On 04/17/2016 09:41 AM, Justin Pryzby wrote:
> Hi All
> 
> I'm trying to understand the difference between shorewall/iptables MARK and
> CLASSIFY.  As I understand, classify used to be done at the TC layer (not
> iptables), but now (can be) done in iptables.  Is there some reason to use
> MARK/CLASSIFY over the other ?

MARK is Netfilter's 'Swiss Army Knife'. Each packet has a 32-bit integer
associated with it and traffic shaping, routing, etc. have the ability
to examine a set of bits in that integer and take action accordingly. In
the case of Traffic Shaping, a 'classifier' filter is required that
examines the mark and if a match is found, then the packet is assigned
to the related tc class. Each tc class is identified internally by a
pair of hex numbers called a 'class id' (the usual 0x prefix is not
written). The CLASSIFY target allows you to specify the class id
directly for the class that is to handle the packet. So it is more
efficient than using marks because a separate classification filter is
not required.

HTH,

-Tom
-- 
Tom Eastep        \ When I die, I want to go like my Grandfather who
Shoreline,         \ died peacefully in his sleep. Not screaming like
Washington, USA     \ all of the passengers in his car
http://shorewall.net \________________________________________________

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