d0995e6a9e
This patch is thanks to an investigation by Leandro Sales de Melo and his
colleagues. They worked out two state diagrams which highlight the fact that
the xxx_TERM states in CCID-3/4 are in fact not necessary.
And this can be confirmed by in turn looking at the code: the xxx_TERM states
are only ever set in ccid3_hc_{rx,tx}_exit(). These two functions are part
of the following call chain:
* ccid_hc_{tx,rx}_exit() are called from ccid_delete() only;
* ccid_delete() invokes ccid_hc_{tx,rx}_exit() in the way of a destructor:
after calling ccid_hc_{tx,rx}_exit(), the CCID is released from memory;
* ccid_delete() is in turn called only by ccid_hc_{tx,rx}_delete();
* ccid_hc_{tx,rx}_delete() is called only if
- feature negotiation failed (dccp_feat_activate_values()),
- when changing the RX/TX CCID (to eject the current CCID),
- when destroying the socket (in dccp_destroy_sock()).
In other words, when CCID-3 sets the state to xxx_TERM, it is at a time where
no more processing should be going on, hence it is not necessary to introduce
a dedicated exit state - this is implicit when unloading the CCID.
The patch removes this state, one switch-statement collapses as a result.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
164 lines
5.3 KiB
C
164 lines
5.3 KiB
C
/*
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* net/dccp/ccids/ccid3.h
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*
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* Copyright (c) 2005-7 The University of Waikato, Hamilton, New Zealand.
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* Copyright (c) 2007 The University of Aberdeen, Scotland, UK
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*
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* An implementation of the DCCP protocol
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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_CCID3_H_
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#define _DCCP_CCID3_H_
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#include <linux/ktime.h>
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#include <linux/list.h>
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#include <linux/types.h>
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#include <linux/tfrc.h>
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#include "lib/tfrc.h"
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#include "../ccid.h"
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/* Two seconds as per RFC 3448 4.2 */
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#define TFRC_INITIAL_TIMEOUT (2 * USEC_PER_SEC)
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/* Parameter t_mbi from [RFC 3448, 4.3]: backoff interval in seconds */
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#define TFRC_T_MBI 64
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/*
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* The t_delta parameter (RFC 3448, 4.6): delays of less than %USEC_PER_MSEC are
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* rounded down to 0, since sk_reset_timer() here uses millisecond granularity.
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* Hence we can use a constant t_delta = %USEC_PER_MSEC when HZ >= 500. A coarse
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* resolution of HZ < 500 means that the error is below one timer tick (t_gran)
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* when using the constant t_delta = t_gran / 2 = %USEC_PER_SEC / (2 * HZ).
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*/
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#if (HZ >= 500)
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# define TFRC_T_DELTA USEC_PER_MSEC
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#else
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# define TFRC_T_DELTA (USEC_PER_SEC / (2 * HZ))
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#warning Coarse CONFIG_HZ resolution -- higher value recommended for TFRC.
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#endif
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enum ccid3_options {
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TFRC_OPT_LOSS_EVENT_RATE = 192,
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TFRC_OPT_LOSS_INTERVALS = 193,
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TFRC_OPT_RECEIVE_RATE = 194,
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};
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/* TFRC sender states */
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enum ccid3_hc_tx_states {
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TFRC_SSTATE_NO_SENT = 1,
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TFRC_SSTATE_NO_FBACK,
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TFRC_SSTATE_FBACK,
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};
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/** struct ccid3_hc_tx_sock - CCID3 sender half-connection socket
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*
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* @x - Current sending rate in 64 * bytes per second
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* @x_recv - Receive rate in 64 * bytes per second
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* @x_calc - Calculated rate in bytes per second
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* @rtt - Estimate of current round trip time in usecs
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* @p - Current loss event rate (0-1) scaled by 1000000
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* @s - Packet size in bytes
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* @t_rto - Nofeedback Timer setting in usecs
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* @t_ipi - Interpacket (send) interval (RFC 3448, 4.6) in usecs
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* @state - Sender state, one of %ccid3_hc_tx_states
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* @last_win_count - Last window counter sent
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* @t_last_win_count - Timestamp of earliest packet with
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* last_win_count value sent
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* @no_feedback_timer - Handle to no feedback timer
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* @t_ld - Time last doubled during slow start
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* @t_nom - Nominal send time of next packet
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* @hist - Packet history
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*/
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struct ccid3_hc_tx_sock {
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u64 x;
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u64 x_recv;
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u32 x_calc;
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u32 rtt;
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u32 p;
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u32 t_rto;
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u32 t_ipi;
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u16 s;
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enum ccid3_hc_tx_states state:8;
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u8 last_win_count;
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ktime_t t_last_win_count;
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struct timer_list no_feedback_timer;
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ktime_t t_ld;
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ktime_t t_nom;
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struct tfrc_tx_hist_entry *hist;
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};
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static inline struct ccid3_hc_tx_sock *ccid3_hc_tx_sk(const struct sock *sk)
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{
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struct ccid3_hc_tx_sock *hctx = ccid_priv(dccp_sk(sk)->dccps_hc_tx_ccid);
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BUG_ON(hctx == NULL);
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return hctx;
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}
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/* TFRC receiver states */
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enum ccid3_hc_rx_states {
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TFRC_RSTATE_NO_DATA = 1,
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TFRC_RSTATE_DATA,
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};
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/** struct ccid3_hc_rx_sock - CCID3 receiver half-connection socket
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*
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* @last_counter - Tracks window counter (RFC 4342, 8.1)
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* @state - Receiver state, one of %ccid3_hc_rx_states
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* @bytes_recv - Total sum of DCCP payload bytes
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* @x_recv - Receiver estimate of send rate (RFC 3448, sec. 4.3)
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* @rtt - Receiver estimate of RTT
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* @tstamp_last_feedback - Time at which last feedback was sent
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* @hist - Packet history (loss detection + RTT sampling)
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* @li_hist - Loss Interval database
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* @s - Received packet size in bytes
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* @p_inverse - Inverse of Loss Event Rate (RFC 4342, sec. 8.5)
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*/
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struct ccid3_hc_rx_sock {
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u8 last_counter:4;
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enum ccid3_hc_rx_states state:8;
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u32 bytes_recv;
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u32 x_recv;
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u32 rtt;
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ktime_t tstamp_last_feedback;
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struct tfrc_rx_hist hist;
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struct tfrc_loss_hist li_hist;
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u16 s;
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#define p_inverse li_hist.i_mean
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};
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static inline struct ccid3_hc_rx_sock *ccid3_hc_rx_sk(const struct sock *sk)
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{
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struct ccid3_hc_rx_sock *hcrx = ccid_priv(dccp_sk(sk)->dccps_hc_rx_ccid);
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BUG_ON(hcrx == NULL);
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return hcrx;
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}
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#endif /* _DCCP_CCID3_H_ */
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