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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
}
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