flannel: added flannel support and helper to make dropins

fleet, flannel, and etcd all generate dropins from config.
To reduce code duplication, factor out a helper to do that.

Documentation/cloud-config.md

@@ -97,6 +97,29 @@ For more information on fleet configuration, see the [fleet documentation][fleet
 
 [fleet-config]: https://github.com/coreos/fleet/blob/master/Documentation/deployment-and-configuration.md#configuration
 
+#### flannel
+
+The `coreos.flannel.*` parameters also work very similarly to `coreos.etcd.*` and `coreos.fleet.*`. They can be used to set enviornment variables for flanneld. Given the following cloud-config...
+
+```yaml
+#cloud-config
+
+coreos:
+    flannel:
+        etcd-prefix: /coreos.com/network2
+```
+
+...will generate systemd unit drop-in like so:
+
+```
+[Service]
+Environment="FLANNELD_ETCD_PREFIX=/coreos.com/network2"
+```
+
+For complete list of flannel configuraion parameters, see the [flannel documentation][flannel-readme].
+
+[flannel-readme]: https://github.com/coreos/flannel/blob/master/README.md
+
 #### update
 
 The `coreos.update.*` parameters manipulate settings related to how CoreOS instances are updated.

config/config.go

@@ -31,6 +31,7 @@ type CloudConfig struct {
 	SSHAuthorizedKeys []string `yaml:"ssh_authorized_keys"`
 	Coreos            struct {
 		Etcd    Etcd    `yaml:"etcd"`
+		Flannel Flannel `yaml:"flannel"`
 		Fleet   Fleet   `yaml:"fleet"`
 		OEM     OEM     `yaml:"oem"`
 		Update  Update  `yaml:"update"`

config/flannel.go

@@ -0,0 +1,9 @@
+package config
+
+type Flannel struct {
+	EtcdEndpoint string `yaml:"etcd-endpoint" env:"FLANNELD_ETCD_ENDPOINT"`
+	EtcdPrefix   string `yaml:"etcd-prefix"   env:"FLANNELD_ETCD_PREFIX"`
+	IPMasq       string `yaml:"ip-masq"       env:"FLANNELD_IP_MASQ"`
+	SubnetFile   string `yaml:"subnet-file"   env:"FLANNELD_SUBNET_FILE"`
+	Iface        string `yaml:"interface"     env:"FLANNELD_IFACE"`
+}

initialize/config.go

@@ -131,6 +131,7 @@ func Apply(cfg config.CloudConfig, env *Environment) error {
 	for _, ccu := range []CloudConfigUnit{
 		system.Etcd{Etcd: cfg.Coreos.Etcd},
 		system.Fleet{Fleet: cfg.Coreos.Fleet},
+		system.Flannel{Flannel: cfg.Coreos.Flannel},
 		system.Update{Update: cfg.Coreos.Update, ReadConfig: system.DefaultReadConfig},
 	} {
 		units = append(units, ccu.Units()...)

system/env.go

@@ -19,6 +19,8 @@ package system
 import (
 	"fmt"
 	"reflect"
+
+	"github.com/coreos/coreos-cloudinit/config"
 )
 
 // dropinContents generates the contents for a drop-in unit given the config.
@@ -40,3 +42,16 @@ func dropinContents(e interface{}) string {
 	}
 	return "[Service]\n" + out
 }
+
+func dropinFromConfig(cfg interface{}, name string) []Unit {
+	content := dropinContents(cfg)
+	if content == "" {
+		return nil
+	}
+	return []Unit{{config.Unit{
+		Name:    name,
+		Runtime: true,
+		DropIn:  true,
+		Content: content,
+	}}}
+}

system/etcd.go

@@ -28,14 +28,5 @@ type Etcd struct {
 
 // Units creates a Unit file drop-in for etcd, using any configured options.
 func (ee Etcd) Units() []Unit {
-	content := dropinContents(ee.Etcd)
+	return dropinFromConfig(ee.Etcd, "etcd.service")
-	if content == "" {
-		return nil
-	}
-	return []Unit{{config.Unit{
-		Name:    "etcd.service",
-		Runtime: true,
-		DropIn:  true,
-		Content: content,
-	}}}
 }

system/flannel.go

@@ -0,0 +1,17 @@
+package system
+
+import (
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+// flannel is a top-level structure which embeds its underlying configuration,
+// config.Flannel, and provides the system-specific Unit().
+type Flannel struct {
+	config.Flannel
+}
+
+// Units generates a Unit file drop-in for flannel, if any flannel options were
+// configured in cloud-config
+func (fl Flannel) Units() []Unit {
+	return dropinFromConfig(fl.Flannel, "flannel.service")
+}

system/flannel_test.go

@@ -0,0 +1,40 @@
+package system
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/coreos/coreos-cloudinit/config"
+)
+
+func TestFlannelUnits(t *testing.T) {
+	for _, tt := range []struct {
+		config config.Flannel
+		units  []Unit
+	}{
+		{
+			config.Flannel{},
+			nil,
+		},
+		{
+			config.Flannel{
+				EtcdEndpoint: "http://12.34.56.78:4001",
+				EtcdPrefix:   "/coreos.com/network/tenant1",
+			},
+			[]Unit{{config.Unit{
+				Name: "flannel.service",
+				Content: `[Service]
+Environment="FLANNELD_ETCD_ENDPOINT=http://12.34.56.78:4001"
+Environment="FLANNELD_ETCD_PREFIX=/coreos.com/network/tenant1"
+`,
+				Runtime: true,
+				DropIn:  true,
+			}}},
+		},
+	} {
+		units := Flannel{tt.config}.Units()
+		if !reflect.DeepEqual(units, tt.units) {
+			t.Errorf("bad units (%q): want %v, got %v", tt.config, tt.units, units)
+		}
+	}
+}

system/fleet.go

@@ -29,14 +29,5 @@ type Fleet struct {
 // Units generates a Unit file drop-in for fleet, if any fleet options were
 // configured in cloud-config
 func (fe Fleet) Units() []Unit {
-	content := dropinContents(fe.Fleet)
+	return dropinFromConfig(fe.Fleet, "fleet.service")
-	if content == "" {
-		return nil
-	}
-	return []Unit{{config.Unit{
-		Name:    "fleet.service",
-		Runtime: true,
-		DropIn:  true,
-		Content: content,
-	}}}
 }