src, dst¶

Use src and dst to define the source and destination IP addresses of the request respectively. host defines the IP or IPs to be matched.

host can also refer to an ipset, using this syntax: ipset:NAME, where NAME is the name of the ipset. The ipset has to be of type hash:ip for this match to work. The source IP or the destination IP will be used for the match, depending if the ipset is given as src or dst.

IPs and ipsets can be mixed together, like this: src 1.1.1.1,ipset:NAME1,2.2.2.2,ipset:NAME2

Examples:

server4 smtp accept src not 192.0.2.1
server4 smtp accept dst 198.51.100.1
server4 smtp accept src not 192.0.2.1 dst 198.51.100.1
server6 smtp accept src not 2001:DB8:1::/64
server6 smtp accept dst 2001:DB8:2::/64
server6 smtp accept src not 2001:DB8:1::/64 dst 2001:DB8:2::/64
    

When attempting to create rules for both IPv4 and IPv6 it is generally easier to use the src4, src6, dst4 and dst6 pairs:

server46 smtp accept src4 192.0.2.1 src6 2001:DB8:1::/64
server46 smtp accept dst4 198.51.100.1 dst6 2001:DB8:2::/64
server46 smtp accept dst4 $d4 dst6 $d6 src4 not $d4 src6 not $s6
    

To keep the rules sane, if one of the 4/6 pair specifies not, then so must the other. If you do not want to use both IPv4 and IPv6 addresses, you must specify the rule as IPv4 or IPv6 only. It is always possible to write a second IPv4 or IPv6 only rule.

srctype, dsttype¶

Use srctype or dsttype to define the source or destination IP address type of the request. type is the address type category as used in the kernel’s network stack. It can be one of:

UNSPEC

an unspecified address (i.e. 0.0.0.0)

UNICAST

a unicast address

LOCAL

a local address

BROADCAST

a broadcast address

ANYCAST

an anycast address

MULTICAST

a multicast address

BLACKHOLE

a blackhole address

UNREACHABLE

an unreachable address

PROHIBIT

a prohibited address

THROW; NAT; XRESOLVE

undocumented

See iptables(8) or run iptables -m addrtype --help for more information. Examples:

server smtp accept srctype not "UNREACHABLE PROHIBIT"


    
    

proto¶

Use proto to match by protocol. The protocol can be any accepted by iptables(8).

mac¶

Use mac to match by MAC address. The macaddr matches to the “remote” host. In an interface, “remote” always means the non-local host. In a router, “remote” refers to the source of requests for servers. It refers to the destination of requests for clients. Examples:

 # Only allow pop3 requests to the e6 host


 client pop3 accept mac 00:01:01:00:00:e6


 # Only allow hosts other than e7/e8 to access smtp


 server smtp accept mac not "00:01:01:00:00:e7 00:01:01:00:00:e8"
    

dscp¶

Use dscp to match the DSCP field on packets. For details on DSCP values and classids, see firehol-dscp(5).

 server smtp accept dscp not "0x20 0x30"


 server smtp accept dscp not class "BE EF"
    

mark¶

Use mark to match marks set on packets. For details on mark ids, see firehol-mark(5).

server smtp accept mark not "20 55"


    
    

tos¶

Use tos to match the TOS field on packets. For details on TOS ids, see firehol-tos(5).

server smtp accept tos not "Maximize-Throughput 0x10"


    
    

custom¶

Use custom to pass arguments directly to iptables(8). All of the parameters must be in a single quoted string. To pass an option to iptables(8) that itself contains a space you need to quote strings in the usual bash(1) manner. For example:

server smtp accept custom "--some-option some-value"
server smtp accept custom "--some-option 'some-value second-value'"
    

inface, outface¶

Use inface and outface to define the interface via which a request is received and forwarded respectively. Use the same format as firehol-interface(5). Examples:

server smtp accept inface not eth0
server smtp accept inface not "eth0 eth1"
server smtp accept inface eth0 outface eth1
    

physin, physout¶

Use physin and physout to define the physical interface via which a request is received or send in cases where the inface or outface is known to be a virtual interface; e.g. a bridge. Use the same format as firehol-interface(5). Examples:

server smtp accept physin not eth0


    
    

uid¶

Use uid to match the operating system user sending the traffic. The user is a username, uid number or a quoted list of the two.

