ipfw.8 revision 20837
1110211Smarcel.Dd July 20, 1996 2110211Smarcel.Dt IPFW 8 SMM 3110211Smarcel.Os FreeBSD 4110211Smarcel.Sh NAME 5110211Smarcel.Nm ipfw 6110211Smarcel.Nd controlling utility for IP firewall 7110211Smarcel.Sh SYNOPSIS 8110211Smarcel.Nm 9110211Smarcel.Ar file 10110211Smarcel.Nm ipfw 11110211Smarcelflush 12110211Smarcel.Nm ipfw 13110211Smarcelzero 14110211Smarcel.Op Ar number 15110211Smarcel.Nm ipfw 16110211Smarceldelete 17110211Smarcel.Ar number 18110211Smarcel.Nm ipfw 19110211Smarcel.Op Fl aftN 20110211Smarcellist 21110211Smarcel.Nm ipfw 22110211Smarceladd 23110211Smarcel.Op Ar number 24110211Smarcel.Ar action 25110211Smarcel.Op Ar log 26110211Smarcel.Ar proto 27110211Smarcelfrom 28110211Smarcel.Ar src 29110211Smarcelto 30110211Smarcel.Ar dst 31110211Smarcel.Oo 32110211Smarcelvia 33110211Smarcel.Ar name | ipno 34110211Smarcel.Oc 35110211Smarcel.Op Ar options 36110211Smarcel.Sh DESCRIPTION 37110211SmarcelIf used as shown in the first synopsis line, the 38110211Smarcel.Ar file 39110211Smarcelwill be read line by line and applied as arguments to the 40110211Smarcel.Nm 41110211Smarcelcommand. 42110211Smarcel.Pp 43110211SmarcelThe 44110211Smarcel.Nm 45110211Smarcelcode works by going through the rule-list for each packet, 46110211Smarceluntil a match is found. 47110211SmarcelAll rules have two associated counters, a packet count and 48110211Smarcela byte count. 49110211SmarcelThese counters are updated when a packet matches the rule. 50110211Smarcel.Pp 51110211SmarcelThe rules are ordered by a ``line-number'' from 1 to 65534 that is used 52110211Smarcelto order and delete rules. Rules are tried in increasing order, and the 53110211Smarcelfirst rule that matches a packet applies. 54110211SmarcelMultiple rules may share the same number and apply in 55110211Smarcelthe order in which they were added. 56110211Smarcel.Pp 57110211SmarcelIf a rule is added without a number, it numbered 100 higher 58110211Smarcelthan the previous rule. If the highest defined rule number is 59110211Smarcelgreater than 65434, new rules are appended to the last rule. 60110211Smarcel.Pp 61110211SmarcelThe delete operation deletes the first rule with number 62110211Smarcel.Ar number , 63110211Smarcelif any. 64110211Smarcel.Pp 65110211SmarcelThe list command prints out the current rule set. 66110211Smarcel.Pp 67110211SmarcelThe zero operation zeroes the counters associated with rule number 68110211Smarcel.Ar number . 69110211Smarcel.Pp 70110211SmarcelThe flush operation removes all rules. 71110211Smarcel.Pp 72110211SmarcelOne rule is always present: 73110211Smarcel.Bd -literal -offset center 74110211Smarcel65535 deny all from any to any 75110211Smarcel.Ed 76110211Smarcel.Pp 77110211SmarcelThis rule is the default policy, i.e., don't allow anything at all. 78110211SmarcelYour job in setting up rules is to modify this policy to match your needs. 79110211Smarcel.Pp 80110211SmarcelThe following options are available: 81110211Smarcel.Bl -tag -width flag 82110211Smarcel.It Fl a 83110211SmarcelWhile listing, show counter values. This option is the only way to see 84110211Smarcelaccounting records. 85110211Smarcel.It Fl f 86110211SmarcelDon't ask for confirmation for commands that can cause problems if misused 87110211Smarcel(ie; flush). 88110211Smarcel.Ar Note , 89110211Smarcelif there is no tty associated with the process, this is implied. 90110211Smarcel.It Fl t 91110211SmarcelWhile listing, show last match timestamp. 92110211Smarcel.It Fl N 93110211SmarcelTry to resolve addresses and service names in output. 94110211Smarcel.El 95110211Smarcel.Pp 96110211Smarcel.Ar action : 97110211Smarcel.Bl -hang -offset flag -width 1234567890123456 98110211Smarcel.It Ar allow 99110211SmarcelAllow packets that match rule. 100110211SmarcelThe search terminates. 101110211Smarcel.It Ar pass 102110211SmarcelSame as allow. 103110211Smarcel.It Ar accept 104110211SmarcelSame as allow. 