Gerrit Renker f76fd327a8 dccp ccid-3: Runtime verification of timer resolution ... The DCCP base time resolution is 10 microseconds (RFC 4340, 13.1 ... 13.3). Using a timer with a lower resolution was found to trigger the following bug warnings/problems on high-speed networks (e.g. local loopback): * RTT samples are rounded down to 0 if below resolution; * in some cases, negative RTT samples were observed; * the CCID-3 feedback timer complains that the feedback interval is 0, since the feedback interval is in the order of 1 RTT or less and RTT measurement rounded this down to 0; On an Intel computer this will for instance happen when using a boot-time parameter of "clocksource=jiffies". The following system log messages were observed: 11:24:00 kernel: BUG: delta (0) <= 0 at ccid3_hc_rx_send_feedback() 11:26:12 kernel: BUG: delta (0) <= 0 at ccid3_hc_rx_send_feedback() 11:26:30 kernel: dccp_sample_rtt: unusable RTT sample 0, using min 11:26:30 last message repeated 5 times This patch defines a global constant for the time resolution, adds this in timer.c, and checks the available clock resolution at CCID-3 module load time. When the resolution is worse than 10 microseconds, module loading exits with a message "socket type not supported". Signed-off-by: Gerrit Renker <gerrit@erg.abdn.ac.uk>		2008-09-04 07:45:40 +02:00
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lib	dccp tfrc/ccid-3: Computing Loss Rate from Loss Event Rate	2008-09-04 07:45:34 +02:00
ccid2.c	tcp/dccp: Consolidate common code for RFC 3390 conversion	2008-09-04 07:45:39 +02:00
ccid2.h	dccp ccid-2: Replace broken RTT estimator with better algorithm	2008-09-04 07:45:39 +02:00
ccid3.c	dccp ccid-3: Runtime verification of timer resolution	2008-09-04 07:45:40 +02:00
ccid3.h	dccp ccid-3: Remove dead states	2008-09-04 07:45:35 +02:00
Kconfig	dccp ccid-2: Remove old infrastructure	2008-09-04 07:45:37 +02:00
Makefile	[DCCP] CCID2: Initial CCID2 (TCP-Like) implementation	2006-03-20 17:41:47 -08:00