kvm/internal/audio/socket_buffer.go

package audio

import (
	"fmt"
	"net"
	"syscall"
)

// Socket buffer sizes are now centralized in config_constants.go

// SocketBufferConfig holds socket buffer configuration
type SocketBufferConfig struct {
	SendBufferSize int
	RecvBufferSize int
	Enabled        bool
}

// DefaultSocketBufferConfig returns the default socket buffer configuration
func DefaultSocketBufferConfig() SocketBufferConfig {
	return SocketBufferConfig{
		SendBufferSize: Config.SocketOptimalBuffer,
		RecvBufferSize: Config.SocketOptimalBuffer,
		Enabled:        true,
	}
}

// HighLoadSocketBufferConfig returns configuration for high-load scenarios
func HighLoadSocketBufferConfig() SocketBufferConfig {
	return SocketBufferConfig{
		SendBufferSize: Config.SocketMaxBuffer,
		RecvBufferSize: Config.SocketMaxBuffer,
		Enabled:        true,
	}
}

// ConfigureSocketBuffers applies socket buffer configuration to a Unix socket connection
func ConfigureSocketBuffers(conn net.Conn, config SocketBufferConfig) error {
	if !config.Enabled {
		return nil
	}

	if err := ValidateSocketBufferConfig(config); err != nil {
		return fmt.Errorf("invalid socket buffer config: %w", err)
	}

	unixConn, ok := conn.(*net.UnixConn)
	if !ok {
		return fmt.Errorf("connection is not a Unix socket")
	}

	file, err := unixConn.File()
	if err != nil {
		return fmt.Errorf("failed to get socket file descriptor: %w", err)
	}
	defer file.Close()

	fd := int(file.Fd())

	if config.SendBufferSize > 0 {
		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF, config.SendBufferSize); err != nil {
			return fmt.Errorf("failed to set SO_SNDBUF to %d: %w", config.SendBufferSize, err)
		}
	}

	if config.RecvBufferSize > 0 {
		if err := syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUF, config.RecvBufferSize); err != nil {
			return fmt.Errorf("failed to set SO_RCVBUF to %d: %w", config.RecvBufferSize, err)
		}
	}

	return nil
}

// GetSocketBufferSizes retrieves current socket buffer sizes
func GetSocketBufferSizes(conn net.Conn) (sendSize, recvSize int, err error) {
	unixConn, ok := conn.(*net.UnixConn)
	if !ok {
		return 0, 0, fmt.Errorf("socket buffer query only supported for Unix sockets")
	}

	file, err := unixConn.File()
	if err != nil {
		return 0, 0, fmt.Errorf("failed to get socket file descriptor: %w", err)
	}
	defer file.Close()

	fd := int(file.Fd())

	// Get send buffer size
	sendSize, err = syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_SNDBUF)
	if err != nil {
		return 0, 0, fmt.Errorf("failed to get SO_SNDBUF: %w", err)
	}

	// Get receive buffer size
	recvSize, err = syscall.GetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_RCVBUF)
	if err != nil {
		return 0, 0, fmt.Errorf("failed to get SO_RCVBUF: %w", err)
	}

	return sendSize, recvSize, nil
}

// ValidateSocketBufferConfig validates socket buffer configuration parameters.
//
// Validation Rules:
//   - If config.Enabled is false, no validation is performed (returns nil)
//   - SendBufferSize must be >= SocketMinBuffer (default: 8192 bytes)
//   - RecvBufferSize must be >= SocketMinBuffer (default: 8192 bytes)
//   - SendBufferSize must be <= SocketMaxBuffer (default: 1048576 bytes)
//   - RecvBufferSize must be <= SocketMaxBuffer (default: 1048576 bytes)
//
// Error Conditions:
//   - Returns error if send buffer size is below minimum threshold
//   - Returns error if receive buffer size is below minimum threshold
//   - Returns error if send buffer size exceeds maximum threshold
//   - Returns error if receive buffer size exceeds maximum threshold
//
// The validation ensures socket buffers are sized appropriately for audio streaming
// performance while preventing excessive memory usage.
func ValidateSocketBufferConfig(config SocketBufferConfig) error {
	if !config.Enabled {
		return nil
	}

	minBuffer := Config.SocketMinBuffer
	maxBuffer := Config.SocketMaxBuffer

	if config.SendBufferSize < minBuffer {
		return fmt.Errorf("send buffer size validation failed: got %d bytes, minimum required %d bytes (configured range: %d-%d)",
			config.SendBufferSize, minBuffer, minBuffer, maxBuffer)
	}

	if config.RecvBufferSize < minBuffer {
		return fmt.Errorf("receive buffer size validation failed: got %d bytes, minimum required %d bytes (configured range: %d-%d)",
			config.RecvBufferSize, minBuffer, minBuffer, maxBuffer)
	}

	if config.SendBufferSize > maxBuffer {
		return fmt.Errorf("send buffer size validation failed: got %d bytes, maximum allowed %d bytes (configured range: %d-%d)",
			config.SendBufferSize, maxBuffer, minBuffer, maxBuffer)
	}

	if config.RecvBufferSize > maxBuffer {
		return fmt.Errorf("receive buffer size validation failed: got %d bytes, maximum allowed %d bytes (configured range: %d-%d)",
			config.RecvBufferSize, maxBuffer, minBuffer, maxBuffer)
	}

	return nil
}

// RecordSocketBufferMetrics records socket buffer metrics for monitoring
func RecordSocketBufferMetrics(conn net.Conn, component string) {
	if conn == nil {
		return
	}

	// Get current socket buffer sizes
	sendSize, recvSize, err := GetSocketBufferSizes(conn)
	if err != nil {
		// Log error but don't fail
		return
	}

	// Record buffer sizes
	socketBufferSizeGauge.WithLabelValues(component, "send").Set(float64(sendSize))
	socketBufferSizeGauge.WithLabelValues(component, "receive").Set(float64(recvSize))
}

// RecordSocketBufferOverflow records a socket buffer overflow event
func RecordSocketBufferOverflow(component, bufferType string) {
	socketBufferOverflowCounter.WithLabelValues(component, bufferType).Inc()
}

// UpdateSocketBufferUtilization updates socket buffer utilization metrics
func UpdateSocketBufferUtilization(component, bufferType string, utilizationPercent float64) {
	socketBufferUtilizationGauge.WithLabelValues(component, bufferType).Set(utilizationPercent)
}