Change unicast connection of DHCPv4 client as a raw socket

.github/workflows/tests.yml

@@ -21,7 +21,7 @@ jobs:
           go get -v -t ./...
           echo "" > "${GITHUB_WORKSPACE}"/coverage.txt
           for d in $(go list ./...); do
-              go test -v -race -coverprofile=profile.out -covermode=atomic "${d}"
+              sudo go test -v -race -coverprofile=profile.out -covermode=atomic "${d}"
               if [ -f profile.out ]; then
                 cat profile.out >> "${GITHUB_WORKSPACE}"/coverage.txt
                 rm profile.out

dhcpv4/nclient4/client.go

@@ -214,7 +214,7 @@
 		if iface == `` {
 			return nil, ErrNoConn
 		}
-		c.conn, err = NewRawUDPConn(iface, ClientPort) // broadcast
+		c.conn, err = NewRawUDPConn(iface, &net.UDPAddr{Port: ClientPort}, UDPBroadcast) // broadcast
 		if err != nil {
 			return nil, fmt.Errorf("unable to open a broadcasting socket: %w", err)
 		}
@@ -349,15 +349,9 @@
 // srcAddr is both:
 // * The source address of outgoing frames.
 // * The address to be listened for incoming frames.
-func WithUnicast(srcAddr *net.UDPAddr) ClientOpt {
+func WithUnicast(iface string, srcAddr *net.UDPAddr) ClientOpt {
 	return func(c *Client) (err error) {
-		if srcAddr == nil {
-			srcAddr = &net.UDPAddr{Port: ClientPort}
-		}
-		c.conn, err = net.ListenUDP("udp4", srcAddr)
-		if err != nil {
-			err = fmt.Errorf("unable to start listening UDP port: %w", err)
-		}
+		c.conn, err = NewRawUDPConn(iface, srcAddr, UDPUnicast)
 		return
 	}
 }

dhcpv4/nclient4/conn_unix.go

@@ -10,12 +10,29 @@
 
 import (
 	"errors"
+	"fmt"
 	"io"
 	"net"
 
+	"github.com/mdlayher/arp"
 	"github.com/mdlayher/ethernet"
 	"github.com/mdlayher/raw"
 	"github.com/u-root/uio/uio"
+	"github.com/vishvananda/netlink"
+)
+
+// UDPConnType indicates the type of the udp conn.
+type UDPConnType int
+
+const (
+	// UDPBroadcast specifies the type of udp conn as broadcast.
+	//
+	// All the packets will be broadcasted.
+	UDPBroadcast UDPConnType = 0
+
+	// UDPUnicast specifies the type of udp conn as unicast.
+	// All the packets will be sent to a unicast MAC address.
+	UDPUnicast UDPConnType = 1
 )
 
 var (
@@ -28,13 +45,16 @@
 var (
 	// ErrUDPAddrIsRequired is an error used when a passed argument is not of type "*net.UDPAddr".
 	ErrUDPAddrIsRequired = errors.New("must supply UDPAddr")
+
+	// ErrHWAddrNotFound is an error used when getting MAC address failed.
+	ErrHWAddrNotFound = errors.New("hardware address not found")
 )
 
-// NewRawUDPConn returns a UDP connection bound to the interface and port
-// given based on a raw packet socket. All packets are broadcasted.
+// NewRawUDPConn returns a UDP connection bound to the interface and udp address
+// given based on a raw packet socket.
 //
 // The interface can be completely unconfigured.
-func NewRawUDPConn(iface string, port int) (net.PacketConn, error) {
+func NewRawUDPConn(iface string, addr *net.UDPAddr, typ UDPConnType) (net.PacketConn, error) {
 	ifc, err := net.InterfaceByName(iface)
 	if err != nil {
 		return nil, err
@@ -43,7 +63,12 @@
 	if err != nil {
 		return nil, err
 	}
-	return NewBroadcastUDPConn(rawConn, &net.UDPAddr{Port: port}), nil
+
+	if typ == UDPUnicast {
+		return NewUnicastRawUDPConn(rawConn, addr), nil
+	}
+
+	return NewBroadcastUDPConn(rawConn, addr), nil
 }
 
