Update README regarding promisc and sampling.

Author: aabc

README

@@ -389,9 +389,11 @@ ipt_NETFLOW linux 2.6.x-3.x kernel module by <abc@telekom.ru> -- 2008-2014.
    sampler=deterministic:123
    sampler=random:123
    sampler=hash:123
-     - enables Flow Sampling. To disable set to the empty value. Note, that
-       this is flow sampling (as of RFC 7014), not packet sampling (PSAMP).
-       There is two standard sampling modes:
+     - enables Flow Sampling. To disable set to the empty value or to `0'.
+       Note, that this is flow sampling (as of RFC 7014), not packet
+       sampling (PSAMP).
+
+       There is three sampling modes:
 
          deterministic:  select each N-th observed flow; in IPFIX this mode
                          is called Systematic count-based Sampling;
@@ -523,6 +525,9 @@ ipt_NETFLOW linux 2.6.x-3.x kernel module by <abc@telekom.ru> -- 2008-2014.
        to reduce load on exporting CPU by increasing this interval. Value are
        in kernel jiffies units (which is x/HZ seconds).
 
+   promisc = 1
+     - Enable promisc hack. See README.promisc Solution.1 for details.
+
 
 ====================
 = HOW TO READ STAT =

README.promisc

@@ -38,6 +38,13 @@ If you wish to account with ipt-netflow module traffic mirrored on switch you ma
   let iptables to see promisc traffic. That traffic will not be routed anywhere
   and discarded just after passing PREROUTING chain.
 
+   Do not enable this option if you have kernel already patched with promisc
+  patch, as this may cause double accounting. Just keep it disabled or remove
+  the patch. Promisc patching is completely custom and non-standard, so if you
+  did not apply it - you are most probably safe to use promisc option. But, if
+  in doubt - measure if module seeing traffic in raw/PREROUTING, if it isn't - you
+  don't have the patch applied and certainly safe to use the option.
+
 
 
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@@ -88,6 +95,7 @@ Voila.
 ps. For Debian Squeeze instructions look at raw_promisc_debian_squeeze6.patch
 
 
+
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     * Solution 3 *
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