Allow mtu to be configured at daemon start

config.go

@@ -18,6 +18,7 @@ type DaemonConfig struct {
 	DefaultIp                   net.IP
 	InterContainerCommunication bool
 	GraphDriver                 string
+	Mtu                         int
 }
 
 // ConfigFromJob creates and returns a new DaemonConfig object
@@ -41,5 +42,10 @@ func ConfigFromJob(job *engine.Job) *DaemonConfig {
 	config.DefaultIp = net.ParseIP(job.Getenv("DefaultIp"))
 	config.InterContainerCommunication = job.GetenvBool("InterContainerCommunication")
 	config.GraphDriver = job.Getenv("GraphDriver")
+	if mtu := job.GetenvInt("Mtu"); mtu != -1 {
+		config.Mtu = mtu
+	} else {
+		config.Mtu = DefaultNetworkMtu
+	}
 	return &config
 }

container.go

@@ -582,7 +582,7 @@ func (container *Container) Start() (err error) {
 		params = append(params,
 			"-g", network.Gateway,
 			"-i", fmt.Sprintf("%s/%d", network.IPAddress, network.IPPrefixLen),
-			"-mtu", "1500",
+			"-mtu", strconv.Itoa(container.runtime.config.Mtu),
 		)
 	}
 

docker/docker.go

@@ -40,6 +40,7 @@ func main() {
 		flInterContainerComm = flag.Bool("icc", true, "Enable inter-container communication")
 		flGraphDriver        = flag.String("s", "", "Force the docker runtime to use a specific storage driver")
 		flHosts              = docker.NewListOpts(docker.ValidateHost)
+		flMtu                = flag.Int("mtu", docker.DefaultNetworkMtu, "Set the containers network mtu")
 	)
 	flag.Var(&flDns, "dns", "Force docker to use specific DNS servers")
 	flag.Var(&flHosts, "H", "Multiple tcp://host:port or unix://path/to/socket to bind in daemon mode, single connection otherwise")
@@ -87,6 +88,7 @@ func main() {
 		job.Setenv("DefaultIp", *flDefaultIp)
 		job.SetenvBool("InterContainerCommunication", *flInterContainerComm)
 		job.Setenv("GraphDriver", *flGraphDriver)
+		job.SetenvInt("Mtu", *flMtu)
 		if err := job.Run(); err != nil {
 			log.Fatal(err)
 		}

docs/sources/commandline/cli.rst

@@ -37,6 +37,7 @@ To list available commands, either run ``docker`` with no parameters or execute
       -icc=true: Enable inter-container communication
       -ip="0.0.0.0": Default IP address to use when binding container ports
       -iptables=true: Disable docker's addition of iptables rules
+      -mtu=1500: Set the containers network mtu
       -p="/var/run/docker.pid": Path to use for daemon PID file
       -r=true: Restart previously running containers
       -s="": Force the docker runtime to use a specific storage driver

integration/utils_test.go

@@ -32,6 +32,7 @@ func mkRuntime(f utils.Fataler) *docker.Runtime {
 	config := &docker.DaemonConfig{
 		Root:        root,
 		AutoRestart: false,
+		Mtu:         docker.DefaultNetworkMtu,
 	}
 	r, err := docker.NewRuntimeFromDirectory(config)
 	if err != nil {

network.go

@@ -19,6 +19,7 @@ import (
 const (
 	DefaultNetworkBridge = "docker0"
 	DisableNetworkBridge = "none"
+	DefaultNetworkMtu    = 1500
 	portRangeStart       = 49153
 	portRangeEnd         = 65535
 	siocBRADDBR          = 0x89a0
@@ -118,7 +119,6 @@ func CreateBridgeIface(config *DaemonConfig) error {
 		"192.168.44.1/24",
 	}
 
-
 	nameservers := []string{}
 	resolvConf, _ := utils.GetResolvConf()
 	// we don't check for an error here, because we don't really care