It is just a target name
$IPTABLES -N logdropdos
$IPTABLES -A logdropdos -j LOG --log-level INFO --log-prefix "[logdropdos]"
$IPTABLES -A logdropdos -j DROP
Just to make easier the log analisys, you can also use
"-j DROP" instead.
Hamilton Vera
int Administrator (char Network[],char ComputationalSystems[]);
http://antispam.br/
"Google is my shepherd, no want shall I know"
On Thu, 21 Jun 2007, graham wrote:
Hamilton Vera wrote:
You can try to use iptables, to limit the number of TCP connections
$IPTABLES -A INPUT -p TCP -i $WAN -s 0/0 --syn --dport 80 -m connlimit
--connlimit-above 10 -j logdropdos
Sounds good. What's the 'logdropdos'? I don't seem to have it, and google
gives me nothing. Is there a reason not just to use 'REJECT'?
Thanks
Graham
Or implement a Freebsd firewall with QoS, applying shapes to parallel TCP
connections.
I hope this help.
On Thu, 21 Jun 2007, graham wrote:
Hi,
I've just become involved with a system running apache2.0.55 on ubuntu
with linux 2.6.17.
The system is currently unable to run due to repeated downloads of a large
number of pdfs by systems located in China. These are hogging all sockets
and eventually causing apache to die (I'm appending more details below in
case I've got the wrong end of the stick). The ip address of these systems
varies; they are not a single block, although they are obviously working
together (different ip addresses will ask for sequentially related pdfs).
Each ip address will request multiple files in parallel.
I'm told that the limit_ipconn module would solve my problem by limiting
the simultaneous accesses from any one ip address. There is no version of
this available for apache2 on ubuntu. I'm wondering if this is because
similar abilities have been built into apache2 itself, but haven't managed
to find any.
Does anyone have any suggestions?
Thanks
Graham
-----------------------------------------------
Notes from log:
The system is running ok, not at particularly heavy load (<1.0), and
apache is apparently running ok and not reporting errors [corrected
later].
Tailing the apache log file shows that the only accesses to the system are
GETs of pdfs from two chinese systems, 218.4.152.91 and 222.218.254.221,
which are obviously running the same software.
These systems are trying to systematically work their way through
downloading all chinese pdfs. When a pdf is too large and the download
times out, they immediately try again (at any one moment each system is
trying to download 3 or 4 pdfs).
If I restart apache, I immediately get accesses from all over the place,
including the 2 chinese systems. Eventually the Chinese accesses capture
all the apache processes, and nothing else can get access.
'Solution' found for this: turn apache off for a few minutes. The chinese
systems went away, and all was fine again.
One hour later ΒΆ
The chinese systems, and the problems, returned. A little more data this
time.
Once the chinese systems are established, netstat shows that they occupy
most sockets but are mostly in CLOSE_WAIT state. All other requests are
stuck in SYNC_RECV.
After this continues for a while the apache processes gradually start to
die off with the following sequence:
alert] (11): setuid: unable to change to uid: 33 (33 is www-data)
[alert] Child 691 returned a Fatal error... Apache is exiting!
[emerg] (43): couldn't grab the accept mutex
semop: Invalid argument
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