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proxy.go
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proxy.go
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package quicproxy
import (
"net"
"sync"
"sync/atomic"
"time"
"github.com/lucas-clemente/quic-go/internal/protocol"
)
// Connection is a UDP connection
type connection struct {
ClientAddr *net.UDPAddr // Address of the client
ServerConn *net.UDPConn // UDP connection to server
incomingPacketCounter uint64
outgoingPacketCounter uint64
}
// Direction is the direction a packet is sent.
type Direction int
const (
// DirectionIncoming is the direction from the client to the server.
DirectionIncoming Direction = iota
// DirectionOutgoing is the direction from the server to the client.
DirectionOutgoing
// DirectionBoth is both incoming and outgoing
DirectionBoth
)
func (d Direction) String() string {
switch d {
case DirectionIncoming:
return "incoming"
case DirectionOutgoing:
return "outgoing"
case DirectionBoth:
return "both"
default:
panic("unknown direction")
}
}
func (d Direction) Is(dir Direction) bool {
if d == DirectionBoth || dir == DirectionBoth {
return true
}
return d == dir
}
// DropCallback is a callback that determines which packet gets dropped.
type DropCallback func(dir Direction, packetCount uint64) bool
// NoDropper doesn't drop packets.
var NoDropper DropCallback = func(Direction, uint64) bool {
return false
}
// DelayCallback is a callback that determines how much delay to apply to a packet.
type DelayCallback func(dir Direction, packetCount uint64) time.Duration
// NoDelay doesn't apply a delay.
var NoDelay DelayCallback = func(Direction, uint64) time.Duration {
return 0
}
// Opts are proxy options.
type Opts struct {
// The address this proxy proxies packets to.
RemoteAddr string
// DropPacket determines whether a packet gets dropped.
DropPacket DropCallback
// DelayPacket determines how long a packet gets delayed. This allows
// simulating a connection with non-zero RTTs.
// Note that the RTT is the sum of the delay for the incoming and the outgoing packet.
DelayPacket DelayCallback
}
// QuicProxy is a QUIC proxy that can drop and delay packets.
type QuicProxy struct {
mutex sync.Mutex
version protocol.VersionNumber
conn *net.UDPConn
serverAddr *net.UDPAddr
dropPacket DropCallback
delayPacket DelayCallback
// Mapping from client addresses (as host:port) to connection
clientDict map[string]*connection
}
// NewQuicProxy creates a new UDP proxy
func NewQuicProxy(local string, version protocol.VersionNumber, opts *Opts) (*QuicProxy, error) {
if opts == nil {
opts = &Opts{}
}
laddr, err := net.ResolveUDPAddr("udp", local)
if err != nil {
return nil, err
}
conn, err := net.ListenUDP("udp", laddr)
if err != nil {
return nil, err
}
raddr, err := net.ResolveUDPAddr("udp", opts.RemoteAddr)
if err != nil {
return nil, err
}
packetDropper := NoDropper
if opts.DropPacket != nil {
packetDropper = opts.DropPacket
}
packetDelayer := NoDelay
if opts.DelayPacket != nil {
packetDelayer = opts.DelayPacket
}
p := QuicProxy{
clientDict: make(map[string]*connection),
conn: conn,
serverAddr: raddr,
dropPacket: packetDropper,
delayPacket: packetDelayer,
version: version,
}
go p.runProxy()
return &p, nil
}
// Close stops the UDP Proxy
func (p *QuicProxy) Close() error {
return p.conn.Close()
}
// LocalAddr is the address the proxy is listening on.
func (p *QuicProxy) LocalAddr() net.Addr {
return p.conn.LocalAddr()
}
// LocalPort is the UDP port number the proxy is listening on.
func (p *QuicProxy) LocalPort() int {
return p.conn.LocalAddr().(*net.UDPAddr).Port
}
func (p *QuicProxy) newConnection(cliAddr *net.UDPAddr) (*connection, error) {
srvudp, err := net.DialUDP("udp", nil, p.serverAddr)
if err != nil {
return nil, err
}
return &connection{
ClientAddr: cliAddr,
ServerConn: srvudp,
}, nil
}
// runProxy listens on the proxy address and handles incoming packets.
func (p *QuicProxy) runProxy() error {
for {
buffer := make([]byte, protocol.MaxReceivePacketSize)
n, cliaddr, err := p.conn.ReadFromUDP(buffer)
if err != nil {
return err
}
raw := buffer[0:n]
saddr := cliaddr.String()
p.mutex.Lock()
conn, ok := p.clientDict[saddr]
if !ok {
conn, err = p.newConnection(cliaddr)
if err != nil {
p.mutex.Unlock()
return err
}
p.clientDict[saddr] = conn
go p.runConnection(conn)
}
p.mutex.Unlock()
packetCount := atomic.AddUint64(&conn.incomingPacketCounter, 1)
if p.dropPacket(DirectionIncoming, packetCount) {
continue
}
// Send the packet to the server
delay := p.delayPacket(DirectionIncoming, packetCount)
if delay != 0 {
time.AfterFunc(delay, func() {
// TODO: handle error
_, _ = conn.ServerConn.Write(raw)
})
} else {
_, err := conn.ServerConn.Write(raw)
if err != nil {
return err
}
}
}
}
// runConnection handles packets from server to a single client
func (p *QuicProxy) runConnection(conn *connection) error {
for {
buffer := make([]byte, protocol.MaxReceivePacketSize)
n, err := conn.ServerConn.Read(buffer)
if err != nil {
return err
}
raw := buffer[0:n]
packetCount := atomic.AddUint64(&conn.outgoingPacketCounter, 1)
if p.dropPacket(DirectionOutgoing, packetCount) {
continue
}
delay := p.delayPacket(DirectionOutgoing, packetCount)
if delay != 0 {
time.AfterFunc(delay, func() {
// TODO: handle error
_, _ = p.conn.WriteToUDP(raw, conn.ClientAddr)
})
} else {
_, err := p.conn.WriteToUDP(raw, conn.ClientAddr)
if err != nil {
return err
}
}
}
}