For example, to limit which users can access POP3 and IMAP by preventing replies for certain users from being sent:

client "pop3 imap" accept user not "user1 user2 user3"


    
    

Similarly, this will allow all requests to reach the server but prevent replies unless the web server is running as apache:

server http accept user apache


    
    

gid¶

Use gid to match the operating system group sending the traffic. The group is a group name, gid number or a quoted list of the two.

connlog¶

Use connlog to log only the first packet of a connection.

log, loglimit¶

Use log or loglimit to log matching packets to syslog. Unlike iptables(8) logging, this is not an action: FireHOL will produce multiple iptables(8) commands to accomplish both the action for the rule and the logging.

Logging is controlled using the FIREHOL_LOG_OPTIONS and FIREHOL_LOG_LEVEL environment variables - see firehol-defaults.conf(5). loglimit additionally honours the FIREHOL_LOG_FREQUENCY and FIREHOL_LOG_BURST variables.

Specifying level (which takes the same values as FIREHOL_LOG_LEVEL) allows you to override the log level for a single rule.

dport, sport¶

FireHOL also provides dport, sport and limit which are used internally and rarely needed within configuration files.

dport and sport require an argument port which can be a name, number, range (FROM:TO) or a quoted list of ports.

For dport port specifies the destination port of a request and can be useful when matching traffic to helper commands (such as nat) where there is no implicit port.

For sport port specifies the source port of a request and can be useful when matching traffic to helper commands (such as nat) where there is no implicit port.

limit¶

limit requires the arguments frequency and burst and will limit the matching of traffic in both directions.

connlimit¶

connlimit matches on the number of connections per IP. It has been added to FireHOL since v3.

saddr matches on source IP. daddr matches on destination IP. mask groups IPs with the mask given upto matches when the number of connections is up to the given limit above matches when the number of connections above to the given limit

The number of connections counted are system wide, not service specific. For example for saddr, you cannot connlimit 2 connections for SSH and 4 for SMTP. If you connlimit 2 connections for SSH, then the first 2 connections of a client can be SSH. If a client has already 2 connections to another service, the client will not be able to connect to SSH.

So, connlimit can safely be used:

•

with daddr to limit the connections a server can accept

•

with saddr to limit the total connections per client to all services.

hashlimit¶

hashlimit has been added to FireHOL since v3.

hashlimit hashlimit uses hash buckets to express a rate limiting match (like the limit match) for a group of connections using a single iptables rule. Grouping can be done per-hostgroup (source and/or destination address) and/or per-port. It gives you the ability to express “N packets per time quantum per group” or “N bytes per seconds” (see below for some examples).

A hash limit type (upto, above) and name are required.

name The name for the /proc/net/ipt_hashlimit/name entry.

upto amount[/second|/minute|/hour|/day] Match if the rate is below or equal to amount/quantum. It is specified either as a number, with an optional time quantum suffix (the default is 3/hour), or as amountb/second (number of bytes per second).

above amount[/second|/minute|/hour|/day] Match if the rate is above amount/quantum.

burst amount Maximum initial number of packets to match: this number gets recharged by one every time the limit specified above is not reached, up to this number; the default is 5. When byte-based rate matching is requested, this option specifies the amount of bytes that can exceed the given rate. This option should be used with caution - if the entry expires, the burst value is reset too.

mode {srcip|srcport|dstip|dstport},... A comma-separated list of objects to take into consideration. If no mode option is given, srcip,dstport is assumed.

srcmask prefix When –hashlimit-mode srcip is used, all source addresses encountered will be grouped according to the given prefix length and the so-created subnet will be subject to hashlimit. prefix must be between (inclusive) 0 and 32. Note that srcmask 0 is basically doing the same thing as not specifying srcip for mode, but is technically more expensive.

dstmask prefix Like srcmask, but for destination addresses.

htable-size buckets The number of buckets of the hash table

htable-max entries Maximum entries in the hash.

htable-expire msec After how many milliseconds do hash entries expire.

htable-gcinterval msec How many milliseconds between garbage collection intervals.

Examples:

matching on source host: “1000 packets per second for every host in 192.168.0.0/16”

src 192.168.0.0/16 hashlimit mylimit mode srcip upto 1000/sec
    

matching on source port: “100 packets per second for every service of 192.168.1.1”

src 192.168.1.1 hashlimit mylimit mode srcport upto 100/sec
    

matching on subnet: “10000 packets per minute for every /28 subnet (groups of 8 addresses) in 10.0.0.0/8”

src 10.0.0.8 hashlimit mylimit mask 28 upto 10000/min
    

matching bytes per second: “flows exceeding 512kbyte/s”

hashlimit mylimit mode srcip,dstip,srcport,dstport above 512kb/s
    

matching bytes per second: “hosts that exceed 512kbyte/s, but permit up to 1Megabytes without matching”

hashlimit mylimit mode dstip above 512kb/s burst 1mb