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transport_udp.go
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transport_udp.go
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package protocols
import (
"fmt"
"net"
"time"
)
// =============================== UDP Transport ===============================
const (
DefaultRetries = 3
)
type udpTransportProvider struct {
net string
bufferSize int
}
func UdpTransport() TransportProvider {
return UdpTransportB(512)
}
func UdpTransportB(bufferSize int) TransportProvider {
return &udpTransportProvider{"udp4", bufferSize}
}
func (trans *udpTransportProvider) String() string {
return trans.net + " transport"
}
func (trans *udpTransportProvider) Resolve(addr string) (Addr, error) {
return trans.newAddr(net.ResolveUDPAddr(trans.net, addr))
}
func (trans *udpTransportProvider) ResolveIP(ip string) (Addr, error) {
return trans.newAddr(net.ResolveUDPAddr(trans.net, net.JoinHostPort(ip, "0")))
}
func (trans *udpTransportProvider) doResolveLocal(server_addr *net.UDPAddr) (*net.UDPAddr, error) {
// TODO find simpler way to get the local address for a remote server
conn, err := net.DialUDP(trans.net, nil, server_addr)
if err != nil {
return nil, err
}
local_addr, ok := conn.LocalAddr().(*net.UDPAddr)
if !ok {
return nil, fmt.Errorf("Failed to convert to *net.UDPAddr: %v", conn.LocalAddr())
}
_ = conn.Close() // Drop error
return local_addr, nil
}
func (trans *udpTransportProvider) ResolveLocal(remote_addr string) (Addr, error) {
server_addr, err := net.ResolveUDPAddr(trans.net, remote_addr)
if err != nil {
return nil, err
}
return trans.newAddr(trans.doResolveLocal(server_addr))
}
func (trans *udpTransportProvider) Listen(local Addr, protocol Protocol) (Listener, error) {
udp, err := toUdpAddr(local)
if err != nil {
return nil, err
}
udpConn, err := net.ListenUDP(trans.net, udp.udp)
conn, err := trans.newConn(udpConn, nil, protocol, err)
if err != nil {
return nil, err
}
return &udpListener{conn}, nil
}
func (trans *udpTransportProvider) Dial(remote Addr, protocol Protocol) (Conn, error) {
udp, err := toUdpAddr(remote)
if err != nil {
return nil, err
}
local, err := trans.doResolveLocal(udp.udp)
if err != nil {
return nil, err
}
conn, err := net.ListenUDP(trans.net, local)
return trans.newConn(conn, udp, protocol, err)
}
func (trans *udpTransportProvider) newAddr(udp *net.UDPAddr, err error) (*udpAddr, error) {
if err == nil {
return &udpAddr{trans, udp}, nil
} else {
return nil, err
}
}
func (trans *udpTransportProvider) newConn(udp *net.UDPConn, remote_addr *udpAddr, protocol Protocol, err error) (*udpConn, error) {
if err != nil {
return nil, err
}
local, ok := udp.LocalAddr().(*net.UDPAddr)
if !ok {
return nil, fmt.Errorf("Could not convert LocalAddr to *net.UDPAddr: %v", udp.LocalAddr())
}
return &udpConn{
trans: trans,
udp: udp,
protocol: protocol,
local: udpAddr{trans, local},
remote: remote_addr,
retries: DefaultRetries,
}, nil
}
// =============================== UDP Addr ===============================
type udpAddr struct {
trans *udpTransportProvider
udp *net.UDPAddr
}
func (addr *udpAddr) String() string {
return addr.udp.String()
}
func (addr *udpAddr) Network() string {
return addr.udp.Network()
}
func (addr *udpAddr) IP() net.IP {
return addr.udp.IP
}
func toUdpAddr(addr Addr) (*udpAddr, error) {
if udp, ok := addr.(*udpAddr); ok {
return udp, nil
} else {
return nil, fmt.Errorf("Could not convert to *udpAddr: %v", addr)
}
}
// ============================== UDP Listener ==============================
type udpListener struct {
conn *udpConn
}
func (listener *udpListener) Accept() (Conn, error) {
packet, err := listener.conn.Receive(time.Duration(0))
if err != nil {
return nil, err
}
return &udpAcceptedConn{
listener: listener,
packet: packet,
}, nil
}
func (listener *udpListener) Close() error {
return listener.conn.Close()
}
func (listener *udpListener) LocalAddr() Addr {
return listener.conn.LocalAddr()
}
// ============================ UDP accepted Conn ============================
type udpAcceptedConn struct {
listener *udpListener
packet *Packet
received bool
closed bool
}
func (conn *udpAcceptedConn) Send(packet *Packet, timeout time.Duration) error {
if err := conn.checkClosed(); err != nil {
return err
}
return conn.listener.conn.doSend(packet, conn.packet.SourceAddr, timeout)
