added mtu param

DOCS.md

@@ -15,6 +15,7 @@ Use the Docker plugin to build and push Docker images to a registry. The followi
 * `storage_driver` - use `aufs`, `devicemapper`, `btrfs` or `overlay` driver
 * `storage_path` - location of docker daemon storage on disk
 * `build_args` - [build arguments](https://docs.docker.com/engine/reference/commandline/build/#set-build-time-variables-build-arg) to pass to `docker build`
+* `mtu` - custom [mtu settings](https://docs.docker.com/v1.8/articles/networking/#docker0) when starting the docker daemon
 
 The following is a sample Docker configuration in your .drone.yml file:
 

main.go

@@ -58,6 +58,11 @@ func main() {
 			Usage:  "docker daemon bride ip address",
 			EnvVar: "PLUGIN_BIP",
 		},
+		cli.StringFlag{
+			Name:   "daemon.mtu",
+			Usage:  "docker daemon custom mtu setting",
+			EnvVar: "PLUGIN_MTU",
+		},
 		cli.StringSliceFlag{
 			Name:   "daemon.dns",
 			Usage:  "docker daemon dns server",
@@ -164,6 +169,7 @@ func run(c *cli.Context) {
 			Debug:         c.Bool("daemon.debug"),
 			Bip:           c.String("daemon.bip"),
 			DNS:           c.StringSlice("daemon.dns"),
+			MTU:		   c.String("daemon.mtu"),
 		},
 	}
 

plugin.go

@@ -21,6 +21,7 @@ type (
 		Debug         bool     // Docker daemon started in debug mode
 		Bip           string   // Docker daemon network bridge IP address
 		DNS           []string // Docker daemon dns server
+		MTU			  string   // Docker daemon mtu setting
 	}
 
 	// Login defines Docker login parameters.
@@ -206,6 +207,9 @@ func commandDaemon(daemon Daemon) *exec.Cmd {
 	for _, dns := range daemon.DNS {
 		args = append(args, "--dns", dns)
 	}
+	if len(daemon.MTU) != 0 {
+		args = append(args, "--mtu", daemon.MTU)
+	}
 	return exec.Command(dockerExe, args...)
 }