1.\" 2.\" $FreeBSD$ 3.\" 4.Dd October 25, 2012 5.Dt IPFW 4 6.Os 7.Sh NAME 8.Nm ipfw 9.Nd IP packet filter and traffic accounting 10.Sh SYNOPSIS 11To compile 12the driver 13into the kernel, place the following option in the kernel configuration 14file: 15.Bd -ragged -offset indent 16.Cd "options IPFIREWALL" 17.Ed 18.Pp 19Other related kernel options 20which may also be useful are: 21.Bd -ragged -offset indent 22.Cd "options IPFIREWALL_DEFAULT_TO_ACCEPT" 23.Cd "options IPFIREWALL_VERBOSE" 24.Cd "options IPFIREWALL_VERBOSE_LIMIT=100" 25.Ed 26.Pp 27To load 28the driver 29as a module at boot time, add the following line into the 30.Xr loader.conf 5 31file: 32.Bd -literal -offset indent 33ipfw_load="YES" 34.Ed 35.Sh DESCRIPTION 36The 37.Nm 38system facility allows filtering, 39redirecting, and other operations on 40.Tn IP 41packets travelling through 42network interfaces. 43.Pp 44The default behavior of 45.Nm 46is to block all incoming and outgoing traffic. 47This behavior can be modified, to allow all traffic through the 48.Nm 49firewall by default, by enabling the 50.Dv IPFIREWALL_DEFAULT_TO_ACCEPT 51kernel option. 52This option may be useful when configuring 53.Nm 54for the first time. 55If the default 56.Nm 57behavior is to allow everything, it is easier to cope with 58firewall-tuning mistakes which may accidentally block all traffic. 59.Pp 60To enable logging of packets passing through 61.Nm , 62enable the 63.Dv IPFIREWALL_VERBOSE 64kernel option. 65The 66.Dv IPFIREWALL_VERBOSE_LIMIT 67option will prevent 68.Xr syslogd 8 69from flooding system logs or causing local Denial of Service. 70This option may be set to the number of packets which will be logged on 71a per-entry basis before the entry is rate-limited. 72.Pp 73The user interface for 74.Nm 75is implemented by the 76.Xr ipfw 8 77utility, so please refer to the 78.Xr ipfw 8 79manpage for a complete description of the 80.Nm 81capabilities and how to use it. 82.Sh SEE ALSO 83.Xr setsockopt 2 , 84.Xr divert 4 , 85.Xr ip 4 , 86.Xr ipfw 8 , 87.Xr sysctl 8 , 88.Xr syslogd 8 , 89.Xr pfil 9 90