feat: add ability to specify the initial container network

Closes #4477

plugins/network/network.go

@@ -20,11 +20,14 @@ var (
 		"bind-all-interfaces": "false",
 		"attach-post-create":  "",
 		"attach-post-deploy":  "",
+		"initial-network":     "",
 		"tld":                 "",
 	}
 
 	// GlobalProperties is a map of all valid global network properties
-	GlobalProperties = map[string]bool{}
+	GlobalProperties = map[string]bool{
+		"initial-network": true,
+	}
 )
 
 // BuildConfig builds network config files

plugins/network/report.go

@@ -13,10 +13,13 @@ func ReportSingleApp(appName string, format string, infoFlag string) error {
 	}
 
 	flags := map[string]common.ReportFunc{
-		"--network-bind-all-interfaces": reportBindAllInterfaces,
-		"--network-attach-post-create":  reportAttachPostCreate,
-		"--network-attach-post-deploy":  reportAttachPostDeploy,
-		"--network-web-listeners":       reportWebListeners,
+		"--network-bind-all-interfaces":      reportBindAllInterfaces,
+		"--network-attach-post-create":       reportAttachPostCreate,
+		"--network-attach-post-deploy":       reportAttachPostDeploy,
+		"--network-computed-initial-network": reportComputedInitialNetwork,
+		"--network-global-initial-network":   reportGlobalInitialNetwork,
+		"--network-initial-network":          reportInitialNetwork,
+		"--network-web-listeners":            reportWebListeners,
 	}
 
 	flagKeys := []string{}
@@ -42,6 +45,23 @@ func reportAttachPostDeploy(appName string) string {
 	return common.PropertyGet("network", appName, "attach-post-deploy")
 }
 
+func reportComputedInitialNetwork(appName string) string {
+	value := reportInitialNetwork(appName)
+	if value == "" {
+		value = reportGlobalInitialNetwork(appName)
+	}
+
+	return value
+}
+
+func reportGlobalInitialNetwork(appName string) string {
+	return common.PropertyGet("network", "--global", "initial-network")
+}
+
+func reportInitialNetwork(appName string) string {
+	return common.PropertyGet("network", appName, "initial-network")
+}
+
 func reportWebListeners(appName string) string {
 	return strings.Join(GetListeners(appName, "web"), " ")
 }

plugins/network/src/triggers/triggers.go

@@ -18,6 +18,15 @@ func main() {
 
 	var err error
 	switch trigger {
+	case "docker-args-process-build":
+		appName := flag.Arg(0)
+		err = network.TriggerDockerArgsProcess(appName)
+	case "docker-args-process-deploy":
+		appName := flag.Arg(0)
+		err = network.TriggerDockerArgsProcess(appName)
+	case "docker-args-process-run":
+		appName := flag.Arg(0)
+		err = network.TriggerDockerArgsProcess(appName)
 	case "install":
 		err = network.TriggerInstall()
 	case "network-build-config":

plugins/network/triggers.go

@@ -2,6 +2,7 @@ package network
 
 import (
 	"fmt"
+	"io/ioutil"
 	"os"
 	"strings"
 	"unicode/utf8"
@@ -10,6 +11,22 @@ import (
 	"github.com/dokku/dokku/plugins/config"
 )
 
+// TriggerDockerArgsProcess outputs the network plugin docker options for an app
+func TriggerDockerArgsProcess(appName string) error {
+	stdin, err := ioutil.ReadAll(os.Stdin)
+	if err != nil {
+		return err
+	}
+
+	initialNetwork := reportComputedInitialNetwork(appName)
+	if initialNetwork != "" {
+		fmt.Printf(" --network=%s ", initialNetwork)
+	}
+
+	fmt.Print(string(stdin))
+	return nil
+}
+
 // TriggerInstall runs the install step for the network plugin
 func TriggerInstall() error {
 	if err := common.PropertySetup("network"); err != nil {