NAME

     ipfw — IP packet filter and traffic accounting

SYNOPSIS

     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_DEFAULT_TO_ACCEPT
           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:

           ipfw_load="YES"

DESCRIPTION

     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 traffic.

     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.

SEE ALSO

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