1 files changed, 208 insertions, 0 deletions
diff --git a/dhcpv4/async/client.go b/dhcpv4/async/client.go
new file mode 100644
index 0000000..e6c7302
--- /dev/null
+++ b/dhcpv4/async/client.go
@@ -0,0 +1,208 @@
+package async
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+	"time"
+
+	"github.com/fanliao/go-promise"
+	"github.com/insomniacslk/dhcp/dhcpv4"
+)
+
+// Default ports
+const (
+	DefaultServerPort = 67
+	DefaultClientPort = 68
+)
+
+// Client implements an asynchronous DHCPv4 client
+// It doesn't use the broadcast socket! Which means it should be used only when
+// the network is already established.
+// https://github.com/insomniacslk/dhcp/issues/143
+type Client struct {
+	ReadTimeout  time.Duration
+	WriteTimeout time.Duration
+	LocalAddr    net.Addr
+	RemoteAddr   net.Addr
+	IgnoreErrors bool
+
+	connection   *net.UDPConn
+	cancel       context.CancelFunc
+	stopping     *sync.WaitGroup
+	receiveQueue chan *dhcpv4.DHCPv4
+	sendQueue    chan *dhcpv4.DHCPv4
+	packetsLock  sync.Mutex
+	packets      map[uint32]*promise.Promise
+	errors       chan error
+}
+
+// NewClient creates an asynchronous client
+func NewClient() *Client {
+	return &Client{
+		ReadTimeout:  dhcpv4.DefaultReadTimeout,
+		WriteTimeout: dhcpv4.DefaultWriteTimeout,
+	}
+}
+
+// Open starts the client. The requests made with Send function call are first
+// put to the buffered channel and dispatched in FIFO order. BufferSize
+// indicates the number of packets that can be waiting to be send before
+// blocking the caller exectution.
+func (c *Client) Open(bufferSize int) error {
+	var (
+		addr *net.UDPAddr
+		ok   bool
+		err  error
+	)
+
+	if addr, ok = c.LocalAddr.(*net.UDPAddr); !ok {
+		return fmt.Errorf("Invalid local address: %v not a net.UDPAddr", c.LocalAddr)
+	}
+
+	// prepare the socket to listen on for replies
+	c.connection, err = net.ListenUDP("udp4", addr)
+	if err != nil {
+		return err
+	}
+	c.stopping = new(sync.WaitGroup)
+	c.sendQueue = make(chan *dhcpv4.DHCPv4, bufferSize)
+	c.receiveQueue = make(chan *dhcpv4.DHCPv4, bufferSize)
+	c.packets = make(map[uint32]*promise.Promise)
+	c.packetsLock = sync.Mutex{}
+	c.errors = make(chan error)
+
+	var ctx context.Context
+	ctx, c.cancel = context.WithCancel(context.Background())
+	go c.receiverLoop(ctx)
+	go c.senderLoop(ctx)
+
+	return nil
+}
+
+// Close stops the client
+func (c *Client) Close() {
+	// Wait for sender and receiver loops
+	c.stopping.Add(2)
+	c.cancel()
+	c.stopping.Wait()
+
+	close(c.sendQueue)
+	close(c.receiveQueue)
+	close(c.errors)
+
+	c.connection.Close()
+}
+
+// Errors returns a channel where runtime errors are posted
+func (c *Client) Errors() <-chan error {
+	return c.errors
+}
+
+func (c *Client) addError(err error) {
+	if !c.IgnoreErrors {
+		c.errors <- err
+	}
+}
+
+func (c *Client) receiverLoop(ctx context.Context) {
+	defer func() { c.stopping.Done() }()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case packet := <-c.receiveQueue:
+			c.receive(packet)
+		}
+	}
+}
+
+func (c *Client) senderLoop(ctx context.Context) {
+	defer func() { c.stopping.Done() }()
+	for {
+		select {
+		case <-ctx.Done():
+			return
+		case packet := <-c.sendQueue:
+			c.send(packet)
+		}
+	}
+}
+
+func (c *Client) send(packet *dhcpv4.DHCPv4) {
+	c.packetsLock.Lock()
+	p := c.packets[packet.TransactionID()]
+	c.packetsLock.Unlock()
+
+	raddr, err := c.remoteAddr()
+	if err != nil {
+		p.Reject(err)
+		return
+	}
+
+	c.connection.SetWriteDeadline(time.Now().Add(c.WriteTimeout))
+	_, err = c.connection.WriteTo(packet.ToBytes(), raddr)
+	if err != nil {
+		p.Reject(err)
+		return
+	}
+
+	c.receiveQueue <- packet
+}
+
+func (c *Client) receive(_ *dhcpv4.DHCPv4) {
+	var (
+		oobdata  = []byte{}
+		received *dhcpv4.DHCPv4
+	)
+
+	c.connection.SetReadDeadline(time.Now().Add(c.ReadTimeout))
+	for {
+		buffer := make([]byte, dhcpv4.MaxUDPReceivedPacketSize)
+		n, _, _, _, err := c.connection.ReadMsgUDP(buffer, oobdata)
+		if err != nil {
+			if err, ok := err.(net.Error); !ok || !err.Timeout() {
+				c.addError(fmt.Errorf("Error receiving the message: %s", err))
+			}
+			return
+		}
+		received, err = dhcpv4.FromBytes(buffer[:n])
+		if err == nil {
+			break
+		}
+	}
+
+	c.packetsLock.Lock()
+	if p, ok := c.packets[received.TransactionID()]; ok {
+		delete(c.packets, received.TransactionID())
+		p.Resolve(received)
+	}
+	c.packetsLock.Unlock()
+}
+
+func (c *Client) remoteAddr() (*net.UDPAddr, error) {
+	if c.RemoteAddr == nil {
+		return &net.UDPAddr{IP: net.IPv4bcast, Port: DefaultServerPort}, nil
+	}
+
+	if addr, ok := c.RemoteAddr.(*net.UDPAddr); ok {
+		return addr, nil
+	}
+	return nil, fmt.Errorf("Invalid remote address: %v not a net.UDPAddr", c.RemoteAddr)
+}
+
+// Send inserts a message to the queue to be sent asynchronously.
+// Returns a future which resolves to response and error.
+func (c *Client) Send(message *dhcpv4.DHCPv4, modifiers ...dhcpv4.Modifier) *promise.Future {
+	for _, mod := range modifiers {
+		message = mod(message)
+	}
+
+	p := promise.NewPromise()
+	c.packetsLock.Lock()
+	c.packets[message.TransactionID()] = p
+	c.packetsLock.Unlock()
+	c.sendQueue <- message
+	return p.Future
+}