105110211Smarcel.It Ar count 106110211SmarcelUpdate counters for all packets that match rule. 107110211SmarcelThe search continues with the next rule. 108110211Smarcel.It Ar deny 109110211SmarcelDiscard packets that match this rule. 110110211SmarcelThe search terminates. 111110211Smarcel.It Ar reject 112110211SmarcelDiscard packets that match this rule, and try to send an ICMP notice. 113110211SmarcelThe search terminates. 114110211Smarcel.It Ar divert port 115110211SmarcelDivert packets that match this rule to the divert socket bound to port 116110211Smarcel.Ar port . 117110211SmarcelThe search terminates. 118110211Smarcel.El 119110211Smarcel.Pp 120110211SmarcelWhen a packet matches a rule with the 121110211Smarcel.Ar log 122110211Smarcelkeyword, a message will be printed on the console. 123110211SmarcelIf the kernel was compiled with the 124110211Smarcel.Dv IP_FIREWALL_VERBOSE_LIMIT 125110211Smarceloption, then logging will cease after the number of packets 126110211Smarcelspecified by the option are received for that particular 127110211Smarcelchain entry. Logging may then be re-enabled by clearing 128110211Smarcelthe packet counter for that entry. 129110211Smarcel.Pp 130110211Smarcel.Ar proto : 131110211Smarcel.Bl -hang -offset flag -width 1234567890123456 132110211Smarcel.It Ar ip 133110211SmarcelAll packets match. 134110211Smarcel.It Ar all 135110211SmarcelAll packets match. 136110211Smarcel.It Ar tcp 137110211SmarcelOnly TCP packets match. 138110211Smarcel.It Ar udp 139110211SmarcelOnly UDP packets match. 140110211Smarcel.It Ar icmp 141110211SmarcelOnly ICMP packets match. 142110211Smarcel.It Ar <number|name> 143110211SmarcelOnly packets for the specified protocol matches (see 144110211Smarcel.Pa /etc/protocols 145110211Smarcelfor a complete list). 146110211Smarcel.El 147110211Smarcel.Pp 148110211Smarcel.Ar src 149110211Smarceland 150110211Smarcel.Ar dst : 151110211Smarcel.Pp 152110211Smarcel.Bl -hang -offset flag 153110211Smarcel.It <address/mask> [ports] 154110211Smarcel.El 155110211Smarcel.Pp 156110211SmarcelThe 157110211Smarcel.Em <address/mask> 158110211Smarcelmay be specified as: 159110211Smarcel.Bl -hang -offset flag -width 1234567890123456 160110211Smarcel.It Ar ipno 161110211SmarcelAn ipnumber of the form 1.2.3.4. 162110211SmarcelOnly this exact ip number match the rule. 163110211Smarcel.It Ar ipno/bits 164110211SmarcelAn ipnumber with a mask width of the form 1.2.3.4/24. 165110211SmarcelIn this case all ip numbers from 1.2.3.0 to 1.2.3.255 will match. 166110211Smarcel.It Ar ipno:mask 167110211SmarcelAn ipnumber with a mask width of the form 1.2.3.4:255.255.240.0. 168110211SmarcelIn this case all ip numbers from 1.2.0.0 to 1.2.15.255 will match. 169110211Smarcel.El 170110211Smarcel.Pp 171110211SmarcelWith the TCP and UDP 172110211Smarcel.Em protocols , 173110211Smarcelan optional 174110211Smarcel.Em port 175110211Smarcelmay be specified as: 176110211Smarcel.Pp 177110211Smarcel.Bl -hang -offset flag 178110211Smarcel.It Ns {port|port-port} Ns Op ,port Ns Op ,... 179110211Smarcel.El 180110211Smarcel.Pp 181110211SmarcelService names (from 182110211Smarcel.Pa /etc/services ) 183110211Smarcelmay not be used instead of a numeric port value. 184110211SmarcelAlso, note that a range may only be specified as the first value, 185110211Smarceland the port list is limited to 186110211Smarcel.Dv IP_FW_MAX_PORTS 187110211Smarcel(as defined in 188110211Smarcel.Pa /usr/src/sys/netinet/ip_fw.h ) 189110211Smarcelports. 190110211Smarcel.Pp 191110211SmarcelIf ``via'' 192110211Smarcel.Ar name 193110211Smarcelis specified, only packets received via or on their way out of an interface 194matching 195.Ar name 196will match this rule. 197.Pp 198If ``via'' 199.Ar ipno 200is specified, only packets received via or on their way out of an interface 201having the address 202.Ar ipno 203will match this rule. 204.Pp 205.Ar options : 206.Bl -hang -offset flag -width 1234567890123456 207.It frag 208Matches if the packet is a fragment and this is not the first fragment 209of the datagram. 