxBytes: data["rx_bytes"],
+		RxPackets: data["rx_packets"],
+		RxErrors:  data["rx_errors"],
+		RxDropped: data["rx_dropped"],
+		TxBytes:   data["tx_bytes"],
+		TxPackets: data["tx_packets"],
+		TxErrors:  data["tx_errors"],
+		TxDropped: data["tx_dropped"]}, nil
+}
+
+// Reads all the statistics available under /sys/class/net/<EthInterface>/statistics as a map with file name as key and data as integers.
+func readSysfsNetworkStats(ethInterface string) (map[string]uint64, error) {
+	out := make(map[string]uint64)
+
+	fullPath, err := filepath.Abs(filepath.Join("/sys/class/net", ethInterface, "statistics/"))
+	if err != nil {
+		return out, nil
+	}
+	err = filepath.Walk(fullPath, func(path string, _ os.FileInfo, _ error) error {
+		// skip fullPath.
+		if path == fullPath {
+			return nil
+		}
+		base := filepath.Base(path)
+		data, err := ioutil.ReadFile(path)
+		if err != nil {
+			return err
+		}
+		value, err := strconv.ParseUint(strings.TrimSpace(string(data)), 10, 64)
+		if err != nil {
+			return err
+		}
+		out[base] = value
+		return nil
+	})
+	return out, err
+}

network/strategy.go

@@ -19,7 +19,7 @@ var strategies = map[string]NetworkStrategy{
 // NetworkStrategy represents a specific network configuration for
 // a container's networking stack
 type NetworkStrategy interface {
-	Create(*Network, int, map[string]string) error
+	Create(*Network, int, map[string]string, string) error
 	Initialize(*Network, map[string]string) error
 }
 

network/veth.go

@@ -16,7 +16,7 @@ type Veth struct {
 
 const defaultDevice = "eth0"
 
-func (v *Veth) Create(n *Network, nspid int, context map[string]string) error {
+func (v *Veth) Create(n *Network, nspid int, context map[string]string, dataPath string) error {
 	var (
 		bridge = n.Bridge
 		prefix = n.VethPrefix
@@ -45,7 +45,8 @@ func (v *Veth) Create(n *Network, nspid int, context map[string]string) error {
 	if err := SetInterfaceInNamespacePid(name2, nspid); err != nil {
 		return err
 	}
-	return nil
+	networkRuntimeInfo := NetworkRuntimeInfo{VethHost: name1, VethChild: name2}
+	return writeNetworkRuntimeInfo(&networkRuntimeInfo, dataPath)
 }
 
 func (v *Veth) Initialize(config *Network, context map[string]string) error {

nsinit/stats.go

@@ -7,7 +7,8 @@ import (
 
 	"github.com/codegangsta/cli"
 	"github.com/docker/libcontainer"
-	"github.com/docker/libcontainer/cgroups/fs"
+	"github.com/docker/libcontainer/api"
+	"github.com/docker/libcontainer/network"
 )
 
 var statsCommand = cli.Command{
@@ -22,7 +23,12 @@ func statsAction(context *cli.Context) {
 		log.Fatal(err)
 	}
 
-	stats, err := getContainerStats(container)
+	networkRuntimeInfo, err := loadNetworkRuntimeInfo()
+	if err != nil {
+		log.Fatal(err)
+	}
+
+	stats, err := getContainerStats(container, &networkRuntimeInfo)
 	if err != nil {
 		log.Fatalf("Failed to get stats - %v\n", err)
 	}
@@ -31,8 +37,8 @@ func statsAction(context *cli.Context) {
 }
 
 // returns the container stats in json format.
-func getContainerStats(container *libcontainer.Config) (string, error) {
+func getContainerStats(container *libcontainer.Config, networkRuntimeInfo *network.NetworkRuntimeInfo) (string, error) {
-	stats, err := fs.GetStats(container.Cgroups)
+	stats, err := libcontainer.GetContainerStats(container, networkRuntimeInfo)
 	if err != nil {
 		return "", err
 	}

nsinit/utils.go

@@ -7,6 +7,7 @@ import (
 	"path/filepath"
 
 	"github.com/docker/libcontainer"
+	"github.com/docker/libcontainer/network"
 )
 
 func loadContainer() (*libcontainer.Config, error) {
@@ -24,6 +25,17 @@ func loadContainer() (*libcontainer.Config, error) {
 	return container, nil
 }
 
+func loadNetworkRuntimeInfo() (network.NetworkRuntimeInfo, error) {
+	data, err := network.LoadNetworkRuntimeInfo(dataPath)
+	if err != nil {
+		if err == network.ErrNetworkRuntimeInfoNotFound {
+			return network.NetworkRuntimeInfo{}, nil
+		}
+		return network.NetworkRuntimeInfo{}, err
+	}
+	return data, nil
+}
+
 func openLog(name string) error {
 	f, err := os.OpenFile(name, os.O_CREATE|os.O_RDWR|os.O_APPEND, 0755)
 	if err != nil {