interface dhcp configuration

dhcp should be an opt-in option because running it can cause delays
on pod startup on environments that don't have dhcp enabled.

Change-Id: I2905788c261583d86a5701576c2e61a245138c02

Author: aojea

pkg/apis/types.go

@@ -41,6 +41,10 @@ type InterfaceConfig struct {
 	// to be assigned to the interface.
 	Addresses []string `json:"addresses,omitempty"`
 
+	// DHCP, if true, indicates that the interface should be configured via DHCP.
+	// This is mutually exclusive with the 'addresses' field.
+	DHCP *bool `json:"dhcp,omitempty"`
+
 	// MTU is the Maximum Transmission Unit for the interface.
 	MTU *int32 `json:"mtu,omitempty"`
 

pkg/apis/validation.go

@@ -128,6 +128,10 @@ func validateInterfaceConfig(cfg *InterfaceConfig, fieldPath string) (allErrors
 		}
 	}
 
+	if cfg.DHCP != nil && *cfg.DHCP && len(cfg.Addresses) > 0 {
+		allErrors = append(allErrors, fmt.Errorf("%s: dhcp and addresses are mutually exclusive", fieldPath))
+	}
+
 	if cfg.MTU != nil {
 		if *cfg.MTU < MinMTU {
 			allErrors = append(allErrors, fmt.Errorf("%s.mtu: must be at least %d, got %d", fieldPath, MinMTU, *cfg.MTU))

pkg/apis/validation_test.go

@@ -253,6 +253,25 @@ func TestValidateInterfaceConfig(t *testing.T) {
 			expectErr: true,
 			errCount:  1,
 		},
+		{
+			name:      "valid with dhcp",
+			cfg:       &InterfaceConfig{Name: "eth0", DHCP: ptr.To(true)},
+			fieldPath: "iface",
+			expectErr: false,
+		},
+		{
+			name:      "invalid with dhcp and addresses",
+			cfg:       &InterfaceConfig{Name: "eth0", DHCP: ptr.To(true), Addresses: []string{"10.0.0.1/24"}},
+			fieldPath: "iface",
+			expectErr: true,
+			errCount:  1,
+		},
+		{
+			name:      "valid with dhcp false and addresses",
+			cfg:       &InterfaceConfig{Name: "eth0", DHCP: ptr.To(false), Addresses: []string{"10.0.0.1/24"}},
+			fieldPath: "iface",
+			expectErr: false,
+		},
 		{
 			name:      "multiple errors",
 			cfg:       &InterfaceConfig{Name: "eth/0", Addresses: []string{"badip"}, MTU: ptr.To[int32](0)},

pkg/driver/dhcp.go

@@ -27,7 +27,7 @@ import (
 	"github.com/vishvananda/netlink"
 )
 
-func getDHCP(ifName string) (ip string, routes []apis.RouteConfig, err error) {
+func getDHCP(ctx context.Context, ifName string) (ip string, routes []apis.RouteConfig, err error) {
 	link, err := netlink.LinkByName(ifName)
 	if err != nil {
 		return "", nil, err
@@ -43,7 +43,7 @@ func getDHCP(ifName string) (ip string, routes []apis.RouteConfig, err error) {
 	}
 	defer dhclient.Close()
 
-	lease, err := dhclient.Request(context.Background())
+	lease, err := dhclient.Request(ctx)
 	if err != nil {
 		return "", nil, fmt.Errorf("fail to obtain DHCP lease on interface %s  up: %v", ifName, err)
 	}

pkg/driver/dra_hooks.go

@@ -166,12 +166,25 @@ func (np *NetworkDriver) prepareResourceClaim(ctx context.Context, claim *resour
 			podCfg.Network.Interface.Name = ifName
 		}
 
-		// If there is no custom addresses then use the existing ones
-		if len(podCfg.Network.Interface.Addresses) == 0 {
+		// If DHCP is requested, do a DHCP request to gather the network parameters (IPs and Routes)
+		// ... but we DO NOT apply them in the root namespace
+		if podCfg.Network.Interface.DHCP != nil && *podCfg.Network.Interface.DHCP {
+			klog.V(2).Infof("trying to get network configuration via DHCP")
+			contextCancel, cancel := context.WithTimeout(ctx, 5*time.Second)
+			defer cancel()
+			ip, routes, err := getDHCP(contextCancel, ifName)
+			if err != nil {
+				errorList = append(errorList, fmt.Errorf("fail to get configuration via DHCP for %s: %w", ifName, err))
+			} else {
+				podCfg.Network.Interface.Addresses = []string{ip}
+				podCfg.Network.Routes = append(podCfg.Network.Routes, routes...)
+			}
+		} else if len(podCfg.Network.Interface.Addresses) == 0 {
+			// If there is no custom addresses and no DHCP, then use the existing ones
 			// get the existing IP addresses
 			nlAddresses, err := nlHandle.AddrList(link, netlink.FAMILY_ALL)
 			if err != nil && !errors.Is(err, netlink.ErrDumpInterrupted) {
-				klog.Infof("fail to get ip addresses for interface %s : %v", ifName, err)
+				errorList = append(errorList, fmt.Errorf("fail to get ip addresses for interface %s : %w", ifName, err))
 			} else {
 				for _, address := range nlAddresses {
 					// Only move IP addresses with global scope because those are not host-specific, auto-configured,
@@ -185,21 +198,6 @@ func (np *NetworkDriver) prepareResourceClaim(ctx context.Context, claim *resour
 			}
 		}
 
-		// If there are no addresses configured on the interface and the user is not setting them
-		// this may be an interface that uses DHCP, so we bring it up if necessary and do a DHCP
-		// request to gather the network parameters (IPs and Routes) ... but we DO NOT apply them
-		// in the root namespace
-		if len(podCfg.Network.Interface.Addresses) == 0 {
-			klog.V(2).Infof("trying to get network configuration via DHCP")
-			ip, routes, err := getDHCP(ifName)
-			if err != nil {
-				klog.Infof("fail to get configuration via DHCP: %v", err)
-			} else {
-				podCfg.Network.Interface.Addresses = []string{ip}
-				podCfg.Network.Routes = append(podCfg.Network.Routes, routes...)
-			}
-		}
-
 		// Obtain the existing supported ethtool features and validate the config
 		if podCfg.Network.Ethtool != nil {
 			client, err := newEthtoolClient(0)