22cd0d47fa
This makes the user interface a little hostile. People thing of an MTU of 1500 bytes, but the corresponding packet is really 1514 bytes (including the 14 byte Ethernet header). A more friendly solution would configure the MTU (as before), but then derive the packet buffer size by adding the MAC header length. Instead, we define the packet buffer size then derive the MTU.
The MTU is not common currency in networking. On the wire, the only real issue is the MSS which is derived from MTU by subtracting the IP header and TCP header sizes (for the case of TCP). Now it is derived for the PKTSIZE by subtracting the IP header, the TCP header, and the MAC header sizes. So we should be all good and without the recurring 14 byte error in MTU's and MSS's.
Squashed commit of the following:
Trivial update to fix some spacing issues.
net/: Rename several macros containing _MTU to _PKTSIZE.
net/: Rename CONFIG_NET_SLIP_MTU to CONFIG_NET_SLIP_PKTSIZE and similarly for CONFIG_NET_TUN_MTU. These are not the MTU which does not include the size of the link layer header. These are the full size of the packet buffer memory (minus any GUARD bytes).
net/: Rename CONFIG_NET_6LOWPAN_MTU to CONFIG_NET_6LOWPAN_PKTSIZE and similarly for CONFIG_NET_TUN_MTU. These are not the MTU which does not include the size of the link layer header. These are the full size of the packet buffer memory (minus any GUARD bytes).
net/: Rename CONFIG_NET_ETH_MTU to CONFIG_NET_ETH_PKTSIZE. This is not the MTU which does not include the size of the link layer header. This is the full size of the packet buffer memory (minus any GUARD bytes).
net/: Rename the file d_mtu in the network driver structure to d_pktsize. That value saved there is not the MTU. The packetsize is the memory large enough to hold the maximum packet PLUS the size of the link layer header. The MTU does not include the link layer header.
180 lines
5.4 KiB
C
180 lines
5.4 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 <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 navail;
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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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* availability.
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*/
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navail = iob_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 (navail > CONFIG_IOB_THROTTLE)
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{
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navail -= CONFIG_IOB_THROTTLE;
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}
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else
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{
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navail = 0;
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}
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#endif
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/* Are there any IOBs available for read-ahead buffering? */
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if (navail > 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 = (navail * 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 /* if (navail == 0) */
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#endif
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{
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/* No IOBs are available. The only buffering available is within the
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* packet buffer itself. We can buffer no more than the MSS (unless
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* 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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