diff options
| author | Eric Dumazet <edumazet@google.com> | 2014-03-19 21:02:21 -0700 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2014-04-14 06:47:20 -0700 |
| commit | 652c3e3e38667d11e6e7ca204497930c24d059c3 (patch) | |
| tree | 0c86a4c00cce57ad5d19eea52002cfd18607d6e0 | |
| parent | 3927dace523706cc00f808520eaf2125dd7c07b5 (diff) | |
tcp: syncookies: do not use getnstimeofday()
[ 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@google.com>
Cc: Florian Westphal <fw@strlen.de>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| -rw-r--r-- | include/net/tcp.h | 11 |
1 files changed, 6 insertions, 5 deletions
diff --git a/include/net/tcp.h b/include/net/tcp.h index 9250d6292059..197b02045721 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -480,20 +480,21 @@ 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; } u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th, |