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net: dccp: switch rx_tstamp_last_feedback to monotonic clock 

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>
This commit is contained in:
Eric Dumazet 2018-06-22 06:44:15 -07:00 committed by David S. Miller
parent 74174fe563
commit 0ce4e70ff0
1 changed files with 7 additions and 4 deletions
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11
net/dccp/ccids/ccid3.c
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@ -600,7 +600,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
{
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) {
@ -632,7 +632,7 @@ static void ccid3_hc_rx_send_feedback(struct sock *sk,
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;
@ -679,7 +679,8 @@ static int ccid3_hc_rx_insert_options(struct sock *sk, struct sk_buff *skb)
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) {
@ -687,7 +688,9 @@ static u32 ccid3_first_li(struct sock *sk)
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");