1\fBhashlimit\fP uses hash buckets to express a rate limiting match (like the 2\fBlimit\fP match) for a group of connections using a \fBsingle\fP iptables 3rule. Grouping can be done per-hostgroup (source and/or destination address) 4and/or per-port. It gives you the ability to express "\fIN\fP packets per time 5quantum per group" (see below for some examples). 6.PP 7A hash limit option (\fB\-\-hashlimit\-upto\fP, \fB\-\-hashlimit\-above\fP) and 8\fB\-\-hashlimit\-name\fP are required. 9.TP 10\fB\-\-hashlimit\-upto\fP \fIamount\fP[\fB/second\fP|\fB/minute\fP|\fB/hour\fP|\fB/day\fP] 11Match if the rate is below or equal to \fIamount\fP/quantum. It is specified as 12a number, with an optional time quantum suffix; the default is 3/hour. 13.TP 14\fB\-\-hashlimit\-above\fP \fIamount\fP[\fB/second\fP|\fB/minute\fP|\fB/hour\fP|\fB/day\fP] 15Match if the rate is above \fIamount\fP/quantum. 16.TP 17\fB\-\-hashlimit\-burst\fP \fIamount\fP 18Maximum initial number of packets to match: this number gets recharged by one 19every time the limit specified above is not reached, up to this number; the 20default is 5. 21.TP 22\fB\-\-hashlimit\-mode\fP {\fBsrcip\fP|\fBsrcport\fP|\fBdstip\fP|\fBdstport\fP}\fB,\fP... 23A comma-separated list of objects to take into consideration. If no 24\-\-hashlimit\-mode option is given, hashlimit acts like limit, but at the 25expensive of doing the hash housekeeping. 26.TP 27\fB\-\-hashlimit\-srcmask\fP \fIprefix\fP 28When \-\-hashlimit\-mode srcip is used, all source addresses encountered will be 29grouped according to the given prefix length and the so-created subnet will be 30subject to hashlimit. \fIprefix\fP must be between (inclusive) 0 and 32. Note 31that \-\-hashlimit\-srcmask 0 is basically doing the same thing as not specifying 32srcip for \-\-hashlimit\-mode, but is technically more expensive. 33.TP 34\fB\-\-hashlimit\-dstmask\fP \fIprefix\fP 35Like \-\-hashlimit\-srcmask, but for destination addresses. 36.TP 37\fB\-\-hashlimit\-name\fP \fIfoo\fP 38The name for the /proc/net/ipt_hashlimit/foo entry. 39.TP 40\fB\-\-hashlimit\-htable\-size\fP \fIbuckets\fP 41The number of buckets of the hash table 42.TP 43\fB\-\-hashlimit\-htable\-max\fP \fIentries\fP 44Maximum entries in the hash. 45.TP 46\fB\-\-hashlimit\-htable\-expire\fP \fImsec\fP 47After how many milliseconds do hash entries expire. 48.TP 49\fB\-\-hashlimit\-htable\-gcinterval\fP \fImsec\fP 50How many milliseconds between garbage collection intervals. 51.PP 52Examples: 53.TP 54matching on source host 55"1000 packets per second for every host in 192.168.0.0/16" => 56\-s 192.168.0.0/16 \-\-hashlimit\-mode srcip \-\-hashlimit\-upto 1000/sec 57.TP 58matching on source port 59"100 packets per second for every service of 192.168.1.1" => 60\-s 192.168.1.1 \-\-hashlimit\-mode srcport \-\-hashlimit\-upto 100/sec 61.TP 62matching on subnet 63"10000 packets per minute for every /28 subnet (groups of 8 addresses) 64in 10.0.0.0/8" => 65\-s 10.0.0.8 \-\-hashlimit\-mask 28 \-\-hashlimit\-upto 10000/min 66