IPFW(4)                   BSD Kernel Interfaces Manual                   IPFW(4)

     ipfw — IP packet filter and traffic accounting

     To compile the driver into the kernel, place the following option in the
     kernel configuration file:

           options IPFIREWALL

     Other related kernel options which may also be useful are:

           options IPFIREWALL_VERBOSE
           options IPFIREWALL_VERBOSE_LIMIT=100

     To load the driver as a module at boot time, add the following line into
     the loader.conf(5) file:


     The ipfw system facility allows filtering, redirecting, and other
     operations on IP packets travelling through network interfaces.

     The default behavior of ipfw is to block all incoming and outgoing traffic.
     This behavior can be modified, to allow all traffic through the ipfw
     firewall by default, by enabling the IPFIREWALL_DEFAULT_TO_ACCEPT kernel
     option.  This option may be useful when configuring ipfw for the first
     time.  If the default ipfw behavior is to allow everything, it is easier to
     cope with firewall-tuning mistakes which may accidentally block all

     To enable logging of packets passing through ipfw, enable the
     IPFIREWALL_VERBOSE kernel option.  The IPFIREWALL_VERBOSE_LIMIT option will
     prevent syslogd(8) from flooding system logs or causing local Denial of
     Service.  This option may be set to the number of packets which will be
     logged on a per-entry basis before the entry is rate-limited.

     The user interface for ipfw is implemented by the ipfw(8) utility, so
     please refer to the ipfw(8) manpage for a complete description of the ipfw
     capabilities and how to use it.

     setsockopt(2), divert(4), ip(4), ipfw(8), sysctl(8), syslogd(8), pfil(9)

BSD                             October 25, 2012                             BSD