This is a note to let you know that I've just added the patch titled
tcp: syncookies: do not use getnstimeofday()
to the 3.13-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
tcp-syncookies-do-not-use-getnstimeofday.patch
and it can be found in the queue-3.13 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From foo@baz Thu Apr 10 22:03:04 PDT 2014
From: Eric Dumazet <[email protected]>
Date: Wed, 19 Mar 2014 21:02:21 -0700
Subject: tcp: syncookies: do not use getnstimeofday()
From: Eric Dumazet <[email protected]>
[ 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 <[email protected]>
Cc: Florian Westphal <[email protected]>
Acked-by: Florian Westphal <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
include/net/tcp.h | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -480,20 +480,21 @@ struct sock *cookie_v4_check(struct sock
#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;
}
u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
Patches currently in stable-queue which might be from [email protected] are
queue-3.13/tcp-fix-get_timewait4_sock-delay-computation-on-64bit.patch
queue-3.13/inet-frag-make-sure-forced-eviction-removes-all.patch
queue-3.13/tcp-tcp_release_cb-should-release-socket-ownership.patch
queue-3.13/pkt_sched-fq-do-not-hold-qdisc-lock-while-allocating.patch
queue-3.13/net-unix-non-blocking-recvmsg-should-not-return.patch
queue-3.13/tcp-syncookies-do-not-use-getnstimeofday.patch
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