I have thought this over - the solutions I came up with were all complicated
and I think it is not worth making it more complicated if the issue only occurs
every 11.9 hours. But added a warning note in the timer comments, so that other
timestamp users may take preventive action, if necessary.
--------------------> Patch v2 <-----------------------------------------
[DCCP]: Provide 10s of microsecond timesource
This provides a timesource, conveniently used for DCCP timestamps, which
returns the elapsed time in 10s of microseconds since initialisation.
This makes for a wrap-around time of about 11.9 hours, which should be
sufficient for most applications.
Signed-off-by: Gerrit Renker <gerrit@xxxxxxxxxxxxxx>
---
net/dccp/dccp.h | 2 ++
net/dccp/options.c | 2 +-
net/dccp/proto.c | 2 ++
net/dccp/timer.c | 21 +++++++++++++++++++++
4 files changed, 26 insertions(+), 1 deletion(-)
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -396,6 +396,8 @@ extern int dccp_insert_options(struct so
extern int dccp_insert_option_elapsed_time(struct sock *sk,
struct sk_buff *skb,
u32 elapsed_time);
+extern u32 dccp_timestamp(void);
+extern void dccp_timestamping_init(void);
extern int dccp_insert_option_timestamp(struct sock *sk,
struct sk_buff *skb);
extern int dccp_insert_option(struct sock *sk, struct sk_buff *skb,
--- a/net/dccp/options.c
+++ b/net/dccp/options.c
@@ -372,7 +372,7 @@ EXPORT_SYMBOL_GPL(dccp_insert_option_ela
int dccp_insert_option_timestamp(struct sock *sk, struct sk_buff *skb)
{
- __be32 now = htonl(((suseconds_t)ktime_to_us(ktime_get_real())) / 10);
+ __be32 now = htonl(dccp_timestamp());
/* yes this will overflow but that is the point as we want a
* 10 usec 32 bit timer which mean it wraps every 11.9 hours */
--- a/net/dccp/proto.c
+++ b/net/dccp/proto.c
@@ -1076,6 +1076,8 @@ static int __init dccp_init(void)
rc = dccp_sysctl_init();
if (rc)
goto out_ackvec_exit;
+
+ dccp_timestamping_init();
out:
return rc;
out_ackvec_exit:
--- a/net/dccp/timer.c
+++ b/net/dccp/timer.c
@@ -291,3 +291,24 @@ void dccp_init_xmit_timers(struct sock *
inet_csk_init_xmit_timers(sk, &dccp_write_timer, &dccp_delack_timer,
&dccp_keepalive_timer);
}
+
+static ktime_t dccp_timestamp_seed;
+/**
+ * dccp_timestamp - 10s of microseconds time source
+ * Returns the number of 10s of microseconds since loading DCCP. This is native
+ * DCCP time difference format (RFC 4340, sec. 13).
+ * Please note: This will wrap around about circa every 11.9 hours.
+ */
+u32 dccp_timestamp(void)
+{
+ s64 delta = ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
+
+ do_div(delta, 10);
+ return delta;
+}
+EXPORT_SYMBOL_GPL(dccp_timestamp);
+
+void __init dccp_timestamping_init(void)
+{
+ dccp_timestamp_seed = ktime_get_real();
+}
-
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