 // BroadcastRawUDPConn uses a raw socket to send UDP packets to the broadcast
@@ -157,3 +182,76 @@
 	// Broadcasting is not always right, but hell, what the ARP do I know.
 	return upc.PacketConn.WriteTo(packet, &raw.Addr{HardwareAddr: BroadcastMac})
 }
+
+// UnicastRawUDPConn inherits from BroadcastRawUDPConn and override the WriteTo method
+type UnicastRawUDPConn struct {
+	*BroadcastRawUDPConn
+}
+
+// NewUnicastRawUDPConn returns a PacketConn which sending the packets to a unicast MAC address.
+func NewUnicastRawUDPConn(rawPacketConn net.PacketConn, boundAddr *net.UDPAddr) net.PacketConn {
+	return &UnicastRawUDPConn{
+		BroadcastRawUDPConn: NewBroadcastUDPConn(rawPacketConn, boundAddr).(*BroadcastRawUDPConn),
+	}
+}
+
+// WriteTo implements net.PacketConn.WriteTo.
+//
+// WriteTo try to get the MAC address of destination IP address before
+// unicast all packets at the raw socket level.
+func (upc *UnicastRawUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
+	udpAddr, ok := addr.(*net.UDPAddr)
+	if !ok {
+		return 0, ErrUDPAddrIsRequired
+	}
+
+	// Using the boundAddr is not quite right here, but it works.
+	packet := udp4pkt(b, udpAddr, upc.boundAddr)
+	dstMac, err := getHwAddr(udpAddr.IP)
+	if err != nil {
+		return 0, ErrHWAddrNotFound
+	}
+
+	return upc.PacketConn.WriteTo(packet, &raw.Addr{HardwareAddr: dstMac})
+}
+
+// getHwAddr from local arp cache. If no existing, try to get it by arp protocol.
+func getHwAddr(ip net.IP) (net.HardwareAddr, error) {
+	neighList, err := netlink.NeighListExecute(netlink.Ndmsg{
+		Family: netlink.FAMILY_V4,
+		State:  netlink.NUD_REACHABLE,
+	})
+	if err != nil {
+		return nil, err
+	}
+
+	for _, neigh := range neighList {
+		if ip.Equal(neigh.IP) && neigh.HardwareAddr != nil {
+			return neigh.HardwareAddr, nil
+		}
+	}
+
+	return arpResolve(ip)
+}
+
+func arpResolve(dest net.IP) (net.HardwareAddr, error) {
+	// auto match the interface based on routes
+	routes, err := netlink.RouteGet(dest)
+	if err != nil {
+		return nil, err
+	}
+	if len(routes) == 0 {
+		return nil, fmt.Errorf("no route to %s found", dest.String())
+	}
+	ifc, err := net.InterfaceByIndex(routes[0].LinkIndex)
+	if err != nil {
+		return nil, err
+	}
+
+	c, err := arp.Dial(ifc)
+	if err != nil {
+		return nil, err
+	}
+
+	return c.Resolve(dest)
+}

dhcpv4/nclient4/conn_unix_test.go

@@ -0,0 +1,74 @@
+package nclient4
+
+import (
+	"net"
+	"testing"
+
+	"github.com/vishvananda/netlink"
+)
+
+const (
+	linkName = "neigh0"
+	ipStr    = "10.99.0.1"
+	macStr   = "aa:bb:cc:dd:00:01"
+)
+
+func TestGetHwAddrFromLocalCache(t *testing.T) {
+	mac, err := net.ParseMAC(macStr)
+	if err != nil {
+		t.Fatal(err)
+	}
+	ip := net.ParseIP(ipStr)
+
+	if err := addNeigh(ip, mac); err != nil {
+		t.Fatal(err)
+	}
+	defer func() {
+		if err := delNeigh(ip, mac); err != nil {
+			t.Fatal(err)
+		}
+	}()
+
+	_, err = net.InterfaceByName(linkName)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if hw, err := getHwAddr(ip); err != nil && hw != nil && hw.String() == macStr {
+		t.Fatal(err)
+	}
+}
+
+func addNeigh(ip net.IP, mac net.HardwareAddr) error {
+	dummy := netlink.Dummy{LinkAttrs: netlink.LinkAttrs{Name: linkName}}
+	if err := netlink.LinkAdd(&dummy); err != nil {
+		return err
+	}
+	newlink, err := netlink.LinkByName(dummy.Name)
+	if err != nil {
+		return err
+	}
+	dummy.Index = newlink.Attrs().Index
+
+	return netlink.NeighAdd(&netlink.Neigh{
+		LinkIndex:    dummy.Index,
+		State:        netlink.NUD_REACHABLE,
+		IP:           ip,
+		HardwareAddr: mac,
+	})
+}
+
+func delNeigh(ip net.IP, mac net.HardwareAddr) error {
+	dummy, err := netlink.LinkByName(linkName)
+	if err != nil {
+		return err
+	}
+
+	return netlink.NeighDel(&netlink.Neigh{
+		LinkIndex:    dummy.Attrs().Index,
+		State:        netlink.NUD_REACHABLE,
+		IP:           ip,
+		HardwareAddr: mac,
+	})
+}
+

