Allows you to restrict the number of parallel connections to a server per
client IP address (or client address block).
.TP
[\fB!\fP] \fB--connlimit-above\fP \fIn\fP
Match if the number of existing connections is (not) above \fIn\fR.
.TP
\fB--connlimit-mask\fR \fIprefix_length\fR
Group hosts using the prefix length. For IPv4, this must be a number between
(including) 0 and 32. For IPv6, between 0 and 128.
.P
Examples:
.TP
# allow 2 telnet connections per client host
iptables -A INPUT -p tcp --syn --dport 23 -m connlimit --connlimit-above 2 -j REJECT
.TP
# you can also match the other way around:
iptables -A INPUT -p tcp --syn --dport 23 -m connlimit ! --connlimit-above 2 -j ACCEPT
.TP
# limit the number of parallel HTTP requests to 16 per class C sized \
network (24 bit netmask)
iptables -p tcp --syn --dport 80 -m connlimit --connlimit-above 16
--connlimit-mask 24 -j REJECT
.TP
# limit the number of parallel HTTP requests to 16 for the link local network \
(ipv6)
ip6tables -p tcp --syn --dport 80 -s fe80::/64 -m connlimit --connlimit-above
16 --connlimit-mask 64 -j REJECT