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 ¶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 ---------------------------------------------------------------------The official User-To-User support forum of the Apache HTTP Server Project.See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx------------------------------------------------------------------------ --------------------------------------------------------------------- The official User-To-User support forum of the Apache HTTP Server Project. See <URL:http://httpd.apache.org/userslist.html> for more info. To unsubscribe, e-mail: users-unsubscribe@xxxxxxxxxxxxxxxx " from the digest: users-digest-unsubscribe@xxxxxxxxxxxxxxxx For additional commands, e-mail: users-help@xxxxxxxxxxxxxxxx
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