feat: support metric values for DHCP

This PR adds a "DHCPOptions" field to the config. This field contains a
single subfield currently, "RouteMetric". Setting this well ensure that
any routes provided from the DHCP server are given this metric upon
injection into the routing table.

Signed-off-by: Spencer Smith <robertspencersmith@gmail.com>

docs/website/content/v0.7/en/configuration/v1alpha1.md

@@ -1320,6 +1320,22 @@ Type: `bool`
 Indicates if the interface is a dummy interface.
 Type: `bool`
 
+#### dhcpOptions
+
+DHCP specific options.
+DHCP *must* be set to true for these to take effect.
+
+Type: `DHCPOptions`
+
+---
+
+### DHCPOptions
+
+#### routeMetric
+
+The priority of all routes received via DHCP
+Type: `uint32`
+
 ---
 
 ### Bond

internal/app/networkd/pkg/address/dhcp.go

@@ -18,6 +18,7 @@ import (
 
 	"github.com/talos-systems/go-procfs/procfs"
 
+	"github.com/talos-systems/talos/pkg/machinery/config"
 	"github.com/talos-systems/talos/pkg/machinery/constants"
 )
 
@@ -25,6 +26,7 @@ import (
 type DHCP struct {
 	Ack         *dhcpv4.DHCPv4
 	NetIf       *net.Interface
+	DHCPOptions config.DHCPOptions
 }
 
 // Name returns back the name of the address method.

internal/app/networkd/pkg/networkd/netconf.go

@@ -46,7 +46,7 @@ func buildOptions(device config.Device, hostname string) (name string, opts []ni
 
 		opts = append(opts, nic.WithAddressing(s))
 	case device.DHCP():
-		d := &address.DHCP{}
+		d := &address.DHCP{DHCPOptions: device.DHCPOptions()}
 		opts = append(opts, nic.WithAddressing(d))
 	default:
 		// Allow master interface without any addressing if VLANs exist

internal/app/networkd/pkg/nic/nic.go

@@ -17,6 +17,7 @@ import (
 	"time"
 
 	"github.com/hashicorp/go-multierror"
+	"github.com/insomniacslk/dhcp/dhcpv4"
 	"github.com/jsimonetti/rtnetlink"
 	"github.com/jsimonetti/rtnetlink/rtnl"
 	"github.com/mdlayher/netlink"
@@ -338,7 +339,9 @@ func (n *NetworkInterface) configureInterface(method address.Addressing, link *n
 
 	if method.Address() != nil {
 		// Check to see if we need to configure the address
-		addrs, err := n.rtnlConn.Addrs(method.Link(), method.Family())
+		var addrs []*net.IPNet
+
+		addrs, err = n.rtnlConn.Addrs(method.Link(), method.Family())
 		if err != nil {
 			return err
 		}
@@ -368,20 +371,9 @@ func (n *NetworkInterface) configureInterface(method address.Addressing, link *n
 
 	// Add any routes
 	for _, r := range method.Routes() {
-		// If gateway/router is 0.0.0.0 we'll set to nil so route scope decision will be correct
-		gw := r.Router
-		if net.IPv4zero.Equal(gw) {
-			gw = nil
-		}
-
-		src := method.Address()
-		// if destination is the ipv6 route,and gateway is LL do not pass a src address to set the default geteway
-		if net.IPv6zero.Equal(r.Dest.IP) && gw.IsLinkLocalUnicast() {
-			src = nil
-		}
-
-		if err := n.rtnlConn.RouteAddSrc(method.Link(), *r.Dest, src, gw); err != nil {
-			log.Println("failed to configure route: " + err.Error())
+		err = n.addRoute(method, r)
+		if err != nil {
+			return err
 		}
 	}
 
