SYNOPSIS

protection [reverse] strong [requests/period [burst]]

protection [reverse] flood-protection-type [requests/period [burst]]

protection [reverse] { bad-packets | packet-protection-type }

protection [reverse] connlimit connections [mask prefix]

protection [reverse] connrate rate [burst amount] [srcmask prefix] [htable-size buckets] [htable-max entries] [htable-expire msec] [htable-gcinterval msec]

DESCRIPTION

The protection subcommand sets protection rules on an interface or router.

Flood protections honour the values requests/period and burst. They are used to limit the rate of certain types of traffic.

The default rate FireHOL uses is 100 operations per second with a burst of 50. Run iptables -m limit --help for more information.

The protection type strong will switch on all protections (both packet and flood protections) except all-floods. It has aliases full and all.

The protection type bad-packets will switch on all packet protections but not flood protections.

You can specify multiple protection types by using multiple protection commands or by using a single command and enclosing the types in quotes.

Note

On a router, protections are normally set up on inface.

The reverse option will set up the protections on outface. You must use it as the first keyword.

PACKET PROTECTION TYPES

bad-packets:

Drops all the bad packets detected by these rules.

invalid

Drops all incoming invalid packets, as detected INVALID by the connection tracker.

See also FIREHOL_DROP_INVALID in firehol-variables(5) which allows setting this function globally.

fragments

Drops all packet fragments.

This rule will probably never match anything since iptables(8) reconstructs all packets automatically before the firewall rules are processed whenever connection tracking is running.

new-tcp-w/o-syn

Drops all TCP packets that initiate a socket but have not got the SYN flag set.

malformed-xmas

Drops all TCP packets that have all TCP flags set.

malformed-null

Drops all TCP packets that have all TCP flags unset.

malformed-bad

Drops all TCP packets that have illegal combinations of TCP flags set.

EXAMPLES

protection bad-packets

FLOOD PROTECTION TYPES

icmp-floods [requests/period [burst]]

Allows only a certain amount of ICMP echo requests.

syn-floods [requests/period [burst]]

Allows only a certain amount of new TCP connections.

Be careful to not set the rate too low as the rule is applied to all connections regardless of their final result (rejected, dropped, established, etc).

all-floods [requests/period [burst]]

Allows only a certain amount of new connections.

Be careful to not set the rate too low as the rule is applied to all connections regardless of their final result (rejected, dropped, established, etc).

EXAMPLES

protection all-floods 90/sec 40

CLIENT LIMITING TYPES

These protections were added in v3.

These protections are used to limit the connections client make, per interface or router.

They support appending optional rule parameters to limit their scope to certain clients only.

protection [reverse] connlimit connections [mask prefix]

Allow only a number of connections per client (implemented with connlimit with fixed type=saddr).

protection [reverse] connrate rate [burst amount] [srcmask prefix] [htable-size buckets] [htable-max entries] [htable-expire msec] [htable-gcinterval msec]

Allow up to a rate of new connections per client (implemented with hashlimit with fixed type=upto and mode=srcip).

EXAMPLES

Limit the number of concurrent connections to 10 per client

protection connlimit 10 mask 32

Limit the number of concurrent connections to 100 per client class-C and also limit it to 5 for 1.2.3.4

protection connlimit 100 mask 24
protection connlimit 5 src 1.2.3.4

In the last example above, if you want to give client 1.2.3.4 more connections than all others, you should exclude it from the first connlimit statement, like this:

protection connlimit 100 mask 24 src not 1.2.3.4
protection connlimit 200 src 1.2.3.4

Limit all clients to 10 concurrect connections and 60 connections/minute

protection connlimit 10
protection connrate 60/minute

KNOWN ISSUES

When using multiple types in a single command, if the quotes are forgotten, incorrect rules will be generated without warning.

When using multiple types in a single command, FireHOL will silently ignore any types that come after a group type (bad-packets, strong and its aliases). Only use group types on their own line.

AUTHORS