spoofer

type Opts struct {
	// OnTCPConn is the eager, compatibility TCP callback. Spoofer completes the
	// intercepted client handshake before it calls this function. A failure to
	// connect the real upstream can therefore not make the original Dial fail.
	// Forward proxies that need correct connection results must use PrepareTCP.
	OnTCPConn func(net.Conn, stack.TransportEndpointID)
	// PrepareTCP prepares the real upstream before Spoofer accepts an
	// intercepted TCP connection. If preparation fails, Spoofer resets the
	// client flow and calls OnTCPError. If it succeeds, Spoofer completes the
	// client handshake and passes the connection to the prepared handler.
	// PrepareTCP takes priority when both TCP callbacks are set.
	PrepareTCP func(context.Context, stack.TransportEndpointID) (PreparedTCPHandler, error)
	// OnTCPError reports preparation and client-endpoint errors from the
	// connection-gated PrepareTCP path. Spoofer calls it from a forwarding
	// goroutine. The callback must be safe for concurrent use.
	OnTCPError func(stack.TransportEndpointID, error)
	// TCPPrepareTimeout limits each PrepareTCP call. The default is 30 seconds.
	// Values less than or equal to zero use the default. PrepareTCP must stop
	// work and release partial resources when its context is done.
	TCPPrepareTimeout time.Duration
	// OnUDPConn is called when a new UDP stream is forwarded.
	// The callback receives a packet connection and the transport endpoint ID.
	OnUDPConn func(gonnect.PacketConn, stack.TransportEndpointID)

	// Endpoint is the link-layer endpoint used by the netstack.
	// Set it via WithRWCEndpoint or WithTunEndpoint before calling Launch.
	Endpoint stack.LinkEndpoint

	// TCPSendBufferSize sets the default TCP send buffer size.
	TCPSendBufferSize int
	// TCPReceiveBufferSize sets the default TCP receive buffer size.
	TCPReceiveBufferSize int
	// TTL sets the default TTL for outgoing packets.
	TTL int
	// ICMPBurst sets the ICMP rate limiter burst size.
	ICMPBurst int
	// ICMPLimit sets the ICMP rate limit (packets per second).
	ICMPLimit float64
	// CongestionControlAlg sets the TCP congestion control algorithm name
	// (e.g., "cubic", "reno").
	CongestionControlAlg string
	// DisableNagle disables Nagle's algorithm (TCP_NODELAY).
	DisableNagle bool
	// DisableTCPModRecBuff disables TCP moderate receive buffer auto-tuning.
	DisableTCPModRecBuff bool
	// TCPRec sets the TCP recovery option for tail loss probe.
	TCPRec *tcpip.TCPRecovery

	// TCPKeepAlive enables TCP keep-alive on forwarded connections.
	TCPKeepAlive bool
	// TCPKeepAliveIdle sets the time before sending keep-alive probes.
	TCPKeepAliveIdle time.Duration
	// TCPKeepaliveInterval sets the interval between keep-alive probes.
	TCPKeepaliveInterval time.Duration
	// TCPKeepaliveCount sets the maximum number of unacknowledged keep-alive probes.
	TCPKeepaliveCount int

	// TCPForwardWnd sets the TCP receive window size for forwarded connections.
	TCPForwardWnd int
	// TCPForwardAttempts sets the maximum concurrent TCP connection forwarding attempts.
	TCPForwardAttempts int

	// NetStackOpts provides additional netstack configuration options.
	NetStackOpts *helpers.Opts
}

type PreparedTCPHandler interface {
	HandleTCP(net.Conn)
	Close() error
}

type PreparedTCPHandlerFuncs struct {
	HandleFunc func(net.Conn)
	CloseFunc  func() error
}