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Date: Tue, 24 Sep 2013 10:40:12 -0400 (EDT) From: David Miller <davem@...emloft.net> To: fw@...len.de Cc: netdev@...r.kernel.org Subject: Re: [PATCH v3 -next 1/2] tcp: syncookies: reduce cookie lifetime to 128 seconds From: Florian Westphal <fw@...len.de> Date: Fri, 20 Sep 2013 22:32:55 +0200 > We currently accept cookies that were created less than 4 minutes ago > (ie, cookies with counter delta 0-3). Combined with the 8 mss table > values, this yields 32 possible values (out of 2**32) that will be valid. > > Reducing the lifetime to < 2 minutes halves the guessing chance while > still providing a large enough period. > > While at it, get rid of jiffies value -- they overflow too quickly on > 32 bit platforms. > > getnstimeofday is used to create a counter that increments every 64s. > perf shows getnstimeofday cost is negible compared to sha_transform; > normal tcp initial sequence number generation uses getnstimeofday, too. > > Reported-by: Jakob Lell <jakob@...oblell.com> > Signed-off-by: Florian Westphal <fw@...len.de> Applied. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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