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.
123 lines
4.8 KiB
C
123 lines
4.8 KiB
C
/****************************************************************************
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* include/nuttx/net/slip.h
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*
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* Copyright (C) 2014 Gregory Nutt. All rights reserved.
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* Author : Gregory Nutt <gnutt@nuttx.org>
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*
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* Includes some definitions that a compatible with the LGPL GNU C Library
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* header file of the same name.
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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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#ifndef __INCLUDE_NUTTX_NET_SLIP_H
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#define __INCLUDE_NUTTX_NET_SLIP_H
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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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#ifdef CONFIG_NET_SLIP
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/****************************************************************************
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* Pre-processor Definitions
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****************************************************************************/
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/* Configuration ***********************************************************/
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/* SLIP Configuration:
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*
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* CONFIG_NET_SLIP - Enables building of the SLIP driver
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* CONFIG_NET_SLIP_STACKSIZE - Provides the stack size for SLIP RX and TX
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* threads. Default: 2048
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* CONFIG_NET_SLIP_DEFPRIO - Provides the priority for SLIP RX and TX
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* threads. Default 128.
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* CONFIG_NET_NET_SLIP_PKTSIZE - Provides the size of the SLIP packet buffers.
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* Default 296
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*
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* The Linux slip module hard-codes its MTU size to 296 (40 bytes for the
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* IP+TPC headers plus 256 bytes of data). So you might as well set
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* CONFIG_NET_SLIP_PKTSIZE to 296 as well.
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*
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* There may be an issue with this setting, however. I see that Linux
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* uses a MTU of 296 and window of 256, but actually only sends 168 bytes
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* of data: 40 + 128. I believe that is to allow for the 2x worst cast
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* packet expansion. Ideally we would like to advertise the 256 MSS,
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* but restrict transfers to 128 bytes (possibly by modifying the
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* tcp_mss() macro).
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*
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* CONFIG_NET_SLIP_NINTERFACES determines the number of physical interfaces
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* that will be supported.
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*/
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/****************************************************************************
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* Public Data
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****************************************************************************/
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#ifdef __cplusplus
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#define EXTERN extern "C"
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extern "C"
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{
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#else
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#define EXTERN extern
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#endif
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/****************************************************************************
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* Public Function Prototypes
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****************************************************************************/
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/****************************************************************************
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* Name: slip_initialize
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*
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* Description:
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* Instantiate a SLIP network interface.
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*
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* Input Parameters:
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* intf - In the case where there are multiple SLIP interfaces, this
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* value identifies which is to be initialized. The number of
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* possible SLIP interfaces is determined by
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* devname - This is the path to the serial device that will support SLIP.
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* For example, this might be "/dev/ttyS1"
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*
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* Returned Value:
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* OK on success; Negated errno on failure.
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*
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* Assumptions:
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*
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****************************************************************************/
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int slip_initialize(int intf, FAR const char *devname);
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#undef EXTERN
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#ifdef __cplusplus
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}
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#endif
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#endif /* CONFIG_NET_SLIP */
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#endif /* __INCLUDE_NUTTX_NET_SLIP_H */
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