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| author | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2010-09-19 20:10:52 +0200 |
|---|---|---|
| committer | Gerrit Renker <gerrit@erg.abdn.ac.uk> | 2010-09-21 12:14:26 +0200 |
| commit | 792e6d3389061ad449429b9ba228eb758c247ea0 (patch) | |
| tree | 31a238fb2fc28e465e95b7d98b5e0698461cdadf /net/dccp/ccids | |
| parent | 80763dfbac4ed1e6dfe6ec08ef748e0e9aec3260 (diff) | |
| download | linux-792e6d3389061ad449429b9ba228eb758c247ea0.tar.gz linux-792e6d3389061ad449429b9ba228eb758c247ea0.tar.bz2 linux-792e6d3389061ad449429b9ba228eb758c247ea0.zip | |
dccp tfrc/ccid-3: computing the loss rate from the Loss Event Rate
This adds a function to take care of the following, separate cases occurring in
the computation of the Loss Rate p:
* 1/(2^32-1) is mapped into 0% as per RFC 4342, 8.5;
* 1/0 is mapped into 100%, the maximum;
* to avoid that p = 1/x is rounded down to 0 when x is very large, since this
means accidentally re-entering slow-start indicated by p == 0, the minimum
resolution value of p is now returned instead;
* a bug in ccid3_hc_rx_getsockopt is fixed: 1/0 was mapped into ~0U.
Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Diffstat (limited to 'net/dccp/ccids')
| -rw-r--r-- | net/dccp/ccids/ccid3.c | 9 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/tfrc.h | 1 | ||||
| -rw-r--r-- | net/dccp/ccids/lib/tfrc_equation.c | 14 |
3 files changed, 19 insertions, 5 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c index 90bc0a7da8e4..9715eebf1551 100644 --- a/net/dccp/ccids/ccid3.c +++ b/net/dccp/ccids/ccid3.c @@ -400,10 +400,10 @@ static void ccid3_hc_tx_packet_recv(struct sock *sk, struct sk_buff *skb) /* Update loss event rate (which is scaled by 1e6) */ pinv = opt_recv->ccid3or_loss_event_rate; - if (pinv == ~0U || pinv == 0) /* see RFC 4342, 8.5 */ + if (pinv == 0) hc->tx_p = 0; - else /* can not exceed 100% */ - hc->tx_p = scaled_div(1, pinv); + else + hc->tx_p = tfrc_invert_loss_event_rate(pinv); /* * Update allowed sending rate X as per draft rfc3448bis-00, 4.2/3 @@ -834,8 +834,7 @@ static int ccid3_hc_rx_getsockopt(struct sock *sk, const int optname, int len, return -EINVAL; rx_info.tfrcrx_x_recv = hc->rx_x_recv; rx_info.tfrcrx_rtt = hc->rx_rtt; - rx_info.tfrcrx_p = hc->rx_pinv == 0 ? ~0U : - scaled_div(1, hc->rx_pinv); + rx_info.tfrcrx_p = tfrc_invert_loss_event_rate(hc->rx_pinv); len = sizeof(rx_info); val = &rx_info; break; diff --git a/net/dccp/ccids/lib/tfrc.h b/net/dccp/ccids/lib/tfrc.h index 01bb48e96c2e..f8ee3f549770 100644 --- a/net/dccp/ccids/lib/tfrc.h +++ b/net/dccp/ccids/lib/tfrc.h @@ -57,6 +57,7 @@ static inline u32 tfrc_ewma(const u32 avg, const u32 newval, const u8 weight) extern u32 tfrc_calc_x(u16 s, u32 R, u32 p); extern u32 tfrc_calc_x_reverse_lookup(u32 fvalue); +extern u32 tfrc_invert_loss_event_rate(u32 loss_event_rate); extern int tfrc_tx_packet_history_init(void); extern void tfrc_tx_packet_history_exit(void); diff --git a/net/dccp/ccids/lib/tfrc_equation.c b/net/dccp/ccids/lib/tfrc_equation.c index 22ca1cf0eb55..a052a4377e26 100644 --- a/net/dccp/ccids/lib/tfrc_equation.c +++ b/net/dccp/ccids/lib/tfrc_equation.c @@ -687,3 +687,17 @@ u32 tfrc_calc_x_reverse_lookup(u32 fvalue) index = tfrc_binsearch(fvalue, 0); return (index + 1) * 1000000 / TFRC_CALC_X_ARRSIZE; } + +/** + * tfrc_invert_loss_event_rate - Compute p so that 10^6 corresponds to 100% + * When @loss_event_rate is large, there is a chance that p is truncated to 0. + * To avoid re-entering slow-start in that case, we set p = TFRC_SMALLEST_P > 0. + */ +u32 tfrc_invert_loss_event_rate(u32 loss_event_rate) +{ + if (loss_event_rate == UINT_MAX) /* see RFC 4342, 8.5 */ + return 0; + if (unlikely(loss_event_rate == 0)) /* map 1/0 into 100% */ + return 1000000; + return max_t(u32, scaled_div(1, loss_event_rate), TFRC_SMALLEST_P); +} |