210.It in 211Matches if this packet was on the way in. 212.It out 213Matches if this packet was on the way out. 214.It ipoptions Ar spec 215Matches if the IP header contains the comma separated list of 216options specified in 217.Ar spec . 218The supported IP options are: 219.Ar ssrr 220(strict source route), 221.Ar lsrr 222(loose source route), 223.Ar rr 224(record packet route), and 225.Ar ts 226(timestamp). 227The absence of a particular option may be denoted 228with a ``!''. 229.It established 230Matches packets that have the RST or ACK bits set. 231TCP packets only. 232.It setup 233Matches packets that have the SYN bit set but no ACK bit. 234TCP packets only. 235.It tcpflags Ar spec 236Matches if the TCP header contains the comma separated list of 237flags specified in 238.Ar spec . 239The supported TCP flags are: 240.Ar fin , 241.Ar syn , 242.Ar rst , 243.Ar psh , 244.Ar ack , 245and 246.Ar urg . 247The absence of a particular flag may be denoted 248with a ``!''. 249.It icmptypes Ar types 250Matches if the ICMP type is in the list 251.Ar types . 252The list may be specified as any combination of ranges 253or individual types separated by commas. 254.El 255.Sh CHECKLIST 256Here are some important points to consider when designing your 257rules: 258.Bl -bullet -hang -offset flag 259.It 260Remember that you filter both packets going in and out. 261Most connections need packets going in both directions. 262.It 263Remember to test very carefully. 264It is a good idea to be near the console when doing this. 265.It 266Don't forget the loopback interface. 267.El 268.Sh FINE POINTS 269There is one kind of packet that the firewall will always discard, 270that is an IP fragment with a fragment offset of one. 271This is a valid packet, but it only has one use, to try to circumvent 272firewalls. 273.Pp 274If you are logged in over a network, loading the LKM version of 275.Nm 276is probably not as straightforward as you would think. 277I recommend this command line: 278.Bd -literal -offset center 279modload /lkm/ipfw_mod.o && \e 280ipfw add 32000 allow all from any to any 281.Ed 282.Pp 283Along the same lines, doing an 284.Bd -literal -offset center 285ipfw flush 286.Ed 287.Pp 288in similar surroundings is also a bad idea. 289.Sh PACKET DIVERSION 290A divert socket bound to the specified port will receive all packets diverted 291to that port; see 292.Xr divert 4 . 293If no socket is bound to the destination port, or if the kernel 294wasn't compiled with divert socket support, diverted packets are dropped. 295.Sh EXAMPLES 296This command adds an entry which denies all tcp packets from 297.Em hacker.evil.org 298to the telnet port of 299.Em wolf.tambov.su 300from being forwarded by the host: 301.Pp 302.Dl ipfw add deny tcp from hacker.evil.org to wolf.tambov.su 23 303.Pp 304This one disallows any connection from the entire hackers network to 305my host: 306.Pp 307.Dl ipfw addf deny all from 123.45.67.0/24 to my.host.org 308.Pp 309Here is good usage of list command to see accounting records: 310.Pp 311.Dl ipfw -at l 312.Pp 313or in short form 314.Pp 315.Dl ipfw -a l 316.Pp 317This rule diverts all incoming packets from 192.168.2.0/24 to divert port 5000: 318.Pp 319.Dl ipfw divert 5000 all from 192.168.2.0/24 to any in 320.Sh SEE ALSO 321.Xr divert 4 , 322.Xr ip 4 , 323.Xr ipfirewall 4 , 324.Xr protocols 5 , 325.Xr services 5 , 326.Xr reboot 8 , 327.Xr syslogd 8 328.Sh BUGS 329.Pp 330.Em WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!!WARNING!! 331.Pp 332This program can put your computer in rather unusable state. When 333using it for the first time, work on the console of the computer, and 334do 335.Em NOT 336do anything you don't understand. 337.Pp 338When manipulating/adding chain entries, service and protocol names are 339not accepted. 340.Sh AUTHORS 341Ugen J. S. Antsilevich, 342Poul-Henning Kamp, 343Alex Nash, 344Archie Cobbs. 345API based upon code written by Daniel Boulet for BSDI. 346.Sh HISTORY 347.Nm 348first appeared in 349.Fx 2.0 . 350