From 8c27bd75f04fb9cb70c69c3cfe24f4e6d8e15906 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 20 Sep 2013 22:32:55 +0200 Subject: [PATCH] tcp: syncookies: reduce cookie lifetime to 128 seconds 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 Signed-off-by: Florian Westphal Signed-off-by: David S. Miller --- Reading git-format-patch failed