From: Eric Dumazet <edumazet@xxxxxxxxxx>
3.12-stable review patch. If anyone has any objections, please let me know.
===============
[ Upstream commit 632623153196bf183a69686ed9c07eee98ff1bf8 ]
While it is true that getnstimeofday() uses about 40 cycles if TSC
is available, it can use 1600 cycles if hpet is the clocksource.
Switch to get_jiffies_64(), as this is more than enough, and
go back to 60 seconds periods.
Fixes: 8c27bd75f04f ("tcp: syncookies: reduce cookie lifetime to 128 seconds")
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Florian Westphal <fw@xxxxxxxxx>
Acked-by: Florian Westphal <fw@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
include/net/tcp.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 51dcc6faa561..31c48908ae32 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -484,20 +484,21 @@ extern struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
#ifdef CONFIG_SYN_COOKIES
#include <linux/ktime.h>
-/* Syncookies use a monotonic timer which increments every 64 seconds.
+/* Syncookies use a monotonic timer which increments every 60 seconds.
* This counter is used both as a hash input and partially encoded into
* the cookie value. A cookie is only validated further if the delta
* between the current counter value and the encoded one is less than this,
- * i.e. a sent cookie is valid only at most for 128 seconds (or less if
+ * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
* the counter advances immediately after a cookie is generated).
*/
#define MAX_SYNCOOKIE_AGE 2
static inline u32 tcp_cookie_time(void)
{
- struct timespec now;
- getnstimeofday(&now);
- return now.tv_sec >> 6; /* 64 seconds granularity */
+ u64 val = get_jiffies_64();
+
+ do_div(val, 60 * HZ);
+ return val;
}
extern u32 __cookie_v4_init_sequence(const struct iphdr *iph,
--
1.9.2
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