move UDP receive buffer size manipulation to a separate file

sys_conn_buffers.go

@@ -0,0 +1,48 @@
+package quic
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"sync"
+
+	"github.com/quic-go/quic-go/internal/protocol"
+	"github.com/quic-go/quic-go/internal/utils"
+)
+
+func setReceiveBuffer(c net.PacketConn, logger utils.Logger) error {
+	conn, ok := c.(interface{ SetReadBuffer(int) error })
+	if !ok {
+		return errors.New("connection doesn't allow setting of receive buffer size. Not a *net.UDPConn?")
+	}
+	size, err := inspectReadBuffer(c)
+	if err != nil {
+		return fmt.Errorf("failed to determine receive buffer size: %w", err)
+	}
+	if size >= protocol.DesiredReceiveBufferSize {
+		logger.Debugf("Conn has receive buffer of %d kiB (wanted: at least %d kiB)", size/1024, protocol.DesiredReceiveBufferSize/1024)
+		return nil
+	}
+	// Ignore the error. We check if we succeeded by querying the buffer size afterward.
+	_ = conn.SetReadBuffer(protocol.DesiredReceiveBufferSize)
+	newSize, err := inspectReadBuffer(c)
+	if newSize < protocol.DesiredReceiveBufferSize {
+		// Try again with RCVBUFFORCE on Linux
+		_ = forceSetReceiveBuffer(c, protocol.DesiredReceiveBufferSize)
+		newSize, err = inspectReadBuffer(c)
+		if err != nil {
+			return fmt.Errorf("failed to determine receive buffer size: %w", err)
+		}
+	}
+	if err != nil {
+		return fmt.Errorf("failed to determine receive buffer size: %w", err)
+	}
+	if newSize == size {
+		return fmt.Errorf("failed to increase receive buffer size (wanted: %d kiB, got %d kiB)", protocol.DesiredReceiveBufferSize/1024, newSize/1024)
+	}
+	if newSize < protocol.DesiredReceiveBufferSize {
+		return fmt.Errorf("failed to sufficiently increase receive buffer size (was: %d kiB, wanted: %d kiB, got: %d kiB)", size/1024, protocol.DesiredReceiveBufferSize/1024, newSize/1024)
+	}
+	logger.Debugf("Increased receive buffer size to %d kiB", newSize/1024)
+	return nil
+}