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-rw-r--r--net/dccp/ccids/ccid3.c13
-rw-r--r--net/dccp/dccp.h5
-rw-r--r--net/dccp/timer.c3
3 files changed, 18 insertions, 3 deletions
diff --git a/net/dccp/ccids/ccid3.c b/net/dccp/ccids/ccid3.c
index 0d406f82e43..f566eb76aeb 100644
--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -869,6 +869,19 @@ MODULE_PARM_DESC(ccid3_debug, "Enable debug messages");
static __init int ccid3_module_init(void)
{
+ struct timespec tp;
+
+ /*
+ * Without a fine-grained clock resolution, RTTs/X_recv are not sampled
+ * correctly and feedback is sent either too early or too late.
+ */
+ hrtimer_get_res(CLOCK_MONOTONIC, &tp);
+ if (tp.tv_sec || tp.tv_nsec > DCCP_TIME_RESOLUTION * NSEC_PER_USEC) {
+ printk(KERN_ERR "%s: Timer too coarse (%ld usec), need %u-usec"
+ " resolution - check your clocksource.\n", __func__,
+ tp.tv_nsec/NSEC_PER_USEC, DCCP_TIME_RESOLUTION);
+ return -ESOCKTNOSUPPORT;
+ }
return ccid_register(&ccid3);
}
module_init(ccid3_module_init);
diff --git a/net/dccp/dccp.h b/net/dccp/dccp.h
index 1585fa26488..b63a82ccb2b 100644
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -86,10 +86,13 @@ extern void dccp_time_wait(struct sock *sk, int state, int timeo);
*/
#define DCCP_RTO_MAX ((unsigned)(64 * HZ))
+/* DCCP base time resolution - 10 microseconds (RFC 4340, 13.1 ... 13.3) */
+#define DCCP_TIME_RESOLUTION 10
+
/*
* RTT sampling: sanity bounds and fallback RTT value from RFC 4340, section 3.4
*/
-#define DCCP_SANE_RTT_MIN 100
+#define DCCP_SANE_RTT_MIN (10 * DCCP_TIME_RESOLUTION)
#define DCCP_FALLBACK_RTT (USEC_PER_SEC / 5)
#define DCCP_SANE_RTT_MAX (3 * USEC_PER_SEC)
diff --git a/net/dccp/timer.c b/net/dccp/timer.c
index e02d5a94f4c..16359e29e7f 100644
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -281,8 +281,7 @@ u32 dccp_timestamp(void)
{
s64 delta = ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
- do_div(delta, 10);
- return delta;
+ return div_u64(delta, DCCP_TIME_RESOLUTION);
}
EXPORT_SYMBOL_GPL(dccp_timestamp);