From 1a21e49a8d60f588c1276f765198b14d5688a778 Mon Sep 17 00:00:00 2001 From: Gerrit Renker Date: Sun, 10 Dec 2006 00:02:12 -0200 Subject: [DCCP] ccid3: Finer-grained resolution of sending rates This patch * resolves a bug where packets smaller than 32/64 bytes resulted in sending rates of 0 * supports all sending rates from 1/64 bytes/second up to 4Gbyte/second * simplifies the present overflow problems in calculations Current sending rate X and the cached value X_recv of the receiver-estimated sending rate are both scaled by 64 (2^6) in order to * cope with low sending rates (minimally 1 byte/second) * allow upgrading to use a packets-per-second implementation of CCID 3 * avoid calculation errors due to integer arithmetic cut-off The patch implements a revised strategy from http://www.mail-archive.com/dccp@vger.kernel.org/msg01040.html The only difference with regard to that strategy is that t_ipi is already used in the calculation of the nofeedback timeout, which saves one division. Signed-off-by: Gerrit Renker Acked-by: Ian McDonald Signed-off-by: Arnaldo Carvalho de Melo --- net/dccp/ccids/ccid3.h | 33 ++++++++++++++++++++++++++------- 1 file changed, 26 insertions(+), 7 deletions(-) (limited to 'net/dccp/ccids/ccid3.h') diff --git a/net/dccp/ccids/ccid3.h b/net/dccp/ccids/ccid3.h index 07596d704ef..cd4fc542f73 100644 --- a/net/dccp/ccids/ccid3.h +++ b/net/dccp/ccids/ccid3.h @@ -75,14 +75,14 @@ enum ccid3_hc_tx_states { /** struct ccid3_hc_tx_sock - CCID3 sender half-connection socket * - * @ccid3hctx_x - Current sending rate - * @ccid3hctx_x_recv - Receive rate - * @ccid3hctx_x_calc - Calculated send rate (RFC 3448, 3.1) + * @ccid3hctx_x - Current sending rate in 64 * bytes per second + * @ccid3hctx_x_recv - Receive rate in 64 * bytes per second + * @ccid3hctx_x_calc - Calculated rate in bytes per second * @ccid3hctx_rtt - Estimate of current round trip time in usecs * @ccid3hctx_p - Current loss event rate (0-1) scaled by 1000000 - * @ccid3hctx_s - Packet size - * @ccid3hctx_t_rto - Retransmission Timeout (RFC 3448, 3.1) - * @ccid3hctx_t_ipi - Interpacket (send) interval (RFC 3448, 4.6) + * @ccid3hctx_s - Packet size in bytes + * @ccid3hctx_t_rto - Nofeedback Timer setting in usecs + * @ccid3hctx_t_ipi - Interpacket (send) interval (RFC 3448, 4.6) in usecs * @ccid3hctx_state - Sender state, one of %ccid3_hc_tx_states * @ccid3hctx_last_win_count - Last window counter sent * @ccid3hctx_t_last_win_count - Timestamp of earliest packet @@ -91,7 +91,7 @@ enum ccid3_hc_tx_states { * @ccid3hctx_idle - Flag indicating that sender is idling * @ccid3hctx_t_ld - Time last doubled during slow start * @ccid3hctx_t_nom - Nominal send time of next packet - * @ccid3hctx_delta - Send timer delta + * @ccid3hctx_delta - Send timer delta (RFC 3448, 4.6) in usecs * @ccid3hctx_hist - Packet history * @ccid3hctx_options_received - Parsed set of retrieved options */ @@ -171,4 +171,23 @@ static inline struct ccid3_hc_rx_sock *ccid3_hc_rx_sk(const struct sock *sk) return ccid_priv(dccp_sk(sk)->dccps_hc_rx_ccid); } +static inline u64 scaled_div(u64 a, u32 b) +{ + BUG_ON(b==0); + a *= 1000000; + do_div(a, b); + return a; +} + +static inline u32 scaled_div32(u64 a, u32 b) +{ + u64 result = scaled_div(a, b); + + if (result > UINT_MAX) { + DCCP_CRIT("Overflow: a(%llu)/b(%u) > ~0U", + (unsigned long long)a, b); + return UINT_MAX; + } + return result; +} #endif /* _DCCP_CCID3_H_ */ -- cgit v1.2.3-70-g09d2