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Subject[PATCH 4.14 22/92] net: dccp: switch rx_tstamp_last_feedback to monotonic clock
Date
4.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Dumazet <edumazet@google.com>

[ Upstream commit 0ce4e70ff00662ad7490e545ba0cd8c1fa179fca ]

To compute delays, better not use time of the day which can
be changed by admins or malicious programs.

Also change ccid3_first_li() to use s64 type for delta variable
to avoid potential overflows.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Gerrit Renker <gerrit@erg.abdn.ac.uk>
Cc: dccp@vger.kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
net/dccp/ccids/ccid3.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/net/dccp/ccids/ccid3.c
+++ b/net/dccp/ccids/ccid3.c
@@ -599,7 +599,7 @@ static void ccid3_hc_rx_send_feedback(st
{
struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
struct dccp_sock *dp = dccp_sk(sk);
- ktime_t now = ktime_get_real();
+ ktime_t now = ktime_get();
s64 delta = 0;

switch (fbtype) {
@@ -631,7 +631,7 @@ static void ccid3_hc_rx_send_feedback(st
return;
}

- ccid3_pr_debug("Interval %ldusec, X_recv=%u, 1/p=%u\n", (long)delta,
+ ccid3_pr_debug("Interval %lldusec, X_recv=%u, 1/p=%u\n", delta,
hc->rx_x_recv, hc->rx_pinv);

hc->rx_tstamp_last_feedback = now;
@@ -678,7 +678,8 @@ static int ccid3_hc_rx_insert_options(st
static u32 ccid3_first_li(struct sock *sk)
{
struct ccid3_hc_rx_sock *hc = ccid3_hc_rx_sk(sk);
- u32 x_recv, p, delta;
+ u32 x_recv, p;
+ s64 delta;
u64 fval;

if (hc->rx_rtt == 0) {
@@ -686,7 +687,9 @@ static u32 ccid3_first_li(struct sock *s
hc->rx_rtt = DCCP_FALLBACK_RTT;
}

- delta = ktime_to_us(net_timedelta(hc->rx_tstamp_last_feedback));
+ delta = ktime_us_delta(ktime_get(), hc->rx_tstamp_last_feedback);
+ if (delta <= 0)
+ delta = 1;
x_recv = scaled_div32(hc->rx_bytes_recv, delta);
if (x_recv == 0) { /* would also trigger divide-by-zero */
DCCP_WARN("X_recv==0\n");

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