This is an idea-test, not a full patch. But I have found it to work.
The idea is to start the timer when DCCP is loaded. This gives
2^32-1 usecs = circa 49 days before the clock wraps around.
What I have tested is the RTT sampling for the initial SYN RTT and
that worked well with the hack below.
Here is a transcript (after the patch)
$ iperf -c 10.0.0.1 -d
------------------------------------------------------------
Client connecting to 10.0.0.1, DCCP port 5001
NOTE: running in bytestream-mode (maximum speed)
DCCP datagram buffer size: 104 KByte (default)
------------------------------------------------------------
[ 3] local 10.0.0.176 port 53425 connected with 10.0.0.1 port 5001
Aug 21 15:04:04 gerrit kernel: delta = 171 <=
Aug 21 15:04:04 gerrit kernel: SYN RTT = 171us <=
[ 3] 0.0-10.0 sec 112 MBytes 93.9 Mbits/se
Will try to clean this up for the other cases - but is the idea ok?
---
net/dccp/dccp.h | 1 +
net/dccp/input.c | 4 ++--
net/dccp/options.c | 2 +-
net/dccp/proto.c | 7 +++++++
4 files changed, 11 insertions(+), 3 deletions(-)
--- a/net/dccp/dccp.h
+++ b/net/dccp/dccp.h
@@ -413,6 +413,7 @@ 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 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
@@ -365,7 +365,7 @@ 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() / 10);
/* 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
@@ -52,6 +52,12 @@ struct inet_hashinfo __cacheline_aligned
EXPORT_SYMBOL_GPL(dccp_hashinfo);
+static ktime_t dccp_timestamp_seed;
+u32 dccp_timestamp(void)
+{
+ return ktime_us_delta(ktime_get_real(), dccp_timestamp_seed);
+}
+
/* Forward Declarations. */
static void dccp_handle_passive_close(struct sock *sk);
@@ -1134,6 +1140,7 @@ static int __init dccp_init(void)
rc = dccp_sysctl_init();
if (rc)
goto out_ackvec_exit;
+ dccp_timestamp_seed = ktime_get_real();
out:
return rc;
out_ackvec_exit:
--- a/net/dccp/input.c
+++ b/net/dccp/input.c
@@ -648,8 +648,8 @@ u32 dccp_sample_rtt(struct sock *sk, kti
DCCP_WARN("packet without timestamp echo\n");
return DCCP_SANE_RTT_MAX;
}
- ktime_sub_us(t_recv, or->dccpor_timestamp_echo * 10);
- delta = ktime_to_us(t_recv);
+ delta = dccp_timestamp() - or->dccpor_timestamp_echo * 10;
+ printk("delta = %lld\n", (long long)delta);
} else
delta = ktime_us_delta(t_recv, *t_hist);
-
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