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d2c726309d
This removes the RTT-sampling function tfrc_tx_hist_rtt(), since
1. it suffered from complex passing of return values (the return value both
indicated successful lookup while the value doubled as RTT sample);
2. when for some odd reason the sample value equalled 0, this triggered a bug
warning about "bogus Ack", due to the ambiguity of the return value;
3. on a passive host which has not sent anything the TX history is empty and
thus will lead to unwanted "bogus Ack" warnings such as
ccid3_hc_tx_packet_recv: server(e7b7d518): DATAACK with bogus ACK-28197148
ccid3_hc_tx_packet_recv: server(e7b7d518): DATAACK with bogus ACK-26641606.
The fix is to replace the implicit encoding by performing the steps manually.
Furthermore, the "bogus Ack" warning has been removed, since it can actually be
triggered due to several reasons (network reordering, old packet, (3) above),
hence it is not very useful.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
159 lines
5.1 KiB
C
159 lines
5.1 KiB
C
/*
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* Packet RX/TX history data structures and routines for TFRC-based protocols.
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*
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* Copyright (c) 2007 The University of Aberdeen, Scotland, UK
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* Copyright (c) 2005-6 The University of Waikato, Hamilton, New Zealand.
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*
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* This code has been developed by the University of Waikato WAND
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* research group. For further information please see http://www.wand.net.nz/
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* or e-mail Ian McDonald - ian.mcdonald@jandi.co.nz
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*
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* This code also uses code from Lulea University, rereleased as GPL by its
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* authors:
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* Copyright (c) 2003 Nils-Erik Mattsson, Joacim Haggmark, Magnus Erixzon
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*
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* Changes to meet Linux coding standards, to make it meet latest ccid3 draft
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* and to make it work as a loadable module in the DCCP stack written by
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* Arnaldo Carvalho de Melo <acme@conectiva.com.br>.
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*
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* Copyright (c) 2005 Arnaldo Carvalho de Melo <acme@conectiva.com.br>
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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#ifndef _DCCP_PKT_HIST_
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#define _DCCP_PKT_HIST_
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#include <linux/list.h>
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#include <linux/slab.h>
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#include "tfrc.h"
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/**
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* tfrc_tx_hist_entry - Simple singly-linked TX history list
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* @next: next oldest entry (LIFO order)
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* @seqno: sequence number of this entry
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* @stamp: send time of packet with sequence number @seqno
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*/
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struct tfrc_tx_hist_entry {
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struct tfrc_tx_hist_entry *next;
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u64 seqno;
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ktime_t stamp;
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};
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static inline struct tfrc_tx_hist_entry *
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tfrc_tx_hist_find_entry(struct tfrc_tx_hist_entry *head, u64 seqno)
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{
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while (head != NULL && head->seqno != seqno)
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head = head->next;
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return head;
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}
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extern int tfrc_tx_hist_add(struct tfrc_tx_hist_entry **headp, u64 seqno);
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extern void tfrc_tx_hist_purge(struct tfrc_tx_hist_entry **headp);
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/* Subtraction a-b modulo-16, respects circular wrap-around */
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#define SUB16(a, b) (((a) + 16 - (b)) & 0xF)
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/* Number of packets to wait after a missing packet (RFC 4342, 6.1) */
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#define TFRC_NDUPACK 3
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/**
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* tfrc_rx_hist_entry - Store information about a single received packet
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* @tfrchrx_seqno: DCCP packet sequence number
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* @tfrchrx_ccval: window counter value of packet (RFC 4342, 8.1)
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* @tfrchrx_ndp: the NDP count (if any) of the packet
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* @tfrchrx_tstamp: actual receive time of packet
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*/
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struct tfrc_rx_hist_entry {
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u64 tfrchrx_seqno:48,
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tfrchrx_ccval:4,
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tfrchrx_type:4;
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u64 tfrchrx_ndp:48;
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ktime_t tfrchrx_tstamp;
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};
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/**
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* tfrc_rx_hist - RX history structure for TFRC-based protocols
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* @ring: Packet history for RTT sampling and loss detection
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* @loss_count: Number of entries in circular history
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* @loss_start: Movable index (for loss detection)
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* @rtt_sample_prev: Used during RTT sampling, points to candidate entry
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*/
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struct tfrc_rx_hist {
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struct tfrc_rx_hist_entry *ring[TFRC_NDUPACK + 1];
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u8 loss_count:2,
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loss_start:2;
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#define rtt_sample_prev loss_start
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};
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/**
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* tfrc_rx_hist_index - index to reach n-th entry after loss_start
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*/
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static inline u8 tfrc_rx_hist_index(const struct tfrc_rx_hist *h, const u8 n)
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{
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return (h->loss_start + n) & TFRC_NDUPACK;
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}
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/**
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* tfrc_rx_hist_last_rcv - entry with highest-received-seqno so far
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*/
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static inline struct tfrc_rx_hist_entry *
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tfrc_rx_hist_last_rcv(const struct tfrc_rx_hist *h)
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{
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return h->ring[tfrc_rx_hist_index(h, h->loss_count)];
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}
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/**
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* tfrc_rx_hist_entry - return the n-th history entry after loss_start
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*/
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static inline struct tfrc_rx_hist_entry *
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tfrc_rx_hist_entry(const struct tfrc_rx_hist *h, const u8 n)
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{
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return h->ring[tfrc_rx_hist_index(h, n)];
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}
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/**
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* tfrc_rx_hist_loss_prev - entry with highest-received-seqno before loss was detected
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*/
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static inline struct tfrc_rx_hist_entry *
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tfrc_rx_hist_loss_prev(const struct tfrc_rx_hist *h)
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{
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return h->ring[h->loss_start];
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}
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/* indicate whether previously a packet was detected missing */
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static inline bool tfrc_rx_hist_loss_pending(const struct tfrc_rx_hist *h)
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{
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return h->loss_count > 0;
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}
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extern void tfrc_rx_hist_add_packet(struct tfrc_rx_hist *h,
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const struct sk_buff *skb, const u64 ndp);
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extern int tfrc_rx_hist_duplicate(struct tfrc_rx_hist *h, struct sk_buff *skb);
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struct tfrc_loss_hist;
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extern int tfrc_rx_handle_loss(struct tfrc_rx_hist *h,
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struct tfrc_loss_hist *lh,
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struct sk_buff *skb, const u64 ndp,
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u32 (*first_li)(struct sock *sk),
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struct sock *sk);
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extern u32 tfrc_rx_hist_sample_rtt(struct tfrc_rx_hist *h,
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const struct sk_buff *skb);
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extern int tfrc_rx_hist_alloc(struct tfrc_rx_hist *h);
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extern void tfrc_rx_hist_purge(struct tfrc_rx_hist *h);
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#endif /* _DCCP_PKT_HIST_ */
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