Iptables Method for limiting concurrent TCP connections of a single IP Address

Article Title: iptables method that limits concurrent TCP connections of a single IP address. Linux is a technology channel of the IT lab in China. Includes basic categories such as desktop applications, Linux system management, kernel research, embedded systems, and open source.
The method of limiting concurrent TCP connections of a single IP address is suitable for protecting various TCP services on Linux. It is implemented using iplimit patch in patch-o-matic in iptables, which is more common for various TCP services.

Practice:

Configure the Linux core, use 2.4.20, and use patch-o-matic in www.netfilter.org
Iplimit in the base patch. Compile the configuration to install the new core.
Use iptables 1.2.8 of www.netfilter.org to install it in the system.

Example:

1. the maximum number of connections allowed to telnet a single IP address to the local machine is 2. Connections exceeding the limit are denied:
Iptables-I INPUT-p tcp -- dport 23-m iplimit -- iplimit-above 2-j REJECT

2. Restrict the web services connected to the local machine. The number of concurrent connections of one IP segment C cannot exceed 100, and the number of connections exceeding the limit is denied:
Iptables-I INPUT-p tcp -- dport 80-m iplimit -- iplimit-above 100 -- iplimit-mask 24-j REJECT