@@ -414,3 +406,89 @@ func (n *NetworkInterface) Reset() {
 	// nolint: errcheck
 	n.rtnlConn.LinkDown(link)
 }
+
+// addRoute is a function loosely copied from https://github.com/jsimonetti/rtnetlink/blob/154ecd417600f79d7847278a1e984056dc647acc/rtnl/route.go
+// and merged with our logic on determining gw, src, dst, etc.
+// we need this b/c we need to craft the route message ourselves to add attributes.
+// nolint: gocyclo
+func (n *NetworkInterface) addRoute(method address.Addressing, r *dhcpv4.Route) error {
+	dst := *r.Dest
+
+	// If gateway/router is 0.0.0.0 we'll set to nil so route scope decision will be correct
+	gw := r.Router
+	if net.IPv4zero.Equal(gw) {
+		gw = nil
+	}
+
+	src := method.Address()
+	// if destination is the ipv6 route,and gateway is LL do not pass a src address to set the default geteway
+	if net.IPv6zero.Equal(r.Dest.IP) && gw.IsLinkLocalUnicast() {
+		src = nil
+	}
+
+	// determine if this is ipv4 or 6
+	var af int
+	if dst.IP.To4() != nil {
+		af = unix.AF_INET
+	} else if len(dst.IP) == net.IPv6len {
+		af = unix.AF_INET6
+	}
+
+	ifc := method.Link()
+
+	// Determine scope
+	var scope uint8
+
+	switch {
+	case gw != nil:
+		scope = unix.RT_SCOPE_UNIVERSE
+
+	case len(dst.IP) == net.IPv6len && dst.IP.To4() == nil:
+		scope = unix.RT_SCOPE_UNIVERSE
+
+	default:
+		// Set default scope to LINK
+		scope = unix.RT_SCOPE_LINK
+	}
+
+	attr := rtnetlink.RouteAttributes{
+		Dst:      dst.IP,
+		OutIface: uint32(ifc.Index),
+	}
+
+	// Set DHCP specific options
+	if dhcpObj, ok := method.(*address.DHCP); ok {
+		if dhcpObj.DHCPOptions != nil {
+			attr.Priority = dhcpObj.DHCPOptions.RouteMetric()
+		}
+
+		if attr.Priority == uint32(0) {
+			attr.Priority = uint32(1024)
+		}
+	}
+
+	if gw != nil {
+		attr.Gateway = gw
+	}
+
+	var srclen int
+	if src != nil {
+		srclen, _ = src.Mask.Size()
+		attr.Src = src.IP
+	}
+
+	dstlen, _ := dst.Mask.Size()
+
+	tx := &rtnetlink.RouteMessage{
+		Family:     uint8(af),
+		Table:      unix.RT_TABLE_MAIN,
+		Protocol:   unix.RTPROT_BOOT,
+		Type:       unix.RTN_UNICAST,
+		Scope:      scope,
+		DstLength:  uint8(dstlen),
+		SrcLength:  uint8(srclen),
+		Attributes: attr,
+	}
+
+	return n.rtnlConn.Conn.Route.Add(tx)
+}

pkg/machinery/config/provider.go

@@ -115,6 +115,12 @@ type Device interface {
 	DHCP() bool
 	Ignore() bool
 	Dummy() bool
+	DHCPOptions() DHCPOptions
+}
+
+// DHCPOptions represents a set of DHCP options.
+type DHCPOptions interface {
+	RouteMetric() uint32
 }
 
 // Bond contains the various options for configuring a

pkg/machinery/config/types/v1alpha1/v1alpha1_provider.go

@@ -749,6 +749,23 @@ func (d *Device) Dummy() bool {
 	return d.DeviceDummy
 }
 
+// DHCPOptions implements the MachineNetwork interface.
+func (d *Device) DHCPOptions() config.DHCPOptions {
+	// Default route metric on systemd is 1024. This sets the same.
+	if d.DeviceDHCPOptions == nil {
+		return &DHCPOptions{
+			DHCPRouteMetric: uint32(0),
+		}
+	}
+
+	return d.DeviceDHCPOptions
+}
+
+// RouteMetric implements the MachineNetwork interface.
+func (d *DHCPOptions) RouteMetric() uint32 {
+	return d.DHCPRouteMetric
+}
+
 // Network implements the MachineNetwork interface.
 func (r *Route) Network() string {
 	return r.RouteNetwork

pkg/machinery/config/types/v1alpha1/v1alpha1_types.go

@@ -832,6 +832,16 @@ type Device struct {
 	DeviceIgnore bool `yaml:"ignore"`
 	//   description: Indicates if the interface is a dummy interface.
 	DeviceDummy bool `yaml:"dummy"`
+	//   description: |
+	//     DHCP specific options.
+	//     DHCP *must* be set to true for these to take effect.
+	DeviceDHCPOptions *DHCPOptions `yaml:"dhcpOptions"`
+}
+
+// DHCPOptions contains options for configuring the DHCP settings for a given interface.
+type DHCPOptions struct {
+	//   description: The priority of all routes received via DHCP
+	DHCPRouteMetric uint32 `yaml:"routeMetric"`
 }
 
 // Bond contains the various options for configuring a