5 files changed, 50 insertions, 43 deletions

diff --git a/dhcpv4/nclient4/client_test.go b/dhcpv4/nclient4/client_test.go
index c299697..df851ab 100644
--- a/dhcpv4/nclient4/client_test.go
+++ b/dhcpv4/nclient4/client_test.go
@@ -61,7 +61,7 @@ func serveAndClient(ctx context.Context, responses [][]*dhcpv4.DHCPv4, opts ...C
 	}
 
 	h := &handler{responses: responses}
-	s, err := server4.NewServer(nil, h.handle, server4.WithConn(serverConn))
+	s, err := server4.NewServer("", nil, h.handle, server4.WithConn(serverConn))
 	if err != nil {
 		panic(err)
 	}
diff --git a/dhcpv4/nclient4/conn_linux.go b/dhcpv4/nclient4/conn_linux.go
index af6485f..064e6ca 100644
--- a/dhcpv4/nclient4/conn_linux.go
+++ b/dhcpv4/nclient4/conn_linux.go
@@ -10,13 +10,10 @@ import (
 	"fmt"
 	"io"
 	"net"
-	"os"
 
-	"github.com/insomniacslk/dhcp/dhcpv4"
 	"github.com/mdlayher/ethernet"
 	"github.com/mdlayher/raw"
 	"github.com/u-root/u-root/pkg/uio"
-	"golang.org/x/sys/unix"
 )
 
 var (
@@ -26,41 +23,6 @@ var (
 	BroadcastMac = net.HardwareAddr([]byte{255, 255, 255, 255, 255, 255})
 )
 
-// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
-// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
-//
-// The interface must already be configured.
-func NewIPv4UDPConn(iface string, port int) (net.PacketConn, error) {
-	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
-	if err != nil {
-		return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
-	}
-	f := os.NewFile(uintptr(fd), "")
-	// net.FilePacketConn dups the FD, so we have to close this in any case.
-	defer f.Close()
-
-	// Allow broadcasting.
-	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
-		return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
-	}
-	// Allow reusing the addr to aid debugging.
-	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
-		return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
-	}
-	if len(iface) != 0 {
-		// Bind directly to the interface.
-		if err := dhcpv4.BindToInterface(fd, iface); err != nil {
-			return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
-		}
-	}
-	// Bind to the port.
-	if err := unix.Bind(fd, &unix.SockaddrInet4{Port: port}); err != nil {
-		return nil, fmt.Errorf("cannot bind to port %d: %v", port, err)
-	}
-
-	return net.FilePacketConn(f)
-}
-
 // NewRawUDPConn returns a UDP connection bound to the interface and port
 // given based on a raw packet socket. All packets are broadcasted.
 //
diff --git a/dhcpv4/server4/conn.go b/dhcpv4/server4/conn.go
new file mode 100644
index 0000000..84d6aa3
--- /dev/null
+++ b/dhcpv4/server4/conn.go
@@ -0,0 +1,45 @@
+package server4
+
+import (
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/insomniacslk/dhcp/dhcpv4"
+	"golang.org/x/sys/unix"
+)
+
+// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
+// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
+//
+// The interface must already be configured.
+func NewIPv4UDPConn(iface string, port int) (net.PacketConn, error) {
+	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
+	if err != nil {
+		return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
+	}
+	f := os.NewFile(uintptr(fd), "")
+	// net.FilePacketConn dups the FD, so we have to close this in any case.
+	defer f.Close()
+
+	// Allow broadcasting.
+	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
+		return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
+	}
+	// Allow reusing the addr to aid debugging.
+	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
+		return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
+	}
+	if len(iface) != 0 {
+		// Bind directly to the interface.
+		if err := dhcpv4.BindToInterface(fd, iface); err != nil {
+			return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
+		}
+	}
+	// Bind to the port.
+	if err := unix.Bind(fd, &unix.SockaddrInet4{Port: port}); err != nil {
+		return nil, fmt.Errorf("cannot bind to port %d: %v", port, err)
+	}
+
+	return net.FilePacketConn(f)
+}
diff --git a/dhcpv4/server4/server.go b/dhcpv4/server4/server.go
index 5567bae..fe4ef09 100644
--- a/dhcpv4/server4/server.go
+++ b/dhcpv4/server4/server.go
@@ -123,7 +123,7 @@ func WithConn(c net.PacketConn) ServerOpt {
 }
 
 // NewServer initializes and returns a new Server object
-func NewServer(addr *net.UDPAddr, handler Handler, opt ...ServerOpt) (*Server, error) {
+func NewServer(ifname string, addr *net.UDPAddr, handler Handler, opt ...ServerOpt) (*Server, error) {
 	s := &Server{
 		Handler: handler,
 	}
@@ -133,7 +133,7 @@ func NewServer(addr *net.UDPAddr, handler Handler, opt ...ServerOpt) (*Server, e
 	}
 	if s.conn == nil {
 		var err error
-		conn, err := net.ListenUDP("udp4", addr)
+		conn, err := NewIPv4UDPConn(ifname, addr.Port)
 		if err != nil {
 			return nil, err
 		}
diff --git a/dhcpv4/server4/server_test.go b/dhcpv4/server4/server_test.go
index d24d49b..a596d04 100644
--- a/dhcpv4/server4/server_test.go
+++ b/dhcpv4/server4/server_test.go
@@ -73,7 +73,7 @@ func setUpClientAndServer(t *testing.T, iface net.Interface, handler Handler) (*
 		IP:   loAddr,
 		Port: randPort(),
 	}
-	s, err := NewServer(&saddr, handler)
+	s, err := NewServer("", &saddr, handler)
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -81,7 +81,7 @@ func setUpClientAndServer(t *testing.T, iface net.Interface, handler Handler) (*
 		_ = s.Serve()
 	}()
 
-	clientConn, err := nclient4.NewIPv4UDPConn("", caddr.Port)
+	clientConn, err := NewIPv4UDPConn("", caddr.Port)
 	if err != nil {
 		t.Fatal(err)
 	}