157 lines
4.7 KiB
C
157 lines
4.7 KiB
C
/****************************************************************************
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* net/tcp/tcp_recvwindow.c
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*
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* Licensed to the Apache Software Foundation (ASF) under one or more
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* contributor license agreements. See the NOTICE file distributed with
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* this work for additional information regarding copyright ownership. The
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* ASF licenses this file to you under the Apache License, Version 2.0 (the
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* "License"); you may not use this file except in compliance with the
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* License. You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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* License for the specific language governing permissions and limitations
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* under the License.
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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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FAR struct tcp_conn_s *conn)
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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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int niob_avail;
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int nqentry_avail;
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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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/* 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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/* 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 for the device packet
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* buffer. This logic here assumes that all IOBs are available for
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* 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
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* available 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);
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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 (IOB_QEMPTY(&conn->readahead))
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{
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/* Advertise maximum segment size for window edge if here is no
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* available iobs on current "free" connection.
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*/
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recvwndo = mss;
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}
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else /* nqentry_avail == 0 || niob_avail == 0 */
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{
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/* No IOB chains or noIOBs are available.
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* Advertise the edge of window to zero.
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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 = 0;
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}
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return recvwndo;
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}
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