From 4779f1d2bfaa2feeda1378a597b79f48a0f6c236 Mon Sep 17 00:00:00 2001
From: Paul Fisher <pfisher@lyft.com>
Date: Wed, 1 Nov 2017 10:14:04 -0700
Subject: [PATCH] ipvlan: support enslaving an interface returned by ipam

For IP allocation schemes that cannot be interface agnostic, master can be set
to "ipam". In this configuration, the IPAM plugin is required to return a single
interface name for the ipvlan plugin to enslave.
---
 plugins/main/ipvlan/README.md      |  3 ++-
 plugins/main/ipvlan/ipvlan.go      | 20 ++++++++++++-----
 plugins/main/ipvlan/ipvlan_test.go | 36 ++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 6 deletions(-)

diff --git a/plugins/main/ipvlan/README.md b/plugins/main/ipvlan/README.md
index 988555ef..f0abc4f5 100644
--- a/plugins/main/ipvlan/README.md
+++ b/plugins/main/ipvlan/README.md
@@ -27,7 +27,7 @@ Because all ipvlan interfaces share the MAC address with the host interface, DHC
 
 * `name` (string, required): the name of the network.
 * `type` (string, required): "ipvlan".
-* `master` (string, required): name of the host interface to enslave.
+* `master` (string, required): name of the host interface to enslave or "ipam" to enslave an interface returned by ipam.
 * `mode` (string, optional): one of "l2", "l3". Defaults to "l2".
 * `mtu` (integer, optional): explicitly set MTU to the specified value. Defaults to the value chosen by the kernel.
 * `ipam` (dictionary, required): IPAM configuration to be used for this network.
@@ -38,3 +38,4 @@ Because all ipvlan interfaces share the MAC address with the host interface, DHC
 Therefore the container will not be able to reach the host via `ipvlan` interface.
 Be sure to also have container join a network that provides connectivity to the host (e.g. `ptp`).
 * A single master interface can not be enslaved by both `macvlan` and `ipvlan`.
+* For IP allocation schemes that cannot be interface agnostic, master can be set to `ipam`. In this configuration, the ipam plugin is required to return a single interface name for the ipvlan plugin to enslave.
diff --git a/plugins/main/ipvlan/ipvlan.go b/plugins/main/ipvlan/ipvlan.go
index 74a98863..73cd5a54 100644
--- a/plugins/main/ipvlan/ipvlan.go
+++ b/plugins/main/ipvlan/ipvlan.go
@@ -138,11 +138,6 @@ func cmdAdd(args *skel.CmdArgs) error {
 	}
 	defer netns.Close()
 
-	ipvlanInterface, err := createIpvlan(n, args.IfName, netns)
-	if err != nil {
-		return err
-	}
-
 	// run the IPAM plugin and get back the config to apply
 	r, err := ipam.ExecAdd(n.IPAM.Type, args.StdinData)
 	if err != nil {
@@ -157,6 +152,21 @@ func cmdAdd(args *skel.CmdArgs) error {
 	if len(result.IPs) == 0 {
 		return errors.New("IPAM plugin returned missing IP config")
 	}
+
+	if n.Master == "ipam" {
+		// Use an IPAM supplied master interface
+		if len(result.Interfaces) == 1 && result.Interfaces[0].Name != "" {
+			n.Master = result.Interfaces[0].Name
+		} else {
+			return errors.New("IPAM plugin returned missing master interface")
+		}
+	}
+
+	ipvlanInterface, err := createIpvlan(n, args.IfName, netns)
+	if err != nil {
+		return err
+	}
+
 	for _, ipc := range result.IPs {
 		// All addresses belong to the ipvlan interface
 		ipc.Interface = current.Int(0)
diff --git a/plugins/main/ipvlan/ipvlan_test.go b/plugins/main/ipvlan/ipvlan_test.go
index a2b92179..94ac3bf9 100644
--- a/plugins/main/ipvlan/ipvlan_test.go
+++ b/plugins/main/ipvlan/ipvlan_test.go
@@ -224,4 +224,40 @@ var _ = Describe("ipvlan Operations", func() {
 		})
 		Expect(err).NotTo(HaveOccurred())
 	})
+
+	It("errors if master should originate from ipam but an ipam interface is not returned", func() {
+		const IFNAME = "ipvl0"
+
+		conf := `{
+    "cniVersion": "0.3.1",
+    "name": "mynet",
+    "type": "ipvlan",
+    "master": "ipam",
+    "ipam": {
+        "type": "host-local",
+        "subnet": "10.1.2.0/24"
+    }
+}`
+		targetNs, err := ns.NewNS()
+		Expect(err).NotTo(HaveOccurred())
+		defer targetNs.Close()
+
+		args := &skel.CmdArgs{
+			ContainerID: "dummy",
+			Netns:       targetNs.Path(),
+			IfName:      IFNAME,
+			StdinData:   []byte(conf),
+		}
+
+		err = originalNS.Do(func(ns.NetNS) error {
+			defer GinkgoRecover()
+
+			_, _, err := testutils.CmdAddWithResult(targetNs.Path(), IFNAME, []byte(conf), func() error {
+				return cmdAdd(args)
+			})
+			Expect(err.Error()).To(Equal("IPAM plugin returned missing master interface"))
+			return nil
+		})
+		Expect(err).NotTo(HaveOccurred())
+	})
 })