nginx limit_req and limit_conn not working to prevent DoS attack

[B.R.]

The original confusion came from the fact you slided away from the basic
mantra of the Unix philosophy stating 'Make each program do one thing well'.

nginx is a Web server, which generalized itself into a stream server. It
serves content and manages access (protects it).
What you are trying to achieve is turning nginx into a firewall, which it
is not.
A content server does not simply cut connections. It behaves and responds
to requests. That is standard.
All you can do at the connection level is limiting their number (cf.
limit_conn).

It has been suggested you used iptables, as it is a firewall. At the
software level, I would rather recommend nftables.
Some log analyzers could help you make the interface between a content
server and a software firewall, such as fail2ban.

You could also go for hardware (D)DoS protection, depending on the scale of
your needs.

​There is nothing to be surprised of, the product you are using merely
doing the job. it has been made for​
---
*B. R.*

On Wed, Aug 2, 2017 at 6:27 AM, Gary Sellani <lists at lazygranch.com> wrote:

> The trouble is nginx does a fair amount of work before blocking the IP
> address, unless things have changed. My recollection is it parses the whole
> request. Obviously it doesn't send any data. So you are better off blocking
> with the firewall.
>
> You do need to know your audience. Something related to a university could
> generate a number of simultaneous users behind one IP. In my case Boeing
> triggered the limit.
>
>
>   Original Message
> From: nginx-forum at forum.nginx.org
> Sent: August 1, 2017 9:08 PM
> To: nginx at nginx.org
> Reply-to: nginx at nginx.org
> Subject: Re: nginx limit_req and limit_conn not working to prevent DoS
> attack
>
> Yes. Firewall would be another option. But before to that, i would like to
> try out all options at nginx level if one or other would resolve the issue
> at nginx layer itself.
>
> cant we put accept() filters? or
> how the deny option works? can we use deny option to not to accept any new
> connections if number of connections already exceeds max limit from a
> client
> IP.?
> are there any third party modules available for nginx to embed firewall
> functionality? something reliable !!
>
> My objective is, using limit_conn directive, when number of connections
> exceeding limit, instead of sending 503, or 444, just do not accept any new
> connections from that specific IP only(if a client is opening 10000
> connections at a time, it should be fine to not accept connections from
> that
> IP citing the reason that it could be malicious).
>
> Thoughts !!
>
> Thanks.
>
> Posted at Nginx Forum: https://forum.nginx.org/read.
> php?2,275796,275801#msg-275801
>
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