}
func (conn *udpAcceptedConn) UnreliableSend(packet *Packet) error {
if err := conn.checkClosed(); err != nil {
return err
}
return conn.listener.conn.doUnreliableSend(packet, conn.packet.SourceAddr)
}
func (conn *udpAcceptedConn) Receive(timeout time.Duration) (*Packet, error) {
if err := conn.checkClosed(); err != nil {
return nil, err
}
if conn.received {
return nil, fmt.Errorf("Can only receive once from a udpAcceptedConn")
}
return conn.packet, nil
}
func (conn *udpAcceptedConn) RemoteAddr() Addr {
return conn.packet.SourceAddr
}
func (conn *udpAcceptedConn) LocalAddr() Addr {
return conn.listener.conn.LocalAddr()
}
func (conn *udpAcceptedConn) Close() error {
if err := conn.checkClosed(); err != nil {
return err
}
conn.closed = true
return nil
}
func (conn *udpAcceptedConn) checkClosed() error {
if conn.closed {
return fmt.Errorf("Already closed")
}
return nil
}
// =============================== UDP Conn ===============================
type udpConn struct {
trans *udpTransportProvider
udp *net.UDPConn
local udpAddr
remote *udpAddr
protocol Protocol
retries int
}
func (conn *udpConn) LocalAddr() Addr {
return &conn.local
}
func (conn *udpConn) RemoteAddr() Addr {
return conn.remote
}
func (conn *udpConn) Close() error {
return conn.udp.Close()
}
func (conn *udpConn) Send(packet *Packet, timeout time.Duration) error {
if conn.remote == nil {
return fmt.Errorf("Cannot send on this connection")
}
return conn.doSend(packet, conn.remote, timeout)
}
func (conn *udpConn) doSend(packet *Packet, addr Addr, timeout time.Duration) error {
udpAddr, b, err := conn.prepareSend(packet, addr)
if err != nil {
return err
}
receiveTimeout := timeout / time.Duration(conn.retries)
if receiveTimeout == 0 {
receiveTimeout = time.Duration(1)
}
defer conn.resetTimeout()
var ackErr error
for i := 0; i < conn.retries; i++ {
if err := conn.send(b, udpAddr.udp); err != nil {
return fmt.Errorf("Error sending to %v: %v", addr, err)
}
if err := conn.timeout(timeout); err != nil {
return err
}
ackErr = conn.receiveAck(udpAddr.udp)
if ackErr == nil {
return nil
}
}
return fmt.Errorf("Gave up sending to %v after %v retries. Error: %v", addr, conn.retries, ackErr)
}
func (conn *udpConn) UnreliableSend(packet *Packet) error {
if conn.remote == nil {
return fmt.Errorf("Cannot send on this connection")
}
return conn.doUnreliableSend(packet, conn.remote)
}
func (conn *udpConn) doUnreliableSend(packet *Packet, addr Addr) error {
udpAddr, b, err := conn.prepareSend(packet, addr)
if err != nil {
return err
}
return conn.send(b, udpAddr.udp)
}
func (conn *udpConn) prepareSend(packet *Packet, addr Addr) (udp *udpAddr, b []byte, err error) {
udp, err = toUdpAddr(addr)
if err != nil {
return
}
b, err = Marshaller.MarshalPacket(packet)
return
}
func (conn *udpConn) Receive(timeout time.Duration) (*Packet, error) {
if timeout > 0 {
defer conn.resetTimeout()
if err := conn.timeout(timeout); err != nil {
return nil, err
}
}
buf, addr, err := conn.receive()
if err != nil {
return nil, fmt.Errorf("Error receiving: %v", err)
}
// TODO check if Ack was received...
packet, err := Marshaller.UnmarshalPacket(buf, conn.protocol)
if err != nil {
return nil, err
}
if err := conn.sendAck(addr); err == nil {
packet.SourceAddr = &udpAddr{conn.trans, addr}
return packet, nil
} else {
return nil, err
}
}
func (conn *udpConn) timeout(timeout time.Duration) error {
return conn.udp.SetDeadline(time.Now().Add(timeout))
}
func (conn *udpConn) resetTimeout() {
var zeroTime time.Time
_ = conn.udp.SetDeadline(zeroTime)
}
func (conn *udpConn) send(b []byte, addr *net.UDPAddr) error {
n, err := conn.udp.WriteToUDP(b, addr)
if err == nil && n != len(b) {
err = fmt.Errorf("Wrong number of bytes sent (%v != %v)", n, len(b))
}
return err
}
func (conn *udpConn) receive() ([]byte, *net.UDPAddr, error) {
size := conn.trans.bufferSize + 1 // One extra for >= check
buf := make([]byte, size)
n, addr, err := conn.udp.ReadFromUDP(buf)
if err == nil && n >= size {
err = fmt.Errorf("Receive buffer %v too small (received %v)", conn.trans.bufferSize, n)
}
return buf[:n], addr, err
}
func (conn *udpConn) sendAck(addr *net.UDPAddr) error {
// TODO write Ack mechansim
return nil
}
func (conn *udpConn) receiveAck(expectedAddr *net.UDPAddr) error {
// TODO write Ack mechansim
return nil
}