S. J. van Harmelen wrote:

> Today I tried to put my Shorewall config in production, but had to undo it
> really fast because I had connection problems. When trying to connect to our
> website I noticed that it connected, but then wasn't able to load the whole
> page in one time. Now I understand how a webpage is loaded (each picture is
> a separate call to the webserver) so I know it has something to do with the
> limit action that I set...
> 
> You already explained how the limit action works:
> 
> "The Limit action works by keeping track of how many connections were
> made in the last period"
> 
> But I still have trouble understanding what you are saying here (sorry). In
> the example of loading a webpage with a few pictures in it... Is every
> request to the server counted as a new connection?

I neither know nor do I care when Web browsers decide to open new
connections to a server. I know that if I look at about:config in my
Firefox (Iceweasel) browser, there is a max-connections-per-server
setting that has the value 15. So I further assume that any limiting of
connections to less than 15 in a short period of time would cause issues
for my browser.

> In that case I guess it's
> not really useful to set a limit action on a http rule, right? As then it's
> quite hard to set the correct limit number to enable normal browsing but
> prevent DoS'ing...

I think, as in all such things, you should start out with a conservative
setting and go from there.

> 
> I also read about the connlimit option. Should that be a better option in
> this case? I take it that this option does indeed just count the total
> numbers of concurrent TCP sessions from a specific IP address, the only
> drawback is that the connection aren't counted per rule but in total over
> all rules, correct?

That's correct.
> 
> Any pros and cons I miss? And the doc's don't say what happens when a new
> session is started when then limit is reached? Will the w session be logged
> and dropped?

Like any netfilter rule, if the rule doesn't match then the connection
is passed on to the next rule.

-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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