go.mod

@@ -6,12 +6,14 @@ require (
 	github.com/fanliao/go-promise v0.0.0-20141029170127-1890db352a72
 	github.com/hugelgupf/socketpair v0.0.0-20190730060125-05d35a94e714
 	github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c
+	github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc
 	github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7
 	github.com/mdlayher/netlink v1.1.1
 	github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065
 	github.com/smartystreets/goconvey v1.6.4 // indirect
 	github.com/stretchr/testify v1.6.1
 	github.com/u-root/uio v0.0.0-20210528114334-82958018845c
+	github.com/vishvananda/netlink v1.1.0
 	golang.org/x/net v0.0.0-20201110031124-69a78807bb2b
 	golang.org/x/sys v0.0.0-20210525143221-35b2ab0089ea
 )

go.sum

@@ -19,13 +19,17 @@ github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c h1:7cpGGTQO6+
 github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c/go.mod h1:huN4d1phzjhlOsNIjFsw2SVRbwIHj3fJDMEU2SDPTmg=
 github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
 github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
+github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc h1:m7rJJJeXrYCFpsxXYapkDW53wJCDmf9bsIXUg0HoeQY=
+github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc/go.mod h1:eOj1DDj3NAZ6yv+WafaKzY37MFZ58TdfIhQ+8nQbiis=
+github.com/mdlayher/ethernet v0.0.0-20190313224307-5b5fc417d966/go.mod h1:5s5p/sMJ6sNsFl6uCh85lkFGV8kLuIYJCRJLavVJwvg=
 github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7 h1:lez6TS6aAau+8wXUP3G9I3TGlmPFEq2CTxBaRqY6AGE=
 github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7/go.mod h1:U6ZQobyTjI/tJyq2HG+i/dfSoFUt8/aZCM+GKtmFk/Y=
 github.com/mdlayher/netlink v0.0.0-20190409211403-11939a169225/go.mod h1:eQB3mZE4aiYnlUsyGGCOpPETfdQq4Jhsgf1fk3cwQaA=
 github.com/mdlayher/netlink v1.0.0/go.mod h1:KxeJAFOFLG6AjpyDkQ/iIhxygIUKD+vcwqcnu43w/+M=
 github.com/mdlayher/netlink v1.1.0/go.mod h1:H4WCitaheIsdF9yOYu8CFmCgQthAPIWZmcKp9uZHgmY=
 github.com/mdlayher/netlink v1.1.1 h1:VqG+Voq9V4uZ+04vjIrcSCWDpf91B1xxbP4QBUmUJE8=
 github.com/mdlayher/netlink v1.1.1/go.mod h1:WTYpFb/WTvlRJAyKhZL5/uy69TDDpHHu2VZmb2XgV7o=
+github.com/mdlayher/raw v0.0.0-20190313224157-43dbcdd7739d/go.mod h1:r1fbeITl2xL/zLbVnNHFyOzQJTgr/3fpf1lJX/cjzR8=
 github.com/mdlayher/raw v0.0.0-20190606142536-fef19f00fc18/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
 github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065 h1:aFkJ6lx4FPip+S+Uw4aTegFMct9shDvP+79PsSxpm3w=
 github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
@@ -41,9 +45,14 @@ github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd
 github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/u-root/uio v0.0.0-20210528114334-82958018845c h1:BFvcl34IGnw8yvJi8hlqLFo9EshRInwWBs2M5fGWzQA=
 github.com/u-root/uio v0.0.0-20210528114334-82958018845c/go.mod h1:LpEX5FO/cB+WF4TYGY1V5qktpaZLkKkSegbr0V4eYXA=
+github.com/vishvananda/netlink v1.1.0 h1:1iyaYNBLmP6L0220aDnYQpo1QEV4t4hJ+xEEhhJH8j0=
+github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df h1:OviZH7qLw/7ZovXvuNyL3XQl8UFofeikI1NW1Gypu7k=
+github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df/go.mod h1:JP3t17pCcGlemwknint6hfoeCVQrEMVwxRLRjXpq+BU=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
 golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
+golang.org/x/net v0.0.0-20190313220215-9f648a60d977/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190419010253-1f3472d942ba/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
 golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
@@ -59,6 +68,7 @@ golang.org/x/sys v0.0.0-20190411185658-b44545bcd369/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190418153312-f0ce4c0180be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190606122018-79a91cf218c4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20190606203320-7fc4e5ec1444/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=