Messages in this thread Patch in this message | | | From | Jiri Slaby <> | Subject | [PATCH 3.12 49/72] tcp: syncookies: do not use getnstimeofday() | Date | Fri, 18 Apr 2014 11:22:22 +0200 |
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From: Eric Dumazet <edumazet@google.com>
3.12-stable review patch. If anyone has any objections, please let me know.
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[ 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: Jiri Slaby <jslaby@suse.cz> --- 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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