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- /****************************************************************************
- * net/tcp/tcp_recvwindow.c
- *
- * Copyright (C) 2018 Gregory Nutt. All rights reserved.
- * Author: Gregory Nutt <gnutt@nuttx.org>
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- * notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- * notice, this list of conditions and the following disclaimer in
- * the documentation and/or other materials provided with the
- * distribution.
- * 3. Neither the name NuttX nor the names of its contributors may be
- * used to endorse or promote products derived from this software
- * without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
- /****************************************************************************
- * Included Files
- ****************************************************************************/
- #include <nuttx/config.h>
- #include <stdint.h>
- #include <stdbool.h>
- #include <debug.h>
- #include <net/if.h>
- #include <nuttx/mm/iob.h>
- #include <nuttx/net/netconfig.h>
- #include <nuttx/net/netdev.h>
- #include <nuttx/net/tcp.h>
- #include "tcp/tcp.h"
- /****************************************************************************
- * Public Functions
- ****************************************************************************/
- /****************************************************************************
- * Name: tcp_get_recvwindow
- *
- * Description:
- * Calculate the TCP receive window for the specified device.
- *
- * Input Parameters:
- * dev - The device whose TCP receive window will be updated.
- *
- * Returned Value:
- * The value of the TCP receive window to use.
- *
- ****************************************************************************/
- uint16_t tcp_get_recvwindow(FAR struct net_driver_s *dev)
- {
- uint16_t iplen;
- uint16_t mss;
- uint16_t recvwndo;
- #ifdef CONFIG_NET_TCP_READAHEAD
- int niob_avail;
- int nqentry_avail;
- #endif
- #ifdef CONFIG_NET_IPv6
- #ifdef CONFIG_NET_IPv4
- if (IFF_IS_IPv6(dev->d_flags))
- #endif
- {
- iplen = IPv6_HDRLEN;
- }
- #endif /* CONFIG_NET_IPv6 */
- #ifdef CONFIG_NET_IPv4
- #ifdef CONFIG_NET_IPv6
- else
- #endif
- {
- iplen = IPv4_HDRLEN;
- }
- #endif /* CONFIG_NET_IPv4 */
- /* Calculate the packet MSS.
- *
- * REVISIT: The actual TCP header length is variable. TCP_HDRLEN
- * is the minimum size.
- */
- mss = dev->d_pktsize - (NET_LL_HDRLEN(dev) + iplen + TCP_HDRLEN);
- #ifdef CONFIG_NET_TCP_READAHEAD
- /* Update the TCP received window based on read-ahead I/O buffer
- * and IOB chain availability. At least one queue entry is required.
- * If one queue entry is available, then the amount of read-ahead
- * data that can be buffered is given by the number of IOBs available
- * (ignoring competition with other IOB consumers).
- */
- niob_avail = iob_navail(true);
- nqentry_avail = iob_qentry_navail();
- /* Are the read-ahead allocations throttled? If so, then not all of these
- * IOBs are available for read-ahead buffering.
- *
- * REVISIT: Should also check that there is at least one available IOB
- * chain.
- */
- #if CONFIG_IOB_THROTTLE > 0
- if (niob_avail > CONFIG_IOB_THROTTLE)
- {
- niob_avail -= CONFIG_IOB_THROTTLE;
- }
- else
- {
- niob_avail = 0;
- }
- #endif
- /* Is there a a queue entry and IOBs available for read-ahead buffering? */
- if (nqentry_avail > 0 && niob_avail > 0)
- {
- uint32_t rwnd;
- /* The optimal TCP window size is the amount of TCP data that we can
- * currently buffer via TCP read-ahead buffering plus MSS for the
- * device packet buffer. This logic here assumes that all IOBs are
- * available for TCP buffering.
- *
- * Assume that all of the available IOBs are can be used for buffering
- * on this connection. Also assume that at least one chain is available
- * concatenate the IOBs.
- *
- * REVISIT: In an environment with multiple, active read-ahead TCP
- * sockets (and perhaps multiple network devices) or if there are
- * other consumers of IOBs (such as for TCP write buffering) then the
- * total number of IOBs will all not be available for read-ahead
- * buffering for this connection.
- */
- rwnd = (niob_avail * CONFIG_IOB_BUFSIZE) + mss;
- if (rwnd > UINT16_MAX)
- {
- rwnd = UINT16_MAX;
- }
- /* Save the new receive window size */
- recvwndo = (uint16_t)rwnd;
- }
- else /* nqentry_avail == 0 || niob_avail == 0 */
- #endif
- {
- /* No IOB chains or noIOBs are available. The only buffering
- * available is within the packet buffer itself. We can buffer no
- * more than the MSS (unless we are very fast).
- *
- * NOTE: If no IOBs are available, then the next packet will be
- * lost if there is no listener on the connection.
- */
- recvwndo = mss;
- }
- return recvwndo;
- }
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