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